Recently in HPA were the following posts:
Piecost wrote:
I have read this thread with interest. I do not fly LPP but am trying to understand rubber motors better. Therefore I would like to ask why poeple wind up to near breaking before backing off?
From a small amount of testing I performed on Super-Sport rubber I found that no matter what number of turns I wound to; the unwinding torque versus turns curve was the same. If this is true then there is no benefit in winding so high. The hysteresis took about 50 turns, so I only had to wind 50 turns more than required before backing off to the desired torque.
His graph is attached.
I replied:
I think you have cracked the code. I have also concluded the same, but with a caveat. In my tests, the unwinding curves are equal only after the motor is broken in. In your example, I found if I wind the motor to only 600 turns before the motor is broken in, its unwinding curve falls below that of the 800 turns wind. But once the motor is broken in, the unwinding curve soon become the same after some unwinding.
I believe for many people, winding to 800 then backing off helps because the motor has not been broken in, and the act of winding hard breaks the motor in. On subsequent winds, it's not necessary to wind to max turns/torque.
However, a caveat. my conclusion and yours are arrived at by "looking" at curves and likely from limited experiments. I'm not sure I can say for sure that the unwinding curves are identical, say, to 5% of each other. That is, limited testing probably cannot reveal any advantages under 5%. And in practice, a 5% advantage is huge. I am not ready yet to completely dismiss the observations made by many people over the years. If you have the time, I would encourage more extensive testing.
Blasphemy? Thoughts?
-Kang
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Received on Sun Nov 17 2013 - 18:22:46 CET