View Full Version : Normal Crankshaft fit on Con Rod
Aviation addict
07-05-2006, 08:50 AM
Guys,
The how much play is acceptable between the Crankshaft and the Con Rod (OS50 Hyper). The Con Rod obviously has a brass bush in it and there must be some gap for the lubrication but what's normal?
Sorry, I don't know the answer, but I posted a similar question yesterday about freeplay/slop in the crankshaft on an OS 37 and so far have not had one response. I guess no one on this forum knows anything about crankshaft movement. I don't know if this will help you but I have considerable in and out play in my crankshaft on the 37 and I only have a couple gallons of fuel through it. Good Luck!
Not many people measure this - no real need to
New parts can be as tight as 0.05mm clearance
Well worn parts can be 0.1mm clearance and appear to work ok
RC-Bearings
07-05-2006, 01:08 PM
Sorry, I don't know the answer, but I posted a similar question yesterday about freeplay/slop in the crankshaft on an OS 37 and so far have not had one response. I guess no one on this forum knows anything about crankshaft movement. I don't know if this will help you but I have considerable in and out play in my crankshaft on the 37 and I only have a couple gallons of fuel through it. Good Luck!
Bob,
Didn't you also ask the same question on RunRyder? You got the answer there. If the crank is moving in and out, your fan probably isn't installed tight against the front bearing.
Regarding the rod, the clearances can vary depending on the model. Generally, if you can feel much slop, it is worn out. If you have a GOOD set of inner calipers, measure the diameter parallel and perpendicular to the rod. Any difference means it is time to replace it.
Yes, RC, I did ask the same question on RunRyder. The responses over there were almost immediate. However, I was looking for a second opinion, or, for that matter, as many opinions as I could get. Like I said, no one had an answer here. In fact, there's only been one response since the post was written, and that response was very much appreciated.
Aviation addict
07-07-2006, 08:16 AM
Thanks chaps. I tried the Con Rod (only on month old) on a brand new Crankshaft and the play was minimal. There was slight scoring on the outer edge of the old Crankshaft pinion bit. It is hard to measure these things though as said.