Silver soldering boiler

I am almost ready for silver soldering a new boiler for a small engine. The boiler is copper and phosphor bronze bushes. But there is a copper rod from front to back with bronze nuts. Where do you start do I solder the nuts on to the ends first then solder the end caps on to the main tube then solder the bronze bushes the copper rod has to be tight to hold the ends under pressure.

David

The boiler appears to be quite small. I'd assemble it with perhaps 3 or 4 small bronze screws holding each end plate to the barrel and solder all in one go, including the bushes. The bushes couid be done earlier, maybe with a slightly higher MP solder if you wish, but I don't think I'd bother with that.

Edited By Clive Brown 1 on 09/05/2020 21:22:34

The end caps are held on with the copper bar with bronze nuts but do I solder the bronze nuts at the same time as the end caps which are 12mm lapped on to the tube but about 5 thou clear to allow the solder to go up between them. The tube is 2 1/4 inch diamiter by 6 inch long.

David

Edited By David George 1 on 09/05/2020 22:01:05

5 thou sounds a lot. If you put an end cap in position and hold the barrel vertical will the cap fall out? They want to be a close sliding fit. Otherwise the solder can run straight through the gap and out the other end. I believe the advice to leave a gap for silver solder (and Loctite!) has caused more grief with boilers than any other thing. You need some gap, of course, but not much. I learned that lesson after much anguish and waste of ss.

I would pickle, rinse, assemble, and flux generously, set vertical, solder one end flange, stay and nut, set other end vertical and repeat, then set horizontal and do the bushes. If not confident, or worried about flux exhaustion, do one operation at a time, cooling and pickling between steps. My similar Ellie boiler has plain stay without thread or nut; they are unnecessary and just more work.

I have silver soldered the boiler. I decided to do it in stages, firstly I soldered the three bosses in the top of the boiler, then I soldered the boss for the level plug and the end nuts into the end caps and then the end caps were soldered one at a time on the ends. I pickled between each go and with a clean and flux on to the next stage. After fettle and a bit of scouring pad it looks ok.

David

David, You have made a nice job on your boiler very neat, just one point you really need your pressure gauge on a "U" Bend syphon to form a water slug which protects the gauge from damage by direct steam pressure, although you may know this already.

MichaelR

That's a smashing job David, especially as it's your first one. A very neat job of silver soldering.

Michael is completely correct, it really needs a 'U' bend or a coil of tube but a 'U' bend looks better.

Brian

Thanks for the information about U bend. It's a bit of a learning curve I just thought it looked ok there I will have to include a bit more tube. What pressure would it be tested to for a working pressure of 30 PSI.

David

David, the initial test is normally carried out at twice working pressure and subsequently at 1.5 times W.P. It is best (in my opinion) to pump it up in stages to work harden the copper. Say, up to 10 psi and release, then up to 20 and release etc.

Brian.

Edited By Brian H on 12/05/2020 17:56:11

Hi Brian the U tube. Do you have to put water in the U part or dose it just fill with condensate from the steam. What happens if the steam gets to the gauge?

David

Hello David, yes, the U tube will fill with condensate as soon as steam appears. Not sure what happens if steam gets to the gauge, hopefully someone else can answer that one.

Brian

U bend added to gauge.

That's a very neat job David. Is the boiler just for your personal use?

Brian

Yes Brian I made a wobbler a couple of weeks ago to to pass the time and then realised that I hadn't a way of running it how I liked, so this is the boiler.

David

Hi David,

Very impressed, nice job.

I've been thinking about making a small boiler. I have 4 small engines and would love to see them run on steam.

I have a few questions.

Firstly, boiler material, what type/grade of copper and bronze have you used, also what gauge for the tube and the end plates and what grade of silver solder have you used.

Secondly, what type of torch have you used for your heat source for the annealing and silver soldering.

Finally a general question for anyone. Would this size of boiler be suitable for a small engine up to say stuart 10v size.

Cheers Geoff

Hi Geoff there us a web site                      http://www.stevesworkshop.co.uk/steammodels/simpleoscil/simpleoscil.htm                         I got the idea from there is quite a lot of info there but got material from M machine metals but I upgraded the tube size a bit and am changing a few sizes to suit what I fancy, like I have bought a solid fuel burner and am waiting for it to be delivered so I can set the boiler height to flame. The copper is 16 gauge thickness. I bought some insulating boards which helped with getting the parts hot enough https://www.cousinsuk.com/product/square-soldering-boards with fire bricks underneath. the solder was Cupalloys 455 1mm and easy flow flux.

David

Edited By David George 1 on 14/05/2020 13:35:47

Hi David,

thanks for your reply.

I'll check out Steve's site.

I use M machine as well, good company and thanks for the material details.

What about your torch. Do you have one that attaches via pipes to a large propane gas bottle or have you managed to do all the annealing/soldering with a small gas canister torch?

Geoff

I have a bullfinch blowtorch and bottle. I was surprised how hot it had to be for the solder to flow I was half expecting it to melt the copper and bronze.

David

Hi David

Thanks again. Given the small size of your boiler I was thinking it may be possible to complete the annealing and soldering of a boiler that size with a canister type torch, which is what I have.

Apparently not, I'll give it some more thought as clearly I need equipment with a much greater heat output

Geoff

Cupalloys are doing a special offer www.cupalloys.co.uk you could give them a call on Seivert torches etc.

David