Fixing wrist pin bushing bore in connecting rod?

[NortonDommi]

See the picture of the little end of the rod. The problem isn't sizing the bushing, it's the slot worn in the rods small end.

Hi, I think you might have misinterpreted that post. I was quoting you. With a bushed little end in a connecting rod you fit a new bush, make sure that if there is an oilway that it is correctly aliened or as with many splash lubrication pumps,(that includes I.C.E.), that a new hole is drilled and then you hone the bush to fit the gudgeon pin. Getting the little and big ends in the same plane is vital as otherwise all sorts of stresses get set up and you get accelerated wear on both bearing, the rings, the piston, in all just not good. The problem here is that the unsupported area under the bush is in exactly the place subject to the most force and that area left unsupported will distort. How long it takes is anyone's guess. Probably last a few years if a new bush was fitted and the lubrication sorted. Horses for courses. Belzona Epoxy https://www.belzona.com/en/products/purpose/metal-repair.aspx would have something for this application but the best would be ream then hone it true and round and fit an oversize bush.

 

[Downunder Bob]

Those who are worried about heat killing the epoxy filler. Many good brands, including JB Weld, and Devcon just to name two have suitable compounds that will hold up top higher temperatures than you would experience in the crankcase of compressor. The oil woulod be destroyed long before the epoxy is.

Speaking of oil how about drilling a hole 1/8" or 3mm into the top of the rod after the bush is fitted, make the hole well countersunk such that any oil splashed about can collect there and feed into the bush.

 

[hhscr]

Just an update on progress. I have found what I believe to be the cause of this severe bushing wear. The oil was like black syrup when I opened up the crankcase so that was my first thought, but after getting everything apart and cleaned up. I found that the head pressure unloader was broken and not releasing the head pressure after shutdown. So this compressor has been starting under full head pressure for a long time. I am surprised it would even startup very well, and this is probably also the reason the motor has been changed out.

I took the rod to the local machine shop and he is going to help me get it going and honed properly.

Thanks Again for all the insight.

 

[hhscr]

There is a countersunk oil hole in the top of the rod that you can't see in the photos. I should be ok once I get it back together and keep the oil changed.

 

[fixit]

FYI: when I had my shop here in Florida, I researched compressor oil. The produce I settled on was MOBIL SYNTHETIC LUBRICANT RARUS 827. I never experienced a lubrication related failure with this oil. My primary customer base was building contractors that started their compressors in the morning & only looked at them when they ran out of fuel. Some of them used my monthly maintenance program, where I PM'ed the compressors every month for a fixed price. I never saw any oil fatigue, always clean, I could have cheated & not changed the oil but I never gambled on it.

 

[NortonDommi]

I am a big fan of full synthetic oils, Amsoil being my favourite. Oil analysis is cheap compared to an oil change and can tell you a lot about a machine. Cheap in the long run.

 

[Downunder Bob]

I am a big fan of full synthetic oils, Amsoil being my favourite. Oil analysis is cheap compared to an oil change and can tell you a lot about a machine. Cheap in the long run.

Yes oil analysis is always cheap insurance certainly for an industrial situation , but for hobby machinists is it really justifiable?, just change the oil on an hours run basis, Put an hour meter in the power circuit, if it gets a lot of use, mine I just change the oil once a year. When you change the oil, drain it while still hot after a good run and have a good look at the oli look for any sediment, give it a goods tir with a small magnet. Then pour the oil while still hot through a fine filter, and see what you find.