The boiler plate had to be redesigned because I couldn't find a heating element similar to the original design. The element I chose has a male 1" G-thread, which requires a matching female thread to be cut into the boiler plate. I didn't really want to attempt this in the stainless part I had cut so I bought a 316 stainless bushing adapter and cut it down to fit the hole in the plate. The adapter was brazed into place (rather than welded) to keep the distortion of the plate down.
The inside...
and the out.
A month has flown by but there has been some progress on a number of fronts.
First up, the frame. This $150 (Canadian!) bender from Princess Auto (Harbor Freight's distant cousin) is actually capable of working to a surprisingly high tolerance. It is one of those this-looks-simple-so-why-can't-I-figure-it-out tools. After reading, re-reading, re-re-reading and then finally throwing away the manual I looked on YouTube to find similarly baffled owners. Once you do figure it out though, it will produce parts with two bends in this 1/8th cold-rolled stock to within 1/16th of the desired dimensions.
Vertical posts tack-welded and clamped to the two parts of the base of the frame.
Setting the cross bars that carry the boiler in place and the corner braces to which the feet will also be attached.
Test fit of the boiler (which still has its square pressure-test plate on until I finish the actual boiler plate).
Concluding the day's posts: I needed to make a couple of 1" BSPP (G-thread) x 3/4" copper sweat adaptors that will form the ends of the heat exchanger tube and make the seal with the boiler plate. These are necessarily custom parts as this they adapt from European to North American standards. However, I think that is it reasonable to consider the HX tube as a non-serviceable i.e. a custom part.
Lead-free hex stock after threading, chamfering and cut-off operations.
View from the other side showing the 90 degree included-angle internal chamfer that will seat and seal with the hemispherical "bi-cone" fitting.
The part is flipped and bored to receive the 3/4 copper pipe.
Test fit of the pipe.
I got access to a sand blaster and put the group cap with the off-colour chrome in it to see what would happen.
The hard metal comes off fairly easily revealing the copper layer underneath. The image is a bit pinker than the real thing.
Getting metric rectangular tubing seems like a foolish endeavour, so this part of the project will use North American standard materials. I got a 20' length of nice 1/2 x 1 1/2 x 0.065" wall tubing
Also, 12' lengths of cold-rolled 1018 steel in 3/8" x 3/4" and 3/8' x 1". Working 1018 is such a pleasure after wrestling with that stainless!
Cut to length and cleaned up. A few more things to do here before they can be welded together...
One last part to bring the project documentation up to date. I recently got access to a 3D printer and I thought that I would give it a try to see whether it is useable in production or not. I've avoided buying/building one of these as I have been sceptical about the utility of the parts that one can produce. The massive upside of the process was being able to go from zero drawings to finished part in roughly two hours - which included tackling the learning curve of the software! Print time for this lever rest was around half an hour. Not great for production of large parts, but feasible for a small run of this part.
Part, sitting on a support raft, roughly 75% done.
Finished!
Close up back at the shop - clean up was really easy: a quick scrape with a utility knife...
A perfect fit first time. I tested it at operating temperature (another worry I had about the plastic) and there is no softness immediately apparent. This shot also shows the latest stainless parts installed with the correct hardware. Now I just need the foundry to finish and send me the second (and, I hope, final) iteration of the group body - I ordered it in mid-August and they have been really slow. About a week ago they informed me that they had scrapped the casting during machining. (Deep sigh). I don't want to machine the remaining piston parts until I receive it.
Pressure test day!
All of the plugs are cut and fit to the boiler with a little Teflon tape.
The pickling paste cleaned the stainless welds nicely by removing the surface layer of metal that was oxidized during the welding and brazing.
The 1/4" ply wood blank end started leaking at about 10 psi. I must not have had enough coffee - don't know what I was thinking.
Same blank plate, this time made from a scrap of unidentified aluminum (from Nortel!).
Using a regulator, a manual valve and a check-valve I can up the pressure gradually and keep it there for a bubble test in the sink. 54 psi on the dial - which is 3.75 times the working pressure and more than twice the maximum pressure (the safety valve opens at 1.5 bar). I will not be pressure testing all the way to failure ;-)
The boiler is done!
