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Old 10-09-2004, 03:18 PM   #1
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Bent crank?

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Just rebuilt my YS .45 after low-level crash and the crank is not spinning like I would expect in the brand new bearings.

I'm pretty sure the bearings are installed OK, and they spin well on their own, without the crank in place.

Is there an idiot-proof way to positively tell if the crank is bent?


P.S. I don't have a micrometer or transmutation device.

Man this engine stuff is bringing me down.
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Old 10-09-2004, 03:25 PM   #2
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take the crank out. Put it down on a smooth, flat piece of something, a piece of glass is ideal.... if the crank is bent even a few thousandths your eye will see the wobble.

next best thing is a very smooth flat piece of metal....
Andrew Coholic -MAAC #26287L

1/2A to giant scale, IMAC, SAM, R/C sport, turbine jets, Heli's...
if its got a wing or two and an engine - I like it!
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Old 10-09-2004, 09:54 PM   #3
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If you just installed the bearings and they seem a bit snug do the following. With a prop on and tightened with the prop nut, hold it by the prop with one hand and tap the end of the crank with a hammer. Just a light sharp tap will do. This will seat the bearings in the housing. I do it all the time on assembly. What you are doing is basically setting the preload and then you are away.
If you think it is bent follow Andrews directions but I check with the engine still in the aircraft by having the prop shaft minus spinner near a solid object. Take the plug out and turn it over easy and see if there is a differance in the gap. Usually it is the nose spindle part that bends and It is easier to see. I just repaired an mvvs q500 for the same problem.
John Davidson
Keep the shiny side up and the wheels down
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