# Drive wheel rod pin thread pitch/sizing?



## Nathan3350 (Dec 30, 2017)

The rod pin on the right side of my very first engine is stripped or something. The rods keep falling off after a few minutes of running. (LIMA NYC Mikado #8000). 

I think the threads in the wheel may be stripped, but not too sure yet. Still trying to figure out how to diagnose this, and what parts are even available anymore. 

How does one go about replacing this microscopic hardware?

Correct me if I'm wrong here, but the rod pin is supposed to stay stationary in the wheel, and lock down the eccentric crank to its clocked position on the wheel while a bushing allows rotation of the rod pin in the main rod journals as the wheel spins? I don't understand how all of this is supposed to work to know what's actually wrong yet...

Any help saving this old girl is appreciated!


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## mesenteria (Oct 29, 2015)

It looks like a screw, with threads on one end, and a cap at the other? And you can't seem to tighten the item with a driver?

Sometimes these things do back out. There's a type of Locktite that you can use, I think it's 'purple', that you can use sparingly to run over the thread and then it will keep the item from backing out. It isn't so hard that you can't back it out using the proper tools.

Otherwise, caliper the item for length and diameter, and count the number of threads per cm or inch. See if they sell them locally at a machinist place, or try a brass train importer like Division Point.


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## Nathan3350 (Dec 30, 2017)

Well it's a hex head, a super small one. I don't remember if there's a brass insert in the driver, or its plastic, but I can tighten it (to what I think is 'tight enough' for fear of stripping out the threads).

After I put it back together it's fine for a few minutes, but always backs out and the rods fall off. Since my post I've done a lot of research in case I have to get a set of drivers for it but locktite seems like it would be my best option right now. 

I'm going to check out Division Point just for laughs. I seem to be learning a lot by reading parts catalogs. Thank you for that!:thumbsup:


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