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.

I would want to see proof that sand blasting plus citric acid wouldn't work before I'd consider HF acid for weld cleaning/passivation.

Just a comment on pressure testing, it's usually advised to use as much liquid as possible in the vessel so if there is a catastrophic failure, the damage is small, with 100 PSI water it expands maybe .001%, with air, it would be a lot more impressive, with steam even more so.

Ira

ira wrote: ...with air, it would be a lot more impressive, with steam even more so.

That, is a very good point. I didn't think carefully enough about the testing procedure - I just took care to stand out of the potential path of any of the fittings and wore requisite ear and eye protection.

jonr wrote:I would want to see proof that sand blasting plus citric acid wouldn't work before I'd consider HF acid for weld cleaning/passivation.

Very possibly mechanical abrasion and a far more benign acid would be sufficient for this procedure. I just happened to have some of the HF paste and neutraliser on hand from another project. Electrochemical cleaning is apparently also an option. In any case I certainly don't want to have to do HF passivating myself for a large number of these.

Once again, I find the devil in the details. As a result of this build I am no longer completely convinced that a copper boiler, even though it is likely more labour intensive, wouldn't actually be easier. Minimally, having another casting made for the brew reservoir is looking more attractive.

A few teasers of some work in progress!

First the frame.

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...

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.

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.

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).