Is there a difference between a regular prop and a pusher prop ? I am looking at modifying an Estes Centurian boost glider over to electric power. Any suggestions on the motor / speed control setup would be appreciated. The motor would be mounted similar to a zagi motor setup, mounted in an approx 1"- 1.25" motor mounting hole in the rear of the fuselage. Here's a link on what one looks like...... http://www.estesrockets.com/t25_centurian_boost_88.html it's a 36" wingspan and they do say that it can be converted over to an .049 motor so this might give you an idea. I have a couple 8 cell 750 mah Nimh paks I was considering using for the power. Any suggestions would be appreciated !! Thanks and have a great day and may the wind be light !

There is definitely a difference between pusher and tractor props. As you get into electrics you will discover that a tractor prop will operate as a pusher by reversing the leads on your motor. With nitro power you will have to get a real pusher prop. They are readily available from most major manufacturers. Pushers when operated properly have the blades reversed from regular props. Check with your hobby shop.

The " pusher" props are just props with the blades shaped for rotating the oposite direction of the "tractor" prop. The difference between pusher and tractor is actually determined by where you place the engine/motor... not the prop.

We call the reversed pitch angle props "Pusher" because of the inability of many engines to run properly in the reverse direction. (as in the electric motor example posted above...) It would be more correct to call them "clockwize" and "counterclockwize" props.

You will find that some people will modify a glow engine to run reversed, and then have one clockwise prop and one counterclockwise prop on a twin engine plane such as a P-38. The reverse pitch prop isn't a pusher in this case... but the manufacturer may have called it a pusher prop.

So then if I were to mount the electric motor in the rear of the plane, facing rearward, with a "standard prop" on it, the leads reversed on the motor, then that should work fine in a "pusher" configuration ? Any Idea on what would be a good motor ?

Fred Huber is correct in defining tractor and pusher props as clockwise and counter-clockwise. The example of the P-38 is a perfect one. The idea was to eliminate torque and allow manueverability without counteracting torque forces. It also made takeoffs straight ahead and easier. All P-38's were not so eqipped.
As to your choice of motor everything depends on the design of the airplane. There are a lot of pusher type models available EG: Firebird types, Zagi's etc. check out these designs or look in the model magazines for the list of plans they have. You can use any size motor that will fly your airplane. The rules for running electrics are much simpler than reversing glow engines. Cox and most reed valve or sideport engines will run backwards very often when starting much to the consternation of the pilot who forgets to check before launching.

Joe, the prop has a leading edge and a trailing edge the same as a wing. The leading edge of a "Pusher" cuts into the air and if you reverse the leads on the motor with a tractor prop, all you will get is a tractor prop running backward. It will give thrust, but be inefficient because the trailing edge of the prop will be biting into the air first. Contact Radical RC.com right there in Huber Heights, and get a pusher prop. RC Hobby on Harshman by Stebbins High School also has them.[img]i/expressions/face-icon-small-smile.gif[/img]

BALLGUNNER (and all), On June 10, in discussing tractor and pusher props, you wrote:

<blockquote>Quote
<hr>Fred Huber is correct in defining tractor and pusher props as clockwise and counter-clockwise. The example of the P-38 is a perfect one. The idea was to eliminate torque and allow manueverability without counteracting torque forces. It also made takeoffs straight ahead and easier. All P-38's were not so equipped.<hr></blockquote>

This suggests another aspect of prop rotation that would interest me if and when I ever build a TWIN:

Given that "Every ACTION has an equal and opposite REACTION", and also given that conventional, single-engine aircraft props have CLOCKWISE rotation (as seen from the pilot's seat), and finally, given that the <u>equal and opposite</u> reaction is for the plane to ROTATE (roll) to the left, consider the following question:

Wouldn't it be advisable to have the props on a twin to be: a.) counter-rotating, and b.) to rotate in such a way that the upper part of the rotational disc is moving INBOARD? This would mean that in an <u>engine-out situation</u>, the (opposite) reaction to the power still developed by the starboard engine, for example, would be to to tend to RAISE the left wing panel, thus counteracting (to some degree) the tendancy of the <u>unpowered</u> side to DROP?

EXPERTS, Is this the practice in full-scale twins?

One of the standard ways to counteract the loss of thrust when one engine quits on a twin is to put right thrust on the left engine. The loss of the RH engine will apply torque where you don't want it. The loss of the LH engine will not be a drastic shift in applied torque. The obvious answer to straight and level flight is to have both engines running with equal thrust. Obviously if they rotate in opposite directions all will be well as long as they are both operating. The loss of power on one side can be catastrophic depending on altitude and direction. In full scale aircraft the immediate application of rudder is required while feathering the offending prop. In that case you can feel the difference but RC has no stick feedback to help you. When Piper first came out with the Apache we had a problem checking out new multi-engine pilots. They often feathered the wrong engine and wore out the starter brushes trying for a restart. Many an airplane came back to the field on a truck. Finally with the aid of an accumulator we had an unfeathering kit. Wish we could put it on models. All that aside it is fairly easy to set up an electric by reversing one motor and you can run both on one set of batteries guaranteeing that both will quit at the same time. For nitro engines you will have to acquire one that can be reversed.