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Post by Doug on Jun 1, 2014 20:27:12 GMT
I have been driving my 5" Butch loco for about a year since I finished the restoration it has been a bit tricky to drive with the balancing act very hard to keep it running (steam pressure, water level and fire) one of the three would always need attention. However after a blowout of one of the seals I decided to do away with the graphite and go down the silicon seal route and wow what a transformation it now no longer leaks steam so it runs a treat the axle pump keeps up the pressure stays up even when filling the boiler and the blower can be turned off completely when the engine is running. Fantastic, the only thing is it is a little tight still but I expect it will loosen up with use. here are some pics from today   And my fav pic of the day,........  |
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Post by arch1947 on Jun 1, 2014 23:00:30 GMT
Interwatring, I find driving my Bridget a balancing act also but put it down to my inexperience, maybe there are other factors at play. In what form was the silicone? Washers O-Rings?
Cheers,
Arch
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Post by Doug on Jun 2, 2014 4:53:33 GMT
Interwatring, I find driving my Bridget a balancing act also but put it down to my inexperience, maybe there are other factors at play. In what form was the silicone? Washers O-Rings? Cheers, Arch I fitted orings to the pistons and the piston rods and the valve rods 6 seals in all. If the loco is well designed it should be fairly easy to keep it happy and in balance the problem I had obviously was the loss of steam so it was difficult for the boiler to keep up  |
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Post by Roger on Jun 2, 2014 7:13:09 GMT
What a pretty little locomotive that is, it looks great. I'm surprised that 'O' rings for piston seals were a suitable shape, the ones in the shape of a cross called X-rings might be better. Here's an interesting page with yet another alternative I'd never heard of, a 'D' ring. Even so, it clearly works and sounds a lot better than what you had. I did a search and found this page with a vast variety of materials to experiment with. It even has PTFE 'O' rings but I would have thought they were a bit rigid for this application. |
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 2, 2014 9:01:32 GMT
it is perhaps worthwhile adding that doug originally packed his pistons with graphite asbestos string rather than the proper square braided stuff of the correct size. hence the problem of the blowing pistons shortly after them being fitted.
cheers,
julian
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Post by Doug on Jun 2, 2014 11:38:04 GMT
it is perhaps worthwhile adding that doug originally packed his pistons with graphite asbestos string rather than the proper square braided stuff of the correct size. hence the problem of the blowing pistons shortly after them being fitted. cheers, julian hi Julian the pistons were never designed to have the sq graphite it had rubber orings when i first had it which had gone very hard (over 40 years old) i fitted the graphite string which held quite well considering its the wrong material, it was the (original) string fitted to the glands on the piston rods and valve rods that were leaking badly and eventually blew out. the pistons are a very good fit indeed doubt it would need much of a seal anyway. It does not seem to have much more power now just better use of the availible steam. I cant wait to see what Speedy is capable of the pistons are about 1.5 times bigger. |
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Post by Roger on Jun 2, 2014 13:23:56 GMT
it is perhaps worthwhile adding that doug originally packed his pistons with graphite asbestos string rather than the proper square braided stuff of the correct size. hence the problem of the blowing pistons shortly after them being fitted. cheers, julian hi Julian the pistons were never designed to have the sq graphite it had rubber orings when i first had it which had gone very hard (over 40 years old) i fitted the graphite string which held quite well considering its the wrong material, it was the (original) string fitted to the glands on the piston rods and valve rods that were leaking badly and eventually blew out. the pistons are a very good fit indeed doubt it would need much of a seal anyway. It does not seem to have much more power now just better use of the availible steam. I cant wait to see what Speedy is capable of the pistons are about 1.5 times bigger. I've been in contact with a seal company this morning and they say that Silicone isn't the best choice of material for the 'O' rings. They suggest EPDM for steam up to 150C, and graphite packing if it's above that. Just a note on SPEEDY's cylinders. Julian suggests making them 1/16" smaller in diameter if you haven't finished them to size already. |
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Post by Doug on Jun 2, 2014 13:53:37 GMT
hi Julian the pistons were never designed to have the sq graphite it had rubber orings when i first had it which had gone very hard (over 40 years old) i fitted the graphite string which held quite well considering its the wrong material, it was the (original) string fitted to the glands on the piston rods and valve rods that were leaking badly and eventually blew out. the pistons are a very good fit indeed doubt it would need much of a seal anyway. It does not seem to have much more power now just better use of the availible steam. I cant wait to see what Speedy is capable of the pistons are about 1.5 times bigger. I've been in contact with a seal company this morning and they say that Silicone isn't the best choice of material for the 'O' rings. They suggest EPDM for steam up to 150C, and graphite packing if it's above that. Just a note on SPEEDY's cylinders. Julian suggests making them 1/16" smaller in diameter if you haven't finished them to size already. thanks Roger the seals are a bit of a thorny issue I repplaced the piston seals at the begining of the restoration with EPDM seals and they got all sticky when hot the engine sized solid (they could have been the wrong material sent out but i doubt it as i got it them from simply bearings) thats why i ended up with the graphite as it is stated to be used in the plans and to be fair it worked very well, I had read about someone using silicon orings somewhere and there use is quite widespread in the model loco world infact i puchased this little lot of seals from Blackgates Engineering and rightly or wrongly i would recomend there use from experiance. I am never going to run each and every weekend so I am not concerned about the life of the seals if I get a few years out of them I am happy, hell i managed a year with "wet string"! the cyclinders are all done I am afraid i was awaitng the results of this second run on the silicon seals to decide if thats what i am using on Speedy and TBH i am so happy with the results there is no good reason i can think of why i dont use them. the piston blanks and rods are ready to go (machining). although i fancy a crack at the valve liner inserts first. |
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Post by Roger on Jun 2, 2014 14:40:29 GMT
Fair enough, I'm never sure if these seal people know what they're talking about or not. If the life is reasonable then it's not an issue. I'd be curious to know what the PTFE ones are like though because they ought to be able to withstand the heat. I guess there's a lot more experimentation to be done with other materials and seal types but I guess there's not much need once you've got a locomotive that runs well.
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Post by Doug on Jun 2, 2014 14:53:45 GMT
Fair enough, I'm never sure if these seal people know what they're talking about or not. If the life is reasonable then it's not an issue. I'd be curious to know what the PTFE ones are like though because they ought to be able to withstand the heat. I guess there's a lot more experimentation to be done with other materials and seal types but I guess there's not much need once you've got a locomotive that runs well. the only down side i have encountered with silicon O rings is the wear life it is not anywhere near as good as most of the other materials they are very soft so if you intended to run a passenger service then they are probably not the best choice but by my reconning my loco will be run up to 5 times a year for an hour or two at a time then go into long time storage/display when Speedy is finished so i am ok for a good few years and at £4/5 a set i am not going worry too much if i replace them once. As i found if the loco is not i regular use (display or storage) then its not going to be a runner anyway (the seals dryup and go hard etc). You have to have it tested quite thoughly if you run it. |
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nonort
Part of the e-furniture
If all the worlds a Stage someone's nicked the Horses
Posts: 279 
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Post by nonort on Jun 2, 2014 16:23:13 GMT
Providing that the pistons come out the front off the cylinders easily enough then carry on with the silicone rings there are cheap. Get friendly with your local stockist and blag them for free. Most stockist are very accommodating as they usually deal in large numbers a local stockist near me sells them by weight to large company's? Out of interest the rings that come out off my engine after about three hundred mile are triangular in section? I presume that its the rolling motion of the ring in the groove. ps spotted on the pictures of your lovely loco that there was no break away back up between the loco and the driving truck it would be a great shame to damage the loco for something so simple if it should ever escape!
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 2, 2014 20:22:41 GMT
one of the locos i built still has the original square graphite packing on the pistons and glands fitted circa 1985, and another in 1994, all untouched and still ok.
there is a bit of an art to fitting graphite packing to pistons and glands.
for 'O' rings the bores have to very very smooth to get any decent life out of them. ive only 1 loco that doesnt have inside cylinders and i wouldnt want to mess about with having to refit 'O' rings on inside cylinders!
ive said this before but if you get an ordinary pencil eraser and rub it along the bores (or for that matter some of the ground stainless rod sold as piston rod and valve rod material) see what happens!
cheers,
julian
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dfh
Hi-poster
Posts: 197
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Post by dfh on Jun 2, 2014 21:00:44 GMT
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jma1009
Elder Statesman
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Post by jma1009 on Jun 3, 2014 22:27:21 GMT
hi doug,
as commented by roger re SPEEDY there is no benefit in having cylinders that are too big - all you will end up doing is just cracking the regulator open at working pressure and an inability to notch up properly. big cylinders are ok if you cant fire properly and potter around at 30-40 psi in full gear. my own driving technique is somewhat different!
cheers,
julian
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Post by Roger on Jun 4, 2014 5:18:20 GMT
I've had more feedback from the seal people, and they suggest a hybrid seal that has PTFE as the sliding part, with a Silicone 'O' ring as a 'spring' inside it. By all accounts these are standard items.
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Post by Doug on Jun 4, 2014 6:31:52 GMT
hi doug, as commented by roger re SPEEDY there is no benefit in having cylinders that are too big - all you will end up doing is just cracking the regulator open at working pressure and an inability to notch up properly. big cylinders are ok if you cant fire properly and potter around at 30-40 psi in full gear. my own driving technique is somewhat different! cheers, julian I know exactly what you mean Julian my Butch had that exact issue until recently keeping the pressre up was a real task it is so much easyer to drive when you have adequate steam to play with on my last run I didnt need full gear at all and it shot round the track almost in mid gear and hardly any regulator even on the incline we have. i havent heard about the speedy cylinders being an issue however my great grandfather had already bored one of them back in 72 so my hands were tied anyway. regards, doug |
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Post by Doug on Jun 4, 2014 6:33:45 GMT
I've had more feedback from the seal people, and they suggest a hybrid seal that has PTFE as the sliding part, with a Silicone 'O' ring as a 'spring' inside it. By all accounts these are standard items. I feel, not for the first time that you may be going Maverick on us again Roger  |
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Post by Roger on Jun 4, 2014 9:14:04 GMT
I've had more feedback from the seal people, and they suggest a hybrid seal that has PTFE as the sliding part, with a Silicone 'O' ring as a 'spring' inside it. By all accounts these are standard items. I feel, not for the first time that you may be going Maverick on us again Roger Who? Me? Surely not.... |
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Post by Doug on Aug 18, 2014 9:33:06 GMT
bit of an update on this and its not all good,
after running again at the weekend this is the third thime i have run it since the new seals were fitted,
everything was going well with the useual easy driving and no leaks i did two laps on my own with a single driving car as it was a public running day we decided to couple up a pair of passenger cars, and it didnt make a lap i had some traffic which ment i was stopped for quite a bit and the two or three heavy starts got the cylinders really hot the orings then got a bit "bitey" and everything went very tight indeed then it got pretty much solid. its nice and loose again now its cold.
there are two considerations here, first one is i dont yet know which orings were causing the tightness (piston ring, piston rod or valve rod) or a combination of all of them, however the main issue wont be helped by the piston and valve rod seals being too tightso i may sort this and try again. see what results i get.
as a back up i have some 16mm dia. PTFE bar that i can make some seals from. I dont want to get rid of the silicon orings yet as i like the really good seal i seem to have i just need to make sure they are fitted correctly before i junk the idea and use PTFE instead.
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Post by Roger on Aug 18, 2014 9:37:22 GMT
Hi Doug,
I'd revisit the amount of compression the rings are supposed to have, you may had them too tight. Can you get Silicone 'X' rings in the size you need? I can't help but think those ought to be a better bet, ie more compliant and better sealing edges.
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