Rain forest part 3 - rail corners

Next episode in the on-going subdivision of my piece of exotic ligneous plant: the rail corners.

First job is to put shoulders on the exterior of the round over.

Then the same thing on the inside, finally cutting out a left-over square of stock.

Then, using exactly the same setup as before on the chop saw they get cut to length.

Then, it was time for the biggest head scratcher of the day: how to chamfer all eight interior corners without it taking all day. I'm sure there is a more efficient way to do this, but I don't know what it is.

A quick trip trip on the round-over plus a bit of sanding and they are off to the finishing department.

Done!

Rain forest part 2

More clues...

I chopped up that fabulous piece of lumber and sent it out to be dressed at Atelier Clark, the cooperative shop wing of the Clark artist run centre and general benevolent force in the universe.

Back from the planer, jointer and shaper:

A close-up of the profiles.

Two squares, one with a round over, two different rectangles and one length of left-over.
Of course, I changed my mind on the design and had to laminate a some extra material to one of the profiles. After which I added shoulders to both sides.

Then I made a simple jig to hold the shouldered profile at an angle to the (ripping) blade.

And then I cut off a little tiny wedge that I know is useless, but wont be able to throw away.

On to the chop saw with a block plus a piece of round rod to set the length.
The rod is removed before the cut is made to allow space for the part to move away from the blade safely. The circular form of the rod means that dust/chips can't get between the end of the stock and the block thus guaranteeing a consistent length.

... et voila, the rough part. 

Rinse and repeat 21 more times.

And now I also have a lovely collection of wedgy off cuts that will never ever leave the shop.

Adding a matching shoulder to the top and bottom.

By now, I sure you have all figured out what this is for... but if not, here is a test fit.

A little head-scratching was required to come up with a quick way to chamfer all four corners so that they don't interfere with the inside radius of the sheet metal.

... finally, 22 cup warmer rail stops...

... which all have to be finished with a tiny round-over bit and some old-fashioned sand paper.

Home stretch! The tung-oil finish. I love this stuff. Non-toxic and easy to work with. Just brush it on, let it soak in and wipe off the excess.

And here, after about a day spent more in figuring out how to make them than actually making them, they are.

Rain forest part 1

Teaser for the next installment of the build: 16' of former rainforest.

Sheeeeeeet metal part 4 - powder coat

End of September update: progress has been made on a number of fronts! 

I discussed the auto-fill circuit with a friend who is an electrical engineer. He agrees that in theory at least, an AC circuit is better than DC for this application: "The only potential drawback over an 'AC' based capacitance system is that the probe is always positive and the pot is always negative". In practice however, a DC circuit can be made to work with little or no compromise by limiting the current that passes through it. His suggestion is to use a bipolar transistor which, depending on the components, should limit the current to 1 or 2 uA. Lowering the duty cycle to 1ms per second by strobing the power to the probe may or may not be necessary. In any case, once a layer of scale builds up on the inside of the boiler, all electrolysis bets are off. To be continued when I get around to buying the required parts!

Something much more exciting: after a long delay because of things getting lost in the post, the POWDER COAT PAINT ARRIVED! 

Time to build a paint stand! Two cross bars with pins to fit the holes on the top of the cover: 

...and a pair of U-shaped legs formed with the bender.

Some quick welds...

...and the stand is done.

Unfortunately, I don't have much documentation of the actual powder coat process. I did it at a friend's shop and it was a bit of a mad rush. Also, because he is set up to paint smaller things, applying the powder took four hands, leaving none for the camera. As with most painting, the hard part is the preparation - you know, Saturday afternoon you decide to paint the living room. First you move out all the stuff: the couch, the tv, 10 years of magazines you never read etc., then it's cleaning and putting masking tape on all the trim and every last switch and electrical outlet, then Sunday just after Home Depot closes you realize you forgot to wash the  &*^*%$ing roller and brushes last time so now your whole house is upside down until you have another free weekend... Can you tell I love painting?

Prepping for powder coat is still arduous, but the end result is so much more satifying. First, I sanded the entire inside and outside of the cover to remove every last trace of rust. Then, the part has to be completely de-greased. I started with a commercial water-based de-greaser and then finished with 99% isopropyl alcohol. Then it's into the oven so that the metal can off-gas. As this is mild steel, it turned a pretty color after what is essentially also an annealing process.

Applying the powder itself relies on creating opposing electrostatic charges between the paint particles and the part itself.




After application the part goes back into the oven to melt the polyester resin so that it forms a permanent bond with the substrate.

The date on the first drawing for the cover is the 4th of February 2017. So after eight months and twenty more minutes in the oven, this part is DONE! I think that we might just be starting to see some light at the end of this tunnel.

Controller part 10 - GICARs of the world unite

A collection of GICAR controller circuits.

CIV`s Cimbali Junior 





Dynamos' Gaggia lever 














Circuit from 1998 RL30 GICAR from an Aurora

Controller part 9 - autofill, electrolysis and GICARs

After an interesting discussion on the Home Barista forum about the possibility of a constant DC voltage causing electrolysis of the autofill probe I thought it would be a good idea to revisit the auto-fill circuitry. 

When I repaired the GICAR in my machine, I looked fairly closely at the circuit. I took a few notes, but I didn't draw it completely. Looking back at the notes, what I did see was an AC transformer with two taps, marked as 15V and the other for 20V (these measured 19 and 27 VAC (with no load)). I'm pretty sure that the probe was connected after a rectifier and that a capacitor was used to provide hysteresis. I therefore assumed that there was a constant DC voltage going to the probe. However, I just took the cover off my machine at home and put a multi-meter on the probe. The readings are not conclusive. I see roughly +160mV which seems to drop occasionally, possibly below zero. I don't see AC, but this is on a 200V scale with a cheap digital meter... I'll bring home a better meter this evening. It seems pretty unlikely that there is 19V or 27V AC present though.

Here are the photos of the GICAR controller that I took way back when:

Controller part 8 - eagle fight

Canada is a great place: trees, more trees, beer that doesn't taste like water, Montreal. We even have a puppy for prime minister. Getting things to Canada from the US on the other hand, is like chewing pebbles. I've been waiting since the end of July for paint samples to come by USPS. Lost in the mail. Resent. Still waiting. 

In the interim, I've been in a grim death-struggle with Eagle CAD, candidate for "World's Most Un-intuitive CAD Package". I also wired up the prototype controller. All the AC and signals to the lower board (the bull-dog clips are holding a piece of rubber over the exposed AC connections on the bottom) :

Then I made a break-out for the IO to the micro-controller from a piece of protoboard and some jumper wires. It plugs into un-used analog pins on the Arduino.

Overall it's a bit messy, but not too bad given that it is frankensteined together from various different projects. The only real problem is that the USB port is at the opposite end from all of the other connections. This is inconvenient for positioning the box in the base of the frame. The other mild annoyance is that the LCD screen is just too wide to fit across the short side of the box. So, at least for now, the interface will have to read from the side of the machine. 

The next step is to make custom boards for the keypad/screen and the power distribution/sensors/relays because protoboard just ain't gonna cut it. Ultimately, it would be better to incorporate all three boards into a single one, but that is a lengthy task which requires a much higher volume to make it worthwhile. Here is a first bash at the keypad shield. 

This is a pretty simple board: just the connections between the LCD and the microcontroller to make, plus an IDC connector to hook up a few flavors of power, ground and a bunch of pins to the lower board. The keypad design is clever - all the buttons are on a single analog pin, pressing one of them engages one of five different resistors. The pin reads the resistance and thus can distinguish which button has been pressed. 

There is, however, a mistake in the original design which has been blindly duplicated hundreds of thousands of times. The transistor that controls the LCD back-light is missing a diode (or minimally a resistor) to prevent current flowing back to the IO pin on the microcontroller and burning it out.

Suffice it to say that this shall be remedied.