Fitting a Prop

[Anthony Billings]

Hi all,

on reading a post where a member had a prop explode on him, a number of people asked if the spinner was in contact with the prop, and this got me thinking that I have not seen anything on the correct way to fit a prop or the correct order the component parts are assembled. As I am a newb, I thought I had better check before I have an accident.

so here we have my component parts, the motor with mounting plate fitted, a threaded prop shaft with it's mounting bolts, a beveled spacer, the prop and spinner.

a closer view, the spacer is showing the beveled side, the other side is flat, the prop is showing the scalloped side, the other is flat.

the flat side of the spacer and prop.

So I presume the spacer goes on the shaft first but flat side to the motor or prop ? then the prop, flat side to motor, scalloped side forward ? then the spinner.

Or have I got this all wrong ? all answers greatfully received.

Tony

[PatMc]

If i was using that prop shaft I'd put the prop on first, discard the bevelled washer use a plain one then the nut.

But my preference would be to dump that prop shaft & push the motor shaft right through then use a collet type prop holder.

[John Privett]

Anthony, the item you call a spinner would normally be described as a domed prop nut, and can't be the cause of a problem as mentioned in the other thread.

A spinner is usually similar to this;

and problems can arise if the blades of the prop come into contact with the body of the spinner - it is often necessary to increase the size of the cutouts to ensure adequate clearance for the prop blades. This will not be an issue with your prop nut. Otherwise follow Pat's advice!

[Anthony Billings]

Ah I see, so prop, plain washer then domed prop nut, got it.

I do have the option of pushing the original motor shaft through as a correct size collet was also supplied, but I do like the look when assembled with the domed prop nut.

Thanks for making things clear.

Tony

[Braddock, VC]

Use the washer with the bevel facing away from the prop, ie with the flat against the prop.

The thickness of the washer is intended to prevent deformation in the event of overtightening of the nut thus applying equal pressure over the whole of the flat side.

Plain washers have been known to deform unless they are as least as thick as the unbevelled part of the bevelled washer if that makes sense.

With regard to the prop, each blade has an airfoil section and the back of the blade (ie faces toward the rear of the plane) is the flatter face of the blade. This is true if the plane has either a normal or pusher prop.

Edited By John Gibbs on 29/02/2012 08:20:42

[Anthony Billings]

Cheers for that John,

so it's prop with flat side to rear, scalloped side forward, beveled spacer flat to prop then domed prop nut.

Cheers all

Tony

[John Tee]

Should be prop driver, prop with size marking to the front, washer (chamfer to front) and then the nut

John

[PatMc]

Posted by John Gibbs on 29/02/2012 08:18:51:

Plain washers have been known to deform unless they are as least as thick as the unbevelled part of the bevelled washer if that makes sense.

If you tighten with enough force to deform a plain washer your overtightening to the point that the prop hub is likely to be damaged, even if the washer's thick enough not to distort.