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svond
09-08-2005, 05:38 PM
I have this motor...it is recommended as a substitute for .40 glow. It swings a 13/8 prop. This seems unusually great compared with what one usually puts on a .40 size plane. Any thoughts?

svond

Mike Parsons
09-08-2005, 06:13 PM
svond,
Unusually great as in larger than a glow prop? An electric motor is generally a low RPM, high thrust. To get the desired results a larger prop must be utilized for electrics.

svond
09-08-2005, 07:44 PM
Thanks. Makes sense to me now.

svond

fdix
09-09-2005, 01:14 AM
Have a look at this table, it should give you a pretty precise idea of what you can expect from the motor.

http://www.bnhof.de/~ho1645/d_bl_axi.pdf

Tweet
09-09-2005, 10:30 AM
Also, because you can use different numbers of battery cells (voltages) with the motors you have a wider variety of props you can use with the same motor.

For example, I get the same performance using a 4130/16 on 5 lipoly cells on my Kadet Senior as my friends do with their Saito .91s. However instead of the 14x7 they use on their Satios I used a 17x10.

Mike Parsons
09-09-2005, 11:57 AM
Also, because you can use different numbers of battery cells (voltages) with the motors you have a wider variety of props you can use with the same motor.

Exactly. Performance with a 4130-16, 6S and 16" prop is almost the same as a 4130-16, 5S and 17" prop. As cells are adjusted down, the prop comes up to get amps and watts to level out.

I have bee watching Gary Wright do this for years in swinging outrageously large props on low voltage setups in his 3D machines.

-Mike

Tweet
09-09-2005, 12:28 PM
My setup with the 5S4P setup provides 30 minutes of flying time. I have two of these batteries and will use them together in series for my 28% Wild Hare Extra. If you get creative and plan ahead you can manage the battery costs.

svond
09-09-2005, 02:28 PM
Fdix:
Thanks for the hint on the table. I have understood most (with my limited aviation german) but please help me with "Eingangsleistung (P in) und Standschub natuerlich immer in Relation zur Strahlgeschwindigkeit". Input power and stationary thrust always in relation to ? "Strahlgeschwindigkeit" = ??beam speed??
The other one I need help with is the third header: VProp (m/s).
Thanks

fdix
09-09-2005, 03:27 PM
Eingangsleistung is the power which enters the motor so to say, in watts. Watt = Volts * Amps.

"Eingangsleistung (P in) und Standschub natuerlich immer in Relation zur Strahlgeschwindigkeit"
My interpretation of this phrase is that you have to keep in mind the velocity of the wake of the prop when comparing power and static thrust of different motors. In other words: even if you have 500g of thrust you won't put this motor/prop combination on a 3D slowfly if you have a wake speed of 50m/s.

VProp (m/s) is the theoretical speed of the wake of the prop at that rpm. Theoretical because it assumes 100% efficiency of the prop.
This speed is given by
VProp = (pitch * rpm) / 60
pitch must be in meters!

Hope this is clear enough, if not just ask :D