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Ruston Proctor piston rings (Wiston Kit)

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Peter Bell29/08/2018 14:58:14
264 forum posts
123 photos

As you do, just starting to look around the engine and doesnt seem to bad, well so far!

Why are the piston rings so broad?

Its got a 2" bore, the piston is 1.25" long overall but the rings are 0.236" (6mm) wide, 0.123" and very difficult to compress so I would imagine create a lot of friction?

Thanks Peter

piston.jpg

Neil Wyatt29/08/2018 16:32:11
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15681 forum posts
659 photos
73 articles

>Boggle<

Tubal Cain wrote a very long article explaining that steam piston rings only need to be very light compared to those for IC engines, backed up by tests and calculations he showed that many models with rings 'to spec' were wasting a large part of their power on ring friction, presumably with extra wear. This may have helped power the shift towards using viton and teflon rings.

Bear in mind he was an authority of diesel engine design (as Tom Walshaw) so he knew a thing or three about the subject.

Neil

MichaelR29/08/2018 19:00:19
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310 forum posts
50 photos

I think I would be inclined to use Graphite packing rather than rings of that section, packing can give a good seal over quite a long period. Mike

duncan webster29/08/2018 19:27:27
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1953 forum posts
44 photos

The article in ME by Tubal Cain had lots of imsprints, but I've got a paper copy if you need it. For one of my locos (1.5" bore) I made the rings 0.045" square section to TC's instructions and they seem to work fine

Paul Kemp29/08/2018 23:41:00
236 forum posts
9 photos

Peter,

I have one of those, rebuilt it from the bottom up, there were many issues with it, one howler was the crank has flats milled on it to locate the eccentrics, trouble is they were in the wrong place! You can find an account of the rebuild on Traction Talk if you are interested. Regarding the piston rings that is one thing I left alone and used as is. Was very tight to start with and as others say probably well OTT in terms of wall pressure but they soon ran in and it's done a lot of miles since. I have not opened it up to have a look recently but I took the front cover off after the first seasons running (2011 off the top of my head) and there was no indication of wear starting then. It's a good little engine, reasonable turn of speed without thrashing it. One common problem to look out for is the fit between liner and cylinder casting, some of the kits were dire and leaked. Only proper fix is bore out the cylinder and fit an oversize liner. Luckily this was one thing that was good on mine!

Paul.

Peter Bell30/08/2018 09:08:20
264 forum posts
123 photos

Paul,

Good to hear that yours has done a lot of miles without trouble since you sorted things out. I've heard of the liner problem before but we will see. Interesting the flats in the wrong place for the eccentrics. Not sure of ours but the valve events look ok.

lf your rings have worked we will leave that alone for now, just seemed so over the top.

Thanks for the rebuild info on Traction Talk, found and I'll digest.

Been looking at the boiler back expecting to see some cert stamps but cannot see anything, are they only visible when the cladding is removed?

Not got the Tubal Cain article Duncan but I would be interested in viewing if I could be guided me to a copy or date when it was in the ME?

Peter

duncan webster30/08/2018 10:15:07
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1953 forum posts
44 photos

the articles started in issue 3961, 21 Jan 1994. as I said I seem to remember a few misprints. There is also a summary in The Model Engineer's Handbook, pages 11.5 et seq. ISBN 1-85486-134-4 if you can get it from your library. I've no doubt the 6mm wide ones work, but the wil cause for friction than narrow ones, and not seal any better. They are not difficult to make

Peter Bell30/08/2018 17:19:23
264 forum posts
123 photos

Thanks Duncan, ordered a copy.

Howard Lewis30/08/2018 22:38:58
1798 forum posts
2 photos

Considering that full scale Diesel engines (around 75 Kw and upwards) use just three rings (two compression and oil control) about 3 -4mm wide, for cylinder pressures and speeds much higher than our model steam engines, it ought to be possible to use quite narrow rings on a model. In that way, friction losses should be minimised.

As already said, PTFE rings will reduce friction, compared to metallic rings, and temperatures are not going to be high enough to risk the PTFE degrading.

Howard

Edited By Howard Lewis on 30/08/2018 22:39:32

Clive Hartland30/08/2018 22:49:06
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2410 forum posts
40 photos

Are PTFE rings available? I have never seen them advertised. I made my 9F pistons to the Drwg. and the slots are as wide as shown above.

Edited By Clive Hartland on 30/08/2018 22:49:28

Paul Lousick30/08/2018 23:19:47
1003 forum posts
467 photos

My Ruston Proctor has a 2 3/4" bore and I have made the piston to suit two 1/4" cast iron rings but I have put them both side by side in the same groove. The theory is that if they are assembled with the opening in the rings 180 degrees apart there will be no gap for leakage. (time will tell if this works).

The bore in the steam chest was machined with an interference fit with the cylinder liner (one end with a slightly bigger diameter that the other for assembly of the liner) and heated in a BBQ oven prior to inserting the liner. It then only required a light press to assemble. No leaks when tested to twice operation pressure. The problem which I did have was that the ends of the liner were squashed when the steam chest cooled and had to be honed back to size.

The cast iron rings were turned from solid bar as a slide fit with the liner bore and cut with a thin Dremel disk. I then sprung the rings apart and inserted a piece of 5mm diameter rod in the gap and suspended the ring by the rod. The rings were then heated until they fell off the rod. This resulted in gap of about 3-4mm, easily compressed when assembled in the cylinder.

Paul

Paul Kemp02/09/2018 22:22:39
236 forum posts
9 photos

Posted by Peter Bell on 30/08/2018 09:08:20:

Paul,

Good to hear that yours has done a lot of miles without trouble since you sorted things out. I've heard of the liner problem before but we will see. Interesting the flats in the wrong place for the eccentrics. Not sure of ours but the valve events look ok.

lf your rings have worked we will leave that alone for now, just seemed so over the top.

Thanks for the rebuild info on Traction Talk, found and I'll digest.

Been looking at the boiler back expecting to see some cert stamps but cannot see anything, are they only visible when the cladding is removed?

Not got the Tubal Cain article Duncan but I would be interested in viewing if I could be guided me to a copy or date when it was in the ME?

Peter

Peter,

From memory my boiler was stamped low down on the backhead just above the foundation ring. I think it is JW 68 so not a big number! Also just done in perhaps 4mm letter / number stamps so if it's been well painted you might have to look hard! If it's all assembled the stampings will be somewhere behind the rear axle if they are in the same spot. Are your tubes welded in? Not a great idea when it comes to a retube! I had bosses welded onto mine at the clack locations and sized them so an endoscope can be put through so an internal visual inspection can be done. Winson just drilled and tapped the barrel, it's thick enough but not really good practice.

Paul.

Peter Bell03/09/2018 13:09:12
264 forum posts
123 photos

Paul,

Presume you mean under the stays? Gave it a good clean around that area but cannot see anything using a mirror and light, difficult really to get down there, hope to find it when I remove the boiler.

Yes the tubes are welded, so not so good to re tube.

The blurb from Winstons mentioned a hand pump but nothing fitted or found with the box of bits that came with it, does your have one?

Would certainly like to fit one but not sure of size or if drawings or even casting are available. Saw this very neat neat pump on another engine of a similar size. Never had any dealing with small steam engines so lots of learning!

Peter

hand pump.jpg

Paul Kemp03/09/2018 22:13:23
236 forum posts
9 photos

Peter,

I have found a picture! On the original you can zoom in and just see the JW but you can't read the number (it's actually 38 not 68 as I thought!). The number is just below the bottom row of stays, just above the foundation ring and just right of centre. I don't know if you will be able to zoom in and see it on the uploaded version.

Bare boiler

As to a hand pump......... Yes I have one fitted, it is mounted within the water space of the tender under the coal space. I have an aluminium 'box' that sits in the coal space to hold coal with a rubber sheet glued to the underside of the box forming a seal against dirt falling into the water space through the slot for the pump handle. The bypass for the crank pump is routed to the same position so I can see if I wish too that the pump is operating. The hand pump is teed into the crank pump delivery pipe downstream of the bypass valve so to use it the bypass must be closed.

Is it any good? Well that's subjective! My opinion is it is only really useful for filling the boiler from cold or for pressure testing it. I have never been in the position where either the crank pump or the injector have both let me down but from the rate of delivery of the hand pump I would say it's worse than useless for normal running and only any good as a last resort get you home emergency measure! The pump itself I would say is original Winson as like most things they did it is carved out of a solid block! It's a tee shape if I remember correct probably an inch thick slab, milled down in places, about half inch bore and probably about 3/4" stroke. I will have another look another time and see if I have any pictures of it. You don't need a casting to make one though if you want to fit one, you could follow Winsons lead and mill from a solid block or silver solder fabricate. The Winson drawings I have show it bolted to the outside of the tender behind the LH rear wheel (dreadful idea if you want the engine to look reasonable!). I am now building a 6" engine and not bothering with a hand pump at all on that!

The 'tool tray' that sits on the back of the tender is another from solid abomination! No small wonder they went bust when many parts were machined from solid generating more swarf than actual metal left in the finished item! I may have the former I made to produce flanged side plates from 2mm steel sheet lying around somewhere to make the proper prototype tool box, if I can find it you are welcome to borrow it if you want to go the same route, I won't have the press tooling I used to bend the back sheet though, that would have been left in Trinidad where I made it!

Paul.

Paul Kemp03/09/2018 22:30:38
236 forum posts
9 photos

Peter,

Found this picture of the hand pump mounted as per Winson plans. This is my engine / pump but from a previous owner before I rebuilt it and put the pump inside the tender. I think the picture is a print from Station Road Steam info according to the info at the side of the page, it came to me as hard copy print with the engine so I hope there are no copyright issues!

Hand pump

Paul.

Peter Bell04/09/2018 08:27:24
264 forum posts
123 photos

Paul,

That's brilliant, thanks! Can just about make your stampings out.

Looked at the back of mine again but no numbers as per yours, so the hunt continues, see pic. I suppose all will be revealed when we dismantle and remove the boiler to get it tested.

I have had a suitable lump of brass that would do for a pump laying around for years so could copy without needing to silver solder/fabricate. It just feels so helpless not being able to top up the cold boiler easily. Ours has complicated looking bypass valve mounted where the pump could go so expect we will need to alter the plumbing to suit.

Sounds like you've really got the bug if a 6" is on the stocks!

Peter

back boiler.jpg

Paul Gilby15/12/2018 19:06:08
5 forum posts
2 photos
Posted by Peter Bell on 04/09/2018 08:27:24:

It just feels so helpless not being able to top up the cold boiler easily.

Hi Peter,

No need for a pump when topping up from cold, just use a piece of rubber tube pushed onto the blowdown valve outlet about 2 feet long with a funnel in the other end, raise it above the boiler, open the blowdown and fill the boiler as required, not forgetting to open the blower or injector steam valve to let the air out.

I have a water container in my riding trolley with a 12 volt caravan water pump in it that is used to fill the boiler and also the tender whilst running.

Paul

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