Converting the Webley Senior from a piston ring to a leather seal?

[dvd]

Not sure how relevant the very different set up in a diesel engine is?

But refer back to the opening post and the link there - my MKI with leather washer is reasonably powerful and certainly trumps my Senior with piston ring that doesn't seal...

The relevance is that both Webly and diesels use rings to achieve the same task, ie building up pressure rapidly. One caveat for metal rings in both instances is that the bore must be perfectly round and not scored to achieve a perfect seal.
Leather/synthetic seals are more forgiving in this respect as they adapt and swell to fill any imperfections in the cylinder.

[ggggr]

Before machining a piston down to take a leather seal, I would be tempted to drill and tap the end and fit a ptfe one from a Premier to see if that improves things. You would lose a little off the stroke but if the Bronze ring is that bad then the slightly shorter stroke shold not make much difference if the Premier seal works.
If the Premeir seal works, you can then either leave it in place or go for the leather washer. If there was no improvement you could still go for the leather seal (I do like leather seals) but I'd be thinking that maybe it was the cylinder that was out of plonk.

[felix gunner]

Before machining a piston down to take a leather seal, I would be tempted to drill and tap the end and fit a ptfe one from a Premier to see if that improves things. You would lose a little off the stroke but if the Bronze ring is that bad then the slightly shorter stroke shold not make much difference if the Premier seal works.
If the Premeir seal works, you can then either leave it in place or go for the leather washer. If there was no improvement you could still go for the leather seal (I do like leather seals) but I'd be thinking that maybe it was the cylinder that was out of plonk.

I don't know Guy, TBH I'm looking for reliable fit and forget and my experience with good old leather is it works.

There is also a part of me that is horrified about introducing a 'plastic' part into my lovely old Senior.

[coburn]

Years ago in the AGW there was an article on using an O ring as replacement in the Senior, I tried it once with little success, I still have the nos Senior piston ring I bought in an Edinburgh gunshop in the early 80's, but never fitted lying around somewhere!

[bcham]

some one converted a senior to a c02 pistol.
https://forum.vintageairgunsgallery....l-john-walker/

[wild boar]

engines usually use 2 or more rings so that the gap is overlaped so i guess to be perfect you could make a couple of thinner rings on a lathe - it would be intresting to see if it makes much difference but it should seal very well

[ChasP]

I recently replaced the spring and breech seal in my Senior and it has increased the power but not dramatically. After reading the OP I measured the hole in the new rubber breech seal to be 3.5mm
With a 4.5mm barrel I would have thought this is a restriction but don't know enough about fluid dynamics - tempting to drill it out to 4.5mm but I'll do a bit of googling on transfer ports and breech seals!
I know what you mean about introducing plastic into a Senior - it doesn't seem right even using a rubber breech seal. I would be tempted to leave well alone and just get something else if you need more power. Any gains you get will be so minimal anyway. It is frustrating that the piston ring doesn't seal a bit better though - but I wonder if the stepped design seals much better under power - ie at slow speeds it isn't compressed against itself or the groove it rides in.

[felix gunner]

The relevance is that both Webly and diesels use rings to achieve the same task, ie building up pressure rapidly. One caveat for metal rings in both instances is that the bore must be perfectly round and not scored to achieve a perfect seal.
Leather/synthetic seals are more forgiving in this respect as they adapt and swell to fill any imperfections in the cylinder.

Hmmm, I think this is being dragged off topic but maybe the use of a ring (single in the Senior) that happens to be split is as much of a similarity as it gets. The ft is much tighter in an engine, oil is a critical part and there are usually three of them.