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Dopey question from a leccy beginner

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Adrian Smith 126/10/2016 17:02:09
2317 forum posts
1102 photos

while I don't have problem tightening up a prop on an I/C engine, I can' t see how to do it successfully on an electric motor as the barrel of the motor turns as well. What am I to do as I am missing something?

Biggles' Elder Brother - Moderator26/10/2016 17:18:36
15748 forum posts
1460 photos

Is the prop a little lose on the shaft Adrian? That might cause a prolem.

TBH I usually find that if I do it it up finger tight (holding the shaft) then subsequently pinching it up tight with a spanner whilst holdng on blade of the prop isn't a problem.


Cliff 195926/10/2016 17:45:10
359 forum posts
72 photos

I thought this was going to be a question on Doping tissue, now I'm showing my age lol.

Chris Bott - Moderator26/10/2016 17:57:16
6707 forum posts
1392 photos
1 articles
Adrian in this sort of situation I have sometimes got away with roughening the face of the motors prop driver and the rear of the prop to make just enough friction. In one case I ended up glueing a disk of sandpaper to the back of the prop.
Adrian Smith 126/10/2016 18:20:58
2317 forum posts
1102 photos

Well the spinner, despite using a spanner to tighten the prop driver nut, still turns slightly. The idea of installing a disc of sand paper might just work. I have used a dab of threadlock on the prop nut but I am not convinced all will be well. I will give it a try.

Martin Harris26/10/2016 18:40:47
9070 forum posts
224 photos

Is there sufficient thread to prevent the nut "bottoming"?

Adrian Smith 126/10/2016 18:44:48
2317 forum posts
1102 photos

Yes Martin there is plenty of thread so I don't think that is the problem.

Dave Hopkin26/10/2016 19:19:34
3672 forum posts
294 photos

I am assuming the culprit is the compression adaptor and that the motor is buried inside a cowl?

You can try holding the prop and applying a slight twisting pressure so the prop barrel grips the shaft giving enough purchase to tighten the nut sufficiently tight for the adaptor to grip the shaft

Failing than a dowel can be used to jam/wedge the motor can while you tighten the prop nut

Mike Blandford26/10/2016 19:23:31
573 forum posts
22 photos

I frequently use a hacksaw to cut a slot into the front of the threaded part of the prop adapter. This allows me to use a screwdriver in the slot to prevent the prop adapter rotating while I tighten the prop nut.


Adrian Smith 126/10/2016 19:23:50
2317 forum posts
1102 photos

Yes you got it Dave. Motor tucked in the cowl as you say. I think I will keep in mind the dowl trick in case all else fails.

Dave Hopkin26/10/2016 19:43:30
3672 forum posts
294 photos

Mikes slot cutting method is also a good one that I have resorted to in the past, though I use the dremmel to cut the slot

Adrian Smith 126/10/2016 19:59:31
2317 forum posts
1102 photos

Yes Mike's method is a good one. I have a Dremel too.

Allan Bennett26/10/2016 20:05:50
1594 forum posts
44 photos

I've resorted to gripping the protruding threaded end of the shaft in a pair of long-nose pliers in the past, just enough to get the nut tightened down enough that the collet grips the shaft. Then holding the prop while applying the final torque.

But Mike's slot idea sounds even better, for my method sometimes slightly damages the threads on the shaft, resulting in similar problems when trying to get the nut off!

Denis Watkins26/10/2016 21:44:01
4046 forum posts
75 photos

You are certainly not dopey Adrian, a dope would not ask a good question for assistance

Edited By Denis Watkins on 26/10/2016 21:45:22

Adrian Smith 126/10/2016 22:05:53
2317 forum posts
1102 photos

Thanks Denis. It is just that being used to hefty petrol aircraft safety is a major consideration. Even with a comparatively small electric I just thought I needed be sure I was doing right - out of control props is my big phobia.

Adrian Smith 127/10/2016 11:53:00
2317 forum posts
1102 photos

Well I think I have solved it with out any sort of prop shaft modifications.

p1040154.jpgI managed to get some pliers on the the prop driver scallops (shown above) through the cowl top to hold the shaft still to allow me to tighten the nut to my satisfaction. Seems to have done the trick. Thanks for all the advice gents.

Edited By Adrian Smith 1 on 27/10/2016 11:53:20

PatMc27/10/2016 16:45:29
4288 forum posts
524 photos

May not be applicable for Adrian but I file a couple of flats on the prop driver to take a spanner (Actualy as the driver is ali I use a sanding disc) as per attached photos.
For a close fitting spinner I use a thin, cheap stamped metal spanner.

Flat on collet

spanner job

Shaunie27/10/2016 23:36:42
943 forum posts
78 photos

Just a reminder that of course the prop driver needs to be properly tight before flight. I saw a twin go in on takeoff when it spat the adaptor off the motor shaft, a spin ensued before the pilot identified the problem. A couple of months ago I was doing touch and goes with my foam-e Wot4, I powered up and it spat the prop adaptor of the motor while it was on the ground and rolled to a stop. I'll often run the motor with no adaptor on it and touch the spindle with a bit of wet and dry to take the shine off.


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