RE: RE: Re: Torque curve equation?

From: <leop_at_lyradev.com>
Date: 15 Oct 2013 19:04:19 -0700

With respect to Kang's winding numbers, Bill's formula, and Fred Rash's numbers, we must remember that the winds on a motor depends greatly on the winder and his or her technique. For Kang's 9" motor which was 598mg with O-rings, I will assume the working rubber (less O-rings and knot) weighed 580mg. This gives 1620 winds at 0.45 oz-in from Bill's formula. Kang's motor was broken in hard being wound several times eventually up to 0.4 oz-in.
  
 As a comparison, I used a similar linear density 5/99 motor (about 5% more linear density for my motor) for my final F1L flight at Kibbie and the first two flights at Urbana (23:11, 19:29, and 19:16 respectively). The breakin was by stretching to 920% length for 3 minutes. The wind data for the 14.5" at 980mg effective weight motor were:
  
 7/1/2013 2520 at 0.47 oz-in
 8/9/2013 2570 at 0.47 oz-in
 8/9/2013 2650 at 0.45 oz-in
  
 Bill's formula gives 2540 at 0.48 oz-in
  
 So, my third wind got to 104% of Bill's numbers while Kang got 106% over. I was more conservative and kept to a lower torque as I needed to backwind a great deal and was not in the last round of a contest where I needed a good flight to make the WC team. But, the numbers work out about the same for both of us and show how the motors change with winds.
  
 Second, the number or molecular chains per cross section in our motors does not change as they stretch and thin with use. However, the amount of folding of the chains in the relaxed state is a bit less and this is why the motors get thinner and longer. The winding breaks up the binding points where the folds meet and the used rubber does not relax back to the same amount of binding points (cross-linking is the technical term). But, since the number of chain stays the same, we get to have about the same ultimate stress (torque in winding) just under the breaking point with both a new and used motor (not taking into account any extra nicks in the used motor). And, because we have a bit less cross linking, we can often get more elongation with the same stress (torque).
  
 LeoP
  
 

---In Indoor_Construction_at_yahoogroups.com, <indoor_construction_at_yahoogroups.com> wrote:

 One thing to keep in mind is that my loop length was for the motor when it was made, that is, before it was broken in and lengthened. I had pre-wound the motor 3 or 4 times (to .2, .3, .4, in-oz, etc) before getting to 1700 turns. Each pre-wind resulted in a slightly longer and thinner motor.

Received on Tue Oct 15 2013 - 19:04:19 CEST