Posted by: Mike Clark
Both ball and roller types must cause a bending action on the piston rod but obviously not enough to matter. I suppose the roller type is better at discouraging the wristpin from rocking laterally and this is important if like most of us you are using self-aligning bearings in the big ends - although again the ball type seems to work on my own 20hp engine.
I used ball not roller for originality because I am running a dry engine (with, as you see, an added drip feed). Some (with "wet" engines) now use a rounded section bronze slider which runs in the same grooves but I was doubtful of being able to oil it enough. The roller type has an advantage because you can put a small oil hole in the top groove of the crosshead which lets oil dribble onto the wristpin which is genreally the worst oiled bit of the whole engine. You can't do this with the ball type as the ball bounces over the hole - hence my drip feed.
I am going to try to put a picture in here which should show as a thumbnail on which you click to see it bigger. If this fails I'll put a link to the picture.
Oh well that's what I had to do!!
Edited 1 times. Last edit at 01/14/05 04:20PM by Mike Clark.