Re: Wind hard or not so hard?

From: William Gowen <wdgowen_at_gmail.com>
Date: Sun, 17 Nov 2013 23:38:25 -0500

This sounds like a conversation I had with someone on the way to Kent a
few years ago.

On 11/17/2013 11:34 PM, ykleetx_at_gmail.com wrote:
>
> What Piecost and I are suggesting is to wind above launch torque then
> unwind, but not wind all the way to near breaking torque.
>
>
> For example, for a F1L flight at Urbana where the desired launch
> torque is 0.15 in-oz, wind to .35 in-oz, then back wind to 0.15 in-oz
> to launch. Do this instead of winding to the max torque of 0.45 or
> 0.5 in-oz, then back winding down to 0.15 in-oz.
>
>
> We both found that the turns versus torque are identical (wind hard
> versus not so hard) as the motor unwinds down from 0.15 in-oz.
>
>
>
> ---In Indoor_Construction_at_yahoogroups.com, <wdgowen_at_...> wrote:
>
> Wait a minute. I think this idea is counter to everything we know
> about winding rubber motors. The reason that I wind to higher torque
> and back down is because when you reach the desired torque coming down
> from a higher torque the motor will have more turns than if you only
> wound up to the desired launch torque.
>
> So basically I don't think what Piecost said is true but the only
> possible proof one way or the other is to do the test.
>
> Also I remember Don S. saying several years ago that he thought
> winding motors to the maximum destroyed the rubber. I actually used
> that line of thinking for a few years and did okay with it. Lately
> I've been trying to squeeze max turns out of my motors even for
> situations that require a lot of backoff. It would be nice to know for
> sure whether this is a good practice.
>
>
> On 11/17/2013 9:22 PM, ykleetx_at_... <mailto:ykleetx_at_...> wrote:
>
>> 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
>
>
Received on Sun Nov 17 2013 - 20:38:26 CET