Plumbing part 5 - HX inlet and solenoid

Pluuuumbing! 

First order of today's business is the line from the inlet to the HX - this one is always open but requires an additional connection to the expansion valve at the sump. 

I found that the tubing bender has a tendency to drag the section around the mandrel which screws both the tube and the placement of the bend. In order to get them in exactly the right place, I am using a clamp collar as a stopper. The marks on the tubing are either the start, middle or end of the bend and are aligned with the degree marks on the bender where they will end up when the bend is made; by measuring or simply rolling the straight tube around the mandrel (if that is even sort of clear). 

Here it is in the bender.

This creates a bend with a radius of about 2.75", but I need this one to be smaller so I tightened it up with the Alien-critter-tool afterwards. Two more bends added and one to go.

This is a skill that needs a fair amount of practice in order to deliver good (and precise) results. I haven't done this for a while, so the first one took quite a bit of time (and plenty of adjustment). I have lots of admiration for the electrical conduit trade (ever looked at a manual for one of those deceptively simple looking tubing benders they use?). There is no correcting bends in that stuff with your bare hands!

The glands are pulled into axial alignment with the fitting when the nut is tightened, so there can't be too much fudging. Next is the auto-fill for the boiler with the solenoid in the line...

...and the connection from the solenoid to the inlet.  

This one was done using 8mm line, which was far easier and more pleasant to work with than the 10mm. Next time, I will use only 8mm 'cause life is too short. 

Now the really fun part :)

After cleaning the parts, I put little flux on the joint and a ring of the filler metal...

...and use a reducing flame (less oxygen than gas to avoid oxidizing the metals) to heat up the parts. Once the flux melts completely showing that the parts have reached temperature, the silver filler material flows into the joint perfectly. Mustn't forget to thread both nuts on the line because otherwise you are just starting over.

Plumbing part 4 - fill reservoir and water inlet

Cutting the copper tubing can be done with a pipe cutter, but this pinches the annealed tube too much as these small diameters.
I prefer to cut with a mitre and an x-acto micro saw. This method allows you to cut extremely precisely and to remove a tiny section from the end, which is difficult to do with a regular pipe cutter.

I mounted the custom bending dies I made on a cheapo 4" machinist vise. Somehow it reminds me of the critter from Alien. 




























Starting with a roughly 2.5" radius bend made with the regular tool, the custom bender can tighten up the radius to about 1.5".

This image of the line from the exit of the HX to the brew reservoir shows both a large bend used where there is space and a tighter one where there isn't.



























I got caught up in the process of making this bracket and it was all done before I realized that I hadn't taken any process shots:



























I cut off a 3" section of 1/8" x 2 1/4" cold-rolled steel and then cut that in two lengthways. Mark and centre punch the hole position, then drill using first a small bit to locate, a couple of intermediate sizes and then the finished sized bit. Then I did a "don't try this at home" by putting the 1/8" stock in my new 16 gauge rated (i.e. half the thickness) V-jaw metal brake. It is [i]just [/i]strong enough to bend the inch-wide piece of material - any wider and it would be hammer time. The V-jaw makes a nice sharp bend - close to the material thickness in radius.

Here is the bracket with the 3/8 BSPP parts it will support: the line in and the two feeds for the HX and boiler. 

Frame part 3 - LRFs and more plumbing

Before I go on with the plumbing, I think we need to get LRF equipped. I haven't sourced the final LRFs yet, so I looked through the LRF drawer and found some temporary ones. First, drill and tap some holes in the corner plates.

I have a little set of blocks with holes sized exactly for the tap that serve as guides to keep the holder perpendicular to the workpiece.

Not the best photo, but we are now officially Little Rubber Feet equipped. 

First up for plumbing is the sump. This plastic part is a huge improvement over the cast-metal one in both of my machines. Both of those are tiny and often silt up with grounds. Appart from being perhaps eights times the size, this one also has a large outflow.

A quick hole in the side and the expansion valve can be attached. I'm not going to bolt the sump in place until I have the rest of the lines sorted out.

Picopan - File under things you never knew you needed.

I've done some sheet metal in the past, but not a great deal. I decided that it would be a good idea to try out something small to see what can be done in house and what needs to be outsourced. Cutting is cheap, but bending still requires lots of manual setup and is consequently expensive for small runs. 

I had access to a shop with a shear and box pan so I tried out a couple of tests in aluminum to work out the bending order and to verify the proportions. I glued on the tab to hang the brush as cutting it is out is pretty much impossible with hand tools.

Real parts in 20g stainless ready for polishing and bending:

This was a good exercise to test out the design tools and supply chain for the far more complex parts for the bodywork; almost all of which will have to be fabricated with grown-up tools that I don't have.

Plumbing part 3 - HX tube continued

The next step is to throw everything away and start over.  :{(

What I didn't notice while I was happily bending the tube is that the inside die, which is made of plywood, had split and allowed the tube to crumple. The outside of the bend looks great, but the inside was a mess. Likely, the tubing is work-hardening as it bends and needs to be re-annealed a couple more times. Also, the setup would be much stiffer if it were in a proper arbor press with metal dies. Given that the flow rate through this part is tiny, it wouldn't have made a difference but as this proved not to be a viable method for making a bunch of these, I went back to the original plan of hard brazing parts together. 

Plumbing part 2 - the HX tube

Starting with some heavy-wall 3/4" copper tube. First we heat it up to cherry red to anneal the copper.

You can't see it in this picture, but once it cools, it's the color of eggplant, I swear.

Fill up the the pipe with sand to stop the walls from collapsing during the bend.

Install the big bender in the vise and tighten the vise.....

little...

by little....

Plumbing part 1 - make your own tube bending tools

Next up, a tiny bit of plumbing, which is pretty much where I stopped on the build itself for want of a bunch of parts and time to work with them.

This was essentially a trial run to figure out the best way to bend the tubing and where to put the pressure gauge. I used North American 1/4" tube which is really close to the 6mm it is supposed to be but waaaaaaaaaaay cheaper because of the absence of the novelty factor. I welded a socket head cap screw onto the frame to act as a stud and then machined some a spacer to get the pressure gauge set back at the correct distance from the plane of the back splash. This is just a temporary measure until I sort out exactly which adapters and gauge will be used - then I'll design a bracket with the appropriate forward/aft offset and up/down & port/starboard tolerances.

I sourced a couple of tools for bending the copper tubing but in the end because some of the radii are super tight, I built a some custom tools that can be dropped into the bench vise.

I was pretty sure these tools would work really well for small diameter tube, but I wanted to try to make the main HX tube the same way to avoid having to hard braze the connections (silver solder ain't exactly cheap...).