MySwag.org The Off-road Camper Trailer Forum
General => General Discussion => Topic started by: Animall on July 21, 2015, 01:20:13 PM
-
Hi guys just a heads up to all with air bags on their Utes , I work in a smash repair shop in cairns and the number of Utes we have come in with broken back is not good , air bags and overloading is a bad thing and some insurance companies are starting to refuse claims if air bags are fitted , your better off with proper uprated leaf springs as they spread the load better and don't push up against the chassis , better still is to have the chassis strengthened and blue plated as well if you regularly carry full loads and tow a heavy trailer or van , can't think of anything worse than being half way up the OTT and bang goes your chassis just because it cheaper to fit air bags , thanks for looking
-
The issue is more about overloading than the Airbags. Airbags don't magically give you a GVM upgrade. They're load levelling devices. Yet people whack them in and assume they can add more weight. Then they start towing bloody heavy trailers too.
http://www.4x4australia.com.au/drive/1504/bent-utes/ (http://www.4x4australia.com.au/drive/1504/bent-utes/)
"For another expert opinion on airbag suspension, we spoke to Beau Smith, the sales manager of Polyair Springs; arguably the oldest and biggest airbag suspension supplier in Australia. He, like me, knows of an awful lot of vehicles without airbags that have cracked their chassis. “100 per cent of photos and stories I have heard regarding this issue is to do with vehicles that are carrying huge amounts of load and/or towing. Most people that have this issue are not aware of the weight they are carrying and many are over their GVM without realising it,” he said.
Importantly he added: “Airbags are in no way designed to increase the vehicles GVM, we clearly state this on our marketing hand-outs, product packaging and instructions. From an engineering stand point, the airbags create a third point of contact (usually at the bump stop strike plate which is designed to handle severe impact) to ‘assist’ in the load carrying of the vehicle,” he continued. “In cases where we know the vehicle will constantly be on its upper limit of capacity, we recommend that the leaf pack and even shock absorbers be upgraded from factory spec for a more even load share along the chassis rail.”
-
:worthles: :worthles: they are always good for a laugh!
-
Hey mate - with all those bent ute chassis coming in - can you give me an indication of:
# Total number bent that your shop has repaired in say the past 12 months.
# How many were basic single cabs with trays; vs
# The Tub variety; (double cab; extra cab types?)
# Were they 2x4s; or 4x4s etc?
# What are the insurance company(s) that are knocking back these claims - that you have seen..?
I have a single cab 4x4 ute (not the tub type) - with air bags and an upgraded leaf pack; (I think a 400kg leaf pack?) ... I always try to make sure the ute "looks level" - and that the load is distributed across the 3 points of the bags, and the leafs .... but these attempts are are far from an exact science - (aka "guess work").....
Hi guys just a heads up to all with air bags on their Utes , I work in a smash repair shop in cairns and the number of Utes we have come in with broken back is not good , air bags and overloading is a bad thing and some insurance companies are starting to refuse claims if air bags are fitted
-
Its not just utes that have failed i know of a few wagons cracking due to air bag issues as well.
-
When you say you see the utes with bent/cracked chassis in smash repairs, does that mean they are repairable and get back onto the road? I thought utes with the bent chassis where written off and scrapped.
-
Its not just utes that have failed i know of a few wagons cracking due to air bag issues as well.
Airbag issues or overloading issues? ie what's the proof that is airbag related and not just overloading beyond GVM? Correlation does not equal Causation.
No, I don't work for an airbag supplier - I'm just sceptical that its airbags causing this rather than peeps overloading their rigs. Some of whom also happen to have airbags.
-
My neighbour got home from a Simpson trip on Saturday, and his BT50 is now a write off with a bent chassis.
He doesn't have airbags, but he was loaded and hit a concealed washout at speed.
Airbags or not, it all depends on the load, and the circumstances...............
It's a bit like saying we should not fit bullbars, because we will bend the front chassis if we hit a cow.....................bulbar or not, ya cars F%&#@D because of what you did, not because of your accessories ?
-
If we try and keep this thread informative this will be good ...
So for the engineers out there the question I have always wanted answered is this
A leaf spring has shackles on one end and when force IE load is applied in a downward fashion the spring flattens out and absorbs some of this load through its dynamic nature ..RIGHT
No genius statement there I know ;D ;D so when force is applied from underneath IE rough roads etc the spring also flattens out absorbing the load ...so it manages the upward forces and the rebound of the down ward forces
If I were to place a massive block of wood between the centre of the dynamic and flexible spring in its centre and a solid non moveable part ..like the chassis rail HOW DOES THE SPRING NOW WORK AS DESIGNED ?
this is not me saying this a fact or anything I just really want to know the answer as i simply cant work it out. By virtue of the position of the airbag and its design it will limit or totally stop the leaf spring from working as intended would it not ?.
I know with coils it simply slows down the rate of compression when a air bag is fitted inside the coil spring, to me this makes sense as it does not change the force direction in terms of where its placed. If i put an air bag horizontally between the rings of my coil spring i reckon i would have some major issues.
I think personally its the design of the air bag used on leaf trucks and the way they are fundamentally opposing the way the leaf would want to work ..up and back etc a long air bag that somehow was placed between the leaf spring and the chassis and allowed the spring to flex but slowed its rate would be better in my mind as it would compliment the leaf spring instead of working against it.
Just trying to think out loud and see what those more qualified think.
Jet ;D ;D
-
Airbag issues or overloading issues? ie what's the proof that is airbag related and not just overloading beyond GVM? Correlation does not equal Causation.
No, I don't work for an airbag supplier - I'm just sceptical that its airbags causing this rather than peeps overloading their rigs. Some of whom also happen to have airbags.
Hey you could be right. But same brand same engine roughly similar years. All 3 had airbags. Now the brand some people will say no way best 4wd etc etc. Could be right. Just strange how the 3 that i know of had airbags.
i have also got airbags, and yes i know they are to only "help" your load NOT carry.
-
Answers to a couple of questions . Yes obviously the air bags alone are not causing chassis damage but when fitted people seem to think they can carry twice as much weight , in the last 12 month we have had about 14 Utes with damaged chassis all where fitted with airbags and all where double or extra cab . No single cabs proably because you can put more of your load in front of chassis rather than on it or behind it . All but one have been repaired ( not all buy insurance ) but once repaired they are weaker than before unless you plate the sides of the chassis which then requires a blue plate and engineering checks .but then some insurance companies will not insure because it's modified and if involved in a accedent from the rear will not crumple as designed to and could cause more damage or injury to the ocupunts of the vehicle that hits the rear . As for which insurance companies are not paying out I will have to find out as work on the floor not in office .
-
thanks for those answers - really appreciated ...
14 in the last year from one shop is pretty bad...
As total guess work - say there is 500 panel shops in Aust and 2% are having this sort of carnage -
that makes for a minimum of 140 F-ed utes.... per year... ??
(Another reason to "purchase new" - if doable?)....
-
If we try and keep this thread informative this will be good ...
Hahahahahahaha.... Your always good far a laugh Jet. ;D ;D
Talking about bent dual cabs and airbags is always going to bring out the stories of someone's friends, uncles, mother in laws bent ute... :cheers:
-
(Another reason to "purchase new" - if doable?)....
newer more modern utes would be weaker than old over engineered ones...
-
Hahahahahahaha.... Your always good far a laugh Jet. ;D ;D
Talking about bent dual cabs and airbags is always going to bring out the stories of someone's friends, uncles, mother in laws bent ute... :cheers:
I've just spent the last few hours helping my neighbour strip his accessories off his "about to be written off" bent BT50 that does not have airbags
CAVAET- I do not possess technical knowledge on the subject, but as this is a discussion forum, here is my opinion ;D
I think the advantage that airbags offer, and their true design purpose, is they give you flexibility in your rear spring settings. Generally you would replace your leaf spring pack with one that is rated to the load you intend carrying most of the time. That's fine if you carry a constant load all of the time. but if you use your car as a daily runabout, and load it up for the odd trip away, you are stuck with a leaf pack that is either too harsh when empty, or too soft when loaded. Both of those scenarios are less than ideal for handling.
This is where I think air bags offer the versatility of being able to have a spring that is suited to your vehicles normal use, but gives you the ability to add a bit of air to supplement / assist the springs when carrying more load. And I'd like to stress "supplement / assist", they do not magically increase your GVM.
I agree that on a leaf sprung vehicle, where they are fitted seems to be in contrast with how the spring is mounted, but I do not have the knowledge or expertise needed to fully understand the load forces.
My assumption would be that people that are bending utes are suffering from a combination of problems like vehicle overload, airbags pumped too hard, and external factors applying additional or extreme forces to the rear suspension (cresting sand dunes at speed, severe corrugations, or sharp dips at speed).
All the examples that I've seen appear on the interweb seem to have come from areas where these types of conditions are prevalent IE;- Birdsville (utes broken on the Simpson sand dunes}, Cairns / Weipa (utes broken on the Capes corrugations}, and around areas like Frazer (utes broken after hitting washouts). These are all areas where people would generally have a loaded up duel cab towing their camper / van?
I had airbags in my duel cab Navara for about 5 years with no problems encountered after numerous trips (although I was mindful of the perceived issue and careful about how I loaded), and I have airbags in my current Cruiser wagon. In both instances they have improved the handling of the vehicle whilst towing.
I'll refer back to my "bullbar" comment in my previous post, and qualify that comment. Airbags are like any accessory that we fit to our vehicle. They have design limits and guidelines for proper use. If we use them in ways that are beyond they're design parameters, or expose them to extreme forces, then I'd expect something will break.
Donning flame suit and ducking for cover now.................... ;D
-
I've just spent the last few hours helping my neighbour strip his accessories off his "about to be written off" bent BT50 that does not have airbags
:worthles:
-
:worthles:
Maybe tomorrow when we finish the job. Didn't want to offend him by taking pictures today, he seemed dejected enough :'(
The rear of the chassis has deflected down by about 20mm. Passenger side has bent just in-front of where the bump stop has hit the chassis rail, and the driver side is bent just behind where the bump stop has hit the chassis. The ute has aftermarket suspension with 350kg constant load springs. It's used as a work ute and is always loaded, but I suspect it was maxed (plus a bit more) for this trip, and was towing a camper.
-
Maybe tomorrow when we finish the job. Didn't want to offend him by taking pictures today, he seemed dejected enough :'(
that's fair enough too.... so whats he replacing it with?
-
I also read a couple of articles recently in CT an 4WD magazines.
Reminds me of that ad for Ford Ranger, "can carry 1 tonne more than........" :cup:
Overloading when of the bitumen seems to be the problem, I believe........
-
"A leaf spring has shackles on one end and when force IE load is applied in a downward fashion the spring flattens out and absorbs some of this load through its dynamic nature ..RIGHT"
Well here's what's happening-
https://www.youtube.com/watch?v=1uRMiF2YRv0 (https://www.youtube.com/watch?v=1uRMiF2YRv0)
" so when force is applied from underneath IE rough roads etc the spring also flattens out absorbing the load ...so it manages the upward forces and the rebound of the down ward forces"
Well actually the leaf springs resist the upward force progressively (softly at first and then progressively harder as more leaves come together and act as one) and they'll act equally with upward force on the 4 chassis points except for minor vector force loss acting backwards along the chassis due to the rear shackle movement (ie the leaf springs are elongating toward the rear). As for the rebound (or sudden wheel drop into a pothole) that's the job of the shock absorbers and rebound damping preventing the loaded springs expanding downwards quickly so the shockers are already acting up and down on the chassis rails in the middle of the leaf springs anyway. Ipso facto there are 3 load points on a chassis rail to be engineered for and an air bag addon would be adding to a load point with the shock.
"If I were to place a massive block of wood between the centre of the dynamic and flexible spring in its centre and a solid non moveable part ..like the chassis rail HOW DOES THE SPRING NOW WORK AS DESIGNED ?"
Answer is it wouldn't but would simply become a solid 3 point load on each chassis rail - ie at each ends of the spring and the now solid effective shocker and the rear shackle cannot move back and forth any longer so it's another fixed point for load.
"By virtue of the position of the airbag and its design it will limit or totally stop the leaf spring from working as intended would it not ?."
No it wouldn't act like the solid block of wood because it can work up and down just like the shocker and just like the end rubber mounted shocker it has some flexibility to move fore and aft with the elongating spring and allow its normal operation, albeit adding somewhat to the resistance of all the undercarriage being rammed up into the chassis. It's there that that the air bag would place some extra load on the midpoint of the chassis like the shock does and where you need to be careful with overloading (the same consideration would apply with pump up shocks here)
"I know with coils it simply slows down the rate of compression when a air bag is fitted inside the coil spring, to me this makes sense as it does not change the force direction in terms of where its placed. If i put an air bag horizontally between the rings of my coil spring i reckon i would have some major issues."
Well actually the air bag on a coil spring is largely acting in between the coils (squeezing out in between them) as an aid to resisting compression so again the overloading precaution applies and spada is correct with his analysis that it's nigh impossible to set sprung suspensions up for unloaded comfort and yet handle maxm loads to boot. Air bags can assist but judiciously and you need to be aware of the tradeoff imposed over really rough stuff ie slow down to reduce really heavy impact forces via the air bag but that also applies to the whole suspension in general. Basically you could overload the rig to a very large degree on the tar but it's the shock loads on the rough stuff that will find it all out.
-
Speaking of suspension vector forces acting on the vehicle chassis with its load and passengers here's how rear motorcycle suspension (scroll down) has developed so that upward forces are split to produce some forward force that acts to thrust the bike forward rather than directly upwards like the old twin shock design-
http://www.carbibles.com/suspension_bible_bikes.html (http://www.carbibles.com/suspension_bible_bikes.html)
Yes leaf springs produce a very small rearward vector force but motorcycle suspension kills that for forward thrust vectoring of the upward force although with much lighter resistive/inertia mass than a car it certainly needs to.
-
that's fair enough too.... so whats he replacing it with?
New for old insurance coverage, so the replacement will be the same.
-
I believe there is a vehicle manufacturer that derates their vehicles towing capacity off road.
Along the lines of what jw2170 said above it is the weights when off the black top, even if within the GVM, making the suspension work harder and creating more stress on the vehicle.
Remember when Mercedes took those G wagons in the outback for testing and they had to keep flying in shocks because they kept failing. Precision German engineering.
-
I believe there is a vehicle manufacturer that derates their vehicles towing capacity off road.
Along the lines of what jw2170 said above it is the weights when off the black top, even if within the GVM, making the suspension work harder and creating more stress on the vehicle.
Remember when Mercedes took those G wagons in the outback for testing and they had to keep flying in shocks because they kept failing. Precision German engineering.
Land Rover changes their maximum tow weights from 3500kg to just 1000kg when off-road.
-
Yes that's the temptation with air bag assist for initial load levelling is to believe the rig can take more load when the complete opposite is true with rough stuff shock loading. Now I recall with an early Dove and an 81' Corona wagon I added a pair of pump up shocks to do the job my coil air bags do on the Suzy nowadays. When the BIL (new pommy immigrant) was going on a first bush trip from Adelaide up to Darwin with a workmate in his small Daihatsu 4WD at the time he did likewise after seeing mine. Trouble was he was pumping them up to max to cover some mild overloading and had to limp into Alice because he'd knocked the rubber eye bushes out completely on the air shocks (nolathane bush fans take note here of another possible tradeoff)
On the flip side of the coin my old man was in charge of the survey section for the Gove mine/refinery complex back in the late 60s early 70s and they had the first small 4 cyl Hilux utes for the survey crews (bigger ones were Lite Stouts and Chrysler VJ Valiants) Trouble with the Hiluxes was they were oversprung at the rear and with only light survey gear on corrugated dirt roads were skating all over the road and downright dangerous with a couple of nasty prangs. He wanted the site workshops to take some leaves out of the springs but too busy/too hard was the reply(well you would be with Alusuisse mining engineers used to autos that drove the manual Valiants around in second gear everywhere) but one thing the construction site had was plenty of spare concrete. Some quick vol/density calcs and the right height board across the tray in front of the wheel arches and fill the front third up with conc and float her off and bobsyeruncle handling the dirt roads after that :cup:
-
I'm no engineer but I've got a theory on this and airbags and suspension are only a small part of the story. Its all about vehicle construction, weight placement, G forces and Archimedes...!
If you do a Google image search on bent dual cab utes, you'll see a plethora of photos of the same thing. They are all bent at the point between the back of the cab and the front of the tray or tub. This can't be a coincidence. Its an obvious weak point and here's why...
You hear how vehicle manufacturers have to put extra bracing in the chassis of a convertible car that was originally designed as a sedan or hardtop. Instead of having a rigid shell, all the strength is now in the floorplan alone and as a result it becomes all floppy and requires extra bracing to get additional rigidity. Interestingly it is never as much as the sedan or hardtop.
Its basically the same effect with dual cab utes. Half of the vehicle is a standard sedan and the other half is essentially a convertible and there is nothing joining the 2 halves together other than sharing a common chassis.
Now I know there are differences between a monocoque chassis of a modern day sedan and the rigid ladder chassis of a 4WD, but rigidity is rigidity regardless. Even a heavy ladder frame chassis would have additional rigidity if it was braced from front to back with a full length steel shell body of a wagon stuck on top of it.
Add to this the placement of the tow point of a dual cab ute in relation to the rear wheels compared to a 4wd Wagon. In the case of a BT50, its nearly half the length of the space between the front and rear wheels. What was it that Archimedes said...Give me a lever long enough and a fulcrum on which to place it, and I shall move the world...?
Now the final piece of the puzzle. What happens when you bounce on a trampoline or fall onto a concrete path from a height? You experience various G forces as your momentum is arrested by the trampoline or the ground. The effect is your weight increases relative to the rate of deceleration. The trampoline gives you a gradual deceleration but the hard concrete floor provides no give at all. You don't break any bones on the trampoline but hitting concrete from the same height is a different matter. Again...same with cars suspension. Leaf springs systems are more rigid than coils, hence their ability to carry a load. Problem is when this load travels up and down with the movement of the car, g forces increase the weight and because there's no give in the spring (worse if air bags are in the picture) the force has to go somewhere and that will be the weakest point. Guess where that might be...? Right at the point these things are bending. Between the tub and the cab. Put a heavy trailer on the back where the additional leverage is obtained, add the g forces to that weight and I bet your tripling the weight on the back of the chassis even just by going over a speed hump. Imagine the forces at play on a lumpy, corrugated, potholed sandy track.
As I said I'm no engineer but this all seems pretty obvious. It will be interesting to see if the wagon versions of the current crop of dual cab utes (Fortuna, MUX, Everest, etc) suffer the same bent chassis issues to the same extent. Bet they don't...!
-
To try and understand what is happening here you have to first look at the difference between weight and mass. Weight is simply a measure of the pull of gravity. Mass is the amount of material in something.
A brick for example might weigh say 3 kilos. When you place it on the ground, it does not float away or move because gravity is trying to pull it down to the centre of the earth. If you place some scales between the brick and the ground, you will get a 3 kilo reading. That 3 kilos does not change.
The brick did not damage the scales but if you pick it up to head height and drop it onto them, there is a good chance that it will. Why did that happen you could ask because it still weighs only 3 kilos? The difference is the material (mass) in the brick was put into motion. It built up momentum and did not want to sop. When the scales brought it to a sudden stop, it hit them hard causing a lot of damage in the process.
That is what is causing all of these bent chassis. All of the material that you put behind the rear axle will fall and build up momentum when the wheels drop into a depression in the road. It does not want to stop anymore than the brick did. It takes the end of the chassis down with it but it is unrestrained because there is no spring between the end of the chassis and the road. The restraint is the springs and axle housing that are well over a metre further forward. In other words the end of your chassis behind the rear axle is sticking out like a diving board and just like a diving board, there is nothing supporting the far end of it.
When the wheels come back up again a split second later, the falling material behind the axle still wants to fall. It thumps the end of the chassis down hard as the chassis tries to catch it and instantly heave it back up again. This pivots the chassis on the rear axle bearings and tries to lift the front.
The springs can't help very much. They just compress and pivot with the chassis.
It is a bit like a see saw. You can load it up with a very heavy man on one end and a slightly lighter one on the other and one end will go down while the other will go up. If you placed a spring between the plank and the cross bar, it will compress but the plank will still go down at one end and up at the other.
Imagine what this is doing to the rear of your chassis, particularly on rough roads. It is constantly flexing the end of the chassis up and down and any chassis can only take so much of that before something drastic happens.
The reason why the front of the chassis does not bend, even with heavy bull bars and winches on it is because it is so short in length. There is no serious leverage effect.
Look at your car from side on. There is very little overhang in front of the front axle but there is a mile of it out the back. That distance out the back is really a long lever that further amplifies the forces generated by all of that moving material.
To see an example of that, look up the specifications for the Defender on Land Rover’s site. It says 150 kg on the tow ball will add 206 kg to the rear axle. That is because that 150 is back on the end of a lever. Imagine the forces going into the chassis near its pivot point when the 150 is in motion and constantly changing direction up and down.
Those forces are further increased when you add the weight of whatever is in the rear of the tray.
The reason why air bags seem to be blamed more often than not is they don't compress like a leaf spring. A leaf spring compresses in proportion to the load i.e double the load and you double the compression. An air bag is an exponential spring. It just keeps on getting harder. The more you try and compress it, the more it resists further compression. They work a bit like a linear spring for about 40% of their travel then harden up rapidly after that to the point where they are like rocks at around 70% compressed.
A leaf or coil will keep compressing until they reach the bump rubbers which are also exponential springs. An air bag is like an oversize bump rubber and is not the sort of thing you want operating in a location designed for leaf springs. There is a good chance that an air bag will stop the downward movement of the chassis before the leaf springs would have. That is why they can be so destructive. It explains why more cars bend chassis with them than without.
I have heard many people claiming the high carrying capacities up in the vicinity of 1 ton are unrealistic and you can't load them up to that level without having the rear dragging on the ground. It may sound impossible but maximum capacities require precise loading and it can be done. Each load bearing area must carry its full share of the load.
To load one to the maximum you must start with 5 large football player size people. This will give you around 500 kg in the cabin. A manufacturer has to design a car to carry large people. It is no use setting it up for five size 6 women. The next step will be to fill the fuel tank. That should add about 70 to 80 kg. The remaining 420 kg can then go into the tub out the back with the heaviest items as far forward as possible.
That will leave the car fully loaded and sitting at exactly the height that the manufacturer intended. If you have a family consisting of two average size adults and three toddlers, you may have a combined weight of only 200 kgs. You are definitely going to have the rear sagging if you then try and put the remaining 720 kg in the back.
All of these maximum loads are for good highway conditions only and should be reduced when in the bush. The editorial in the 4X4 Australia bent chassis story said about 30 to 40 % should be knocked off the maximum capacity. The best place for advice about this is the car manufacturer’s customer advice service. Contact details will be on their web site. Don’t ask a dealer.
We then have towing weights and once again the advertised weights of 3000 to 3500kg seem unrealistic but they may not be. The manufacturer states a maximum capacity but does not specify what you can or can not tow.
Have a look at this old Leyland Brothers DVD and stop it on 1 minute and 24 seconds. https://www.youtube.com/watch?v=MPXKKFnhqdQ (https://www.youtube.com/watch?v=MPXKKFnhqdQ) A modern dual cab could tow a trailer like that with a total weight of 3500 kgs but there would be no more than about 20 kg on the tow ball.
The manufacturer says their car can tow something weighing 3500 kg somewhere but they don’t claim it can tow anything that heavy anywhere. It is up to the owner to ask a few questions about both the car and their trailer before buying anything.
Another big killer of ute chassis is the tow ball weight. 4X4 Australia mentions this and says the trailer can jerk the back of the car up and down. It may not always be apparent to the driver but the chassis will notice it. This all comes down to reducing towing capacities as the conditions get rougher. Some manufacturers tell you to do this and the Armed Forces always do it but how many owners have simply looked at the maximum and gone no further thinking they were well within limits?
My ute has a maximum towing capacity of 1800 kg with a maximum ball weight of 180kg. If I bought a camper trailer of say 1250 kgs with a ball weight of 120 kg I should be fine but I would have to keep it on fairly smooth roads. The reason is the specifications also state that the end of the chassis must be lifted by a load leveling device (WDH) for any ball weigh above 90 kg. A WDH is not practical and can cause some damage in the type of conditions camper trailers are often driven in so I can’t use one. If I ignored that direction from the manufacturer, I would be 30 kg overweight on the ball and the chassis could be at risk.
These are just a few of the things that you have to look thoroughly into before you head off into the bush. You can not afford to have too much heavy material way out the back on the end of the chassis. The very best heavier aftermarket springs or air bags are not going to take it away. They will certainly hold it up a little higher but they can not stop the end of the chassis from flexing up and down.
It is also no use saying you have weigh bridge certificates proving you were 250 kgs or whatever under GVM so your bent chassis is the car manufacturer’s fault.
-
Great explanation Metters :cup: Thanks for posting
KB
-
some great info her guys .. :cup: :cup: :cup:
Jet :D
-
As I said I'm no engineer but this all seems pretty obvious. It will be interesting to see if the wagon versions of the current crop of dual cab utes (Fortuna, MUX, Everest, etc) suffer the same bent chassis issues to the same extent. Bet they don't...!
You are correct they won't because they will be coil sprung.
Also you mentioned elsewhere in your post about a ladder chassis being braced by the body of the vehicle'mounted to it but our wagon has rubber spacers to cushion the ride. It can be weird seeing the bullbar vibrating like nothing else and not feeling it in the cab. Looks like the bar is going to fall off.
-
4x4 Australia have written an article (http://www.4x4australia.com.au/drive/1504/bent-utes/) on this in April this year
-
Thanks Metters and Darcy7 for your huge efforts with those very informative posts..
:cheers:
-
:worthles:
as requested.
The ute in question
(http://i59.tinypic.com/258v7l1.jpg)
Close up showing the gap
(http://i57.tinypic.com/25aqmvl.jpg)
Passenger side chassis rail
(http://i59.tinypic.com/14uz6f9.jpg)
Driver side chassis rail
(http://i57.tinypic.com/2vblatj.jpg)
We've taken the tray back off and put the original tub back on, replaced the standard suspension, removed the duel battery, winch, bash plates, recovery point, UHF, trailer brakes, and some other bits and pieces. Thankfully he still had all the original stuff in the shed :D Hopefully the bulbar & towbar come off after the assessor has done his bit.
-
Is it me or they have place the flush out opening where they shouldnt have. Notice how the crease work it way toward the flush out point. I would dare to say, it woild be different if the offending holes werent there.
-
Hey Spada, how much longer was the tray compared to the tub?
KB
-
Hey Spada, how much longer was the tray compared to the tub?
KB
Roughly the same length I think, maybe a touch longer ? I didn't really notice much of a difference when we changed them over. He uses the ute as a work vehicle, so a tray back is more practical for that.
-
Disgusting to think that bt50 will be written off. No wonder insurance premiuims are ridiculous. It could be repaired and improved on. Chassis have been bending on trucks and utes for yonks. How many old one tonners do you remember seeing bent and hardly anybody bother repairing them but when you did they were better than new.
-
Sorry metters, but your waaaayyyy to smart for this forum. ;)
-
I would dare to say, it woild be different if the offending holes werent there.
It would not make any difference wasn. The side panels in chassis rails like this are just separators. The real strength is in the top and bottom flanges. They are either in compression or tension and do all the work. An I beam axle under the front of a heavy truck is the same. The single web in the centre just keeps the upper and lower flanges apart and adds little to the overall strength of the axle.
In this case the lower flange was crushed. Had the hole been a contributing factor, I would imagine the crease would have gone straight to it.
I have seen a badly cracked Trition out in the desert. The crack was about 5 mm wide across the top flange just in front of the front spring hanger. It had extended about a third of the way down the sides in an area where I can't remember seeing any holes. The car did not have air bags but it did have an extended tray with a heap of gear in it plus an extended tow bar with 220 kgs on it. You just can't do things like that and expect to get away with it. That car was way outside its design limits.
This old video gives you a basic insight into car testing back in the 1930s. https://www.youtube.com/watch?v=c1gcC6RiB-I (https://www.youtube.com/watch?v=c1gcC6RiB-I) The chassis on the vibrating test rig is being given a hell of a hard time. The rest of the video is mainly a stunt show but the factory test programs would have been just as tough and extended to breaking point in each case.
Today's car manufacturers have had a lot of practice designing chassis and they know what they are doing. The chassis and its number is legally the identity of the car. If it fails and cannot be repaired economically under warranty then the whole car has to be replaced. No manufacturer wants to be faced with a problem like that, especially when it could involve thousands of cars.
-
It would not make any difference wasn. The side panels in chassis rails like this are just separators. The real strength is in the top and bottom flanges. They are either in compression or tension and do all the work.
Too true and you can see that most obviously here with this swiss cheese chassis and where the top and bottom flanges have to be furthest apart for strength-
http://www.al-ko.co.uk/pages/caravan-chassis.html (http://www.al-ko.co.uk/pages/caravan-chassis.html)
As far as the bent chassis is concerned there's no doubt the air bags were the pivot point of the long lever back to the towball which is in turn acted upon by the trailer's drawbar leverage. What we do know is is these dual cabs are very long and say a Triton chassis doesn't have the full body support of its Challenger cousin and similar for other brands so that's problem number one here. Then how much was the ute and trailer loaded and how was it distributed and what terrain was it being belted over. We can guess now the chassis is bent but was it really the fault of the airbags? My guess is while the airbags most likely disguised the overloading and impending failure, they merely shifted the bending of the chassis to the mid point of the leaf springs instead of a more likely point forard of the front mounts of the leaf springs and most likely up where the cab ends and the tray begins like so- http://www.4x4australia.com.au/drive/1504/bent-utes/ (http://www.4x4australia.com.au/drive/1504/bent-utes/)
The end result is the same but it's easy to blame the air bags when there's a lot more to it than that, although to be fair air bags can give the inexperienced a false sense of security with what it's all about. It's the same old monumental human hubris in thinking anyone can possibly create a system of GCMs, ATMs, towball weights, etc that Joe Blow can keep below and everything will be apples anywhere and everywhere. Laughable and generations got by without the nonsense of it (didn't you just love that pic of the Leylands with Landrovers and the dog trailer) Still it all makes work for office jocks and helps them feel important :cheers:
-
The end result is the same but it's easy to blame the air bags when there's a lot more to it than that, although to be fair air bags can give the inexperienced a false sense of security with what it's all about.
I agree. The "airbag" debate seems to ignore the issue that most of these Utes that are bent, are all bent at the same point in the chassis............whether they had airbags or not.
Whilst I agree that airbags change the suspension dynamics on a leaf sprung vehicle (wagon or ute), I think load distribution is the "big picture" that should be debated ?
-
From what I have experienced and seen with airbags. They work great on the black top for carrying heavy loads and making the vehicle more stable.
Off the bitumen IMO they are a bent chassis waiting to happen.
The "Ya won't bend a Land Cruiser chassis" is bull $hit, I have seen both a single cab and a dual cab with broken backs, both fitted with airbags. If a Landcruiser is bending what hope does a Triton have
I have 75 series Cruiser ute that I put airbags on a couple of years ago. IMO the airbags made the ute handle like crap offroad when a little bit of flex was needed.
If I was only driving on road then I might consider airbags again, but for the type of driving we do both around the farm and off road, I'll go airbag less.
:cheers:
-
It doesn't help when airbag manufacturers say this in their advertising:
Air suspension the perfect solution for load carrying. Maintain a safe & level ride under all load & road conditions.
-
Not much to do with airbags but they help with the illusion of being able to carry more load.
Ill almost guarantee many of the cracked ones are overloaded let alone poor weight distribution.
Most manufacturers claim load must be equally distributed, ie between two axles, THAT means very little behind rear axle which unfortunately is all dual cabs have.
Also most claim rough off road use is severe duty and loads should have been adjusted accordingly
Full vehicle load behind rear axle also can make them fairly unstable. Newer dual cabs, the cabs get bigger and trays smaller, GVM go up
Some steel trays are very heavy and overhang increasing moment arm even further.
That hole in BT50 chassis sure looks to be in poor location.
In lighter utes, single cab chassis are made to handle this problem better.
-
It doesn't help when airbag manufacturers say this in their advertising:
Air suspension the perfect solution for load carrying. Maintain a safe & level ride under all load & road conditions.
Bearing in mind that MOST breakages appear to be occurring because of overloading and poor weight distribution, probably in conjunction with airbags, it is fair to assume that the airbags are being over-inflated (misused) also.
Abuse all round is the word that come to mind.
-
Saw this photo today on Stalk book. (Cape York Trip Gone Wrong' Page)
(http://i1285.photobucket.com/albums/a590/pogasarus/Mobile%20Uploads/FB_IMG_1437637827740_zpsntg9zmtb.jpg) (http://s1285.photobucket.com/user/pogasarus/media/Mobile%20Uploads/FB_IMG_1437637827740_zpsntg9zmtb.jpg.html)
Apparently another 'Cape' Victim.
Not sure if it had airbags or not, but the design is just terrible. Too much overhand behind the axle.
-
Looking at that over hang its huge.
-
Most of these pictures have popped up already on the other "airbags in utes" threads on here, but lets not let that stop us >:D
I have no idea if any of these have airbags or not, most likely some/most have................
But they definitely all have one thing in common, and that is they all appear to have significant weight suspended from skyhooks?
It's got me stumped why they bent ??? ...........
(http://i59.tinypic.com/2e21d6x.png)
(http://i59.tinypic.com/wv36dc.jpg)
(http://i59.tinypic.com/241qlfs.png)
(http://i60.tinypic.com/iqwhvb.png)
(http://i61.tinypic.com/2s954rs.jpg)
(http://i59.tinypic.com/2n7qio9.png)
(http://i60.tinypic.com/bi9idg.jpg)
(http://i62.tinypic.com/1znn3ba.jpg)
-
I have no idea if any of these have airbags or not, most likely some/most have..
The Triton at the top does have them, the Hilux under it does not. I don't know what the others have. It looks like the rope up to their skyhooks has broken on all of them.
Its the same old story though, their owners are expecting them to carry an F series load, poorly disrtibuted, in the worst conditions they are ever likely to be driven in. You can't do it and expect any degree of reliability.
I posted this email from Mitsubishi on this site about two years ago. It is on towing capacities but the same applies to carrying. Both must be reduced for off road conditions.
Dear Mr O’Keefe,
Case Reference Number HQ-123456
We acknowledge receipt and thank you for your recent enquiry regarding the Mitsubishi Triton.
Please be advised that Mitsubishi Motors Australia Ltd (MMAL) only release towing
specifications for vehicles being used under normal conditions such as highway driving. We would not recommend towing this amount while driving on 4WD tracks or surfaces of this nature. The 3 Tonne towing capacity is a statement of the maximum permissible towing weight possible for this vehicle.
Thank you again for your enquiry.
Kind Regards,
Simon
Mitsubishi Customer Assistance Centre
Mitsubishi Motors Australia Ltd
GPO Box 1851 Adelaide SA 5001
Even then you need more information than that before you roar off into the bush. The two most obvious questions would be how far below maximum should you go in the conditions you intend driving through and what is the maximum ball weight for those conditions?
As for air bags: on another forum a couple of years ago, Collyn Rivers answered someone's question on air bags by saying they can be useful for softening the ride on a harsh ridding unladen ute but they should not be used for raising sagged suspensions or carrying extra weight. It was either in that answer or another one that he mentioned the destructive forces they can generate. This comes about by the fact that they are an exponential spring. They can and sometimes do create serious problems in aftermarket installations.
If anyone is wondering who he is and what he would know about the subject, this link should help. http://caravanandmotorhomebooks.com/collyn-rivers/# (http://caravanandmotorhomebooks.com/collyn-rivers/#)
-
I realise I'm taking this slightly off topic, but I have airbags in my playdo.
I think they are fantastic. I put about 8-10 psi in them when towing the hawk as I found without them it tended to bounce a lot in the rear on the rough bumps and dirt tracks .
Installed the airbags and it took this out completely. I can still drive with or without them as they are not for carrying "extra" load or weight, just to reduce the severity of bumps.
I guess from a very non technical point of view, to stiffen up the springs.
That said, I'm getting an upgrade of the towing capacity for the new van and one of the things they do is install airbags in the rear.
I assume there will be a slight increase in towball weight, but I'm expecting around 220kgs. (from what they have told me)
I've never actually weighed the new hawk, but it can't be far off that anyway.
Accepting that this is a playdo not a ute.............
BUT...................
Can anyone see any trouble or problems with what I'm trying to do.
And before you tell me to buy a landsnoozer, NO....
I can't afford the Retreat and a new cruiser.
I have been led to believe the towing capacity of the playdo is rated higher overseas and have been told that this is so they can sell more 200's.....
I realise talk is cheap, but surely the playdo is up to the task????
I see heaps of them towing 2.5 tonne vans............ ??? ??? ???
Any help comments or criticism?
Brian
-
Any help comments or criticism?
These two articles are always worth a read if you just getting into caravans
http://caravanandmotorhomebooks.com/caravan-dynamics/ (http://caravanandmotorhomebooks.com/caravan-dynamics/)
http://caravanbuyersguide.com.au/tow-vehicle-caravan-weight/ (http://caravanbuyersguide.com.au/tow-vehicle-caravan-weight/)
Another thing to keep in mine when you start changing suspension designs is car manufacturers have set their cars up to understeer since the 1950s because the average driver can not handle oversteer. They do it placing more weight on the outside front wheel than the outside rear wheel in corners so the front tends to roll out a little wider. You redesign the springs and sway bars to transfer more weight onto the outside rear wheel in corners if you want the rear end of the car to drift out first which is oversteer.
If you stiffen the rear suspension without doing exactly the same to the front, you can easily upset the manufacturer’s front and rear weight transfer ratio and make the car prone to going into sudden oversteer.
There is nothing unusual or mysterious about this, it has been part of the basics principles of setting up suspensions for as long as anyone can remember.
Make sure whoever alters your car’s suspension understands what they are doing and is not concentrating solely on getting the car to sit level and ride smoothly.
-
I'm trying to find photos of my inlaws defender dual cab which bent the chassis (hit a washout) no airbags and insurance said no thanks better luck next time.
Understandable though, he had a custom made enclosed tub on the back, with too much weight at the back on a long overhang including hanging two spares off it which is why both insurance and warranty wouldn't come to the party
Since been repaired and tub shortened.
-
The overhang shown on those pics posted earlier are rediculous. I'm currently getting a canopy made for my dual cab Cruiser, I shortened it's length by 100mm over a standard tray, and have mounted the spare inside the canopy on the front wall to keep weight forward as much as possible. It amazes me people don't realise how bad their set ups are, they think they can put something more suited to a single cab onto a dual cab and then not have issues. I sort of regret not shortening my canopy by another 50mm just incase, especially seeing my camper has such a heavy tow ball weight.
-
I'm trying to find photos of my inlaws defender dual cab which bent the chassis (hit a washout) no airbags and insurance said no thanks better luck next time.
Understandable though, he had a custom made enclosed tub on the back, with too much weight at the back on a long overhang including hanging two spares off it.
Since been repaired and tub shortened.
I'd like to see that. If there was a chassis that I would expect could stand up to some extra abuse, it would be a Defender. Not that they are immune to the laws of physics....!
-
I can say with any certainty to verify the claim but after talking to a mate that had this happen to his Triton, a big part of the problem he was told comes from the alleged safety features to meet the 5 Star ANCAP rating and to achieve the required crumple effect in the rear of the utes, the target area of the bending chassis is part of the design to achieve the required crumple zone.
So it sounds like a lot of different factors may be at play causing these problems. People have been loading up their utes or dual cabs for as long as they have had them and worked them just as hard as they are now without the high numbers of bent chassis, so it has to be something more recent causing them to bend. The crumple zone may be the weakening factor causing the chassis to bend.
Just my thoughts, don't what others with more engineering knowledge think of it.
-
These two articles are always worth a read if you just getting into caravans
http://caravanandmotorhomebooks.com/caravan-dynamics/ (http://caravanandmotorhomebooks.com/caravan-dynamics/)
http://caravanbuyersguide.com.au/tow-vehicle-caravan-weight/ (http://caravanbuyersguide.com.au/tow-vehicle-caravan-weight/)
Another thing to keep in mine when you start changing suspension designs is car manufacturers have set their cars up to understeer since the 1950s because the average driver can not handle oversteer. They do it placing more weight on the outside front wheel than the outside rear wheel in corners so the front tends to roll out a little wider. You redesign the springs and sway bars to transfer more weight onto the outside rear wheel in corners if you want the rear end of the car to drift out first which is oversteer.
If you stiffen the rear suspension without doing exactly the same to the front, you can easily upset the manufacturer’s front and rear weight transfer ratio and make the car prone to going into sudden oversteer.
There is nothing unusual or mysterious about this, it has been part of the basics principles of setting up suspensions for as long as anyone can remember.
Make sure whoever alters your car’s suspension understands what they are doing and is not concentrating solely on getting the car to sit level and ride smoothly.
Good points and good reads.
The people I'm getting to do it specialise in prado upgrades for Kedron.
I am also assured that the prado can handle it no trouble at all.
I am relying on others points of view to learn a bit, so this answer is exactly the type of thing I needed.
Many thanks
Brian
-
Good points and good reads.
The people I'm getting to do it specialise in prado upgrades for Kedron.
I am also assured that the prado can handle it no trouble at all.
I am relying on others points of view to learn a bit, so this answer is exactly the type of thing I needed.
Many thanks
Brian
Prado's have a coil rear suspension, so I'm guessing the bags will be fitted up the guts of the existing coil springs. That means your suspension dynamics wont really change.
The topic of this thread centres around fitting airbags to a leaf sprung rear ends in utes.
You should be fine. ;D
-
Prado's have a coil rear suspension, so I'm guessing the bags will be fitted up the guts of the existing coil springs. That means your suspension dynamics wont really change.
The topic of this thread centres around fitting airbags to a leaf sprung rear ends in utes.
You should be fine. ;D
Yup. Bags inside the rear coils on a Prado. Bump stop has to be shaved to accomodate.
-
Just my thoughts, don't what others with more engineering knowledge think of it.
It is a good thought Al but the car would still be able to do whatever the manufacturer claims.
This DVD https://www.youtube.com/watch?v=jH1Vke2Z6VY (https://www.youtube.com/watch?v=jH1Vke2Z6VY) makes the problem a lot easier to understand. The truck has its lifting cable running from the top of the jib down on an angle to the bogged car. It simply levered the rear end down and the front went up. The chassis was not designed to withstand forces like that. Had the cable gone from a tow bar back to the car, there would be no leverage being applied to the chassis and this would not have happened.
A snatch strap is another good example. They can induce staggering forces into the chassis but it does not bend.
It makes no difference whether you pull the rear end of the chassis down slowly or flex it repeatedly a short distance up and down with a lot of heavy material pressing down on the end of it, the result will still be the same
-
The overhang shown on those pics posted earlier are rediculous. I'm currently getting a canopy made for my dual cab Cruiser, I shortened it's length by 100mm over a standard tray, and have mounted the spare inside the canopy on the front wall to keep weight forward as much as possible. It amazes me people don't realise how bad their set ups are, they think they can put something more suited to a single cab onto a dual cab and then not have issues. I sort of regret not shortening my canopy by another 50mm just incase, especially seeing my camper has such a heavy tow ball weight.
What length tray did you go for?
I was talking to a bloke the other day who had fitted a 7' tray to his dual cab cruiser.
If that doesn't brake the cruisers back I'll eat my hat!
-
What length tray did you go for?
I was talking to a bloke the other day who had fitted a 7' tray to his dual cab cruiser.
If that doesn't brake the cruisers back I'll eat my hat!
wow that is asking for trouble, that's about 2100mm isn't it?...no tray as such on mine, I ordered vehicle without one. The body will be 1700mm long on mine, with as much weight as possible kept to the front of the canopy due to how far forward the rear wheels are on the tray area.
-
awesome info and opinions /suggestions from both experts and lay people like myself , A really good thread :cup:..so many of these go way off the rails and I have learnt a lot from it already and still enjoying the read :cup: :cup: :cup: :cup: to everyone who has contributed.
Jet ;D ;D
-
wow that is asking for trouble, that's about 2100mm isn't it?...no tray as such on mine, I ordered vehicle without one. The body will be 1700mm long on mine, with as much weight as possible kept to the front of the canopy due to how far forward the rear wheels are on the tray area.
Yeah 2100mm..
Bloody ridiculous, and then to make matters worse he had a super long tow ball tongue so that tow ball wasn't so far back under the tray. ???
I had a custom built alloy tray made at 1700mm. Plus it sits up a lot closer to the cab than most trays.
IMO the standard Toyota trays at 1800mm are just to long.
-
It is a good thought Al but the car would still be able to do whatever the manufacturer claims.
Interesting word that one, Would, up there with Should. 8)
The example in the youtube clip was doomed to fail and have seen similar vids.
Personally I think there is more than one factor at play causing the bent chassis phenomenon and until it is seriously looked at with all factors taken into account it will continue to happen at the alarm and distressing rate.
I do believe the loads and load placement do have a very large bearing on the problem. As in the example you gave above with the brick, most utes/dual cabs can carry a 500kg load with no damage, but is that a static 500kg or a dynamic 500kg load. You don't hear of too many bent chassis on a dual lane highway compared to some of the more less maintained roads.
-
but is that a static 500kg or a dynamic 500kg load.
They will all support a lot more than 500kgs while sitting still. It is the dynamics that cause all the problems.
The manufacturers are not going to do anything about it. They decide what price range and segment of the market they want the car to compete in. They design it, build it, test the prototypes to destruction then put it onto the market. If someone takes it outside its design limits and breaks it, it is not their problem.
It is no different to fitting a turbo to a non turbo engine then breaking the pistons. It is not the car manufacturer's fault, they design their turbo engines from the ground up to run with one. They don't simply bolt one to their non turbo designs.
You don't hear of too many bent chassis on a dual lane highway compared to some of the more less maintained roads.
You are right and that is why the manufacturers will tell you to reduce weight on off road conditions. All of this nonsense about GVM upgrades and heavier suspensions is just asking for trouble.
The advertised maximum towing and carrying capacities are for the highways only and I don't mean the Gunbarrel type.
Every manufacturer is capable of building a car that will never break. The only problem is few people would be able to afford to buy it.
-
They will all support a lot more than 500kgs while sitting still. It is the dynamics that cause all the problems.
The manufacturers are not going to do anything about it. They decide what price range and segment of the market they want the car to compete in. They design it, build it, test the prototypes to destruction then put it onto the market. If someone takes it outside its design limits and breaks it, it is not their problem.
It is no different to fitting a turbo to a non turbo engine then breaking the pistons. It is not the car manufacturer's fault, they design their turbo engines from the ground up to run with one. They don't simply bolt one to their non turbo designs.
You are right and that is why the manufacturers will tell you to reduce weight on off road conditions. All of this nonsense about GVM upgrades and heavier suspensions is just asking for trouble.
The advertised maximum towing and carrying capacities are for the highways only and I don't mean the Gunbarrel type.
Every manufacturer is capable of building a car that will never break. The only problem is few people would be able to afford to buy it.
-
Yep gotta agree with you on that. Just seems people just have to take everything and not the minimum when they go tripping around these days
-
awesome info and opinions /suggestions from both experts and lay people like myself , A really good thread :cup:..so many of these go way off the rails and I have learnt a lot from it already and still enjoying the read :cup: :cup: :cup: :cup: to everyone who has contributed.
Jet ;D ;D
X2
-
Just thinking out loud, could we assume that we won't see this sort of damage under similar loads and road conditions with the new Navara seeing as though it has rear coil springs?
-
Yep gotta agree with you on that. Just seems people just have to take everything and not the minimum when they go tripping around these days
There is nothing wrong with taking everything you need. The trick is to choose a car that will carry the lot without modifications and still have plenty left in reserve when you take it into the rough stuff.
This discussion brings back memories of the 1953, '54 and '55 Redex trials. Have a look at the damage suffered by many cars on this results sheet. http://www.uniquecarsandparts.com.au/redex_1955.htm (http://www.uniquecarsandparts.com.au/redex_1955.htm) Click on the BACK or NEXT arrows on the bottom of the page for more information if you are not familiar with these trials.
Local people were driving the same cars on the same roads or tracks without having all of these problems. The difference here was not excessive weight but excessive speed.
With modern 4wds the problem is maximum weight combined with incorrect weight distribution with maybe a just a touch of too much speed in some cases
-
There is nothing wrong with taking everything you need.
agree... its the ones that take everything they need and twice as much Shit as they don't need...
-
Just thinking out loud, could we assume that we won't see this sort of damage under similar loads and road conditions with the new Navara seeing as though it has rear coil springs?
They won't make any difference. The problem is what is on the end of the chassis back past the axle. When the chassis falls and is eventually brought to a stop by the springs, bump rubbers or aftermarket air bags, whatever is behind the axle does not want to stop. It thumps the end of the chassis down hard if the material on it is heavy enough. The chassis then tries to pivot on the axle and tries to lift the other end.
It is the same if the front of the chassis drops down. It pivots on the axle housing and instantly tries to lift the rear end . If the forces generated are beyond the chassis's design limits, it wll bend. It is heavy material on the end of a lever that is causing all the problems. The lever is the distance from the axle back to the material.
Springs can't stop that. Moving the axle back to the far end of the chassis would because there would be nothing extending out the back unsupported. That is probably not all that practical though.
You could try a simple little test of this with an egg carton. Place two eggs in it at one end only. Hold the end of the carton with the eggs in it against your body in a horizontal position with your thumbs on top and a couple of fingers on each hand under each side of it. Rock your fingers slightly so the other end of the carton moves up and down. Note how it feels than turn the carton around and do the same again.
You will notice a considerable difference when the eggs are further away from your hands. The heavy end of the carton does not want to stop when it is going down and it is harder to lift it up quickly. That is what is happening to the end of your chassis. It has been designed to resist a certain amount but it will bend if it is excessive.
I think a lot of aftermarket suspension advertising has lead many owners to believe they can put anything on the back of their car and the suspension will fix it. It will lift the car and maybe improve the ride but it can not remove the excessive weight way down the back that is flexing the chassis up and down beyond the limits that the factory engineers designed it for.
-
There is nothing wrong with taking everything you need. The trick is to choose a car that will carry the lot without modifications and still have plenty left in reserve when you take it into the rough stuff....
Correct.
This is where trailers can come into play (with sensible ball weight). I shudder to see the way some load their cars.
We take everything we need, and also cater to some extent for others.
If one of our travel companions is stuck, then so are we.....
-
It is a bit like doing the maths in this link
https://practicalmotoring.com.au/car-advice/why-a-3500kg-tow-rating-may-not-really-be-a-3500kg-tow-rating/
How many of us have actually loaded up vehicle and trailer and gone to the weighbridge to establish our
Tare (or kerb) weight – how much the vehicle weighs
GVM (Gross Vehicle Mass) – or the maximum the vehicle can legally weigh.
Payload – the difference between the GVM and tare.
Front and rear axle load – how much weight can be placed on either axle.
Braked tow rating – how heavy a trailer the vehicle can tow
GCM (Gross Combined Mass) – How heavy the combination of the vehicle and trailer can be.
And throw in your ball weight to good measure.
I dare say if we did this we would probably scare ourselves.
-
This one covers trailers
https://practicalmotoring.com.au/car-advice/everything-you-need-to-know-about-towing-heavy-trailers/
I guess it comes down to the magical art of where and how to pack your load
-
They are two very good links Al. I have heard of that man but until now I have never come across anything that he has written. It includes everything that I have been saying but I can not take any credit, I have picked it up from other sources over the years ever since I became aware of chassis bending and caravan instability.
He mentions stress on rear axles from ball weight. I noticed in the story in 4X4 Australia that the men they interviewed from Birdsville, Mt Dare and Alice Springs all agreed that trailers were a contributing problem. One said " A heavy ball weight has a significant effect on the chassis, as the 4WD pitches forward and back it accelerates the trailer ball mass up and down with a jerking motion.
“It’s the acceleration of this mass that will contribute significantly to bending and cracking of the chassis,” he continued. “A longer hitch or tow bar, as fitted to some utes with a long tray (itself an issue), compounds this problem of shock loading to the chassis."
It is that word "mass" again. Mass [material] in motion is the real culprit here and the sooner all trailer owners understand it the better.
If they did then more pressure could be put on trailer builders to lift their game.
Car manufactures have been right into vehicle dynamics and suspension design since the late 1930s. Most trailers today look like they could have been designed in the '30s.
In the caravan magazine article titled "Vehicle Dynamics" by Collyn Rivers, he said trailer ball weights are absurdly too high and testing has shown that anywhere from 2% to 20% makes little if any difference. He then added he suspects the recommended ball weight is what it turned out to be when they made the first one.
This is coming from a man who has spent the last twenty years studying all caravan and trailer stability research around the world and is about to release a book on it.
-
(http://i59.tinypic.com/14uz6f9.jpg)
you can see that the bump stop has contacted the top plate, airbags just makes this "stop" of momentum earlier, but if poorly loaded (you don't have to be overloaded) and you continue to hit the bump stops "hard" something will eventually fatigue, and if a large enough force is acted it can be the first such hit.
(http://i1285.photobucket.com/albums/a590/pogasarus/Mobile%20Uploads/FB_IMG_1437637827740_zpsntg9zmtb.jpg)
this one hit a washout in the road- you never get the whole story from one picture
Our trailer tyre which blew at the same time our companions chassis bent
-
Id be heartbroken if that was my new pride and joy
Sent from my iPhone using Tapatalk
-
Great info there guys.
Sorry for going off track, however Spada, did your neighbour get his replacement BT? I am curious as to why you went to the trouble of taking all the old accessories off, if he was getting a new BT he should also be getting all new accessories at the same time. As you stated New for Old replacement.
Cheers
-
Great info there guys.
Sorry for going off track, however Spada, did your neighbour get his replacement BT? I am curious as to why you went to the trouble of taking all the old accessories off, if he was getting a new BT he should also be getting all new accessories at the same time. As you stated New for Old replacement.
Cheers
Still waiting, but I see it parked out front today minus bull bar, so it must be about to go.
All the fruit had to be removed cause it wasn't listed as inclusions on the policy, so they wouldn't replace what wasn't insured.
-
Dual cab Navarra bent chassis at work this week, same story, big load in steel tray
Hardy say it had worked hard, mostly highway use
Yes it had airbags but that was to stop saggy rear.
-
Dual cab Navarra bent chassis at work this week, same story, big load in steel tray
Hardy say it had worked hard, mostly highway use
Yes it had airbags but that was to stop saggy rear.
If it had a saggy rear, it was either over loaded or had incorrect rear suspension.
KB
-
Dual cab Navarra bent chassis at work this week, same story, big load in steel tray
-
Dual cab Navarra bent chassis at work this week, same story, big load in steel tray
I saw another one three days ago going into a Bunnings car park. It was an early 2000s dual cab 2wd Hilux. It had an extra long tray with a lot of heavy looking tools in it. I could not stop and see if the suspension had bags or not.
-
Not sure about air bags?
-
Not sure about air bags?
Is the genny to run the AC ???
-
Not sure about air bags?
not sure about the rampover either...
-
Came across a newish triton today. Another sad end for a holiday maker.
Towing a smallish off rd camper. Air bags fitted. Cannot comment on there load as i saw the end result.
Bent both rails on each sides on the rear top bracket arm.
Joe.
-
Came across a newish triton today. Another sad end for a holiday maker.
Unfortunately I can't see this stopping for a very long time. I would love to see four or five manufacturers of air bags and stiffer aftermarket suspensions on a TV show like Q & A explaining how their products can support the far end of the chassis on an overloaded car and stop it flexing up and down.
-
Unfortunately I can't see this stopping for a very long time. I would love to see four or five manufacturers of air bags and stiffer aftermarket suspensions on a TV show like Q & A explaining how their products can support the far end of the chassis on an overloaded car and stop it flexing up and down.
Easy, they'd just say our products are designed to work within the manufacturer's limits. We cannot be held responsible should you choose to exceed them. I don't think any of them state they'll allow you to overload your vehicle.
I can't see how any of them can be held responsible should the operator choose to overload their vehicle
-
"If it had a saggy rear, it was either over loaded or had incorrect rear suspension"
Yep thats what ive been saying, maybe not just overloaded but poorly distributed.
Rough numbers but concept is there.
Have a look at normal dual cab, 1000kg payload,
5 seats@ 80 kg each, = 400kg - this capacity cant be moved out of the cab.
Fuel + other stuff, 150kg
Give up another 100kg for steel tray........leaves 350 kg payload in the tray max. AND thats if the tray is same length as ute tub, most are much longer. (50kg at the back of a tray could place 3 or 4x the load on the chassis at the axle)
plenty think the 1000kg can be put in the tray
Springs or airbags have little to do with it.
Change to a single cab, and you then can have 600+ kg in tray - a lot more.
-
"If it had a saggy rear, it was either over loaded or had incorrect rear suspension"
Yep thats what ive been saying, maybe not just overloaded but poorly distributed.
Rough numbers but concept is there.
Have a look at normal dual cab, 1000kg payload,
5 seats@ 80 kg each, = 400kg - this capacity cant be moved out of the cab.
Fuel + other stuff, 150kg
Give up another 100kg for steel tray........leaves 350 kg payload in the tray max. AND thats if the tray is same length as ute tub, most are much longer. (50kg at the back of a tray could place 3 or 4x the load on the chassis at the axle)
plenty think the 1000kg can be put in the tray
Springs or airbags have little to do with it.
don't forget 150kg is on the tow-bar, + another 30 odd for a duel battery, + a bit more for the bullbar, got a winch on that ? there's another 30, then add 40 for your Engle full of beer, not to mention another 30 odd for your fancy drop-down fridge slide ? have you got a canopy on that tray ? what about a draw system, have you got any recovery gear ?
So about all you can pack is a box of tissues and a change of jocks (although you could substitute one for the other if your worried about the extra weight)
-
So about all you can pack is a box of tissues and a change of jocks (although you could substitute one for the other if your worried about the extra weight)
Might end up with green "Skidmarks"????
-
I can't see how any of them can be held responsible should the operator choose to overload their vehicle
The Triton at the top of the list of photos that Spada posted on page 2 of this discussion was not overloaded. The owner had carefully watched the weight of the things he was putting into it and had weighbridge certificates showing it was about 200 kg under GVM. He thought he had done the right thing and was blaming the quality of the car for the bent chassis.
It is easy to understand why so many owners have thought everything was ok. The net forums are full of wonderful advice like stock suspensions are crap and a set of air bags or brand X stiffer suspension will fix everything. You then have the magazines and their DVDs plus their advertisers claims saying the same thing. Even the bent chassis story in 4x4 Australia contains a rather dubious piece of advice. The bloke from ARB said air bags are just a band aid solution and “ until they upgrade to some well sorted aftermarket springs and shocks, they’ll continue to have issues”.
As I said before I would like him to explain how his well sorted springs and shocks support the far end of the car. Only a spring between the end of the car and the road surface can do that and I haven’t seen any of those on the market yet.
You then have products like dual wheel carriers. Inexperienced owners see products like this and think it is fine to hang two 35 kg wheels plus the weight of the carrier off the back of their car then put 130 kg on the tow ball. Their ball weight is around half the maximum so that should be ok and the carrier would not be on the market if it was threat to the car's reliability.
Maybe the solution would be for the manufacturers of these aftermarket suspension systems and other accessories to follow the example set by medicine manufacturers and list what their product will cure and what, if any, side effects it can cause. I suppose if they did that though, people will load their cars correctly and not need their products.
-
The Triton at the top of the list of photos that Spada posted on page 2 of this discussion was not overloaded. The owner had carefully watched the weight of the things he was putting into it and had weighbridge certificates showing it was about 200 kg under GVM. He thought he had done the right thing and was blaming the quality of the car for the bent chassis.
It is easy to understand why so many owners have thought everything was ok. The net forums are full of wonderful advice like stock suspensions are crap and a set of air bags or brand X stiffer suspension will fix everything. You then have the magazines and their DVDs plus their advertisers claims saying the same thing. Even the bent chassis story in 4x4 Australia contains a rather dubious piece of advice. The bloke from ARB said air bags are just a band aid solution and “ until they upgrade to some well sorted aftermarket springs and shocks, they’ll continue to have issues”.
As I said before I would like him to explain how his well sorted springs and shocks support the far end of the car. Only a spring between the end of the car and the road surface can do that and I haven’t seen any of those on the market yet.
You then have products like dual wheel carriers. Inexperienced owners see products like this and think it is fine to hang two 35 kg wheels plus the weight of the carrier off the back of their car then put 130 kg on the tow ball. Their ball weight is around half the maximum so that should be ok and the carrier would not be on the market if it was threat to the car's reliability.
Maybe the solution would be for the manufacturers of these aftermarket suspension systems and other accessories to follow the example set by medicine manufacturers and list what their product will cure and what, if any, side effects it can cause. I suppose if they did that though, people will load their cars correctly and not need their products.
I can guarantee that that triton was overloaded- regardless of the weighbridge certificate, the fact he watched his load and the rest of his arguments
there is no way that that particular vehicle would have been under the rear axle load limit for the vehicle, even if under the GVM
as mentioned earlier a lot of weight is supposed to be distributed through the cabin area
that vehicle had twin tyre carriers, an aftermarket fuel tank behind the rear axle and the ball weight
that vehicle had also lengthened the tow hitch so that the trailer hitch could clear the rear tyre carriers.
basically everything that could have been done to make the pivot on the rear (as far rear) as possible was done
(http://publicgallery.stevenbowden.com/albums/Triton/agm.sized.jpg)
its worth noting in this discussion as the GVM is also not the whole picture
there is how the load is distributed. :cheers:
-
The Triton at the top of the list of photos that Spada posted on page 2 of this discussion was not overloaded. The owner had carefully watched the weight of the things he was putting into it and had weighbridge certificates showing it was about 200 kg under GVM. He thought he had done the right thing and was blaming the quality of the car for the bent chassis.
It is easy to understand why so many owners have thought everything was ok. The net forums are full of wonderful advice like stock suspensions are crap and a set of air bags or brand X stiffer suspension will fix everything. You then have the magazines and their DVDs plus their advertisers claims saying the same thing. Even the bent chassis story in 4x4 Australia contains a rather dubious piece of advice. The bloke from ARB said air bags are just a band aid solution and “ until they upgrade to some well sorted aftermarket springs and shocks, they’ll continue to have issues”.
As I said before I would like him to explain how his well sorted springs and shocks support the far end of the car. Only a spring between the end of the car and the road surface can do that and I haven’t seen any of those on the market yet.
You then have products like dual wheel carriers. Inexperienced owners see products like this and think it is fine to hang two 35 kg wheels plus the weight of the carrier off the back of their car then put 130 kg on the tow ball. Their ball weight is around half the maximum so that should be ok and the carrier would not be on the market if it was threat to the car's reliability.
Maybe the solution would be for the manufacturers of these aftermarket suspension systems and other accessories to follow the example set by medicine manufacturers and list what their product will cure and what, if any, side effects it can cause. I suppose if they did that though, people will load their cars correctly and not need their products.
Mate - I was responding to your statement (highlighted):
I would love to see four or five manufacturers of air bags and stiffer aftermarket suspensions on a TV show like Q & A explaining how their products can support the far end of the chassis on an overloaded car and stop it flexing up and down.
My response still stands:
I can't see how any of them can be held responsible should the operator choose to overload their vehicle
-
I can guarantee that that triton was overloaded- regardless of the weighbridge certificate, the fact he watched his load and the rest of his arguments
there is no way that that particular vehicle would have been under the rear axle load limit for the vehicle, even if under the GVM
as mentioned earlier a lot of weight is supposed to be distributed through the cabin area
that vehicle had twin tyre carriers, an aftermarket fuel tank behind the rear axle and the ball weight
that vehicle had also lengthened the tow hitch so that the trailer hitch could clear the rear tyre carriers.
basically everything that could have been done to make the pivot on the rear (as far rear) as possible was done
(http://publicgallery.stevenbowden.com/albums/Triton/agm.sized.jpg)
its worth noting in this discussion as the GVM is also not the whole picture
there is how the load is distributed. :cheers:
What he said :cup:
GVM, GCM is only a part of the picture. Maximum axle weights are very often not taken into consideration.
I weighed a twin cab '79 series with a caravan a couple of years ago. The owner had done a great job. All the mod cons, ARB, TJM and what ever other brands as well. A beautiful aluminium canopy. Tinny and trailer or the top. Very well made.
And he had the GVM upgrade as well because he was worried it was going to be "heavy".
Had a caravan attached, which was also weighed. 220kg ball weight.
Vehicle weights - actual gross weight 4040kg (upgraded GVM 3780kg) 260kg over
actual front axle weight 1280kg (rated at 1480kg) 200kg UNDER
actual rear axle weight 2740kg (rated at 2300kg) 440kg OVER.
So even though the total weight was 260kg over the upgraded GVM, the rear axle was 440kg over. Near enough to half a tonne. Or 1/4 of the total weigh OVER.
Bringing the total weight back to the rated GVM (ditching the caravan) would not fix all the axle weight issue. (In hindsight I should of reweighed the axles again with the caravan disconnected. :-[)
I can give you examples of the heavy vehicle industry where trailer manufacturers have spruiked of their trailers being able to carry X tonnes, which they can, except when hooked up to a truck the rear axle is always overloaded and the front axle is always underloaded. >:(
Peter
-
Simple.. to stop all the bitching don't buy a ****ing ute..
Thread lock time.
-
Simple.. to stop all the bitching don't buy a ****ing ute..
Thread lock time.
only mods can lock threads. Aren't you one yet?
-
only mods can lock threads. Aren't you one yet?
practicing...
-
I can guarantee that that triton was overloaded- regardless of the weighbridge certificate, the fact he watched his load and the rest of his arguments
there is no way that that particular vehicle would have been under the rear axle load limit for the vehicle, even if under the GVM
I agree with you but the point is he thought he was doing the right thing and had all the aftermarket gear that he believed would enable the car to work that way. That belief has come from product advertising and net forum advice. He thought he was building a " tough Outback tourer" and plenty of magazine stories have been based on those three words.
-
I can't see how any of them can be held responsible should the operator choose to overload their vehicle
My response still stands:
It is the use of many of these parts than can directly lead to overloading without the owner being aware of any developing problems
This is an interesting topic that may eventually end up in court one day but not necessarily in regards to bent chassis. As far as I know they have not caused any accidents or loss of life but that may not be the case with suspension modifications.
I just looked through a couple of air bag company web sites and noticed all their information was about suspension adjustability, levelling and ride quality. I could not find anything on what air bags or heavier springs can do to the handling characteristics of the car, particularly at speed on sealed roads with big caravans tagging along behind.
Have a look at these three links. There are posts in them that have been written by two men who have both worked as car manufacturer suspension research engineers. What they are saying is nothing new. It has been well known by suspension modifiers since the days before Sir Jack Brabham drove his first car.
Read the three brief posts by Collyn Rivers in this thread.
http://caravanersforum.com/viewtopic.php?f=2&t=59699 (http://caravanersforum.com/viewtopic.php?f=2&t=59699)
In this one he expands on it a little. The whole thread that he started is very informative, particularly to trailer and caravan owners, but to cut it short read his last post on page three. http://caravanersforum.com/viewtopic.php?f=2&t=22776&hilit=air+bags&start=40 (http://caravanersforum.com/viewtopic.php?f=2&t=22776&hilit=air+bags&start=40)
Next read the post under it by Robi. This gets into leaf spring design. Two posts later is a photo of a compressed spring on a fully loaded ute. Note what he says about it.
All of this seems to fly in the face of the notion of loading the car up then lifting it back up with an aftermarket product. Cars are supposed to be down when loaded.
These suspension alterations affect all cars but dual cabs seem to come off a little worse. I have read on a lot more than one occasion on the net that they do not have a good safety record when towing big vans. They are usually a lot lighter than the big vans you often see them towing. The wheelbase on many of them is not all that long and the distance between the rear axle and the tow ball is about the longest of any type of car. This gives the van a nice long lever to wag the car with.
When you set these utes up with a suspension that has made the car more prone to swinging its rear end out in a corner, you start to see why their accident rate leaves a lot to be desired.
You could say it is still the owners fault, not the aftermarket parts manufacturers, but it reminds me of a report that I found in the State Library in Sydney seven years ago while researching a non automotive subject. It was on the Rogers verses Whitaker medical negligence case in 1992. Prior to this case a doctor was not considered to be negligent if he/she was following the standard procedures carried out by their peers. The court reversed this and found the doctor guilty of failing to inform the patient of a very serious but rare possible side effect of the operation that he was about to perform. There was nothing wrong with the procedure that he followed, it was just that he had a duty of care to inform the patient.
Could the same apply to an air bag or spring installation company if a serious accident, possibly involving fatalities, was to occur and suspension alterations at one end of the car only were found to be a contributing factor and the company had not informed the car owner ?
Only time will tell but that time could start getting a lot closer in the next month or two when Collyn Rivers releases his new book on caravan and tow car dynamics. It is based on research information that he he has been compiling from around the world for the last twenty years.
When you change something on a car you will affect something else. When that something else can lead to accidents or expensive vehicle reliability problems, I think the manufacturers of the parts or the installer has a duty of care to inform the customer.
-
(http://i59.tinypic.com/14uz6f9.jpg)
I'm just looking at the impact mark in the middle of the chassis rail. I fitted new springs to my ute and i left the tails on the new U bolts sticking up. Under full compression, the strike mark from the un-trimmed U-bolt tail was fractionally aft and inboard of the contact mark pictured which I suspect has contributed to the chassis bending.
Upon reflection and getting dusty under my ute, under full compression that would see the bump stop squashed flat, the retainer plate that bolts on top of the spring pack would line up nicely with where the chassis has bent. I zoomed in and you can see that with the bump stop squashed, the forward edge of the top spring plate is folded up for strength, and this will probably will hit around 3/4" to 1" forward of the bump plate, which just so happens is where the rusty dent is. The load on the chassis would be coming down, the springs compress, the bump stop squashes and then all of a sudden the spring plate strikes the chassis. There is no more give available and the chassis bends around this new pivot point.
-
So having just bought a Patrol ute with a steel tray 2400 long I am seriously reconsidering some options after reading this thread. I have planned to get an alloy canopy which I was going to put a wheel carrier on the back of it. That is now in question and has me wondering why I didn't think of this problem before. I guess seeing so many canopies built like this you think "that must be ok as others have done it.
I know having a steel tray is seriously heavy compared to an ally one but that is what came with the ute. The floor of the tray is removeable as it is held in place by bolts. Maybe removing the floor before the canopy goes on will be an option if it is designed to sit on the tray cross members thereby removing some weight.
The ute has had the coil springs removed by the previous owner and has an airbag system (springless) installed. It rides really well but had a chat with the "air bag man" on Friday who informed me that it would have to have new air bags in it to get a suspension lift at a cost near to $1k. Going back to springs sounds like a better option to me especially at a $400 cost if a bag gets a leak.
Back to the drawing board and some serious culling of what will go into the canopy.
I guess one question should be asked is it better to have a heavy trailer than load up the tray (within GVM limits)
-
A patrol ute is a better option for load carrying than these dual cabs. The way the load is transmitted into the suspension differs somewhat too as (most) of the Patrols I have seen are coils, rather than leaf sprung.
Look where the wheels are on a Patrol, they are almost centrally under the load. Most dual cabs the wheels are at the back of the cab and the load area is aft of that. Dump a big load down the back end and they try and lift the front. Because of the weight up front, this isn't going to happen and something gives in the middle.
Don't expect a 1 ton ute to actually carry a full ton and pull 2 ton over all roads and it should be fine.
-
The patrol utes also had issues with chassis cracking around the coil spring perches when loaded up and subjected to rough repetitive roads, usually at the upper end of carrying capacity, and from what I know many were overloaded too
-
The patrol utes also had issues with chassis cracking around the coil spring perches when loaded up and subjected to rough repetitive roads, usually at the upper end of carrying capacity, and from what I know many were overloaded too
It is an issue, but it is fixable and preventable, just google patrol coil tower brace and there are a few options to fix it.
-
Mine already has a Superior Engineering cross brace that ties the chassis rails together. Already installed when I bought it - score