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Post by springcrocus on Aug 16, 2020 15:59:21 GMT
Outvoted, then, not a good idea after all.
Steve
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 721
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Post by oldnorton on Aug 16, 2020 16:46:49 GMT
Because each bent pair are virtually the diameter of the flue they will be kept almost central. You could fit one or two of your cruciforms onto the portions exposed in the radiant area, they won't interfere with cleaning there, and will help keep each pair square.
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uuu
Elder Statesman
your message here...
Posts: 2,858
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Post by uuu on Aug 16, 2020 17:45:28 GMT
If you fit a cruciform in the radiant space, I would suggest turning off the outside, just leaving half-circles, or three-quarter circles where the pipes go through. Then there's no chance of it binding (on crud) as you insert or withdraw the assembly.
Wilf
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Post by springcrocus on Aug 17, 2020 10:00:06 GMT
Because each bent pair are virtually the diameter of the flue they will be kept almost central. You could fit one or two of your cruciforms onto the portions exposed in the radiant area, they won't interfere with cleaning there, and will help keep each pair square. If you fit a cruciform in the radiant space, I would suggest turning off the outside, just leaving half-circles, or three-quarter circles where the pipes go through. Then there's no chance of it binding (on crud) as you insert or withdraw the assembly. Wilf That's why I'm just a simple machinist, not a designer.   Cruciforms are now 1.5mm smaller than the flue. Regards, Steve |
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Post by steamerjohn10 on Aug 17, 2020 10:09:16 GMT
great way of getting the result you wanted. you mention using s 316 tube, is there an advantage over s 304 in this application?
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Post by springcrocus on Aug 17, 2020 10:13:59 GMT
great way of getting the result you wanted. you mention using s 316 tube, is there an advantage over s 304 in this application? Much greater resistance to attack from chlorides and acids. Contains a lot more molybdenum. 304 is fine, though.
Regards, Steve
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Post by Deleted on Aug 17, 2020 12:24:19 GMT
Nice work Steve, I was in agreement with others over the first design but do like your modified version, might look at something similar myself, keep up the great work..
Pete
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timb
Statesman
Posts: 512 
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Post by timb on Aug 17, 2020 16:05:28 GMT
great way of getting the result you wanted. you mention using s 316 tube, is there an advantage over s 304 in this application? Much greater resistance to attack from chlorides and acids. Contains a lot more molybdenum. 304 is fine, though.
Regards, Steve
304 will corrode and suffer from pitting when exposed to temperatures above 450C - 316 has a much better all round corrosion resistance, both from chemicals and heat. The extra nickel and added molybdenum improve the surface oxide layer which is 'self healing'. The only downside is that 316 is more expensive and work hardens quicker making it more difficult to machine. I doulbt that this would have been an issue with the quantity and priduction methods Steve has used.
Tim (ex Outokumpu Stainless)
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Post by Roger on Aug 20, 2020 8:39:56 GMT
Much greater resistance to attack from chlorides and acids. Contains a lot more molybdenum. 304 is fine, though.
Regards, Steve
304 will corrode and suffer from pitting when exposed to temperatures above 450C - 316 has a much better all round corrosion resistance, both from chemicals and heat. The extra nickel and added molybdenum improve the surface oxide layer which is 'self healing'. The only downside is that 316 is more expensive and work hardens quicker making it more difficult to machine. I doulbt that this would have been an issue with the quantity and priduction methods Steve has used.
Tim (ex Outokumpu Stainless)
316L is even better, and not too difficult to source. It's not just the resistance of the virgin material you have to take into account. If you're welding it, that introduces more corrosion issues which are countered by the low carbon content of the 316L. None of these materials are hard to machine in my opinion. You just need sharp tools and lubricant. |
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Post by springcrocus on Aug 28, 2020 7:52:47 GMT
I've now made all the parts for the wet and dry headers and it was time to solder all the parts together. First, thought, the stainless steel hairpins had bronze tails screwed on really tight. To keep the elements from dropping into the wet header tube, I covered an 8mm bolt with correction fluid and set it through the tube.  The two short pipes joining the header to the regulator steam chest were also set in place and the whole lot silver-soldered.  All the various other parts were soldered on at different times, about ten heat-ups all told. I've been a bit generous with the solder but early on I had one joint that didn't go well and had to go back for a second try. This is the assembly seen from the boiler side.  And one more picture with it temporarily fitted in place with the smokebox on. I am using olive connections at the cylinder end of the joining pipes but flat connections at the header end because it will be much easier to fit and seal. The small nipple below the dry header is for the snifter pipe.  Steve |
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timb
Statesman
Posts: 512
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Post by timb on Aug 28, 2020 9:15:00 GMT
Nice and neat Steve, as we have come to expect.
Well done!
Tim
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Post by coniston on Aug 29, 2020 9:16:19 GMT
Very neat solution Steve, I may have to ge back and tidy mine up for the A3 now.
Chris D
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Post by springcrocus on Sept 1, 2020 21:56:00 GMT
Not much of an update today. Because I need to know that the superheater assembly is steamtight, I've made a cover plate for the steam chest end and blanking plugs for the outlet pipes. Tomorrow, I will take the assembly to the club and hook the boiler test rig up using the snifter nipple as the connection point. This way, I can safely test it up to the operating pressure of the boiler without the associated risks of using compressed air.  A slight leak won't matter as the steam will find it easier to move the pistons than to escape via a pinhole but I don't want to find it leaks like a colander. In the meantime, I've been getting on with the boiler and firebox clothing and this is where I've got to so far. The finishing post is slowly drawing into view.  Still on track for a first steam-up before Christmas. Steve |
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Post by springcrocus on Sept 3, 2020 15:52:44 GMT
Well, I'm quite happy with that little test. Pressure was held at 1.5 x working pressure for ten minutes with about a 2 lb drop which could just as easily be back past the pump seal.  Considering that the bronze tails are not soldered to the stainless steel elements, this shows that a well-tightened joint with jointing compound is sufficient to seal the assembly. I could always have fell back on oxy-propane to solder them if needed but unneccessary here. Steve |
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Tony K
Elder Statesman
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Post by Tony K on Sept 3, 2020 16:19:54 GMT
Steve, Good news. What did/will you seal the normal input with - the plate with 8 bolts. Gasket or no gasket, sealant or no sealant or both or neither? I tend to use gasket and sealant, but have not had the confidence to use sealant-only yet, although it says you can on the tin!
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Post by jon38r80 on Sept 4, 2020 11:57:34 GMT
That cladding on the boiler looks very sleek
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Post by springcrocus on Sept 4, 2020 21:46:47 GMT
Tony, I was planning on just using the gasket but, because this setup is so easy to dismantle, I can add some gunk later if it proves neccessary.
Jon, thanks for the compliment but I hope that wasn't a hint. I'm not planning to write up the cladding as I'm currently stumbling along like a first-year student and haven't anything wothwhile to offer in this department.
Regards, Steve
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Post by jon38r80 on Sept 5, 2020 9:26:32 GMT
There is no malicious intent behind the compliment, lm just impressed how neat and tidy the boiler is looking with the smoke box attached.
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Post by springcrocus on Sept 5, 2020 10:25:20 GMT
There is no malicious intent behind the compliment, lm just impressed how neat and tidy the boiler is looking with the smoke box attached. I know that, Jon, you've always been very complimentary. I had wondered if you were asking me to write up my adventures with the thin brass sheet but, to do the job justice, I would need to include all the expletives that I've used while wrestling the beast into shape. All hobbies include aspects that we consider a neccessary evil and tin-bashing is my own pet hate.
Regards, Steve
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 721
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Post by oldnorton on Sept 5, 2020 10:44:08 GMT
Steve,
I'm impressed that those stainless superheater pipes have sealed in the bronze stubs, as evidenced by the pressure test. Surprised because did you use a small amount of sealant (traces of red in the photo?) in the threads at assembly? They were then subjected to around 600degC for the silver soldering and still sealed on cooling, but could not be retightened. This is why I use the words 'impressed' and 'surprised'. You must have cut nice threads.
As you say, a tiny weep here won't matter too much - it just has to be non-audible or visible during the steam test.
Norm
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