Edwin

My Feedback: (2)

OS .48 FS Got it used and it is relatively clean and not much use, did a bearing change which went well. But after assembly test, discovered some binding that I've isolated to the conrod. With the piston not in the cylinder there is naturally no binding. With the piston/ring only (no conrod) in the cylinder, I can push it back and forth with just the ring drag. I wonder if the bearing problem I thought I had in the beginning was actually a bad conrod? OR is it as simple as conrod position on the wrist pin (which I dont really believe)? Opinions?
Edwin

oskartek

Edwin,
           Many connecting rods are not symmetrical and have a front and back.
Try marking one side of the rod and installing it then reversing the rod and try again.

I always mark the rod when disassembling the engine so that I reinstall it as it came out.


Happy flying, Oscar

Edwin

My Feedback: (2)

I did that when I took it apart. It went back in the same way it came out. The piston on the other hand may have gone in the opposite direction. Tried both ways. Didnt make a difference.
Edwin

oskartek

Tried the piston both ways?
Are you sure the liner is in correctly?
Check to see if the exhaust port is lined up correctly.
With the backplateoffcan you see the rod touching anything while turning the crank?
Not trying to be condescending.

Happy flying, Oscar

Motorboy

Oscar, the engine OS FS 48 is a 4 stroke engine..

Check the crankshaft is at right place, no play between rear ball bearing and crank shaft. The con rod has camfered big end bronze bearing, this the part must be placet against the crankshaft size.
Be sure the wrist pin is moving free in the con rod and piston.
Check the con rod is moving free in both way (in direction between crankshaft and back cover)

earlwb

My first thought is that the rear bearing isn't seated all the way in. But has the crankshaft protruding towards the rear a little bit.
If you have to, take the rod out and lay it on a piece of glass, to ensure that the two ends are level and the rod is not bent.

Edwin

My Feedback: (2)

Figured it out. The conrod is bent. Measured both sides and got 25.79mm and 25.87mm. When looking at it, you can JUST BARELY see something doesnt look quite right with it. My guess is someone hit it with a starter while hydro locked. Ordered conrod and wrist pin this morning. Oh well, sometimes you win, sometimes you lose. I bought two of these used from an estate sale to run in a H9 B-25. It'll be good with a new conrod.
Edwin

w8ye

My Feedback: (16)

The OS 52 Surpass conrod is the same as the OS 48.

oskartek

My mistake, Not familiar with OS nomenclature

Happy flying, Oscar

Bax

My Feedback: (11)

If the connecting rod will move smoothly when it's only attached to the crankshaft, and the piston/rod assembly will move smoothly in the cylinder liner when the piston/rod assembly is not attached to the crankshaft, but you get a "hard-to-turn" spot when you put it all together, you have a bent connecting rod. If you replace the rod, you'll find things will work nicely.

Edwin

My Feedback: (2)

Hi Bax,
Figured that out this morning. Part ordered.

This is actually the first bent conrod I've delt with in all the engines I've worked on. Had to show up eventually.
Edwin