Boiler part 8 - front plate redesign

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.

Frame part 2 - bender and assembly

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.

Group cap sandblasting

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.

Frame part 1 - raw materials

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...

3D printed lever stop

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.

Boiler part 7 - pressure testing

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!

Boiler part 6 - BSPP plugs

Before I can pressure test the boiler I need to plug all of the holes!
I ordered a couple of cheapee G-thread dies a couple of months ago, but didn't consider the problem of holding them. They are, very conveniently, different diameters. So I decided that it was finally time to build a die holding system for the lathe. A mild steel handle, some 2" OD aluminum tubing, an acetal hub with a stainless shank and, in the case of the larger diameter die, a 6061 aluminum adaptor.

Once done, cranking out the 1/4 and 3/8 plugs in acetal was a snap. Then I dropped them into the milling machine to cut some shoulders for wrenching. I love working with acetal - you can almost form it by staring at it hard.   

Boiler part 5 - final weld-up

Welding time!

First thing that is required is a stand; made from a couple of scraps of 1x1 mild steel tubing and a piece of L section.

The tube rotates easily in the stand which makes it simple to keep the torch and filler material alignment correct. 

I experimented a bit beforehand using some scraps of the same materials and decided that a fairly agressive butt-weld seemed to offer the best weld consistency. Close-up of the finished weld. 

Lead-free brass parts brazed in place.

A view of the open end. I should probably have fluxed the inside of the tube more than I did to prevent the oxidation.

The lone fitting in the centre of the boiler tube is the brass thermal bridge that will sit inside the brew reservoir to facilitate the heat-transfer.

Last bit of welding it the most tricky as space it tight and the pipe wall thicknesses differ: connecting the brew reservoir to the boiler tube. The boiler is now done except for cleanup with pickling paste. This last task was significantly less fun as handling hydrofluoric acid is not exactly like playing with a bundle of puppies. 

Boiler part 4 - inlets and outlets

Ok - boiler build time!

The second attempt at the boiler bolt ring using 304 stainless M10 set screws. The previous attempt (no picture at the moment) involved brazing socket head cap screws in place. This proved problematic: I ran out of gas (not once, but twice) while attempting to braze them in place with a toy oxy-acetylene torch from the hardware store. I then attempted to finish the brazing using my TIG torch as heat source - which, while technically possible, was, in the hands of this welder, not a good idea. Lot of swearing that day.  :o  Since then, I have finally succumbed and added a real oxy-acetylene setup to the shop.

The biggest problem with cutting the holes in the boiler was holding the 6" diameter pipe in the mill. I finally decided to tack weld the ends in place to give the pipe itself enough rigidity during machining. 

Even having done this, I couldn't get enough clamping pressure and holding force (without spending a day or two on building a jig) to prevent the whole part from lifting when cutting the holes with an end mill. So dumb drilling it had to be. First a centre-drill.

Then I work my way up through drill bits by about a 1/16" at a time...

...till I get to 3/4". I would have built a jig, but I think that I may well be able to have the boiler tube pre-cut with on a laser tube cutter, so I will hold off until I have a better understanding of the requirements.

Image of the holding setup. It was enough to keep the assembly from moving laterally, but didn't generate enough friction from stopping the boiler from lifting when using the end mill...

First row of holes complete and I use a pointed brass spud for a visual alignment of the next bunch. The lead-free fittings that I cut on the lathe are dry-fit for now. I like to mark out the placement with a Sharpie by hand before drilling to avoid the painful forehead slap on the discovery that the part was placed backwards in the vice and consequently the holes are in the wrong place. 

A little cleanup with a deburring tool and we are done! 

Un-boxing CNC group parts

Next up: more presents in the mail - I love un-boxing!

This is the first batch of machined parts from a cnc supplier I am auditioning for the project. The parts are individually bagged and/or wrapped in tissue paper and sheet foam. 

The first part is what I call the bearing plate, it also guides the piston rod and spring. The force is strong in this one - quite literally.

Then, the piston cap, more about this later.

In the same package I also received copies of the retainer plate. Having it fabricated was cheap enough, and mass-producing it in my shop would have been a lot of work, new tools and a whole lot of chips on the floor to sweep up. Here it is along with the group body and the other new parts.

Couldn't resist photos of the mock-up:

As you may have noticed, the bad news is that the chrome finish on the piston cap doesn't match the group body! ARRRRGH.

Different shops, different finishes. My suspicion is the cast-bronze body has been plated with hexavalent chrome whereas the trivalent process has been used for the aluminum piston cap (for those who are interested, the difference is perhaps best summed up in two words: Erin Brockovich; hexavalent chrome is nasty stuff). The caps could be re-chromed, but that requires (chemically) stripping the existing finish first which is as or more expensive than chroming them in the first place. Total PITA. This one is going to have to be resolved some other way.