Leo P. commented that not everybody receives attachments, and requested
the pic about rubber test, so I uploaded it to the Yahoo files area
(there should be a separate message about that.
The tests are made with a stretch method for 30 gram F1B motors, with
pull force recorded at intervals during the release phase, after the
motor is first stretched to maximum stretch (90% of estimated breaking
force). I first tried to measure these by hand, writing down forces from
a scale at 10cm intervals, but that turned to depend heavily on the
intervals. Thus I built a computerized system, where the force is
automatically logged at 1cm intervals (with about 300 measurements per
motor, as full stretch of a F1B motor is 320 to 340 cm). I'm quite
confident with the results, as they show very little variance within a
batch, less than 1% standard deviation, yet show clearly different
energy return values for different batches. Also I found out that
temperature effect the results, and while having repeats of same batches
(made motors to contests at different times), fitted some statistics to
the data, with temperature and batch as independent variables, to find
out that the energy return changes about 0.8% per degree centigrade.
This variation is corrected for in the figure that I posted.
http://f1.grp.yahoofs.com/v1/4F6zSeKetyv0SnWxOME8HE2F1BCnP_4F11Vo1iyHVtFVn9DkBjwUjyXFF9mIQzWb6rHu0cU05v9TMKPg8Tz0PNYBxoQGKlU/rubber.GIF
(I hope the link above works? Anyway, file called rubber.GIF in the
files area...)
-Tapio-
Received on Sat Mar 07 2009 - 22:57:18 CET
