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Preferred thrust washer play on Cox reedie?

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Preferred thrust washer play on Cox reedie?

Old 02-07-2008, 04:15 PM
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lildiesel
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Default Preferred thrust washer play on Cox reedie?

I've just measured the play between the thrust washer and the front of the crankcase bushing on a NIB Babe Bee with a brass feeler as a tight 0.010 and a loose 0.008. What is your preferred tolerance when you reassemble a crankcase, shaft, and thrust washer?

I'm sitting here with an HD crankshaft that I just put in a low running time RC Golden Bee crankcase and wondering if I should draw the thrust washer down to a 0.010 just tight enough that the drag of pulling the feeler will turn the prop a little bit? I've got about a three and a half hour break coming up for cooking dinner and napping through the News Hour before I resume assembly.

You've got that long to tell me everything I'm about to do wrong.
Old 02-07-2008, 07:44 PM
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Default RE: Preferred thrust washer play on Cox reedie?

That sounds about right. There's no point in having it any tighter since the prop pulls the crank forward while running. Now if it was a pusher setup I'd want to add a .005 brass shim washer to that for a 3 to 4 thou clearance so the crank isn't pushing back too far.

You want to leave it with at least that much gap even for a pusher since the case will expand more than the crankshaft. Aluminium has a higher coefficient of temperature expansion than steel. If it doesn't have enough clearance then it can end up binding. 4 thou of clearance will likely reduce down to 1 or 2 thou when hot.
Old 02-07-2008, 08:05 PM
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Default RE: Preferred thrust washer play on Cox reedie?

Thanks for the reply. In years past I've always done this kind of thing using my best guess based on what information I can find for myself. It's really nice to have some reliable feed back just a post away.

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