Re: Rubber "slip" hub in Lightwin prop ?
I have two props for my '56 Lightwin (one's a spare); the ribbed rubber hub in one is a little worn and rotted a bit and the other is in fairly good shape, tight fit. Is there a method to tightening the prop nut so it will slip if it hits something. I hit a rock last fall with the worn out one and the shear pin broke. The newer looking one has such a tight fit I can't see how it would slip before breaking the pin if the sloppy one didn't even spin. When I put the prop nut on I go hand tight then wrench to the next hole, is this correct ?Any comments or information on this subject ? -Thanks
The prop nut has nothing to do with it except to hold the whole thing on the shaft. Snug it down and install the cotter pin.
Now, you need to understand the function of the rubber ring. Notice that it is splined into the propeller and the aluminum hub and rubber ring have rounded ribs/grooves. When you strike a solid obstruction, the soft rubber is supposed to squish enough to hop over one or more of the rounded ribs, then resume driving. For lesser impacts, the rubber simply absorbs the shock.
So.o.o., the secret is the hardness / softness of the rubber ring. Most that you see are old and hard, swollen up, rotted out, etc, etc. If they are not as new, they won't function as intended.
Next item is the shear pin. It is not a "shear" pin, it is a "drive" pin, made of 1/8" diameter x 7/8" long stainless steel. It is supposed to be hard enough to not shear before the rubber ring hops over a rib. If you use anything else, it probably will shear.
Having said all that, it is advisable to carry extra drive pins anyway. They can and do break. Space here doesn't allow me to tell my moose hunter story.
