Gearbox friction model

[magnets]

Originally Posted by DampRobot

I usually use these (highly inaccurate) estimates, based a little on research, and a little on experience:

Belt reductions: about .98 efficient
Gear reductions: about .95 efficient
Chain reductions: about .90 efficient
Planetary reductions: about .8 efficient
Single lead worm reductions about .6 efficient

These are great numbers for design, and I use about the same numbers when I do design estimates. However, if you'd like to get more accurate, you'll need to actually build the thing and do some testing. You'll notice some strange stuff. We saw that we were most inefficient with low loads, and most efficient with medium loads. Lubrication and accurate machining and placement of gears, belts, and pulleys really makes a difference. Another thing that we found interesting was that the efficiency changes a lot with time. When we started our shooter (it used a "hack" 1:1 banebots p60), it was around 2800 rpm. After 1 minute, it was up to 3400 rpm, and after three more minutes it went to 3100 rpm.