Stuart Beam – Cast Iron Piston Rings

[James Hall 3Participant @jameshall3]

I’ve been working on a Stuart Beam kit which I bought second hand a year or so ago. The kit is 1984 vintage and came with two diddy little cast iron piston rings.

Everything is machined and fits together gratifyingly well except the final task of machining the grooves for the rings in the piston. Spent all morning making a nice little cutter to do the job – works fine trying it out on a ‘dummy’ piston made from a spare piece of gunmetal and in went the ring a treat – then disaster: snapped the ring while attempting to spring it out of the groove again.

Now an easy answer would be just to go for an O-ring but I’d like to stick to the original spec., have invested time in the cutter and (of course) it’s now a matter of pride.

Also wondering about inserting the piston into the bore – if I were working on a full-size job I’d be using ring compressors – ain’t got any that small!

I know that ci rings are delicate beasts and was being extremely careful – so at this point would certainly appreciate any advice on going about fitting such rings.

Thanks

James

 

[bernard towersParticipant @bernardtowers37738]

If you make some more make them thinner section they are then much more pliable.

[JasonBModerator @jasonb]

If you are only going to run it unloaded for display then  don’t bother fitting any rings, you will get smoother low speed running

Add a small chamfer to the top of the cylinder to help them in. You can also take a bit of brass shim and wrap it around some 1″ bar, bend the two ends away from the bar and leave about 1/4″ long. You can then use a pair of pliers on the two ends to close them up and compress the rings. Another way some people do it is to turn a tapered hole in some scrap bar end which acts like a funnel and compresses the rings as the piston is slid down into the cylinder.

[Brian Baker 2Participant @brianbaker2]

Hi James, I have even used a cable tie as a ring compressor when I lost the proper one.

Regards

Brian B

[James Hall 3Participant @jameshall3]

Many thanks for the helpful replies. I’m sorry to be so long responding but thought I’d do so when I’d seen how things panned out.
I bought two replacement 1 x 1/16″ rings from Reeves which were much better than the original ones from Stuart – ‘shallower’ and much more flexible so far easier to spring over the piston without risk of breakage and prodoced much less friction against the cylinder walls while still giving a good seal.

I did chamfer the cylinder ends slightly and found that I could get the rings into the cylinder by pushing the piston hard down when friction against any protruding ring allowed me to ease the rigs in with a fingernal and aided by the chamfer.

Jason B: I take the point about not fitting rings, and the piston fit was good enough to run without them, but pride (as I said) dictated that I would at least attempt to get the engine completed ‘as spec’: in the event it actually ran very smoothly and evenly on air at 10 psi at less than 100 rpm – so I’m very gratified – and would expect to do better when run in a little as it’s still a little stiff. I’m actually surprised at how powerful and ‘torquey’ it is.

First steaming tonight as it seems more sensible to run in under hot conditions and I intend to steam it rather than air-drive. Then dismantle and the rather tedious business of painting, etc.

[duncan webster 1Participant @duncanwebster1]

When I had to rebuild IC engines the drill was to slide the piston down till it was resting on the ring, wrap a cord round the ring like a garotte, one end in each hand. Pull the string to compress the ring then get your glamorous assistant to push the piston down. For oil scraper rings you needed a strip of kit e kat tin wrapped to stop the cord going into the groove and getting trapped.

[Howard LewisParticipant @howardlewis46836]

A length of tinplate, compressed by a jubilee clip often worked to compress rings for vehicle engines.

My professional (Sykes Pickavant) ring compressor is only a del luxe version of that!

Howard

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