motor/prop direction - longish post....sorry!

Jul 24, 2004 3 Replies

Is there a preferred rotation direction on common motors such as speed 400s and so on? I realise that polarity changes will reverse direction,- but brushes bed-in etc etc?? I acquired two new speed 480s with the small white gunther props - boxed as being for the multiplex twinjet, complete with suppressors - all for £5 ! ( Ebay...aint it great ) Don't know what I'm gonna fit 'em in yet, but a fiver ! ..... however I digress / ramble... Now, IC engines run counterclockwise, as viewed from the front, and props usually have markings/sizes etc on the front of the hub. The gunthers - D8330 / 302 have markings also, but the motor is not polarity marked. I believe the twinjet is a pusher style, so motors at the back. Now, with the motor turning anti-clock, any normal prop would try and pull the aircraft backwards yes? Therefore one either uses a "pusher style prop", or reverses the motor direction, - which is best? Are these gunthers pushers or pullers, and how do you know - 'cos you could fit 'em on the wrong way around without really knowing. Is the writing always on the "outer facing" side of the blade, as IC types, or is there another golden rule, or no rules at all?? Due to the shape/pitch of the gunther blades the prop has a "flat edge" if laid down on a table, and a curved opposite edge. Which is the leading edge of the prop? Some airscrews do not have such obvious shape /pitch - master airscrew for example. So to summarise...



1) which way do the motors prefer to run
2) how the heck do you know if a prop is pusher /puller
3) does the writing/marking have any relevance

The curved side of the prop is usually the front. If they are new motors you wouldn't need to change the brushes, but would probably have to retime them to get them to run clockwise efficiently. With electrics, you can mount the propellor so it faces foreward on a rear facing engine, and run the motor clockwise to get foreward thrust. I am not familiar with gunther props, so I couldn't tell you if the lettering is usually on the front or back.

Gunther prop wirting goes toward the rear of the airplane.

David

'wirting' ???? Shheeeeshhh, that looked like an TNP post. Should be 'writing' ! ! DOH.

David

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