jma1009
Elder Statesman
Posts: 5,900
|
Post by jma1009 on Apr 19, 2014 9:23:52 GMT
i am shortly due to make the regulator steam pipe bush to be fitted to STEPNEY's smokebox tubeplate.
the regulator steam pipe will be screwed into the Stroudley type regulator as per LBSC, but the question i have is if there is a better method of securing everything at the smokebox end rather than also being threaded into the bush in the smokebox.
ive only made one loco with a regulator steam pipe screwed into the regulator as all my other locos have disc in tube regulators fitted from the smokebox end through a large bush fixed to the tubeplate and bolted to same. the same fixings get used for attaching the wet header.
the one i did make with a screwed in regulator steam pipe had a flange silver soldered on the end bolted to the smokebox bush with gasket in between, and fixed by the wet header bolts. i silver soldered a collar onto the regulator end so the pipe could be screwed up hard without straining the regulator body fixings.
any other methods and suggestions would be gratefully received!
cheers,
julian
|
|
|
|
Post by Deleted on Apr 19, 2014 13:55:00 GMT
Julian, I use a plain bush with a recess in it for an O ring which seals the steampipe to the bush and also seals the superheater header as well. The steam pipe has a plain end and protrudes through the bush and slightly into the superheater header. I think Martin Evans devised this method for Super Simplex? Helen Longish has had this for 7 years now and it's never leaked. I might have a drawing or photo somewhere if I can find it. John  |
|
jma1009
Elder Statesman
Posts: 5,900
|
Post by jma1009 on Apr 19, 2014 21:09:40 GMT
hi john,
many thanks for your reply.
it is a somewhat problematic area of miniature loco design, hence why ive favoured the disc in tube type for all but one of my locos.
incidentally if roger is reading this at some point the SPEEDY internal regulator pipe must be one of the most awkward arrangements imaginable and should be easily improved upon by lowering the regulator.
cheers,
julian
|
|
|
|
Post by Deleted on Apr 19, 2014 21:24:37 GMT
Julian, I use a plain bush with a recess in it for an O ring which seals the steampipe to the bush and also seals the superheater header as well. The steam pipe has a plain end and protrudes through the bush and slightly into the superheater header. I think Martin Evans devised this method for Super Simplex? Helen Longish has had this for 7 years now and it's never leaked. I might have a drawing or photo somewhere if I can find it. John -----------Hello all.. John Ellis recently recommended this exact same type for my Bear Boiler as well..As can be seen it's a much simpler and, more importantly, more positive means of obtaining a 100% seal PLUS a renewability factor of the o-ring ......... |
|
|
|
Post by Doug on Apr 20, 2014 5:46:46 GMT
hi john, many thanks for your reply. it is a somewhat problematic area of miniature loco design, hence why ive favoured the disc in tube type for all but one of my locos. incidentally if roger is reading this at some point the SPEEDY internal regulator pipe must be one of the most awkward arrangements imaginable and should be easily improved upon by lowering the regulator. cheers, julian Very good point Julian is it feasible to run the regulator parallel to the superheater bush that would make the whole thing much easier to line up? regards, doug |
|
|
|
Post by ejparrott on Apr 20, 2014 8:07:49 GMT
I'd suggest the same as baggo, and alternative in use at our club is the main steam pipe protruding through the bush in the front tubeplate, with a sandwich plate an O ring between bush and wet header, with the sandwich plate being bored to accept the O rind, but the thickness is such to give just the right amount of nip on the O ring when the securing bolts are done up.
|
|
jma1009
Elder Statesman
Posts: 5,900
|
Post by jma1009 on Apr 22, 2014 9:22:24 GMT
i will go ahead and use Ed's version of baggo's design and will turn the tubeplate bush up accordingly.
what grade of 'O' ring would you use?
should i order a Viton grade ring?
i can see i will have to make up a gadget for screwing the regulator steam pipe hard into the regulator body.
i could do with a source of thick walled 3/8" OD copper bronze or brass tube. cant seem to find any listed anymore - can anyone please help?
cheers,
julian
|
|
|
|
Post by sncf141r on Apr 22, 2014 10:45:39 GMT
Julian;
I'm coming to the same point for my Martin Evans designed Ivatt locomotive. Just off the phone from Polly - ordering safety valve springs, etc, as it is time to do boiler fittings.
I have no idea how well the O ring seal will work, but as the boiler is built, I'm committed.
Also, I have wondered about the O ring. As it is mainly surrounded by saturated steam, I'd expect that the temperature would be close to that - I still have to look up steam tables, O ring characteristics, and add in a "fudge factor" for heat from the smokebox.
Anyway, I'm looking forward to hearing answers from people here!
Another JohnS.
|
|
|
|
Post by ejparrott on Apr 22, 2014 10:51:03 GMT
Viton, nitrile and silicone don't go that hot I don't think
|
|
|
|
Post by sncf141r on Apr 22, 2014 12:42:00 GMT
Viton, nitrile and silicone don't go that hot I don't think Quickly looking (whilst waiting for a visitor to arrive) 100psi = 170c saturated steam temperature. from www.websealinc.com/oring_temperatures.htmlAFLAS to 232c Flurocarbon to 205 Perflouroelastomer (Parofluor) 260c Silicone to 232c (note, not Fluorosilicone) so, Silicone should work, at first glance, anyway! It is an interesting thing to discuss, as some of the products of degrading (e.g., Viton,  ) rings can be quite dangerous if handled with bare hands. JohnS. |
|
|
|
Post by Doug on Apr 22, 2014 18:03:43 GMT
Julian, I use a plain bush with a recess in it for an O ring which seals the steampipe to the bush and also seals the superheater header as well. The steam pipe has a plain end and protrudes through the bush and slightly into the superheater header. I think Martin Evans devised this method for Super Simplex? Helen Longish has had this for 7 years now and it's never leaked. I might have a drawing or photo somewhere if I can find it. John What material oring did you use in Helen Longish John? |
|
|
|
Post by Deleted on Apr 22, 2014 19:34:07 GMT
Nothing special, just ordinary silicon.
John
|
|
jma1009
Elder Statesman
Posts: 5,900
|
Post by jma1009 on Apr 22, 2014 20:18:51 GMT
thanks john for that further help.
i will try a few ordinary 'O' rings on gas mark 3 and see what happens!
cheers,
julian
|
|
|
|
Post by runner42 on Apr 23, 2014 1:06:30 GMT
John,
This maybe a stupid question but here goes. In fabricating the tube plate bush how deep would the recess have to be. Would it be exactly 1/8th" + 0.070" or slightly less to give some compression of the O ring. If so how much?
Brian
|
|
|
|
Post by Doug on Apr 23, 2014 4:56:11 GMT
Nothing special, just ordinary silicon. John Thanks John can't beat some real experiance if yours has worked that long that's more than good enough for me.  |
|
Geoff
Hi-poster
Posts: 169 
|
Post by Geoff on Apr 23, 2014 5:21:39 GMT
Another silly question:
In the above sketch, is the supeheater header screwed into the tubeplate bush or is it bolted on from within the smokebox? I assume it is the latter.
|
|
Geoff
Hi-poster
Posts: 169
|
Post by Geoff on Apr 23, 2014 5:27:27 GMT
I've just answered my own silly question .... the superheater header would not be able to rotate and can therefore not be screwed.
|
|
|
|
Post by ejparrott on Apr 23, 2014 7:48:59 GMT
2 studs that's what we use, screwed into the tubeplate bush, passing through the wet header, nuts and locknuts on the outside.
|
|
jma1009
Elder Statesman
Posts: 5,900
|
Post by jma1009 on Apr 23, 2014 8:51:40 GMT
thanks Ed and John for all your help.
there are 2 outstanding queries
1. a source of thickwalled tube for the regulator steam pipe to be threaded 3/8" x 40 tpi for fixing into the regulator body. thickest stuff i can find is 16 swg but i would prefer 13 swg.
2. a definitive source of suitable 'O' rings. the large number of various types available seems to be a minefield! i dont use 'O' rings very often - water gauge seals mainly. i do however have plenty of PTFE bar...
cheers,
julian
|
|
|
|
Post by Deleted on Apr 23, 2014 9:27:33 GMT
John, This maybe a stupid question but here goes. In fabricating the tube plate bush how deep would the recess have to be. Would it be exactly 1/8th" + 0.070" or slightly less to give some compression of the O ring. If so how much? Brian Hi Brian, According to the James Walker info, the 'gap' for a 0.070" ring should be 0.051" to 0.061" deep meaning the ring will be compressed by approx. 0.010" to 0.020". What you need to remember for these tables though is that the dimensions given are to withstand far higher pressures than we will ever see. A lot of people make the mistake of using these groove dimensions when using O rings on pistons and the rings end up far too tight in the bore. When you're using them for static seals though it doesn't really matter if they're tight. Incidently, for larger locos I would tend to use a larger section ring for the seal e.g. 0.094". The recommended gap for that section is 0.075/0.080". John |
|
) rings can be quite dangerous if handled with bare hands.
