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Post by vulcanbomber on Nov 24, 2014 22:25:11 GMT
Stainless in general is very good at "picking up". Its one I find very difficult to explain actually but from the motion of a piston rubbing up and down will scratch the surface and the hole effect escalates very quickly into little lumps. Cast Iron if I were you. I fully know this, but I am using PTFE in the rings, not metal. Also cast iron can oxidize no? PTFE rings wont save you. Iron will oxidise if you dont look after it. My 9F will have Fabricated Steel Cylinders for sure but there will be Cast Iron Liners in there for the piston and the valve.
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Post by joanlluch on Nov 24, 2014 22:32:00 GMT
The perfect material for cylinder liners is cast iron Since there is no apparent compelling reason other than tradition, I will use AISI 303 stainless just as every major pneumatic and hydraulic cylinder manufacturer traditionally does.
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Post by Deleted on Nov 24, 2014 22:39:02 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here.....It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _
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Post by vulcanbomber on Nov 24, 2014 22:49:17 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here.....It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _ Would that be Alfred?
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Post by joanlluch on Nov 24, 2014 23:02:02 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here.....It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _ Hi Alan. That's definitely the kind of thing that should be done. I do not have right now the means to do so yet but I will eventually do something on that direction at some time. I am referring to AISI 303 not 304 or 316.
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Post by RGR 60130 on Nov 24, 2014 23:04:38 GMT
Traditionally the liner / piston / piston ring materials are such that they will go through the whole running in / bedding in process and ultimately produce surfaces that are extremely smooth and promote a gas tight seal. Stainless steel would work harden during such a running in process and surfaces resembling ploughed fields would result. If you want to use stainless steel for a cylinder you need to impart a mirror like finish during the machining phase (as the hydraulic and pneumatic cylinder manufacturers do). Contact from a metal piston would need to be fully avoided by soft rings of PTFE or whatever else.
Reg
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Post by Deleted on Nov 24, 2014 23:21:45 GMT
Just a thought but putting aside all the good valid reasons put forward in this thread for not using SS would a stainless steel cylinder not be less efficient too. Would you not get more problems with condensation as SS is not a good conductor of heat. Another thing to consider, stainless steel and the steam locomotive appeared around the same time, certainly stainless steel was here in the early 1900's so why has it not been used before? I'm all for new ideas but when we are talking about a material that was well known during the steam era's hey day then there must be a good sound reason for not using this particular material.
Pete
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Post by gwr14xx on Nov 25, 2014 8:22:42 GMT
Surely, if we are going to consider changing the material for the cylinders, then we also have to make other alterations that are compatible with that change. Normal practice seems to be that we should aim for cast iron rings in cast iron cylinders, but some manufacturers (Winsons, etc.) opted for a cheaper solution by fitting 'O' rings to the pistons. Now, in my infinite wisdom??, a couple of years ago I bought a Winson 1400 that had stood idle for several years - to cut a long story short, it had suffered rusting in the bores and had a very healthy appetite for the piston 'O' rings. After much messing about, I decided to bore the cylinders and fit thin wall stainless liners and continue using the 'O' rings on the pistons. This engine is now utterly reliable and is an absolute 'flyer' - stainless steel liners have transformed it! With regard to aluminium cylinders - back in the 60's, Cross Engineering produced a conversion for Villiers motor cycle engines that used a plain aluminium bore, but instead of rings on the piston, it had some sort of stainless steel wire wound around it - that engine also flew and was easily a match for the 'square barrels' being produced by Greeves, etc.
Eddie.
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pault
Elder Statesman
Posts: 1,496
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Post by pault on Nov 25, 2014 8:39:43 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here..... It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _ Nigel Gresley, William Stanier, George Churchward, Oliver Bulleid??
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Post by Deleted on Nov 25, 2014 16:16:21 GMT
nope !!
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Post by Deleted on Nov 25, 2014 16:19:07 GMT
Remember we're supposed to be Mechanical Engineers...Accuracy is our watchword....but you're ALMOST there...
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Post by Deleted on Nov 25, 2014 16:20:12 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here.....It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _ Would that be Alfred? -----------------sorry, nowhere near I'm afraid
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Post by Ruston92 on Nov 25, 2014 17:08:29 GMT
When I worked at the metal spinning company we had loads of problems with pick up on stainless parts from the Hardened steel rollers.
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Post by joanlluch on Nov 25, 2014 18:07:56 GMT
I decided to bore the cylinders and fit thin wall stainless liners and continue using the 'O' rings on the pistons. This engine is now utterly reliable and is an absolute 'flyer' - stainless steel liners have transformed it! Excellent! Thanks for posting this. That's consistent with what I expected. The key thing for using stainless is to avoid metal to metal friction, but as long as the counter surface is rubber or plastic (PTFE) then the results may outperform traditional cast iron. If you want even more reliable operation use AISI 303 grade, as I suppose it should have (will investigate this) a much lower tendency to grip the piston even if metallic surface goes into contact.
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Post by ettingtonliam on Nov 25, 2014 18:22:47 GMT
Call me old-fashioned if you like but here's an idea}--- Take some time off from computer modelling and build a small test rig consisting of a motorised crankshaft powering a piston ( of interchangeable materials) running in a stainless cylinder.....Put this through varying speed, load, oiled, dry, hot, cold, stopped/re-start cycles over say a week....Tabulate the results and publish on here.....It's the sort of thing the likes of Herbert, Bill, George, Oliver etc. would have done to see for themselves............(A small prize if any of you can identify all those names !! _ Herbert is puzzling me. Yes, William Stanier, yes, Oliver Bulleid, could be George Whale, but knowing you it will have to be Churchward.
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Post by Deleted on Nov 25, 2014 18:27:03 GMT
Here's your "Herbert" >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> en.wikipedia.org/wiki/Nigel_Gresley ------------------ and yes, it was George Jackson Churchward that I had in mind ( Hadn't thought about George Whale in quite the same terms.... will do from now on !!)...........
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pault
Elder Statesman
Posts: 1,496
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Post by pault on Nov 25, 2014 18:37:46 GMT
Assuming Bill is the problem that would leave William Pickersgill or William P. Reid
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Post by Deleted on Nov 25, 2014 18:48:15 GMT
For that "Small Prize".... I've arranged for Roger to send you a nice selection of microns to help with shimming etc !!.............'Ows-zatt??
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Post by Roger on Nov 25, 2014 18:54:29 GMT
Stainless in general is very good at "picking up". Its one I find very difficult to explain actually but from the motion of a piston rubbing up and down will scratch the surface and the hole effect escalates very quickly into little lumps. Cast Iron if I were you. I fully know this, but I am using PTFE in the rings, not metal. Also cast iron can oxidize no? I doubt if it's possible to avoid some metal to metal contact with some parts of the cylinder itself, the cylinder covers, piston rods and glands. Anything that might potentially come into moving contact needs to be of a suitable combination. Personally, I don't think Cast Iron is the 'perfect' material for cylinders because it rusts. That's not an issue for working machines, but it is for those that are used only occasionally. It's a superb bearing material, and if it wasn't for that one issue, it would be almost perfect. Personally, I've chosen SAE660 because it is a good bearing material and won't corrode. It tends to be more expensive if you're casting it but in bar form it's not that expensive. I can't see any benefits in using Stainless Steel over SAE660
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Post by andyhigham on Nov 25, 2014 19:10:45 GMT
Some ceramic materials would make excellent liners but machining with our machines is virtually out.
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