[CS223]

I had to fabricate two replacement hydraulic cylinders for my Mohawk car lift as the replacements are not available from the mfr. The bores on the old cylinders sat with water in them and were pitted beyond any hope of repair. The other parts except for the seals were fine. I replicated the original cylinders exactly in terms of material & dimensions. I sourced 3" ID honed bore hydraulic tube, it's 1/4" wall and 3-1/2" OD. It is NOT chrome lined. I fabricated the trunnions from steel tube sourced from the same supplier, I think it's 1018 but I'd have to check. I also sourced the caps from the same supplier and added the correct port which serves to bleed the air. The caps had a bevel machined on them and I replicated it on the cylinder end when I machined them in the lathe. These cylinders are operated by an electric hydraulic pump which I think is rated at 1800 PSI. They are fed through a hydraulic fuze through the ram bore of the piston. It's a little unconventional, the piston is stationary and the cylinder is the component that moves.

I have a Miller 211 MIG welder 75/25 gas, I also have an ESAB 160 TIG but I'm not comfortable enough with it to lay down a heavy weld.

I'm looking for any suggestions, tips, pitfalls, caveats etc. in welding these together. Cleaning & fixturing goes without saying. I have a manual turntable but I'm thinking that maybe laying the tube horizontal on rollers for welding the cap may be a better way to go. I'm concerned about overheating the tube at the trunnions and causing distortion. The piston would be at its travel limit in that area. I'm also worried about weld porosity at the cap and potential leaks. Hope the pics work, all input is appreciated.

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[BugHunter]

The Piston should be riding on O-rings so I doubt you could cause enough Distortion for that to be a problem. Now if you were to overheat it to the point of changing the surface finish that they put in there, that could be a different story. Typically though, once the inside of a cylinder is honed the Caps are screwed on either with threads on the barrel or using for bolts running the length of the cylinder. But if that cap was commercially available and was intended to be welded on the ends of the tube then it stands to reason it should work without any problem. I would be trying to fill the tube with gas so the inside didn't oxidize when you weld.