model steam engines

Don't know whether this is the right group, but it is to do with model
engineering. I am making a small oscillating steam engine - 12 mm bore
x 16 mm stroke. This is my second. For the first one I used graphite
string to seal the piston. For my present engine I was wondering about
silicone 'o' rings. Does anyone have any opinions?
ps. I am still new to this forum and am still not sure of the
procedures. I asked previously about gear wheels and wanted to thank
contributors, but was not sure how to. Anyway thanks. The two companies
mentioned both make and supply gears, but at a price
Reply to
eddie price
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Don't worry, it is!
I'm not in steam engines (they aren't noisy enough for me), but like to read about them. What I have read, "Vitron" rings seem to be the best. Stock "silicone" (it isn't, it's NBR) seem to get temperatue problems.
HTH, Nick
Reply to
Nick Müller
Eddie My advice - go for the 'o' rings every time - the only reason we ever used graphited string was because they hadn't invented silicone! Use of the string is a very hit and miss affair, generally very subjective as to how much to try and stuff in and even more unpredictable as to how it will compact and perform with use.
I seem to recall that Tubal Cain's 'Model Engineers' Handbook' had tables showing the tolerances to be used for the various sizes of ring. I don't have a copy to hand to confirm that but I'm sure others will pipe up if I'm wrong! --
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
Reply to
Chris Edwards
Hi Nick
In the UK we have a company by the name of Chronos which lists silicone as suitable for steam. I can't find vitron. Anyone in the UK know about Vitron?
Reply to
eddie price
Try "Viton" It's a high temperature material that is sometimes suggested for sealing the likes of compression ignition engine heads and the like. Good stuff but a bit pricier than standard Oring materials.
Cheers Trevor Jones
Reply to
Trevor Jones
In message , eddie price writes
Chronos are not likely to expose themselves too far by selling something that is "not fit for purpose". But the real point is that an oscillating engine is not likely to be running on 90 p.s.i. steam that has been subjected to additional heat to dry it.
Reply to
Mike H
"eddie price" wrote
All you ever wanted to know about 'O' rings... go to
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and under: products, 'O' rings, there is a downloadable guide... if it's the same as my paper version it gives material data, standard sizes, and fits for ring groves..
hope this helps.
Reply to
Jonathan Barnes
--Welcome to the right place! :-) FWIW I'd not recommend silicone because it's too squishy and might tend to rub if lubrication is ever a problem. If you reeeally want to avoid iron rings I'd go with Delrin. It turns very easily and maintains a good seal forever.
Reply to
My experience is that "O" rings, particularly when new, are quite tight in their bores. With the relatively low pressures in oscillating cylinders and the small bore size you may find a lot of the power output disappearing in friction.
You may be able to minumise this effect by using the minimum compression of the "O" ring in the bore and a soft rubber - not the hard type common in hydraulic applications.
Dave Burrage
Reply to
hi, some people have far more experience than me on this "o" rin
business but i find this way works fine, i dont bother with the "o rings, i use Pro seal, blue xs advanced rtv silicone, you can get i from your local motorist accessories shop, its in a blue tube, it take about a day to cure and is excellent for sealing cylinder heads, valv chests, shafts ect, the way i use it to seal the shafts is to firstl put a good dolop of oil onto the shaft and run a bead of sealant righ round till they meet, the oil stops the sealant from sticking to th shaft , get a very thin rod and mix in the two ends, then let it cure this way you get the right size homemade "o" ring, gently tightenin the flange to the gland compresses the seal to the shaft with minima friction on the shaft, i put a little shamfer to each mating face ,thi aids the sealing. i have found it very good as an all round sealant fo machinery it is very strong unlike some other gasket sealants and cos about £4.50 for a fairly large tube. hope this is of help to you
-- blueswar ----------------------------------------------------------------------- blueswarf's Profile:
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