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Post by GWRdriver on Mar 21, 2008 21:15:32 GMT
Gentlemen, I'm about ready to make the pistons for my 2X TICH and have a new (to me) situation to deal with and I would like to hear opinions as to how best to proceed. The pistons will be cast iron, 1.625" OD and .500" thick. The rings are Clupet style, .125"" wide x .075" thick, two rings per piston. My question then is what method to use for providing ring grooves and seats.
My first inclination is to split (halve) the pistons in some way, or provide for a retaining ring, and make a T-ring to provide the ring grooves and a separator between the rings. This assumes that a separator is needed. Also what should the working clearances (side and under) for these rings be? Would someone with experience fitting Clupet rings care to offer advice?
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ewal
Part of the e-furniture
Happiness is a good wife & a steam engine.
Posts: 293
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Post by ewal on Mar 21, 2008 22:14:03 GMT
Hello Harry, the way I do it is both rings in a single groove, 3 thou gap in the rings, one gap at the top & the other at the bottom, the rings need to be free but not sloppy. I use car or motor byke rings & bore the cylinders to suit.
E.W.
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Post by chris vine on Mar 22, 2008 12:48:35 GMT
Hi Harry,
I used Clupet rings on the piston valves of my loco, so there were two separate grooves.
I was advised (and found it true) that you can very gently wring them onto the piston without breaking.
To help, I turned up a little dolly with a tapered end to get them up onto the piston. In addition, the dolly could just cover the empty groove so that the ring could pass over it without dropping in.
Good Luck!! Chris.
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Post by GWRdriver on Mar 22, 2008 18:31:32 GMT
Hi Chris, I just now measured my rings and in their un-compressed state they are about .050" oversize, which suggests they will be easier (less potentially fatal) to spring over the piston than I thought. This then brings another question to mind which is that when compressed they will have considerably more wall pressure than I'd think a steam cylinder should have. I have to trust though that the lads at Clupet know what they are doing.
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Post by chris vine on Mar 22, 2008 21:22:41 GMT
Hi again Harry,
I remember Tubal Cain writing about not having too much wall pressure for steam engines because they don't need it and it just causes friction.
I am sure he was right, however I am also sure that what you have will work just fine!!
It sounds like they should spring ok but I think the trouble to make a tapered sleeve to open them up is worth the few minutes it will take....
Chris.
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Post by GWRdriver on Mar 23, 2008 13:03:28 GMT
Chris, The sleeve is a good idea. I have broken rings before, . . . in my exhuberant (and mis-spent) youth. One thing about the Clupets is their favorable "aspect ratio", . . . width to thickness. Many model rings seem to be as thick as they are wide, or more so, and invite breakage.
On the other end of the stick, it appears that because my rings are surprsiingly oversize in their relaxed state I'll probably save time in the long run if I cobble up a small ring compressor to get them in the bores.
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simonwass
Part of the e-furniture
Cecil Pagets 2-6-2 of 1908. Engine number 2299. Would make a fascinating model....
Posts: 472
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Post by simonwass on Mar 23, 2008 20:34:27 GMT
I'm sure a ring wall should be 1/20th of the bore.
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Post by Tel on Mar 23, 2008 21:08:35 GMT
On the other end of the stick, it appears that because my rings are surprsiingly oversize in their relaxed state I'll probably save time in the long run if I cobble up a small ring compressor to get them in the bores. No need to do that Harry - just use a screw type hose clamp - what we call Utilux clamps over here, you know, the ones with the screw that engages in slots in the clamp strip
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Post by chris vine on Mar 23, 2008 21:42:17 GMT
Hi Tel and Harry,
I think for the moments to make up a taper sleeve to compress the rings, it is probably worth it. I wonder if when tightening a hose clip, it might be rather insensitive (there is usually a lot of friction in them) and you might not notice something hanging up until there is that nasty click sound. Too late.
Harry you mentioned side clearance. Most people say make it as neat as possible. I think you can be too tight, probably a thou is about right BUT: one thing seems important, make sure the sharp corners at the outside of the grooves are very well chamfered. This is so that if there is any wear on the piston itself, caused by rubbing (especially if tight when new) in the bores, the edge of the groove will not get 'wiped' over the edge of the ring. This will then neatly peen the ring in place and stop it working.
How do I know about this? because it happened to me on Bongo. The piston valves were too close a fit and when hot expanded and caused the metal to wipe just enough to hold the rings in. If you look at a commercial piston from a car etc. the edge of the groove is very well chamfered.
Mind you, as always with steam engines, it still worked fine!
Chris.
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Post by GWRdriver on Mar 23, 2008 22:28:26 GMT
Tel, As Chris mentions, the clamp alone might be a little rough on the rings, partly because as often as not they aren't round, but a hose clamp is what I had in mind. The typical automoive ring compressor over here is a sheet of thin steel shim stock rolled and bound with a hose clamp-like strap and so shall mine be.
Chris, the clearance suggestions seem to vary between barely and .003" (elsewhere.) I plan to aim for .001", and I'll mind the chamfer
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Post by Tel on Mar 24, 2008 7:48:55 GMT
Point taken blokes, however, in my 'useful box' I have a number of these things in stainless steel that have been used almost exclusively for this job for many years - I can 'ring' anything from sub 1" to over 3" with 'em and if the need for a bigger one arises a couple of the larger ones can by linked together. Due to prolonged usage over the years, most run as smooth as silk.
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Post by chris vine on Mar 24, 2008 11:36:12 GMT
Hi Tel, An ounce of Practice is worth a ton of theory!!
C
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