pusher type propeller? - RC Groups
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Dec 13, 2003, 01:46 PM
Registered User

pusher type propeller?

If pusher type is unavailable, if it is able to:

1) reverse the NORMAL prop to use?
OR 2) reverse the motor turning direction?

so as to fit the purpose?

I heard that it is needed to adjust the TIMING of a motor when the direction is reversed. Is it true about it? I have no idea what the TIMING of a motor is, can someone kindly help to explain?

Thanks in advance for any replies.

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Dec 13, 2003, 02:09 PM
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Larry3215's Avatar
Which motor are you using? Is it brushed or brushless?

Dec 13, 2003, 02:24 PM
Registered User
There is only a front and a back to a prop. You just have to make sure that the front faces the front of the plane. If you reverse the direction the motor faces you have to reverse it's rotaion. On a brushed motor,this is done by reversing the +V and -V wires (usually red and black on your speed control). On a brushlesss motor, if the rotations is wrong, you just reverse any 2 wires.

Some brushed motors are neutral timed and some aren't. Usually 370 (GWS 300) are forward timed. Usually 280 (GWS 100) are neutral timed. 400 motors may be forward, reverse or neutral timed. To change the timing the back of the motor has to be loosened and rotated.

PS. Getting the prop facing the right direction is much more important than getting the timing correct.
Dec 13, 2003, 02:48 PM
rpage53's Avatar
Pusher props are fairly rare, so the standard is to reverse the motor. A sensorless brushless motor just requires 2 wires to be swapped and you can fly.

A brushed motor or a sensored brushless will require the timing to be changed by rotating the endbell (the brush holder). Some can motors (like the Graupner Speed 400 7.2V) are neutrally timed and can be used in either direction. Depends on your motor.

I suggest you check the FAQ for information about timing. The FAQ is on the links at the bottom of the page.

PS I see you got 2 answers at the same time. Helpful people here.
Last edited by rpage53; Dec 13, 2003 at 02:53 PM.
Dec 13, 2003, 03:00 PM
Tacoma, WA, USA
William A's Avatar
Timing; Not required in brushed unless your trying to squeeze the most out of it.
Dec 13, 2003, 03:36 PM
rpage53's Avatar
Maybe timing is not required in small motors but its still a good idea. If the motor was advanced timed in the first place, the manufacturer obviously thought it was necessary.

Running a Speed 400 or larger motor with reversed timing will cause premature failure of brushes, overheating and waste significant power. Of course, the same happens with small motors but they are usually cheaper. I have no idea why GWS sometimes sells motors with retarded timing.

Dec 14, 2003, 02:00 AM
Registered User
Thank you everyone's kindly replies.

The motor I am asking is a 400 using in a small train type plane, I tried to reverse the blades of a folding prop (which is push-in shaft simple type), and it works and I FEEL the thrust it gives is SIMILAR to previous fix prop. So it is no need to reverse the direction of motor now.

But I have much interest about timing issue is because I am in the e-flight for a while and I bought quite some bigger stuff at , 1 axi4130, 1 pc of China made BL400(dia28x35)<BTW, this little stuff really much power than I thought, I hold the BL400/cobalt 380/05 motor with same prop. and just feel the thrust , I know its not scientific, but I have no time to build some testers for comparison> ,1 pc of cobalt 400 and '05'.

I will follow the threads given to see if I could understand how to reverse the motor in later usage.

I wonder if any long-term mechanical issue will be induced if I reverse the prop/ blades in the bigger motor? I want to use the BL400 or the cobalt 05 in a larger glider with pusher design? Anyone have relevant experience or opinions?

Thank you again for your inputs.

Dec 15, 2003, 01:22 PM
rpage53's Avatar
By reversing your prop blades, the prop will work but it is running backward and will be inefficient. There is only one forward edge and one forward side on a well-designed propeller.

With your Speed 400 motor you are better to use the original prop and reverse the motor without worrying about timing. Cobalt motors should also be re-timed.

Some gearboxes reverse the direction of rotation. Some don't. By choosing the correct gearbox for the timing of your motor, you can avoid having to reverse the motor leads. So a pusher plane with a reversing gearbox will use a normal rotation motor.

Last edited by rpage53; Dec 15, 2003 at 01:25 PM.