Piston rings

Today I took out the pistons of my B1. there as been a bit of steam bypass when running. Looking at the drawings the measurements of the cylinder and the piston are ok. But there is only one piston ring and not two as per the drawing. This piston ring is of the rubber o ring type. So my question is. Is one piston ring enough or should I machine a second the piston to take a second ring. And the second question is a rubber o ring ok, or would a cast iron ring abet a single one be better. If a iron ring is better. What size should I machine to. And what cap size in the ring and how wide should it be. Thanks.

Assuming you cylinder is bronze and not cast iron then a single o ring should be ok. Just select the correct material for the o ring, not standard epdm. Surface finish should be honed to a fine smooth finish. Only a single o ring should be fitted in order for the ring to be adequately lubricated in both directions of travel.

If the cylinder is cast iron then iron rings should be fitted, the reason being surface finish and rusting will cause early failure of a rubber ring. Yes rubber seals are used in brake cylinders etc of cast iron but they are in the presence of lubricants only. A very good YouTube video has just been put up by MrCrispin on cylinder rings, well worth a watch. I am sure some will have a lot to say on the subject, but that is my take.

Thanks. Good information.