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cast iron piston rings

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Sam Longley 108/01/2018 20:14:54
623 forum posts
22 photos

I see that a Hydraulics supplier very near me has 1 inch cast iron rings at £ 9-75 for 4 No.

Are hydraulics rings any good for the rings in a model steam engine or are they a totally different sort of section?

If so what sort of section ring should I expect to use in my 1 inch piston

Thanks

duncan webster08/01/2018 20:29:55
avatar
1409 forum posts
20 photos

TDWalhaw (the UK Tubal Cain) did an excellent series on rings in ME way back. Unfortunately I seem to remember it was full of misprints. The answer to your question is as small section as you can make. I made mine for 1.5" bore cylinder at 0.045" square and didn't break any. The ones sold by the model trade are generally too wide, just causes increased friction. I tried to interest a friend with a surface grinder in taking some down from 1/8 tp 1/16, but he reckoned it woud be a major job as they woudln't by gripped by the magnetic chuck.

Rings sold for petrol engines have too much preload, but they do work, again too much friction

Neil Lickfold09/01/2018 02:19:05
362 forum posts
45 photos

If you want to surface grind piston rings on normal surface grinders with general use mag chucks , it is best to make and inner and outer ring. The outer ring wants to be a good fit to the piston ring, and the inner can have upto 0.05mm clearance. It will make a magentic loop and keep all the parts together as you grind them down. Once you get thinner than 2mm there is not that much holding it in place. But can be done with care. I have also seen where ring were faced using 2 sets of clamps. One clamped from the centre and you could turn from the outside to the centre clamp. Then an outer clamp is used and a boring bar to turn from the inside to the outer clamp. You could also make a special collet and an inner crush washer to support the inside of the ring , with the outer holding the outside of the ring. Then just very carefully turn it back to thickness. You could make the depth of the collet the finished thickness, so when you just touch the marker pen, it is size. Marker pen is about 1 thou in thickness.

Neil

Doug Bauld09/01/2018 03:29:33
avatar
9 forum posts
25 photos

Sam this may help,

www.metalshop.com/technical/wal-ring.

www.jerry-howell.com/Menu-4.html.

also an article just on that in the latest The Home Shop Machinist Jan / Feb 2018. Vol 37. No1 page 20. By Ted Hansen an Englishman I believe and a very good article.

Cheers and Good Luck in your search.

Doug in Canada.

CorRad09/01/2018 07:08:22
17 forum posts

Why do you want to buy piston rings? They are really easy to make. I too, were very reluctant to make them until I made the first batch. I was hugely surprized by how easy it really is. There are many descriptions accompanying model engine plans, articles in magazines and in forums on how to make them. I suggest, take the bull by the horns - you will be well rewarded.

Samsaranda09/01/2018 10:00:06
avatar
324 forum posts
4 photos

Hi Sam, I saw the same advert and purchased four of said rings for a small internal combustion engine that I am making with a 1” bore. The rings are quite solid with stepped ends were they meet, if using for steam they may be a little too rigid due to the cross sectional area, obviously if used for hydraulic purpose that would explain the stiffness and the stepped ends for sealing, possibly bearing against a flexible seal ring. I was pleased with my purchase, I am sure that with very little reworking they will suit my needs, they will save me some time which always seems to be in short supply, especially the older we get.

Dave W

not done it yet09/01/2018 10:41:26
1655 forum posts
11 photos

Don’t know whether this is relevant but I have seen that, rather than parting off with a blade, very narrow rings to close tolerance are better cut with a toolpost grinder with a suitable cutting disc.

Dougie Swan09/01/2018 17:01:40
173 forum posts
40 photos

Whats the name of the supplier?

dougie

Tim Stevens09/01/2018 17:45:46
avatar
799 forum posts

Of course, everyone knows that the piston rings we use today were invented by the Chief Engineer of (I think) the LNER* - a chap called Ramsbottom. He was also the originator of the water-trough between the rails so the loco could refill without stopping. I've never seen such a device on a model track (but perhaps I need to look harder).

So, the correct full name for all metal slotted piston rings is 'Ramsbottom's Metallic Packing'. File this away under 'stuff to impress the neighbours'.

Cheers, Tim

* of course, it was before the 20 century reorganisation, so Great Northern, was it?

Edited By Tim Stevens on 09/01/2018 17:46:54

duncan webster09/01/2018 18:45:38
avatar
1409 forum posts
20 photos

London North Western actually

Samsaranda09/01/2018 19:12:42
avatar
324 forum posts
4 photos

Dougie, I cant remember who the supplier was but found him on EBay.

Dave W

Sam Longley 109/01/2018 19:30:00
623 forum posts
22 photos
Posted by Dougie Swan on 09/01/2018 17:01:40:

Whats the name of the supplier?

dougie

 

Danbury Hydraulics

Danbury Essex

Edited By Sam Longley 1 on 09/01/2018 19:36:35

Ian S C10/01/2018 10:12:41
avatar
6698 forum posts
219 photos

The last set of two rings I made for a steam engine were for a Stuart Turner S9, the cast iron I used was from an old brake disc, after the rings were cracked open, I wedged them open at 1/4" and heat treated them, on this engine the two rings fit side by side in the one groove.

Ian S C

Windy10/01/2018 10:58:45
avatar
649 forum posts
178 photos

In my experiments with the flash steamer have tried steel rings with a little success but found just using cast iron was best.

My rings are Dykes L section the part contacting the cylinder is 0.0625" the depth 0.050" the L section 0.025" it revs to 15,000rpm when not under load.

It lasts about 120 100metre laps before I normally replace it.

You can leave as is with no spring as gas pressure pushes it against the cylinder but I always do put some spring into them.

Howard Lewis12/01/2018 16:16:24
1114 forum posts

Pressure backed rings are good to reduce friction, as they do not press on the cylinder wall on the "non working stroke". The effect will be most noticeable with higher pressures, obviously, as seen in Internal Combustion engines.

Possibly, not likely to happen in a double acting engine

Narrow rings are less prone to flutter at the higher speeds that we are unlikely to see in model engines, unless rotating at very high speeds. So maybe less effective in model steam engines, unless extremely narrow, and thin sections.

Howard

herbert punter12/01/2018 21:05:52
72 forum posts

There is a chap on eBay with the username Gaviscool, his eBay shop is called G C Piston Rings.

AFIK He is able supply you with whatever rings you need.

Bert

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