Pusher motor help. Thank you!

[Smoother]

I'm constructing a pusher plane.
I have changed the plans a bit and i need help about motor mount.
Do i need upthrust and left thrust ?
...because if the motor is in front i need down and right thrust wright?
how can i calculate how much degrees i need?

Thank you in advance
and merry christmas from Portugal!

[FoamCrusher]

I'm constructing a pusher plane.
I have changed the plans a bit and i need help about motor mount.
Do i need upthrust and left thrust ?
...because if the motor is in front i need down and right thrust wright?
how can i calculate how much degrees i need?

Thank you in advance
and merry Christmas from Portugal!


Depending upon the type of plane, you may or may not need to add some down and right thrust. Wings and delta types generally don't need any right thrust, but they may need some down thrust. I have several of each type and all but one had the motor straight on the center line with no down or right thrust. A powered glider with the motor pod above the wing will need some counter thrust built into the pod.

My Unicorn wing is overpowered with a brushless motor and it likes about 1 to 2 degrees of downthust so that it will remain level if the throttle is increased suddenly. This is very noticeable in flight, but it still flys without it. I would try your plane right on the centerline with no angle until you see a need to make any changes.

I think you also wanted to know what right and down thrust looked like for a pusher. Think of an imaginary line through the shaft of the motor extending both front and back. In a tractor configuration, you aim that line down from the centerline and to the right front of the plane to counteract the torque of the motor.

When you use a pusher configuration the thrust must be in the same direction, because the motor has been switched end for end, AND the direction of rotation has been reversed too. The two changes result in your needing to angle the motor in the same way, but now you aim the end of the motor that does not have the propeller shaft down and to the front right of the plane.

The shaft end of the motor will be facing the rear of the plane and be angled up above the centerline and to the left rear of the plane. Oh, and do not forget to put the propeller on the shaft with the leading edge still facing forward - it must still "screw into the air" the same way it did when it was in the tractor configuration. This means the propeller will be backward on the prop adapter (since the adapter is now facing aft rather than forward) and the hole in the prop may need to be reshaped or re-drilled to accommodate the adapter face.

I hope this helps

Merry Christmas !

[Smoother]

Thank you, FoamCrusher for your help!
Excellent explanation, thank you.

Merry christmas and happy new year!

[Sparky Paul]

The amount of offset thrust depends on where the motor is located relative to the wing, mostly.
If it's in-line with the wing, probably nothing is needed.
If it's above the wing, possibly a rear end (on the motor) tilted up could be required.
Allow for a few degrees either way, depending on flight testing to determine which way if any is needed.
The last plane needed some thrust offset as described above. the first hand toss showed the motor was pushing the nose down, when aligned with the fore-and-line on the fuselage. Tilting the rear of the motor up fixed that.
The other two have no thrust offsets.

[olmod]

In your last pix is that a camera poking out the nose ? :eek: if it is it would be a great live feed with tilt :D

[Sparky Paul]

Yes, that's a 1.3 Aiptek.. not the SD.. It did good looking forward. The odd top was a fairing over the servo that clicked the shutter for when the camera was looking to the side, hung outside another plane..

[Ledbetter]

Sparky,

Great concept plane. I have a notion to build an in-line push-pull plane like that with two GWS "stick" gearboxes and motors, one fore and one aft in the fuselage. I assume in such a confiugation, the motors should be in-line with the fuselage and parallel to each other.

Thanks for the pics. Regards.

Mike Ledbetter