Ed,
There is no secret. Rubber that is "broken in" or pre-stretched, has more energy
than virgin rubber.
The evening before you are going to fly, loop your motor to 7 to 10 inches, and
stretch your motor between the doorknob and the top of the door in your motel
room, and let it sit for 5 minutes. Let it rest for 1 hour, and repeat. Let it
rest overnight, and your motor will have much more energy. Some times the loop
will break, and this is a good thing, because it will not break on the day of
the meet. Make a habit of checking for cuts, splices, and delaminations, as I
said. The 0.42" inch strip is actually laminated from two sheets of 0.021",
originally designed for golf ball windings. Some times it parts, but not often.
Look edgewise, instead of flat-on, and you might see it.
Another thing, get in the habit of winding motors until they break, the night
before, or the week before. All the time. This is 100%. Write it down in terms
of TPI, breaking turns per inch.
Then at the meet, you can wind to 95% of these turns with SOME confidence that
the motor will not break. Again, a broke-in motor will take more winds than a
virgin motor. We use the term TPI, or turns per inch. 100 to 110 TPI is a good
bench mark for starting. Thus a 12 inch loop will be good for 1200 to 1300
turns. A broken in motor may be safe at 1400 turns. This can be the difference
between 2nd and third place.
Values of foot pounds or specific numbers are not important, pre stretching and
preparation is.
Obarski was a champ. The best. He has caught that final thermal.
The idea is to prestretch it 7 to 8 times its original length, or until it gets
real tight. Also take some with you that you did not prestretch, and you will
see a difference. Keep it in poly bags and label them.
You mention procedure. Dick and all the rest of us kept notebooks. Buy a spiral
binder. Write down what you do. Keep a record. You can refer to it from time to
time.
Separate you rubber into so-so, good, and very good. Use the first two for
practice and testing, the last for contests. Other modellers may sell you some
of there good batches, as well. We are very friendly, and help each other out.
Carl
________________________________
From: Ed <ednlois_at_citcom.net>
To: Indoor_Construction_at_yahoogroups.com
Sent: Mon, February 28, 2011 3:14:30 PM
Subject: Re: [Indoor_Construction] Re: Rubber Motor O rings
Hello Carl, I've just joined the forum and found this email interesting. When I
first got into indoor it was in Tampa where I met Dick Obarski who was an ole
timer in indoor, you may have known him or heard of him. He took me under his
wing and became my mentor. He was in the middle of testing rubber and was going
through the stretching ( using a scale to measure pounds of pull) as u stated.
He would stretch a certain distance, measure , let the rubber rest then
re-stretch at a greater distance and measure etc. He would do this until he
would come up with a value. However , this was so long ago I forgot his
procedure!!!
Ed Berton
-------Original Message-------
From: Carl Bakay
Date: 2/28/2011 2:02:51 PM
To: Indoor_Construction_at_yahoogroups.com
Subject: Re: [Indoor_Construction] Re: Rubber Motor O rings
I have done a lot of rubber testing thanks to Goldstein's prodding during my
INAV days, testing mostLy 7 inch loops of 1/8 strip, and without exception,
those that broke did so at the knot. These knots were un lubricated, due to the
difficulty of tying a lubed knot. The stye of the knot did not matter ... It
seemed that that was where all of the stress was located.
I wrapped my loops for stretch testing around a nail, over which was slid a
piece of Tygon fuel tubing. This also allowed the knot to move, in keeping with
current FAC technology for short rubber motors in multiple-engine planes.
Carl Bakay
Sent from my iPad
On Feb 28, 2011, at 12:46 PM, "dennisatyson" <ddtyson_at_peoplepc.com> wrote:
Here is another source for 90A durometer o-rings at a great price.
http://www.oringsandmore.com/servlet/StoreFront
--- In Indoor_Construction_at_yahoogroups.com, Warthodson_at_... wrote:
>
>
> From what I have read & experienced, o-rings cut from plastic tubing do not cut
>into the rubber any more than the wire hooks. It seems counter intuitive, but
>many very experienced indoor flyers use plastic tubing for o-rings. Personally,
>I prefer the hard plastic o-ring to a rubber o-ring. I find them easier to hook
>up. I read somewhere that someone boiled their plastic o-rings to remove the
>sharp edges, but I have never met anyone that told me they actually do that. If
>the sharp edge were cutting into the rubber I would expect most of my motors to
>break at the o-ring, but again that has not been my experience.
> Gary
>
>
>
>
>
>
> -----Original Message-----
> From: Terry <jantel98_at_...>
> To: Indoor_Construction_at_yahoogroups.com
> Sent: Mon, Feb 28, 2011 7:05 am
> Subject: [Indoor_Construction] Rubber Motor O rings
>
>
>
>
> What are people using for O rings ?, I have heard of rigid plastic being used,
>if so do it not cut into and damage the rubber ?, I have just cut some thing
>rings from a light plastic (Ear cleaner) tube and was looking for a way to
>smooth them down a little
>
> Terry
>
Received on Mon Feb 28 2011 - 15:30:40 CET