Bearing material selection

[antithesis]

This little overhaul of my benji just keeps getting more and more involved...

I plan on turning a small amount off of the outside diameter of the rear piston block (opposite the pump cup, where the linkage is) and sleeving it with....something?

I think alot of things will do better than steel on brass, but would like opinions on material selection. I am leaning toward either sintered bronze or uhmwpe. I'd like it optimally to have a long wear life, or else I would have used ptfe already and be done with it.

[rsterne]

If I understand you correctly, you are talking about the front end of the piston assembly, the part with the slot in it where the pump linkage connects?.... You want to turn down the OD and sleeve it to reduce the friction between it and the inside of the brass tube?....

First of all, I would not reduce the diameter very much, because there are a lot of compression loads on the pin where the linkage pushes on that piston.... Due to the geometry of the linkage, at the point where the forces are the greatest, when the pump handle is almost closed, the side load on the piston is reduced.... Since you need some oil on the piston seal anyways, there will always be a film of oil on the inside of the brass tube and the piston.... or should be.... Keeping it clean of grit is the primary way to reduce wear....

Something you may not be aware of, is that when you introduce dirt or grit into a bearing interface, it will become imbedded into the softer material, and the result is that the harder material wears away and/or gets grooved.... That is why dirt in a crankshaft bearing causes grooves in the much harder steel crankshaft.... At the moment, the steel piston is more likely to wear inside the lubricated brass tube.... I personally would leave well enough alone.... as a change to a softer material, such as a plastic, is more likely to cause any dirt or grit in the tube to carve grooves in the brass tube.... Ultimately, that is the part you wish to protect, as the piston seal and pumping efficiency depend on that being a smooth surface.... Longitudinal grooves in it would be the worst possible outcome, eventually requiring replacement....

Bob

[antithesis]

Yes removing enough to sleeve and not too much was a concern...but I still perhaps would like to groove the top and put some type of synthetic wicking material in place to more efficiently spread lubricant around. If I were to sleeve that would be a part of the finished product. Closed cell foam maybe? That's another whole topic.

While I agree with the logic you put forth Bob,and will likely heed, if we all left well enough alone this B&L Workshop would likely not exist😆