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Post by andyhigham on Oct 11, 2016 12:58:17 GMT
Just a little thought outside the box. A disc of stainless steel small enough to fit down the flue with 2 holes drilled for the super heater tubes. The tubes can be pushed into the holed and welded around the ends, easy to get to. Then a lump of stainless the same diameter as the disc and about 15mm long is drilled in the end making a cup shape with about 1.5mm wall thickness. This is welded onto the disc, again easy to get at.
Please feel free to shoot me down in flames
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Post by Jim Scott on Oct 11, 2016 13:38:46 GMT
Hi Andy Your suggestion gives a better setup for welding. Indeed David could just cut his return block in half, weld the tube ends as you say and mill out a pocket in the other half to form the return. My usual way of achieving a similar but neater result is to swage the tube ends to a 'D' section, seal between the two then add the return as per the photo below. There was some discussion about this in either Roger's Speedy thread of Julian's Boxhill thread about a year ago. Jim S Swaged and TIG welded superheater return bends for Earlswood
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Post by builder01 on Oct 11, 2016 13:43:05 GMT
Hi Miken,
Glad to know that argon is part of a "normal" TIG set up for welding.
My super heater tubes are 1/4" outside diameter. They will fit into a flue that has an inside diameter of 5/8". Two 1/4" tubes down a 5/8" inside diameter flue should not be a problem.
As for the Hewson type, I'm not sure how I would make the return bend. I'm probably going with the welded type.
David
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Post by andyhigham on Oct 11, 2016 14:28:12 GMT
An alternative on Sweet Pea type boilers is a superheater that goes from the smokebox down one flue, a nice gentle bend over the fire (or even a coil or two) and back up the other flue. The superheater would be inserted from the firebox end
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miken
Part of the e-furniture
Posts: 480
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Post by miken on Oct 11, 2016 16:12:26 GMT
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Post by builder01 on Oct 11, 2016 16:13:50 GMT
I'm building a "traditional" locomotive type of boiler. The super heater must be installed from the smokebox end. Otherwise, that would work also.
David
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Post by builder01 on Oct 11, 2016 16:16:55 GMT
I already have the material, so, that is not a problem. I mentioned this as someone had asked what the diameter of the super heater tubes are.
David
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mbrown
Elder Statesman
Posts: 1,720
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Post by mbrown on Oct 11, 2016 18:28:11 GMT
I've a feeling that Doug has spoken recently in one of the magazines about making his superheaters. Does that ring a bell with anyone? As regards efficiency, did Ballan Baker not have some fitted when he won IMLEC? Reg Yes, in his article on the LNER Y4 in the most recent edition of Engineering in Miniature. Doug simply bends them cold around a former. Malcolm
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Oct 11, 2016 21:32:09 GMT
I would suggest David uses the search facility on here as recently miken, Roger, and Doug have described their examples. Jim Scott has also described in some detail his method with seperate return bends welded on.
This is all up to date stuff and I dont recall anything in ME that goes into the subject in such detail as on here! Apologies for not providing the links to the pages of specific threads on here.
Cheers, Julian
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Post by builder01 on Oct 12, 2016 0:44:03 GMT
Hi Julian,
Yes, I have searched these forums for more information. I have found much useful information. It looks like if my superheater tubes are to go into the fire box, the return bends must be TIG welded.
I don't know how the super heater tubes could be bent cold, around a former as suggested by Malcolm. Maybe it can be done, but, I would think they would collapse for sure. It seems if they were filled with something, the tube would tear at the bend. If it really could be done this way, it sure would eliminate the weld at the return bend.
David
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Post by kiwinoel on Oct 14, 2016 5:49:59 GMT
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Post by kiwinoel on Oct 14, 2016 6:11:24 GMT
Was unable to post some photoes of my super heaters made for 316 stainless steel so will see if Hayden will show me what I am doing wrong
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Post by Roger on Oct 14, 2016 7:25:39 GMT
Was unable to post some photoes of my super heaters made for 316 stainless steel so will see if Hayden will show me what I am doing wrong Take a look at the sticky thread on this, it explains what the problem is and how to get around it.
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Post by Deleted on Oct 14, 2016 19:09:42 GMT
I imagine the 'double bend' superheaters are thick walled tube, else I imagine they would collapse on bending. Maybe they use Wood's Metal to prevent that from happening though. I'd be interested to see how that's done. I've got some unused Hewson superheater elements. The bends appear to have been made cold, by pulling the tube through 180° around a 1/4" diameter bar. The section has collapsed on the bend, so instead of being 0.156" outside diameter, it has become an oblong of 0.170" x 0.123". The outside of the bend has probably thinned at just the point where you would like it to be thicker, to resist burning. I very much doubt that I will use these elements. I'm sure a satisfactory bend could be made though, using proper form tooling and with the material red hot. Another point regarding Doug's double-pass elements is that they completely fill the flue, making it more difficult to clean the accumulated ash out.
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Post by kiwinoel on Oct 14, 2016 21:00:38 GMT
I have just put some photos of my super heaters and regulator on photo bucket the Achilles allbum these we made with 1/4" 20 gauge 316 stainless tube they were made using Bill Steers ideas Model Engineers Mag 2010 but instead of sifabrazing I had the arrow end tig welded using the the argon filled method to ensure full penetration they we then made parallel using formers in a vice, all the other bends were done using my mandrel bender that I made from plan in the Model Engineering Mag, photos of this bender also in the bucket.
Noel 1150.photobucket.com/user/KiwiNoel/library/?sort=6&page=1
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Post by 4fbuilder on Oct 14, 2016 21:16:19 GMT
Good evening all,
I gave up using welded spearhead ends for stainless superheaters on my locomotives many years ago, if they are going to go to the back of the firebox then there is no need for spearheads thus no need for welding, I use a stainless block drilled and tapped with the stainless tube screwed with tight threads with a little smear of jointing and wound in very tight; I've been using 1/4" od material screwed 1/4" X 40 and I get my tube via a well know auction site. When fitted into 3/4" flue tubes cleaning is fairly easy. I've never had a failure, yet!
Regards,
Bob
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Post by kiwinoel on Oct 15, 2016 2:06:57 GMT
Hi, i have a question that is sort of about super heaters the 3/8" copper pipe from the super heater to the steam tee, should the wall thickness be .80 mm or1.2 mm? Noel
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robmort
Hi-poster
3.5" Duchess, finishing 2.5" gauge A3 and building 3.5" King
Posts: 172
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Post by robmort on Oct 17, 2016 15:56:12 GMT
Good evening all, I gave up using welded spearhead ends for stainless superheaters on my locomotives many years ago, if they are going to go to the back of the firebox then there is no need for spearheads thus no need for welding, I use a stainless block drilled and tapped with the stainless tube screwed with tight threads with a little smear of jointing and wound in very tight; I've been using 1/4" od material screwed 1/4" X 40 and I get my tube via a well know auction site. When fitted into 3/4" flue tubes cleaning is fairly easy. I've never had a failure, yet! Regards, Bob Thanks for that; sounds like a simple and effective solution. I guess it's also yours at www.cheltsme.org.uk/index-superheaters.html?Rob
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Post by builder01 on Oct 17, 2016 17:58:59 GMT
I like the idea of the joints on the return bends being threaded. I might be concerned about the joint compound failing at the high temperatures reached inside the fire box. I do have model pipe thread taps and dies for a true tapered threaded pipe joint. Perhaps a smear of some of the high temp joint compound from McMaster-Carr would work as well or even better than the Boss White compound.
David
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Oct 17, 2016 22:10:59 GMT
Hi David,
Return bends of radiant type must be of stainless and welded up and not threaded and sealed with boss white!
They must be sifbronzed up if of the non radiant (ie not extending into the firebox) copper LBSC type.
Martin Evans had very little experience of the use of radiant superheaters, and his designs for them in respect of the return bends were not followed by very many. And hence why commercially made stainless elements were supplied by folks such as Paul Gammon all welded up.
Cheers, Julian
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