Following Nick’s remark about dissimilar materials, I’m certainly no tribologist, but … since Steve’s engine is ‘just a demonstration project’, does life expectancy really matter?
Clearly, it shouldn’t seize during operation, and as with ‘normal’ practice, the two materials should be dissimilar or at least dissimilar in (surface) hardness.
Not that this has been suggested, but for new comers, the very worst situation in my opinion is fitting an aluminium piston into an aluminium cylinder. Once it grabs, forget it!
I’d probably be correct in assuming that the topic addressing ‘dissimilar materials’ has arisen many times before, and that those ‘in the know’ will come to my aid or … ?
However, here are a couple of ten bobs worth …
When I removed the substantially worn and scored gudgeon pin from a small 2-stroke petrol engine years ago, the replacement pin was a near perfect fit in the small end (bronze?) bearing.
In a similar vein, tests on a lawn mower spur gear made from high density, polyethylene meshing with a similar steel gear resulted in the steel gear wearing out.
Also, we used custom-made expandable brass laps for opening up holes a smidgen.
Let us know how you go Steve.
Sam
Edited By Sam Stones on 21/08/2019 03:01:23