mfb
Member
Posts: 2
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Post by mfb on Feb 11, 2009 20:44:41 GMT
hi,
I am confused can anyone tell me which is the best material to use for the 5"Simplex cylinder and piston regarding machinability and wear? Gunmetal seems to be very expensive compared with cast iron. One would think that gunmetal must offer some advantages, if so, what are they?
Regards,
Mal
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Post by alanstepney on Feb 12, 2009 5:01:52 GMT
There isnt really a "best".
Either of them will outlast the life of the builder, (although may need some refurbishment after many hundreds of miles running).
Both can be machined quite easily, (as long as they are cast without hard spots etc).
Both will do the job for which they are intended.
You may then ask, why have two materials to choose from?
GM takes finer details when cast, which can be an advantage on some castings.
But, mainly it is personal preference.
I like to use GM for smaller cylinders, and CI for the larger ones, and I suspect many other people do too.
But, what is large? Again, personal choice.
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Post by drjohn on Feb 12, 2009 8:22:13 GMT
Hi Mal The only comment I will make is that if you use gunmetal for the cylinder, you will more than likely be using a different material (stainless or whatever) for the pistons, and of course "soft" piston rings and a differential expansion effect. At least with cast iron, I certainly use cast iron pistons with cast iron rings and it works for me. As Alan rightly says, though - there is no "best" as such. Good luck with your Simplex - great little engine - just finished my second one  DJ |
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Post by chameleonrob on Feb 12, 2009 9:43:51 GMT
my choice would be cast iron in that size, the cut off being your ability to buy or make the cast iron piston rings, the smaller they are the harder they are to make. as I understand it gun metal and soft packing (or ptfe) is a little more tolerant of machining errors.
rob
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Post by ron on Feb 12, 2009 10:28:15 GMT
Mal
I opted for CI as well, gunmetal is far too expensive for no great advantage I can see, if you are looking for a UK supplier the ones Blackgates sell are excellent, the CI machines like butter, only thing is you need to be a bit patient with their promised delivery dates!
Ron
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mfb
Member
Posts: 2
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Post by mfb on Feb 12, 2009 19:05:41 GMT
Thanks guys very helpful I shall go for cast iron.I will let you know
how I get on.
Regards
Mal
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Post by ducatibob on May 10, 2009 19:25:54 GMT
Mal, I have just finished a Simplex and it is a fine little model. In fact mine has done 45 hours running to date. My cyclinders are cast iron as are the pistons and rings. The downside to using cast iron is you have to lubricate them well after a run otherwise they are liable to sieze with the dreaded rust. I drilled and tapped the side of each vave chest and fitted with a removable plug to oil after running. This works fine... Bob
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Post by Shawki Shlemon on May 11, 2009 9:27:10 GMT
I built a few engines of both metals , the only difference to me is what Bob says about lubricating . I believe the cast iron may be better as they keep the heat better than GM although I use more GM because of the rust problem.
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nigelh
Involved Member
North Cyprus
Posts: 89
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Post by nigelh on Nov 25, 2009 17:56:33 GMT
Been reading on another forum about the use of PTFE strip, (1/16 x 1/4) instead of cast iron rings, in a cast iron cylinder.
Has anyone here tried it and, if so, how good did it perform ?
Sounds almost too good to be true!
Nigel
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nigelh
Involved Member
North Cyprus
Posts: 89
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Post by nigelh on Feb 15, 2010 16:01:39 GMT
Hi foks,
I'm making reasonable progress with my Simplex and have now finished the pistons and rings (all in cast iron) but haven't yet split and heat treated the rings - (the scary time ??)
I am unsure about how much one should wedge open the rings, prior to heat treatment, after splitting them. Have read various articles on it they seem to vary in this particular!
Could some kind person give me the benefit of their experience on this, please?
Thanks very much for any/all comments,
Nigel
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Post by peterseager on Feb 15, 2010 21:25:34 GMT
My Simplex has cast iron cylinders. I always run it on air with the drain cocks open before putting it away. I find it flushes out a worthwhile quantity of water. A previous owner has fitted a small screw in a tapped hole in the the middle of the front cylinder cover - very useful for injecting WD40 or whatever you choose.
Peter
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Post by drjohn on Feb 15, 2010 23:12:33 GMT
Hi foks, I'm making reasonable progress with my Simplex and have now finished the pistons and rings (all in cast iron) but haven't yet split and heat treated the rings - (the scary time ??) I am unsure about how much one should wedge open the rings, prior to heat treatment, after splitting them. Have read various articles on it they seem to vary in this particular! Could some kind person give me the benefit of their experience on this, please? Thanks very much for any/all comments, Nigel Hi Nigel As you say there are varying opinions - I just spread them 4 times the width of the ring - so with a 1/16" ring, spread about 1/4" Be sure to sandwich them between a couple of plates to kep them flat when heating. Good luck DJ |
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nigelh
Involved Member
North Cyprus
Posts: 89
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Post by nigelh on Feb 16, 2010 16:05:54 GMT
Good tip about running on air and the "injection" hole in the cylinder front cover, Peter. Thank you.
Thanks also for the "spreading" guidance John - I'll let you know how it goes. I've got just enough material to make a few spares!!
cheers
Nigel
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Post by drjohn on Feb 17, 2010 0:03:49 GMT
As you know Nigel, I have the snifter valves on the steam chests and after each run I just squirt some oil in and push the loco back and forth with the draincocks open.  Having a plug to unscrew from the front of the cyliders seems unnecessarily complicted, and as for running on air after each steam up - what a footer! DJ |
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nigelh
Involved Member
North Cyprus
Posts: 89
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Post by nigelh on Feb 17, 2010 6:34:28 GMT
I had forgotten about your snifter valves, John - are they spring loaded so you don't have to unscrew anything ?? That does souind like an easier option. Thanks for the reminder!
cheers
Nigel
edit:- Have just googled "snifter valve" and it seems they rely on gravity to open and steam pressure to keep them closed ?
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Post by drjohn on Feb 17, 2010 7:36:21 GMT
Yup Nigel, the balls fall under gravity and seal with the steam pressure. Nothing to unscrew. This is what the innards look like:-  It's one of those "that's so simple, why didn't I think of it" ideas that I came up with 30 over years ago for the first Simplex, along with the derail-proof central drain cock idea which you can find on my website on page 8 or thereabouts of the Simplex bit. When you gonna post some pics of yours, Nigel? DJ |
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nigelh
Involved Member
North Cyprus
Posts: 89
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Post by nigelh on Feb 18, 2010 18:32:12 GMT
Great, John. Thanks very much.
I'll post some pics tomorrow of the two pistons & rings ready for splitting etc. I have spent a fair bit of time getting the connecting and coupling rods and bushes running nice and easily as well as the crossheads - surprising how just a little bit of error can cause things to bind up!! But I'm now quite pleased with them all - can push the chassis along the floor with one finger and no tight spots. Simple pleasures, what.
Cheers - time for a beer!
Nigel
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Post by peterseager on Feb 19, 2010 9:58:09 GMT
Some people think that they operate under the same conditions as other people half a world away.
We are not all blessed with a private track we can occupy to clean our loco and push it backwards and forwards. Mine sits on its trolley whilst at home, of necessity with only enough track to stand on. Shoving Metal Smith's rolling road modules under the loco and running on air works. Enough water is pushed out to make it feel worthwhile.
In our climate we have to lay up for 4 months of the year. We can't get on our field as a club without damaging it. So being able to inject WD40 directly into the cylinders is a definite safeguard. I believe it keeps the rings free. It seems to be better balanced when running after the WD40 treatment. My loco was built without a snifting valve eliminating that option.
Cast iron cylinders do rust solid. Never happened to me - yet - but I know a man who has had it happen.
Peter
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redmog
Part of the e-furniture
Not Morgan weather
Posts: 461 
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Post by redmog on Feb 19, 2010 10:39:29 GMT
So being able to inject WD40 directly into the cylinders is a definite safeguard. I believe it keeps the rings free. It seems to be better balanced when running after the WD40 treatment. My loco was built without a snifting valve eliminating that option. Cast iron cylinders do rust solid. Never happened to me - yet - but I know a man who has had it happen. Peter Is there any disadvantage to injecting oil/WD40 etc. down the blast pipe and lubricating it that way? Chris |
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Post by drjohn on Feb 19, 2010 11:34:14 GMT
Some people think that they operate under the same conditions as other people half a world away. We are not all blessed with a private track we can occupy to clean our loco and push it backwards and forwards. Mine sits on its trolley whilst at home, of necessity with only enough track to stand on. Shoving Metal Smith's rolling road modules under the loco and running on air works. Enough water is pushed out to make it feel worthwhile. In our climate we have to lay up for 4 months of the year. We can't get on our field as a club without damaging it. So being able to inject WD40 directly into the cylinders is a definite safeguard. I believe it keeps the rings free. It seems to be better balanced when running after the WD40 treatment. My loco was built without a snifting valve eliminating that option. Cast iron cylinders do rust solid. Never happened to me - yet - but I know a man who has had it happen. Peter Oh dear Peter - when I lived in Bedfordshire, I used to steam up even when it was snowing, and after blowing down the boiler, injected oil through my snifters, pushed the loco back and forth on the steaming bays then took it home - never got any rust in my cast iron cylinders. We can't all afford rolling roads or waste the time to remove plugs and connect compressed air, ... but each to his own ...  DJ And just a wee bit of chemistry for you -- rust forms faster in warm humid conditions than in cold dry conditions. |
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