Re: Double strand motors?

From: Mark F1diddler <f1diddler_at_yahoo.com>
Date: Wed, 04 May 2011 17:18:06 -0000

--- In Indoor_Construction_at_yahoogroups.com, William Gowen <wdgowen@...> wrote:
>
> John, Phedon, Mark, Dave, et. al.
>
> ...*IF* the question is "will an *equal cross section* motor of more
> strands have different characteristics than the *same cross section* of
> motor with fewer strands" then the answer is there will be little
> difference.>>

Bill, it's possible everyone here was thinking per the above. But to say "there is little difference" still implies there is *some* difference, and that's where (the practical) disagreement exists. If there's ANY difference, that could be important to the original poster. And sorry, I immediately regretted saying "rubber testers treat stretch ratio THE SAME as turns per inch." Of course it's not "the same" but a function of, along with cross section. We've all seen the formulas where torque varies with the 3/2 power of cross section, and turns vary with (I forget) 3/2 power of length/square root of width.

Back to original question: Evidence exists on both sides if one accepts all published claims as "evidence."

From Don Ross FF "Rubber Powered" book, quote, discussing his turns chart:

"Note that it appears as if 8 strands of 1/8th rubber can be wound to the same number of turns per inch as 4 strands of 1/4 inch, but this is not really so. It is a close approximation. You can probably get 5-8% more winds in an equal weight of smaller rubber."

From Model Aviation, March-April 1979, Fred Pearce, "Rubber."
"Would you get more or less energy by using an equivalent skein of many smaller strands? It has been hypothesized that a larger number of smaller strands to the same cross section area would enable one to store more energy" ...snip, Bob Champine experiment, etc ....
"No appreciable difference in torque or energy storage was evidenced. Thus, the only trade-off in using different widths of rubber, other than to get the proper cross-section, is that smaller sizes tie easier knots, but they also offer more edges in a skein to get frayed."

I believe the Fred Pearce article more than the Ross Book in this matter, and the reason I prefaced with, "Opinion," previously.
MB
Received on Wed May 04 2011 - 10:18:13 CEST