Pusher prop direction?

[leonmike]

I am using a pusher prop (9x6) for my paraglider. Anyone can tell me the correct direction of rotation, CW or CCW when facing in front of the prop? Appreciate it...

[joe yap]

You are not giving enough information here. You forget to mention what prop are you using exactly. Using a conventional tractor prop and a commercial pusher prop will be totally different.

However, there are some fundamentals that can help you through, if you understand them fully.

First of all, the convexed side (front) of the prop should always point forward with respect to the flight direction, IRREGARDLESS to the engine or motor orientation.

Second of all, all props are originally designed to run counter-clockwise, viewing from the front of the ENGINE or MOTOR, irregardless of the prop orientation. This is because, until recently, model aircrafts are primarily powered by IC engines, and they all run at COUNTER-CLOCKWISE.

So in order to use the engines for pusher setup, special "Pusher props" are commercially manufactured with negative pitched prop blades, as compared to a conventional tractor prop. If you put both of them side by side to compare, the props are totally mirror image of each other. However, since the motor is facing aft of the fuselage, the pusher prop needs to be mounted with the convex side facing towards the front of the fuselage, not the back.

Since the last decade, electrics models started to become very popular and the advantage of them over IC engines is that they can be wired to run at clockwise direction. This will allow a conventional tractor prop to be setup for pusher configuration, by BOTH flipping the prop the other way round and running the motor at clockwise direction. This is where most novices got confused.

Hope this helps.

[zxyong]

Interesting information Joe,

But the direction probably doesnt matter IMHO, just make sure that the weight distribution and the direction the prop is facing is correct, since you can alter the direction of brushless motor easily.

[leonmike]

You are not giving enough information here. You forget to mention what prop are you using exactly. Using a conventional tractor prop and a commercial pusher prop will be totally different.

However, there are some fundamentals that can help you through, if you understand them fully.

First of all, the convexed side (front) of the prop should always point forward with respect to the flight direction, IRREGARDLESS to the engine or motor orientation.

Second of all, all props are originally designed to run counter-clockwise, viewing from the front of the ENGINE or MOTOR, irregardless of the prop orientation. This is because, until recently, model aircrafts are primarily powered by IC engines, and they all run at COUNTER-CLOCKWISE.

So in order to use the engines for pusher setup, special "Pusher props" are commercially manufactured with negative pitched prop blades, as compared to a conventional tractor prop. If you put both of them side by side to compare, the props are totally mirror image of each other. However, since the motor is facing aft of the fuselage, the pusher prop needs to be mounted with the convex side facing towards the front of the fuselage, not the back.

Since the last decade, electrics models started to become very popular and the advantage of them over IC engines is that they can be wired to run at clockwise direction. This will allow a conventional tractor prop to be setup for pusher configuration, by BOTH flipping the prop the other way round and running the motor at clockwise direction. This is where most novices got confused.

Hope this helps.

Great write-out, appreciate it but just to be sure i got it right, i will post a pic for you to confirm it is working correctly,..

[joe yap]

Interesting information Joe,

But the direction probably doesnt matter IMHO, just make sure that the weight distribution and the direction the prop is facing is correct, since you can alter the direction of brushless motor easily.

You can't over-simplify these as it folks out there without sufficient understanding will get confused further from case to case. And for the reply to this thread starter, we should drop the irrelevant issue like weight distribution in order not to confuse him.

The direction of the rotation, the propellor design and the flight direction are all related to each other.

If I have to drive further, I'll say that mechanically, all electric motors are designed to run at Counter-clockwise facing from the front, even though their polarity can be reversed, unless stated otherwise. Just look at the threads of the prop mount, all of them has right hand thread which will keep the prop nut tightwhen the prop is spinning counter-clockwise. If you were to reverse the motor rotational direction, you will have to use thread lock on the threads, as the prop nut will tends to loosen itself in that direction. Although it can be done this way, it is considered an unorthodox practice. Thus most reputable ARF manufactures often suggest the use of properly designed pusher props with the motors running at counter-clockwise direction to minimise the complaints of props coming loose.

While I'm not too sure about brushless motors, brushed motors are timed to run at it best for thier designed rotational direction. If you reverse the polarity, you will see the drop in performance. That is why we used to re-time our brushed motor previously when we use them to run at clockwise direction.

So, in a nutshell, it is best to use a properly designed and labelled pusher prop with the motor running at Counter-clockwise direction. If the pusher prop is not available, use a tractor prop, reverse the motor rotational direction and don't forget to use thread lock. And always point the front of the prop to the front of the airplane.

[etman]

You don't need a pusher prop (CW) for a paraglider.
Just a conventional CCW will do.

The only time you really need a pusher prop (CW) is to counter the torque by turning clockwise instead of anti-clockwise.
e.g in a twin motor or quadrocopter

CW props are hard to find, limited in sizes, more expensive.

[joe yap]

Errrr.....before more and more confusing and irrelevant factors come in, I think I better show you the sketches. Forget about torque,weight, paraglider or not at the moment, and just to talk about how to make things work. It is the same for any fixed wing aircrafts, hovercraft, etc.


See for yourself. Pay attention to the prop orientation and rotational directions.

[leonmike]

Now that is really getting confusing guys!!!

[etman]

Nothing confusing. What Joe showed is correct.

[leonmike]

Errrr.....before more and more confusing and irrelevant factors come in, I think I better show you the sketches. Forget about torque,weight, paraglider or not at the moment, and just to talk about how to make things work. It is the same for any fixed wing aircrafts, hovercraft, etc.


See for yourself. Pay attention to the prop orientation and rotational directions.

So Joe if my setup for pusher is like drawing 2, my prop rotation will have to be CCW, right??? with the prop nut locking in CW direction?

[joe yap]

So Joe if my setup for pusher is like drawing 2, my prop rotation will have to be CCW, right??? with the prop nut locking in CW direction?

Yes. that is right. Sketch #2 shows the commercial pusher prop used for pusher setup.

However, I am not very sure about your actual setup. It is best that you post a picture to verify.

[leonmike]

Yes. that is right. Sketch #2 shows the commercial pusher prop used for pusher setup.

However, I am not very sure about your actual setup. It is best that you post a picture to verify.

OK bro will post it toniite after i go back from work.

[leonmike]

OK bro will post it toniite after i go back from work.

Bro Joe, pic of my pusher, CCW (arrowed), is this correct?

[leonmike]

Bro Joe, pic of my pusher, CCW (arrowed), is this correct?

My pic...

[joe yap]

Yes, you are using the setup as per sketch #2. Thus, the rotational direction is also correct. However, your prop is still mounted the wrong way. In this view, you should see the backface of the prop, not the numbers.