Winding was: SS 2009 good batch?

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Tue, 29 Mar 2011 12:39:02 +0300

On 27.3.2011 20:15, Bill Gowen wrote:
> 
>
> Several years ago there was a discussion of rubber winding on the FFML.
> I posted a comment about some F1D flyers taking 10 minutes to wind a
> motor to let the heat dissipate during the process. A very well known
> F1B flier told me that was ridiculous.

I'd say that the heat buildup is not an issue for winding indoor rubber
motors. Typically in outdoors, when the heating jackets were allowed
(they were banned about 10 to 15 years ago), the motors were warmed up
to body temperature, and in extremely warm conditions people still cool
the motor tubes (but then the closed space in the motor tube gets warmer
than ambient due to the sunlight). Anyway the heat buildup is not that
big, and I'd guess that the extra heat is irradiated from the motor
during the windup process, especially for indoor motors that are thin ==
high surface area to volume ratio.

Rather, the indoor motors are wound up slowly for two reasons. First is
obvious, to let the load even out throughout the motor, and not develop
local strain peaks, at which the motor would fail prematurely. Another
issue is the number of turns. Last summer I realized that the use of
rubber motors is somewhat different for outdoors and indoor fliers.
Outdoors, there is no ceiling, so the maximum energy return is what you
want from the motor. Therefore wind to a known maximum torque, and while
waiting for the lift, add a couple of had turns to compensate for the
tiring of the motor and keep the max torque up. For indoor, the number
of turns is highly relevant (more turns equals longer flight time), so
it may actually be beneficial to let the motor tire a little, and thus
be able to take a few more turns. So it may be a good thing to take
plenty of time for winding.

I think it was the Ukrainians (Andriukov?) that first presented the
heating jackets to F1B. However, already a few years before a couple of
my countrymen had speculated about the possibility of warming the
rubber, I even saw some heating elements that they planned to laminate
into the motor tubes. But, as usual, conservative buddies convinced them
that the idea did not make any sense, and only later the foreigners
built the system to use...



-Tapio-
Received on Tue Mar 29 2011 - 02:39:06 CEST