Recovery Rings

[Traveller]

G'day folks,

I am interested to know if anyone has any experience with recovery rings, instead of using a traditional snatch block. I thought it might be a good way of getting the weight down if I swing over to synthetic rope from my wire, and then use soft shackles and a recovery ring.

I would be interested in peoples opinions, thanks.

[lincolnland]

Yes they're great. I too reduced weight with soft shackles and ally recovery ring. Also replaced the rear recovery hitch with a radiused ally version. No complaints thus far. Have tested them several times.

Sent from my SM-G950F using Tapatalk

[GBC]

There is a couple of load cell tests on u tube that would suggest that a lot of the mechanical advantage disappears in friction.

[Traveller]

Thanks Lincoln, that sounds good.

[Traveller]

There is a couple of load cell tests on u tube that would suggest that a lot of the mechanical advantage disappears in friction.

Thanks GBC, I will check that out too.

[GGV8Cruza]

I like the look of them, I am worried what happens when you get a bit of slack line of the pull and the rope comes off the ring. I have seen some with some rubber spikes that seem to hold it in place.

Thinking to lighten my load a bit as I carry 2 blocks and a lot of shackles

GG

[HKB Electronics]

Think of a crane, you have attached the load cell to the crane and you lift a weight up and it weighs 1000Kg.

You now connect the weight to two lines that go round a bow shackle and lift it again it is still going to weigh 1000Kg so how can it now weigh
1500Kg?

Even if the ring was totally seized how could the pull be more than a single line as that is what you have reverted to by seizing the ring?

The only way I can think of them getting that result would be to have the brakes in the winch car applied which would cause more drag
or have I missed something?

Also at the start of the video the load cell is connected to the vehicle at the top of the hill, in the later part it seems to have moved to
the fixed side of the winch line.

[GBC]

Think of a crane, you have attached the load cell to the crane and you lift a weight up and it weighs 1000Kg.

You now connect the weight to two lines that go round a bow shackle and lift it again it is still going to weigh 1000Kg so how can it now weigh
1500Kg?

Even if the ring was totally seized how could the pull be more than a single line as that is what you have reverted to by seizing the ring?

The only way I can think of them getting that result would be to have the brakes in the winch car applied which would cause more drag
or have I missed something?

Also at the start of the video the load cell is connected to the vehicle at the top of the hill, in the later part it seems to have moved to
the fixed side of the winch line.

“The load cell is on the rear of the 200 for the single line pull only because there is nowhere else to put it.
For the double pulls you can see he has moved it to the end of the yellow strop so it is measuring the return force in a single part of the pull. If nothing outside the two parts changes (him stepping on the brakes, towing up a steeper section, or hitting a rock we cannot see etc) then the difference in cell readings can only be extra resistance (friction) within the system.  It is a valid test.”

My reply from another forum where this was discussed ages ago. I use cranes and rigging and load cells a bit for work. Not saying I’m a guru, but I am fairly well qualified in that area so a good working knowledge.

The single line pull remained the heaviest load tested, and rightly so. Then they moved the cell to measure one half of the mechanical advantage gained by whatever they were turning the load through (snatch block, snatch ring, and shackle). In a perfect world, the number on the load cell should be exactly 1/2 of the single line pull, but friction adds load into the system, so the difference between 1/2 the single line pull and the actual number is the load created by friction in the system (times 2 because there are 2 parts in the pull).
The actual load on the tow bar of the vehicle at the top of the hill never changes.

They were running (turning) the winch rope through the shackle, IE using it as a snatch block, and it did the job much better than the snatch ring - as he said, it flogged the rope though.

If you want it explained differently just let me know.

Link to the test:

https://www.youtube.com/watch?v=v8EhHdv4QYg

[HKB Electronics]

I understand that but he has the load cell in the winch line buy not the winch side. If for instance the car was suspend off the ground by one cable and the load cell measures two tons
you have a 2 ton load on the car fixing and a 2 ton load on the crane fixing. If we now take a cable from one point on the car and loop it around the crane
hook back to another point on the car assuming its balanced we still have 2 ton load on the cable but a 1 ton load on each of the car fixing points as the car hasn't
got any lighter or is that assumption incorrect?

Also shouldn't the load be heavier in the winch side as its dragging the line through the pulley and not the fixed side. Also if the weight has gone up on the fixed side then it must have gone down on the winch side as again the car hasn't got any heavier therefore the weights on both side should add upto the weight of the car?

[GBC]

Exactly correct. Same in the vid. Load cell in line for the single pull because there is nowhere else to put it.
Then he’s moved it to one of the legs, so the rope is going from the winch (one point) up to the top car, being turned about the sheave, and back to the lower car again (2nd point) via the load cell.

Hope this helps rather than confuses.

[HKB Electronics]

Sorry I added more please see above.

[GBC]

I understand that but he has the load cell in the winch line buy not the winch side. If for instance the car was suspend off the ground by one cable and the load cell measures two tons
you have a 2 ton load on the car fixing and a 2 ton load on the crane fixing. If we now take a cable from one point on the car and loop it around the crane
hook back to another point on the car assuming its balanced we still have 2 ton load on the cable but a 1 ton load on each of the car fixing points as the car hasn't
got any lighter or is that assumption incorrect?

That is straight crane lifting, not gaining a mechanical advantage by turning through a sheave, and without going into included angles of the legs (which also adds mass - longer legs are better), the mass in each leg of that cable is 1/2 the load weight plus 1/2 any friction losses, however miniscule because the legs aren’t moving though a block.

A great example of included angles is bridle straps. Without going too far off track, they must always be shackled (fixed) at each attachment point on the car, and never just run through the two loops on the car and the two eyes shacked together out the front, or jammed in the winch hook. There is a heap of extra and unnecessary force created by doing it the second way. 80 series owners with their front tie downs “looking” at each other - I’m looking at you haha


Also shouldn't the load be heavier in the winch side as its dragging the line through the pulley and not the fixed side. Also if the weight has gone up on the fixed side then it must have gone down on the winch side as again the car hasn't got any heavier therefore the weights on both side should add upto the weight of the car?

No, the mass of the car is always heavier than the mass in each part, and gravity will always pull the load into equilibrium - part of the reason why friction occurs. In the case of a 65% inefficient sheave (snatch ring) there will definitely be microseconds where the load in each part changes and in fact if you turn up the volume you can hear the snatch ring loading up against friction, then spinning again once the winch creates enough force - not pretty. But given a few microseconds, and for the purposes of car recovery 101, the rule of thumb (lots of those in rigging) is that each part carries half the load. Also a very good reason to buy and use an efficient sheave. That and the fact that those snatch rings don’t keep the loose line captive, so you have to scramble up the hill with (hopefully) a remote hand piece and guide the loose winch cable into the sheave just before the weight comes on which is nowhere near where i want my fingers. Climbers have used snatch rings for a long time and they are a great idea for them, but they are also a different shape and the weights involved are much less. The vid above has been out for quite some time now. If I was in the business of selling snatch rings and thought he was peddling rubbish, I’d be off down to the local test bed and getting my own set of results to disprove him quick smart, but I’m not sure I’ve seen any such thing? Happy to be corrected.

[HKB Electronics]

Hi GBC,

Thankyou for the detailed reply, I just couldn't get my head around how the loads on both sides could add up to be more than on a single line pull, now I understand at times they will be high on the winch side and low on the fixed side and at other times the reverse.

The boys on all 4 adventure swear by then, considering how much they have used both types in their show I would have thought that they would have noticed that the rings did not work?

It also brings into question aluminum Alloy Hawse fairleads, sure the same would apply to them if pulling on an angle?

[GBC]

65% inefficient still means you get a 35% better mechanical advantage than a single line pull, and in isolation you are going to think that is marvellous. Yes, a fairlead will create friction losses also if you are turning through them at a weird angle, but the winch generally won't notice because they are so strong. I winched my ute directly up a tree to reseat a front tyre bead - long story but it involved sand and towing. The rope has squashed my number plate and dented the bullbar inwards above the fairlead. Didn't slow the winch down one bit. The only time this stuff is going to make any real difference is when people are right on the limit of their equipment's ability. The other thing to note is that dyneema starts to lose it's structural integrity at 80 degrees celcius and turns to liquid at 130 degrees. With the friction losses they are talking about I'm going to guess there a a heap of heat being generated. I assume the strop off the anchor car is biting pretty hard on the cheeks of the block to make it that inefficient. Perhaps the manufacturers would like to think about having the widest part of the block near the centre of the ring so that the cheeks don't get crushed by the retaining strop?

[HKB Electronics]

"having the widest part of the block near the centre of the ring so that the cheeks don't get crushed by the retaining strop"

Sounds reasonable, I notice the factor 55 ring is Teflon coated, another mob indicates super slippery soft shackle to reduce friction.

[GBC]

"having the widest part of the block near the centre of the ring so that the cheeks don't get crushed by the retaining strop"

Sounds reasonable, I notice the factor 55 ring is Teflon coated, another mob indicates super slippery soft shackle to reduce friction.

Sounds like they might be admitting there is a numbers problem.