Piston Ring Question

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SCBryan
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Piston Ring Question

Post by SCBryan » Thu Jan 07, 2021 11:21 am

On the Kozo Heisler, he calls for graphited asbestos yarn for packing for use as a piston ring. Later projects call for graphited ceramic fiber yarn. These are both for 3/4" scale engines. My question is for a 1-1/2" scale engine, is this the recommended material? Also, if it is the best, where is a good source to obtain it?

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Benjamin Maggi
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Re: Piston Ring Question

Post by Benjamin Maggi » Thu Jan 07, 2021 11:34 am

I bought some from the local Ace Hardware store. It is use for packing plumbing fixtures.
See this link: https://www.acehardware.com/departments ... ng/4200366

Amazon probably has it too.

That being said, I cannot comment on whether it is the right choice for your project.
"One cannot learn to swim without getting his feet wet." - Benjamin Maggi
- Building: 7.25" gauge "Sweet Pea" named "Catherine"

k36no4862002
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Re: Piston Ring Question

Post by k36no4862002 » Fri Jan 08, 2021 2:59 pm

If the cylinders are cast iron then I would.go with proper piston rings.
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1.6" Scale CHallenger 4-6-6-4 (still ongoing)

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kenrinc
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Re: Piston Ring Question

Post by kenrinc » Sat Jan 09, 2021 2:35 am

For 1.5" scale your typically looking at a true piston rings of some sort. You don't mention material. My cylinders are cast iron. I have a 1.5" scale Kozo A3. I had originally bought some rings via a vendor on this site but I was without a lot of knowledge at that point and after I installed them I found that the piston damn near wouldn't move in the bore. Now I realize there is some wear that needs to take place but this was way beyond being able to actually physically push the piston through the bore so I ended up just making my own rings out of cast iron using the excellent instructions from David Moore. I was quite proud of the that fact that I completed them and they worked quite well, for about a year. I always felt like they were leaking. After one particular trip on a local track with some big grades I was sure it had something to do with the rings. The engine just couldn't get out of its own way, so on a tip from Don Yungling, I built new pistons and moved over to glass filled Teflon rings. That was an epiphany. After that, Ill never go back to true piston rings. There is no comparison. My engine became a completely new engine after that. $.02

Ken-

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Dick_Morris
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Re: Piston Ring Question

Post by Dick_Morris » Sat Jan 09, 2021 3:53 am

glass filled Teflon rings
Does that take a two piece piston?

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Bill Shields
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Re: Piston Ring Question

Post by Bill Shields » Sat Jan 09, 2021 7:15 am

I have successfully used graphite yarn.. would never use ceramic yarn as I feel it can be abrasive and damage the bote....ok maybe on a valve stem

I have used cast iron rings in 3/4, 1 and 1.5" engines for decades. I will let you know (or your grand kids) when any of them fail or leak.

Agreed that the PTFE will work well if on a brass cylinder..but in cast iron bore you cannot beat a properly designed and built cast iron ring.
Too many things going on to bother listing them.

bill4227
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Re: Piston Ring Question

Post by bill4227 » Sat Jan 09, 2021 11:41 am

I use cast iron rings from here OTTO GAS ENGINE WORKS 2167 Blue Ball Rd Elkton Maryland 21921-3330 http://www.ringspacers.com/rangcast.htm

Bill

Johnny O
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Re: Piston Ring Question

Post by Johnny O » Sat Jan 09, 2021 12:43 pm

I went with the graphite/teflon rings with an O-ring backer in built up pistons on my A3 in 1.5” scale. Ran well on air, no steam yet. I cant find the pic or info I had on them. I sourced them from McMaster/Car though.

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kenrinc
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Re: Piston Ring Question

Post by kenrinc » Sat Jan 09, 2021 1:34 pm

It's just a single ring. Glass filed Teflon backed up with an o-ring. I use a modified cylinder head with a 1 degree angle cut in it to slip them into the bore.

Ken-
Attachments
A3_rings_1.jpeg
A3_rings_2.jpeg

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pat1027
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Re: Piston Ring Question

Post by pat1027 » Sat Jan 09, 2021 4:51 pm

In the Manual of Model Steam Locomotive Construction, Martin Evans briefly discussed the fit for iron piston rings and mentions using "one or more grooves" packed with graphite yarn. There are enough references to graphited yarns for it to be viable but I would say iron piston rings and polymer seals are the preferred methods.

You've seen my Dad's Pacific at Pepper's. He used overlapping iron rings for both the main piston and piston valves. The rings came from hydraulic cylinder rebuild kits. The cylinder bores are ductile iron and the valve chambers bronze. They have been in service since 1992.

SCBryan
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Re: Piston Ring Question

Post by SCBryan » Sun Jan 10, 2021 3:00 pm

Thanks for the replies. The bores are brass (or bronze) and the piston is stainless steel. (I took over the project from someone else who started it.) There are no ring grooves in the pistons as of yet. I will need to add them to fit whatever I use. So with this setup, would the recommendation be to use a PTFE O-ring with backup rings?

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Bill Shields
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Re: Piston Ring Question

Post by Bill Shields » Sun Jan 10, 2021 4:16 pm

Cast iron rings would not be my first choice with brass or bronze cylinders but they will work well...is just a question of cylinder life @ high ring velocity.

If you have confidence in PTFE rings then go that direction. Nothing to lose

Question is.. why did the first set of rings fail?
Too many things going on to bother listing them.

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