Well, the P is infinite until something wears enough to provide a finite bearing area, so the V doesn't matter.
One solution to that is a special bushing between the pin and the slot. The special part is that the bore for the pin is round, but the outside of the bushing is square or rectangular, so that you start out with finite bearing area on both the rotating and sliding surfaces.
Your ME textbooks should have noted that Scotch Yokes are still a pretty crappy mechanism, because of the impact that accompanies every direction change of the yoke.
You're probably thinking it's too late to throw out your pet mechanism and start over, perhaps with something mechanically simpler and otherwise electronic. When the project is over, if it's ever over, you'll look back and think otherwise.
I suspect from another question that the OP is puzzling through the design of the Bourke engine. When real engine designers decide they need to keep the piston square in the bore they use a crosshead design, not a scotch yoke.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
