Re: Re: Rubber Motor O rings

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Tue, 01 Mar 2011 14:26:32 +0200

On 1.3.2011 14:03, RLBailey_at_care4free.net wrote:
> I tried to test F1D motors by stretching but the knot, frequently
> failed. The same type of knot works perfectly well if the motor is
> tested by winding and measuring torque so I revered to winding to test.

I guess the winding and friction of the strands would together takes off
some load on the knot (if it slips ever so little then the pull is
reduced at the knot), while pulling puts full load also onto the knot.
It seems that the knot that takes full pull load is a tender balance
between not slipping (if the knot slips the strip will cut through
itself) and pulling a knot so that it does not cut itself while
tightening. In F1B, still maybe 1 motor out of 20 will fail. The rest
will go through the break-in and test (both by stretching), but then
after that first contest flight the motor is typically broken at the
knot, so it seems to barely take the break-in and test... On the other
hand, the broken motors give me an ample supply of P-30 motors... :-)

In indoor I also use either pristine or once-used F1B motors, ever since
I found out that my rubber cutter also cuts lubed strip. That way I have
broken-in and tested the rubber strip that I use.



-Tapio-
Received on Tue Mar 01 2011 - 04:26:47 CET