Partial Motors

From: calgoddard <calgoddard_at_yahoo.com>
Date: Mon, 04 Dec 2006 23:00:45 -0000

I tried to post a similar message the other day, but it seems to
have disappeared. I apologize if this is a repeat.

Some prior posts seemed to imply that full motors will exhibit
higher torque than partial motors. Maybe I misread the posts.

My experience has been that, for a given rubber type (e.g. specific
batch of Tan II stored the same way) and thickness (e.g. .093
inches), if, for example, 800 turns on a half-size motor indicates a
torque reading of 1.0 on a torque meter, then 1600 turns on a full-
size motor will also indicate a torque of 1.0 on the same torque
meter. I measure the motor "size" by weight, although I understand
many experts go by the length. Obviously, you can't extrapolate
torque for a motor wound, for example, two times previously to one
that has never been wound.

This is the basis on which our team does half-motor flights and then
extropolates height and time that should result on full motor
flights. We have observed that on a full 2.0 gram motor, double the
winds and the same torque will fairly accurately double the flight
height and flight duration of a flight with a 1.0 gram motor (again
assuming same rubber type, thickness and prior wind history). Of
course, you have to fly the same plane trimmed the same way under
the same conditions.

Apparently the smaller the partial motor is as a percentage of the
full motor, the less reliable the extrapolation. In other words,
half motor flights are generally a better predictor than quarter-
motor flights.

Am I missing something here? Maybe there are minute differencs in
torque but it shouldn't be significant in predicting the performance
of a Science Olympiad plane on full motors based on partial motor
flights. Perhaps it matters in F1D.

Calgoddard
Received on Mon Dec 04 2006 - 15:04:22 CET