Bayou Talker

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OK...I admit I am an idiot but I have done this for a while now.

I am building an Ultimate Bipe and powering it with a Saito 72. I am using an aluminum spinner and an APC prop and I cannot get the prop nut to tighten without the engine turning. The spinner backplate slides on the engine washer and the crankshaft turns instead of the nut getting tighter. I realize that I can remove the engine and lock the crank through the back of the engine, but this seems to be a lot of trouble especially at the field. I have never had problems with this in the past on several planes I have owned, but this one is trying my patience.

Anyone have any suggestions?

Villa

It is hard for me to follow without seeing your set up. With one hand you should be holding the prop to prevent it turning. The spinners that I have used (never an aluminum one, though) have a tab on the backplate that contacts the prop so that the spinner does not turn as you tighten the nut. I think that is how it works. The prop washer you mention, is that the hardened steel washer? It should go on the front of the prop, the side opposite the engine. Hope some of this helps.

Campy

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Make sure you have the grooved side of the backplate facing the thrust washer on the engine. The grooves will keep the backplate of the spinner from turning.

If you have a backplate that does not have any grooves (perfectly smooth ), take a piece of 150 - 220 grit sandpaper and cut a disk out to fit between the the thrust washer on the engine and the backplate of the spinner. Put the grit side towards the spinner, then do as Villa said and it should tighten right up. After the prop nut it tight put your spinner adapter on and make sure that is tight against the prop nut.

You will not be using both nuts with an aluminum spinner. Do not use the lock nut, use the spinner adapter as the lock nut.

Bayou Talker

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Thanks guys.

Villa I mis-typed my self, the "washer" is the thrust washer that Campy is talking about. He put his finger right on the problem, my backplate does not have any grooves on it and does slide on the thrust washer. Campy, your idea sounds like it might just be the ticket, I'll try it tonight.

Stick Jammer

Just so no one is confused, this would be the engine hub, not the thrust washer. The thrust washer is a very thin washer that goes behind the hub.

Bayou Talker

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To be totally accurate, Saito calls it "Taper Collet&Drive Flange" on the parts list on the Saito site