On Mon, 26 Feb 2007, calgoddard wrote:
> Our Science Olympiad team had a disaster at its regionals.
> Their two planes climbed way too quickly and after many collisions
> with the roof, scoreboard, basketball backboards, one plane ended up
> landing on a light fixture and the other crashed.
I have occasionally noticed the same effect: while I assumed launching a
new flight with very conservative torque, the model climbs like a homesick
angel to reach the ceiling and hang up. Embarrasing...
> What's the relationship between temperature and torque/winding? If
> there is a 15% differential between the temp for the test flights and
> the temp for the competition, do you lower launch torque by 15%?
I started to wonder this, as my rubber tests seemed to indicate that there
is a effect. I have tested every single F1B motor that I have used in the
past (almost) 10 years, so there is some data. It seems to me, that the
energy return of the rubber varies surprisingly little with aging, I still
have some -98 and -99 Tan II left, and the energy return from these motors
is within measuring accuracy about the same. So while calculating the
temperature effect I neglected the age of the rubber.
My test temperature has varied between 15C and 28C. I should, some day,
carry my test rig outside in the winter to get actual data on the rubber
performance on freezing conditions, as we routinely fly our (outdoor)
contests in such conditions. I doubt that sxtrapolating the data that far
would give good results.
Anyway, a linear regression between the above-mentioned temperatures
suggests that Tan II rugger loses 0.76% of energy return per degree
Centigrade of temperature reduction, and the same value for SuperSport
(April 04) is 0.86%. In other words, a reduction of temperature of 10C
will cut down the energy return of the rubber by 8 (or 9) per cent.
The larger value for SS is in agreement with the notion that while the
energy return of (04/04) SS is about the same in room temperature as 2002
batches of Tan II, in cold the Tan II seems to work clearly better than
SS.
-Tapio-
Received on Mon Feb 26 2007 - 01:38:28 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:44 CET