I have a OS 120 four stroke w a APC prop +Great plane spinner and my problem is the prop and the spinner slip all the time on the crankshaft and I want to know if I a put some drops of the CA glue if that method will fix my problem because if I tight a little more the nut the crank will brake.
Thanks

Well you are about twenty times over my perferred engine size but here is what I have seen in the slippin' prop department:

1. The shaft is not threaded far enough to allow the prop nut to tighten down on the prop. Or, the threads are bad at some point on the shaft. Solution - use a thicker prop washer or a thicker prop.

2. One, or more, of the players is too smooth; either the prop, washer, or thrust washer. Solution - Either change them or put a surface on that will grip. I had a problem with some fiberglass composite props slipping and solved it by making some sandpaper "washers" that I CA'ed to the prop back.

3. The prop is compressing. Usually only a problem with soft wooden props and not likely with an APC. Solution - Chg the prop.

4. The prop nut is sloppy fit on the shaft because or worn, mis-matched, or buggered threads. Solution - Change the nut and hope the problem is with the nut and not the shaft.


CA might work and you can probably use nitro or debonder to remove it. I would also consider the 'wicking' LocTite (maybe it is #239 ?)if I was going that route.

Hi!
Usually it is not the prop slipping on the backplate ....it's the backplate slipping on the drive washer. That is at least my experience using Tru Turn spinners.
To remedy this I have made a thin washer of 0.4mm plywood, the same diameter as the propdriver, put between the backplate and the drive washer.

Regards!
Jan K
Sweden