I need to put a ring on it.

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marinesteam
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I need to put a ring on it.

Post by marinesteam » Fri Apr 27, 2018 2:09 am

Actually, I need two rings. It's the time in the project were I need to start gathering thoughts on rings. The prints for the York are overall pretty good, but are sorely lacking on information on the rings.

The groove depth is given as .250 but my research so far seems to point to that being too deep (to thick radially) for an appropriate wall pressure for a steam engine. My calculations also bear that out with the ring wall pressure being up there with IC engines.

I am contemplating making rings myself and would like to go with Clupet style rings. The ones available from LiveSteamModels in the UK for the sizes I need are .1875 radial thickness backing up my though that .250 is too thick for rings of this size. They don't have one listed for 5.25 bore but the .1875 radial thickness of their 5-5/8 ring seems to be more appropriate for the calculated wall pressure I am targeting (8psi). The 3" ring at .1875 calculates out to be quite a bit higher than targeted but I can thin this ring out to .100-.125 radial thickness to get it more in line.

I am wondering if any of our UK members have Clupet rings and would share the relaxed (pre-installation) diameters of any sizes that they may have in hand. I'm looking to get a gut check on the calculations that I am doing before committing to using material.

Thanks

Ken
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Re: I need to put a ring on it.

Post by fredrosse » Fri Apr 27, 2018 3:19 am

In the past when using IC engine rings I have made a piece of pipe, with the bore 0.001-0.002 larger than the steam cylinder bore, then placed the IC engine rings into this piece of pipe. The pipe with rings is then placed into the furnace for a few hours, then allowed to cool slowly. This relaxes the spring-ring feature almost entirely.

However when steam pressure gets behind these rings, the steam will tend to add to the ring/cylinder bearing pressure, unless ring expansion due to steam pressure is somehow checked/limited.
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Re: I need to put a ring on it.

Post by Lionel Connell » Fri Apr 27, 2018 3:42 am

The pipe with rings is then placed into the furnace for a few hours, then allowed to cool slowly. This relaxes the spring-ring feature almost entirely.
What temperature do you have in your furnace?

I would think that another option for IC rings may be to machine the internal diameter larger to reduce the radial thickness of the ring.

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Re: I need to put a ring on it.

Post by Mike Rometer » Fri Apr 27, 2018 8:22 am

There seems to be some belief going round the steam world that Clupet rings are something special. They were principally designed to run in a worn bore, so why oh why would anyone consider fitting them in a new bore? They are designed to open and close as the piston travels the length of the ever changing WORN bore diameter.

If you fit a standard style ring correctly, i.e. with the correct end gap there is no need of anything 'extra'. For the correct ring gap in a steam engine, think compressor, 0.001" per 1" of diameter. that allows for the amount of heat and the running in. The gap in service is so small that whatever is used for lubrication will easily seal it (water, oil) for the short moment when it is under pressure.

Fitting Clupet rings in a new bore is just a waste of money!

If you still insist on going that route, what is wrong with two rings in the same groove, set with opposing they will be easily the equal of a Clupet?

Making your own rings is very easy and extremely satisfying. I've done it several times. There are plenty of Youtubes showing how.
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Re: I need to put a ring on it.

Post by fredrosse » Sat Apr 28, 2018 3:53 pm

"What temperature do you have in your furnace?"
Low red heat, typical in a coal furnace, but not blasting bright red heat. In the engineering sense, the objective is to very slowly heat and slowly cool the assembly. Thin stainless steel foil is often used to slow down the heating process, and isolate the iron parts from oxidation. I used to do that before I ran out of stainless steel foil, and discovered how expensive it would be to buy new foil!

"I would think that another option for IC rings may be to machine the internal diameter larger to reduce the radial thickness of the ring."
I guess that might work satisfactorily, however the machining of rings can lead to non-uniform ring pressure around the circumference. I have never tried to work out the mathematics on that method, so I just don't know.
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Re: I need to put a ring on it.

Post by marinesteam » Sat Apr 28, 2018 5:52 pm

I am planning on making my own rings so the cost of materials is mostly the same (due to difference in waste) between standard rings and Clupet rings. From the historic data I can glean, I think the worn bore thing is mostly a marketing ploy since Clew & Co were selling aftermarket. The original patent application puts it as follows:

The invention has for its chief object to
provide a double-coil gapped ring made in
one piece whose coils are of uniform cross
section throughout. Piston rings con
structed in accordance with this invention
expand uniformly and, therefore, do not
wear the cylinder oval or unevenly.

They are also intended to be more gas tight than gapped rings.

Whether any of this really matters is up for debate but from an engineering and manufacturing standpoint I am intrigued by the spiral style rings and would like to give making some a go.

I'm not so much interested in "how to make rings" as there is much information out there already. However, I'm trying to reconcile the available information on sizing rings that I have. I'm coming to the conclusion that the sizing based on model practice and doesn't transfer to full size practice well.
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Re: I need to put a ring on it.

Post by Mike Rometer » Sat Apr 28, 2018 8:01 pm

marinesteam wrote:
The invention has for its chief object to
provide a double-coil gapped ring made in
one piece whose coils are of uniform cross
section throughout. Piston rings con
structed in accordance with this invention
expand uniformly and, therefore, do not
wear the cylinder oval or unevenly.

They are also intended to be more gas tight than gapped rings.
They have been around for a very long time indeed, but never caught on in the motor trade to my knowledge. I've certainly never heard of them being fitted in new engines, and in 60 years connected with the trade I've not seen anyone bother with them more than a handful of times. They were considered a 'dodge' to get around having to rebore an engine block. It is not the ring that wears a bore oval (really more of an egg shape) but the thrust of the piston . There is also a considerable difference in cylinder pressure between steam and I.C.

Wishing to make them as a exercise in engineering is one thing, spending your 'hard earned' on them something entirely different. 'Difference' is something that you will not notice between the performance of the two types in a good bore.

An important part of any ring sealing is not just its fit in the bore but its fit in the piston groove. 0.0005 - 0.001". that will also be all but perfectly sealed by the lubricant. Too big a groove clearance and they can actually pump the lubricant past the piston.
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Re: I need to put a ring on it.

Post by cyberbadger » Sun Apr 29, 2018 2:37 am

For reference...
1902 Toledo Rings, two per piston, different types.
ringsy.jpg
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-CB
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Re: I need to put a ring on it.

Post by marinesteam » Wed Aug 01, 2018 1:08 pm

As it turns out I decided to source rings instead of making them. It really came down to the cost of material and risk of the unknown. The chunk of cast iron would have cost more than I paid for the rings. Then I would have still needed to spend the time making them and probably would have scrapped a few along the way. I purchased from Allegheny York and apart from the order taking awhile because they didn't have the 3" rings in stock, I am extremely pleased with their service.
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