Hi all,
I got back from my little trip late on Monday and my daughter has given me her cold and out of action the last couple of days, grrr....
Anyway I've had some time today to work on my issue of lift with the CF tricopter. Below tests are with the same battery at around 11.6V. The bench tests use my old wiring harness, while the new harness is on the CF tricopter.
Firstly I've weighed everything again.... So it looks like I have a AUW of 1.3 kg (less than 950g without the gimbal and camera) with the new scales. I've managed to confirm that I'm getting 890g of lift per motor at 13A with the 10x4.5 props - not as much as I thought I'd get but it's acceptable, was hoping for 1kg. I'll try a fresh battery tomorrow to see if I can get that last 110g. At full throttle (890g per motor) that should give me a 2.1:1 power ratio, this should be plenty.
However I have noted that I'm only using 24A for a hover and 27A at max throttle when in the air. At 24 /3 = 8A I get just under 500g of lift, this gives me a lift ratio of 1.16:1, so it explains why it is finding it hard to keep it hovering. At 27 / 3 = 9A, I'm getting around 600g of lift, so it explains why I can get off the ground but as soon as I loose voltage it struggles and comes down.
So I'm starting to think that my previous 18A figure for a hover must have been incorrect on the old frame - although flight time does match - so I'm not sure.
I'm thinking you are right Mark, my next move is to replace the ESC 18 AWG with 16 AWG to reduce voltage drop when under load. I'm also thinking that if I move the ESC closer to the frame I'll get less voltage drop on the DC side, AC side will lengthen but AC is less susceptible to voltage drop over distance. This will mean that I will not get the benefit of using the inside of the tubes unless I put it under the frame or I might run the signal wires through the inside instead. If I move them to the frame then they wont get the additional cooling from the air from the props. I could try to use 14 AWG instead to keep the DC side longer but 2 lots of it wont fit inside the square tube with the bolt. I wish I could find 12mm x 12mm CF square tube.
I'll also redo the ESC calibration to make sure it knows what my min and max input signal is.
Once I've gotten my hobby mini table saw (inverted dremel with minisaw attachment) up and running I'll also replace the frame (currently 1.5mm CF) with 1mm CF to help lighten it some more - I dont want to cut any more stuff until I have the right tools up and running.
To work this out I've had to weigh every component to ensure my figures are right. I'm pleased that the CF square tube and frame are lighter than the wooden frame - it was doing my head in. I'll weigh some of the wooden components again on the new scales to make sure I'm comparing apples with apples.
Chris
