piston rings for bronze cylinder

i am well on with my uss monitor engine and would like your opinions on the best material for rings in bronze cylinders gary

Hi Gary

I have used square section PTFE impregnated yarn packing on all my engines with very successful outcome. Unlike an 'o ring' which needs to be just the right fit to avoid friction or be just too loose the packing can be fitted to a piston with a good two thou annular gap undersize and still provide superb compression.

If an engine is to be run on steam pure PTFE can swell and grip and sometimes seize but the yarn does not appear to have quite the same result. I ran a twin Victoria on steam for many years as such without any such effect.

Personally I like it because of the relaxation of tolerances on piston and liner and in the piston groove itself plus the fact that its virtually friction free which makes for a good slow speed on low pressure. Its ability to fit any slight discrepancy in concentricity is a bonus as well.

Unless I was making something that was going to work hard on steam - and all engines made so far now just run air - I wouldn't use anything else because of these reasons.

There is some very nice looking pure PTFE braided square yarn - it's not a suitable alternative as it frays easily and does not compress very well. Bought some for the last build but quickly reverted to the impregnated yarn

Hopes that 's of use to you

Tug

What do you intend to do with the engine? run for display only or make it work, on steam or air?

I've gone over to Viton O rings for both IC and steam although the later only get run on air for display, with the right sized groove I get minimal stiction and a good seal

Infact if you just want it to run slowly on air for display or even steam you could get away with no rings, thousands of Stuart 10 V & H engines can't be wrong.

Another vote for Viton.

Hi Ramon,

Your piston ring looks great. Where do you obtain that ptfe impregnated yarn? My search has only come up with what I think is the braided ptfe.

Ron

Re, Viton O-Rings,

I have a vague recollection of reading somewhere. That Viton after being exposed to steam can have an adverse effect on Human Skin. I think it was something to do with "burns", and not those caused from handling hot objects.

If anyone knows more about this issue then I for one would like to know more about it. As I have fitted Viton O-rings to my Steam Wagon.

Regards

Gray,

I think that when Viton is burnt it gives of f hydrofloric acid that will eat flesh but the heat it will be subject to from steam or IC engines is well below that.

Thanks for that bit of info,

Regards

Gray,

Thanks for your post Ron. I was about to suggest ebay or Blackgates but decided to put it in Google and found this. It may be more than you need but for it's length its definitely, I'd go so far as to say extremely, good value over other suppliers - Just ordered some for myself

If you do go ahead - just make the groove a couple of thou wider than the yarn and a couple of thou shallower, no need for precise dimension, as the material will fill and bed in to give a very friction free but superb seal.

Tug

I notice the link above does not work so here's another go

**LINK**

If that's not working either the company name was 'Bearingboys'

If it's more than you want I'm happy to share mine when it arrives - but not by the inch

Tug

thanks ramon and jason, i intend running it on air to start with but might run it on steam much later, no idea about boilers,feed pumps and lubricators yet. that yarn you use looks a good option ramon and not costly. thanks again gary

Thank you Ramon.

Gary, Ron,

PM received Ron

The total cost of the yarn came to £18.73 including postage and vat. At 8 metres long that works out at £2.34 a mtr. As I certainly don't need that amount I'd be quite happy to share that with you pro-rata plus a small amount for postage if you wish.

Tug

Edited By Ramon Wilson on 18/01/2021 17:42:32

Thanks, Ramon. I would like to take up your offer.

Ron

just my bad luck ramon i ordered a full length this afternoon. gary

It's quite safe - this explains everything

HSE - Fluoroelastomers in Motor Vehicles

OK guys - Once it arrives I'll sort something out and come back on this thread.

Tug

Thank you for taking time out to get the facts, my memory does not serve me well these days and having some hard data means I can file this away for future reference.

Regards

Gray,

Hi Guys -

I now have the packing and have to say it's the 'bees knees'. It's certainly the best I have seen since first using it.

So, Ron, Phil and DR G it works out just shy of £6 for two metres including postage for each of us. I'll PM my address to you to get things moving.

For anyone else who may be interested in using this I can thoroughly recommend purchasing from the source above - it is an excellent product and far less in cost than the usual sources

Tug

Edited By Ramon Wilson on 22/01/2021 09:41:56