Re: RE: RE: Re: Torque curve equation?

From: William Gowen <wdgowen_at_gmail.com>
Date: Wed, 16 Oct 2013 10:53:50 -0400

Kang's motors have a lot more than 580mg of usable rubber.

On 10/15/2013 10:04 PM, leop_at_lyradev.com wrote:
>
> 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 0.45oz-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 Wed Oct 16 2013 - 07:53:55 CEST