jma1009
Elder Statesman
Posts: 5,917
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Post by jma1009 on May 8, 2014 23:28:36 GMT
hi paul,
there is a lot to be said for making the internals of a smokebox as simple as possible and not 'over engineer' things or make things unnecessarily complicated. i tend to do this with my loco backheads and am trying to avoid over complicating the backhead on STEPNEY!
a smokebox is a dirty and corrosive environment. for example a steel bolt with nut that leaves the end of the thread uncovered will result in the end of the thread corroding and virtually impossible to remove said bolt and nut. plus how on earth are you going to ensure that the smokebox ring will fit back in exactly as before with all the holes lining up?
it is far easier to enable the smokebox to be removed leaving the internal pipework intact apart from undoing a few connections. hence my use of screwed in blastpipes and low down connections at the front of the smokebox for the steampipe. i will not have plain pipes and large holes in the bottom of the smokebox covered with fire cement, all being dealt with by mechanical fittings in my smokeboxes.
cheers,
julian
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Post by GWR 101 on May 9, 2014 13:39:41 GMT
Hi Julian, always happy to receive your views as I have explained previously my loco knowledge (both full and scale size)both operational and construction is zero. I am whilst finishing my present build using this also as a learning project for hopefully my next imminent build. I am not sure I fully understand the method you propose to get the feed and exhaust pipes through the smokebox. The drawings show two tee's the tops of which are about 0.75" below the smokebox tube, plain tubes 1/4" and 3/8" dia rise from the tees through plain holes in the bottom of the smokebox. Are you suggesting that I should braze bushes into the base of the smokebox tube which then have connectors underneath to the tees and also connectors on the inside. Apologies if I have not understood your approach, I understand the concerns regarding the environment and was proposing to ensure that the screw threads were flush with the nuts. I assume that smokebox removal is an infrequent event and that I would replace the screws with new ones as a minor expense, I cant claim any originality for this approach as it was shown to me at a recent event in the Midlands. Regards Paul
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jma1009
Elder Statesman
Posts: 5,917
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Post by jma1009 on May 11, 2014 22:22:07 GMT
hi paul,
on a loco such as Juliet there are 3 holes that need to go into the bottom of the smokebox 1. steampipe to cylinders, 2. exhaust/blastpipe, 3. snifting valve.
on the snifting valve i extend the fitting downwards with a threaded pipe. above and below are 2 curved bits (to fit the smokebox curvature) that are drilled clearance hole then underneath is a nut to fit the thread of the pipe. hole in smokebox drilled clearance hole. that deals with the mechanical seal of same.
on the steam pipe i thread same all the way through the bottom of the smokebox. curved washers (to match smokebox curvature) are added underneath and inside with locknuts again top and bottom. again mechanical seal. the union connection for the steam pipe is as low down as possible so that for removing the smokebox the boiler needs just a bit of tilt upwards after removing the top (inside) locknut and curved washer.
on the blastpipe i generally arrange for the exhaust pipe to finish on the underside of the smokebox with a tapped hole for the blastpipe that fits to same with a curved washer to the smokebox wrapper between the two.
cheers,
julian
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Post by GWR 101 on May 12, 2014 9:03:36 GMT
Hi Julian, once again many thanks for coming back with a detailed explanation all of which I have duly noted.... snifting valve !!!!. Just had the drawings out to see why I hadn't got a hole for one and can't find one shown anywhere !!. So had to look in the Shop, Shed and Road to see what it does and LBSC does cover it, he suggests putting it on the top of the smokebox so that they are away from all ballast dust etc. and feed clean air into the top header of the super heater. Is this a sound plan, fortunately I have the smokebox on hold at the present as I am cutting and bending metal for the side tanks which I intend to make up today. As you have previously noted it is a freelance design so I am not bound by a prototype so position is not a real problem. Having said that I am trying to make it look something like GWR101 in general profile. Regards Paul.
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Post by ejparrott on May 13, 2014 10:00:24 GMT
I've been pondering disguising the Roesco lubricators on my Manning Wardle as snifting valves. I can't fit anything to the top of the smokebox, there's no room for one thing, and the proto hasn't got one. I also don't want to put it in the bottom.
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