Re: Wind hard or not so hard?
The way a rubber chemist described it is that the molecules are joined together but not in an orderly fashion. Even though rubber is a polymer and it has a crystalline structure for the molecules to all point in the same direction it must be stretched fairly hard.
I think the difference between good rubber and bad rubber is that after break in the good rubber has a lot more aligned strings of molecules that the poor rubber.
What is interesting is the fact that only natural rubber is suitable for winding. Synthetic rubber is totally unsuitable because it just cannot be made to exhibit a polymeric crystalline structure.
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On Nov 18, 2013, at 6:27 AM, Nick Ray <lasray_at_gmail.com> wrote:
> I tend to thinking of motors as being more analogous to half-lives than to a light switch. I do not believe that a motor hits a point where it simply transitions from being new to being broken in. I think that after the first hardish wind, the motor may be halfway or two thirds of the way broken in. Then successive winds serve to break it in further. I am basing my theory on observing the change in the loop length after successive windings. The loop elongates most after the first winding but continues to lengthen to a lesser degree with each subsequent winding.
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> I think this is why we historically have seen duration increase as the number uses of a motor increases if nothing else changes.
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> Regards,
>
> Nick Ray
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>
> On Mon, Nov 18, 2013 at 9:10 AM, <Warthodson_at_aol.com> wrote:
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>> If I am trying to wind a motor to as close to "max." as I can, without breaking it, I always wind to torque not turns.
>> One other comment. If I wind a motor to "max." I have about a 50% chance of being able to wind it to "max." a second time without it breaking.
>> Gary H
>> -----Original Message-----
>> From: Don Slusarczyk <don_at_slusarczyk.com>
>> To: Indoor_Construction <Indoor_Construction_at_yahoogroups.com>
>> Sent: Sun, Nov 17, 2013 11:18 pm
>> Subject: Re: [Indoor_Construction] Wind hard or not so hard?
>>
>>
>> So you guys wind only to a torque and do not care about actual turn count? I find that amazing. I am just the opposite, I go by turn count then back off to a torque level to regulate the height. So If I want say 1750 launch turns on a motor that can take 2000 I may wind to1850 then back off some turns to get my desired launch torque. If the motor could take 2000 turns, I would not wind to 2000 then back off 250 to 1750. I typically only wind (by turns) past my target minimum required launch turns then back off some to knock off some of the torque. Also any new motor I never fly use until broken in. I take a freshly made motor lube it up generously then say if it would take 2000 turns I wind it to ~1750 or so then unwind and measure the length to see if it stretched, a 14": loop would be like ~14.7" after a break in then I relube and then use that for my flights. Once I do that process and the motor takes a stretch set, the motor is rather consistent over the windings for the day if you done push it too hard. The only time it starts to deviate is if I really push the motor hard multiple times in a row. If I find my model is needing near max turns on each flight and I wind to near max turns on each flight and then say it hangs up, and then I wind max again and hang again, then do it again I find the motor will sag and drop off on these subsequent windings. So I then set that motor aside for a while or make up a new one. Sometimes the "sagging" model will do equal time from less height sometimes it does less time as the model will not climb as high. I noticed this on Nocal a lot as the rules require 3 of 3 flights so often in a contest you take all three in a row and if you are leaning on the motor the first flight, the second flight will be within a few seconds but the third flight will always not climb as high and will either so the same time or sometimes less so on the third flight I usually do not back off as much as I know this will happen. I can usually also tell it is sagging when I start to back off. A sagging motor will drop torque quickly with a few unwinds which is something it did not before. I may have needed 100 unwinds to get my torque but after 3 or 4 full winds of the rubber only 50 backoff gets the same torque then I know the motor is toasted for the day.
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>> Don
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Received on Wed Nov 20 2013 - 00:54:52 CET
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