Re: Re: Comparing Rubber Batches

From: Fred Tellier <fred-tellier_at_cogeco.ca>
Date: Fri, 27 Apr 2007 15:24:11 -0400

Eric

The numbers are only useful in comparison as anyone using the spread sheets will get different values. I have not done any serious testing since the 302 batch. Any SS I have tested was so bad I did not bother creating a series of tests. With winding type testing the turns effect the results much more than actual torque readings and they are equivalent to the stretch of the rubber. Accuracy of the torque meter used, lube and stretch and speed of winding are also factors in the final result. I put Fred Pierce's stretch formulas into a spread sheet and found that in the rubber sizes I used for testing my scale was not accurate enough and bigger rubber was a pain to stretch without a test rig and a winch.

I sent some results to Fred Rash on 5 99 to put in his program since I felt his numbers were too low, I am a hard winder and usually destroy the motor on the 1st or 2nd flight. Getting a lot of turns is a skill that takes a lot of patience and practice to acquire, Jim Richmond is the best I have seen and Doug Schaefer is also very good. Jim winds very slow, I tried Stan Chilton's way of winding and didn't get the results he gets, the only trick I know is stretch as much as you think is enough and then pull a little more, come in slow, I wind to 1/2 final torque before moving in and then come in as slow as possible with the goal of reaching final torque at motor stick length. A trick I learned from Larry Loucka is to leave the motor on the torque meter for a couple minutes before hooking up if you are not backing off turns. I used to have a lot of motors blow up while hooking up or just before launch, now they blow up on the torque meter not on the model and the torque you loose while waiting isn't that much.


Fred Tellier

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Received on Fri Apr 27 2007 - 12:27:51 CEST