I don't think that the difference is measurable, but a full motor puts more stress on a motor stick than a 1/4 or 1/2. Also the stress lasts much longer as it takes so much longer to reduce it as the motor unwinds. The big problem with changing from fractional to full motors is the length of the flight at full torque. It must be remembered that in F1D (new rules ) the models are launched at full torque due to the lack of available rubber dictated by the rules.
Any bad flight tendencies at high torque are many times greater than the ratio of motor size difference. Any slight bad characteristics at 1/4 motors are catastrophic at full motor.
Fred Tellier
----- Original Message -----
From: Nicholas
To: Indoor_Construction_at_yahoogroups.com
Sent: Friday, December 01, 2006 11:15 PM
Subject: [Indoor_Construction] Re:prop pitch
Nick,
The force from a spring (or a rubber band) is a function of the
distance it is stretched. In a wound rubber band, the distance it is
stretched depends on its unstretched length and the number of turns.
So, with a half motor stretched half the length of a full motor and
half as many turns, the force should be approximately equal. If
rubber bands follow Hooke's law, it will be perfectly equal. However,
I doubt that they do. With a scale and some careful measurements, you
could make a mathematical model for the force. So from all this, the
conclusion I draw is that the only difference with half motors is that
all times are half of what a full motor would provide. By times I
mean the total duration, how long it climbs, how long it cruisies,
etc. Of course, this assumes a perfect motor, and no other odd
"real-world" things.
Nicholas Huang
Boise, ID
--- In Indoor_Construction_at_yahoogroups.com, "Nick Ray" <lasray@...> wrote:
>
> John,
> Your assertion is correct. The theory that is currently held by the
> majority of indoor fliers states that if everything thing is done
> properly they results will simply be a scaled down version of the full
> flight. However, in very high torque loads, especially in cold
> weather, where the rubber can hold more energy than normal, the some
> sort of increase in the force trying to collapse the stick seems to be
> happening. In speaking with Fred Tellier, who had noticed the same
> effect, I came to the conclusion that because the dummy part of the
> motor is neutral, and the increase motor section of a full motor is
> pulling on the stick, there should be an increase in the total
> compression load of a full motor when compared to a partial motor.
> Maybe if a few more people see this happening we could give the affect
> a name, and an equation to model the effect it has as the motor is
> scaled up?
> Nick Ray
[Non-text portions of this message have been removed]
Received on Sat Dec 02 2006 - 09:36:26 CET
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