Now I am sure this has been covered, but couldn't find anything when i searched.

I lost my old prop which worked great, and got a new one for my electric motor. The new prop is made for nitro, which meens to me it should still work.

SO anyway, MY QUESTION is , Can you put a pusher prop on backwards? I know there is a proper direction for the props, But why cant I take a puller prop, turn it around OR reverse my motor to create the pitch needed.
Or is there ONLY ONE way for a propeller to work properly.

and how do you know how much pitch you need?

Can someone clarify for me. I almost have my home made foam boat ready, gonna have to get a new prop today for it.

Thanks alot for any/ all help

Yes, a propeller has a direction. A propeller is not just a set of paddles, each blade is an airfoil or wing. Because of this, the 'top' or rounded part of the prop is always facing forward, and the flat part is always to the rear.
The pitch of the prop is reduce the drag of the airfoil at speed; too little pitch(the engine winds out)and the airfoil has a de facto negative AOA, as compared to the air it is going through. Too much pitch will leave too much drag, lower RPM, and slippage. Here is a nice little article:

http://www.eskimo.com/~smallnet/JoeA...ropellors.html

good article Dogmoat, thank you.
So turning a puller prop to be a pusher is not really possible.
Seems like pusher props are harder to come by. I'll go see what i can get in the size i need. Guess I'll get a couple different ones if i can so i can play with pitch.

Is it OK to mount the prop directly to the shaft of an electric motor? or is it going to give too many rpms or wreck the motor?

Thanks again

You can use ether a pusher or a puller prop with any motor as long as you can reveres it. A puller prop can be put on backwards but spun the same direction. So if you have a prop that spins clock wise in the puller position and you want a pusher all you have to do is put the prop on the other way and change the direction of the motor so it is still spinning clock. For example think of your prop staying where it is if you put the motor on the other side of the prop the motor will spin the wrong way so you have to reveres it. Hope this helps

Thats what I was looking for, thanks Pinky.

I just bought 2 new props, an 8x6 and a 9x7, I notice with the writing out, the motor is a puller, writing in, its a pucher, even though they are sold as a pusher. i think they are just a normal one.

As long as they work, then ok!!

I should be able to put pics up of my new HM airboat. Not tested yet, painting and the general boat is sloppy, but more of a trial anyway!

Jared

Not being an EP man , to tell you the truth ... I always thought that an electric motor could be either .... a pusher , or tractor , pending on the flow of current being applied ?

You are right. But reverse your motor, and turn the prop around to mke any prop a pusher or puller, depending on direction of motor and prop.

Also remenber that when you reverse a brushed nonadjustable timed motor that
you loose some rpm's because most have the timing advanced a few degrees
to run in there forward direction , if the timing is set at 0 degrees the motor will
run the same rpm's both direction but not have full rpms that its capable of
producing
The more advance the timing is , the more rpms & less low end torqe it has ,
its not a very big deal as the torqe has moved a tad higher up the rpm range
in the forward running of the motor

This basic info is for why you wonder why its got more power running one direction than
the other on a brushed motor & you reversed it from its normal running direction

Hope this explains a little of whats going on & not to confusing
Now brushless is a whole different ball game

thanks boatman, that helps me with my rc car, it has brushed motors, never touched the timing, because i wasnt sure what they did.

On the boats, i am running brushless. Everythings brushless except my car! I know with the brushless you just swap two leads and it reversed, I don't think there is any performance loss.

Wow ... thats interesting there BOATMAN ... ( see that , and they say you can't teach an old dog something new ... )
Very good info there ...
But , NOW ... how do you "adjust" the timing of an electric brushed engine ?

you just turn the 'can' of the motor. the can is marked with the degrees. At least thats how it is on my RC car. As far as a motor out of a wheelchair (or whichever you have) may be very different!

Most cheaper motors are none adjustable or stock racing motors [&o]
These fine tuning adjustments are normally on the higher end
modified racing motors
A stock motor is 27 turns of wire on the armature & 24 degree
advance timing for ROAR rules

heres a typical fixed timed motor

"The scotty diode is for forward only NO REVERSE if you do it smokes it "
The red dot is the positive side of the motor

heres a adjustable motor


thats about $40 differance in price between the 2 of them
electric can get complex [X(]