GL5 Forum

I am thinking of replacing the Yarn piston packing on my loco.

O ring seems to be a popular option provided they are fitted correctly. However this will mean new pistons. Not a major problem I know.

I have read about Teflon as a piston ring and usualy with an O ring underneath to allow for the expeansion and provide it with support. I could see this method being a direct replacement for the 1/4inch yarn?

Any thoughts would be appreciated.

This is a particularly good read ...
http://www.saunalahti.fi/~animato/3003/index060.html

Keith

Just run my loco this afternoon passenger hauling. Looks like the PFTE piston rings are ok and therefore will be used at next weeks GL5 rally.

What did I do? I simply removed the 1/4inch yarn and replaced it with three O rings sitting in the bottom of the groove. Then made a pair of 1/8th rings to sit on top of these. Machined them 5 thou over size for the bore. Then cut 30 thou gap in the ring. Fitted the gaps opposite each other and did the same for the other piston. They didn't need a lot of persuading to fit into the cylinder and the piston had a nice glide to it. Certainly wasn't rubbing on the cylinder.

No more blocked up drain cocks as the yarn deteriorates - happy chapy.