Good Afternoon. I've begun the process of replacing a couple of brake cylinder cups on our 50 tonner (chain-drive version as opposed to siderod). Do those of you who operate them have a reliable source for cups and brake shoes? I used to get shoes from Birmingham Rail but they're supposedly gone. I don't have the brake cylinders apart yet. Is there anything special about the cups or are they a standard size? Any help is appreciated in order to help speed up the process.

I've never used Birmingham Rail, but their web site looks like they are still there:

https://bhamrail.com/locomotive/parts/

Don't forget McHugh either, they'd done some pretty impressive stuff and worked with museums and excursion operations.

https://www.mchughlocomotive.com/

The really old ones have a leather/rubber ring bolted on the piston. Newer ones use cups. I have a pile of cups if you need them. The rings we got for Spencer's 25tonner from Multiservice Supply I believe, I can check on that.