Rubber

jander14indoor
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Re: Rubber

Postby jander14indoor » Sat Feb 13, 2010 5:37 pm

The answer depends on what the multiplication factor of your winder is. I assume you mean 90 crank turns, which can be 1800 motor turns (20:1) or 1350 (15:1) or 900 (10:1) or 558 (6.2:1, yes such a winder is available commercially) or whatever. So you can see, comparing winder cranks without knowing the multiplication factor might mean you are OK and winding harder than you think. Or your technique might be lousy and you are breaking prematurely.

Another important factor is the quality of the rubber itself. How has your rubber been stored (high temperature, sunlight, and ozone (from electric motors most commonly) are NOT your rubbers friend)? Is it fresh (rubber changes over time)? How cut to width (are there nicks in the edge?)?

Do the curves yourself and you should see for competition, always wind to just short of breaking and backoff to torque that just bumps or misses the ceiling, depending on how brave you are. A common rule of thumb is you want to pick rubber to match prop so that the backoff is about the same as turns remaining on landing.

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Re: Rubber

Postby blue cobra » Sat Feb 13, 2010 7:52 pm

Sorry, it's a 15:1 winder.

And I'm storing my rubber in a plastic baggie with a bit of lube in it in a pretty cool, dry, and dim place. I suspect knicks or maybe torque is to blame, since I usually get quite a few flights before a motor breaks. I'm working on my torque meter as well.
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Re: Rubber

Postby smartkid222 » Sat Feb 13, 2010 10:02 pm

blue cobra wrote:Preferably a torque meter, but if not you can make a hook out of some stiff wire and attach it to something like a 3-inch C clamp and clamp that onto a table or the bleachers.

and you can bring that out onto the field with you when you are competing right?


I have a feeling I might be winding wrong. I can only really get 90 winds into .090 TSS. Maybe I'm winding too quickly or moving in too quickly.

Also, with regards to dewinds, how many are typical? And if I had to dewind, say, 5 times, and I wanted 90 winds, would I have to wind 95 times, then dewind 5?


what type of winder are you using? 1:?
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Re: Rubber

Postby blue cobra » Sat Feb 13, 2010 11:33 pm

Yes, you can bring your winding apparatus into the testing area (I saw one at States last year). They don't have to provide a table to attach it to (though they did at States last year), but most if not all areas are gyms with bleachers. And just out of curiosity, if you're in Division C, why are you so active on the Wright Stuff forum? Do you do things with flight outside of SciOly?

blue cobra wrote:Sorry, it's a 15:1 winder.

And I'm storing my rubber in a plastic baggie with a bit of lube in it in a pretty cool, dry, and dim place. I suspect knicks or maybe torque is to blame, since I usually get quite a few flights before a motor breaks. I'm working on my torque meter as well.
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Re: Rubber

Postby Taran » Sun Feb 14, 2010 2:17 am

What is the Armor all Lube called :?:

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Re: Rubber

Postby smartkid222 » Sun Feb 14, 2010 4:21 am

blue cobra wrote:Yes, you can bring your winding apparatus into the testing area (I saw one at States last year). They don't have to provide a table to attach it to (though they did at States last year), but most if not all areas are gyms with bleachers. And just out of curiosity, if you're in Division C, why are you so active on the Wright Stuff forum? Do you do things with flight outside of SciOly?


Thanks. It's because i'm doing helicopter, but if i post in the helicopter thread i wont get as nearly as good as answer as i would get here (and the principles for both events are the same). I also help the Div B school in my area but pretty much everything i ask is for myself.

Taran wrote:What is the Armor all Lube called :?:


Try googling armor all origional formula.
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Re: Rubber

Postby smartkid222 » Sun Feb 14, 2010 4:25 am

jander14indoor wrote:Another important factor is the quality of the rubber itself. How has your rubber been stored (high temperature, sunlight, and ozone (from electric motors most commonly) are NOT your rubbers friend)? Is it fresh (rubber changes over time)? How cut to width (are there nicks in the edge?)?


This brings up a point i was going to bring up soon anyway. The storage of rubber. High temperature, sunlight, and ozone degrade rubber. Would putting rubber in a freezer be a good way of storing it? How long after aquiring the rubber does it begin to degrade if left in a cool, dry place but not a freezer?
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Re: Rubber

Postby jander14indoor » Sun Feb 14, 2010 12:08 pm

Storing in freezer is common among hard core rubber flyers. Cool, dry, no light will keep it good for years, assuming its not a weird batch.

Note, I've heard that some kinds of plastic storage bags have plasticizers to soften them added that rubber doesn't like. I don't have evidence other than hearsay on this one, but its easy to avoid, so I just keep mine in the original cardboard box, or if cut up, in manila envelopes.

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Rubber breaks at winder end

Postby leetx » Sun Feb 14, 2010 4:47 pm

I have noticed that at least half of the time when the rubber motor breaks, it breaks at the winder, often a fraction of inch from the knot.

Is this because of the extra instantaneous force exerted at the winder, or because of small tears that were formed when tying the knot?

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Re: Rubber

Postby jander14indoor » Mon Feb 15, 2010 1:08 am

Probably damage while tieing the knot. There are some knots that will hold well even if you lube the rubber, which helps protect against tears. I've seen fliers tie the knot under water to lube and the the water dries reducing knot slip.

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Re: Rubber

Postby smartkid222 » Thu Feb 18, 2010 7:56 pm

[quote=jander14indoor] use slices off teflon tubes. I find the black plumbign O-rings to heavy and when the twist, they defeat the purpose!
Stiff enough to stay open when wound, but soft enough so the edges don't damage the rubber.
Low cost, I priced replacing the RC car antenna cover I bought 4 or 5 years ago (the remaining length is getting pretty short) with a new piece and its only 2 or 3 dollars. And I've cut a LOT of rings for the clinics I run from the piece I started with. You can also scrounge them from old ball point pens, spray bottles, etc. for nothing.
Wt, very low. A pair for SO is only .03 gm or so (you could probably go lighter but I don't want to risk the ring failing), less than 2 percent of the 1.5 gm SO max. Maybe I'm clumsy, but I lose more turns getting wound motors without O-rings off a winder and torque meter.

Jeff Anderson
Livonia, MI[/quote]

I dont understand how your O-rings weigh so little. What is the OD/ID?
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Re: Rubber

Postby jander14indoor » Thu Feb 18, 2010 10:41 pm

I'm not home, so this is from memory, but I think its like 3/32 id, by 1/64 or so wall thickness. I slice off pieces about 1/32 long, again from memory, my jig to do this safely and consistently is at home.

Oh, and I found the tubes again, they are not antenna covers, they are pushrod covers. Look in the RC supplies section of your hobby store.

Hope that helps,

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Livonia, MI

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Re: Rubber

Postby smartkid222 » Fri Feb 19, 2010 12:54 am

When you return home could you mass the tube and find how many g/in?

Teflon is a dense material to begin with (2.2 g/cm^3). I have some teflon but it has a large diamter and the O-rings are very heavy. I have another kind that is much thinner but i dont think it can hold.

**edit** nvm i figured out what i was thinking of.

Idk what pushrod covers are.
Thanks
Last edited by smartkid222 on Sat Feb 20, 2010 10:54 pm, edited 1 time in total.
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Re: Rubber

Postby Lowell » Fri Feb 19, 2010 11:26 pm

I just got my shipment of Tan Super Sport 3/32 rubber. Can someone tell me about how many inches will get me to 1.5? I don't have a scale yet and the one at the school does not measure tenths so anything above 1 would show up as 2. :/ Thanks!!

Doh! I just found the answer.

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Re: Rubber

Postby Greg Doe » Sat Feb 20, 2010 4:40 am

Lowell,
I find 24 to 26 inches will yeild a 1.5 gram motor. I tie mine off, and if it's a little heavy,
tie it off again, and cut off the first knot. If it's still too heavy tie it off again! After doing this a few times you will have a good guess at how much weight you can lose each time you
trim. Don't lube your motor until after the last knot, unless you clean your rubber really well.
Greg Doe
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