Wednesday, December 2, 2015

The Coffee Calibration


It was late September, I was still enjoying work at the photocopier warehouse, though it was clear that the work was winding down.  That job did not pay enough despite its value in pointing me towards desirable work.  What it did do was have me looking at machines filled with gears, wires, sensors and rollers all day.  Not something I look do at home typically, but there were special circumstances.

I was planning a camping trip.  It was  trip planned at the end of summer, for near the end of September.  This was one of an ongoing series of field tests designed to ramp up the level of our outdoor adventures.  The core gear was proven and provided by the other member of the expedition.  Both by opportunity and inclination I took on the food.  A very specific set of things got into my head, I ran between several stores in different parts of town looking for and often failing to find what I had aimed to prepare. I spent more money in more places than I was comfortable with.  The last item on the list was coffee, a necessity for me.  The original plan, which is still a good one was to buy Turkish or Lebanese style coffee.  The stuff is finely ground and can be brewed with nothing more than a pot and boiling water. Two days before the trip I was spent from hunting all the other things, leaving the house for one last thing was not going to happen.  Enter the coffee grinder.

The faithful bean crusher.
 On paper, quite literally, my coffee grinder is able to produce a Turkish grind. It says so in the user's manual.  I have a moderately fancy grinder, it is a conical burr grinder, not a blade grinder.  The blade grinder is the one you likely have at home, two little knives spinning in a close little cup.  You hold your hand on the trigger till the beans sound right or your fingers go numb. I could never get consistent results with that, so I upgrade.  The upgrade, solved the consistency problem, I adjust two knobs, fill the upper hopper with beans, push one button and the lower hopper fills with correct amount of correctly ground coffee.  Except when I tried to grind ultra fine. 

The plan was simple.  Grind the coffee as fine as the machine would let me.  Take the powder out to the woods add boiling water let it settle. The reality proved more frustrating and a lot more chewy than planned. I turned the dial, it goes from 9 to 1, 1 being the finest setting.  Somewhere near 2.5 it jammed, it would not budge.  Pushing any harder on the plastic wheel would have risked ripping off the flesh of my thumb or braking the plastic gear.  At that time I had spent more than 8 months with a  screw drive in my hand for most of the day, I was used to big complex machines, even if I was only touching the simplest parts of them.  The demand for coffee in the following morning cemented in my head, I would fix it and I would fix it now.

Step one, was grind some coffee at the setting it jammed on just it case I broke it, this is what I took camping.  Then it was a simple mater, of unplugging it, emptying the bean hopper and separating the top and bottom halves of the machine.  That part actually went well, I had a screw driver fine enough to engage the small phillips heads that held the top half in place, and all the parts I would need to access were at that level.  It was the parts I did not expect that caused the first problem, where did that spring a plastic cap come from.

Now to get a little technical.  This grinder drops the beans between two steel discs fitted with what looks like carbide tool faces, making it the cutest tunnel boring machine ever.  When the grinds are fine enough that the teeth can not longer engage with them the fall out into the lower hopper.  Grind size is controlled by the spacing between the to discs. Simple right.  Thats what I thought.  So I cleaned all the parts I could reach, betting it was gunk jamming things put it back together and tested it.
Lower grinder. All the gears removed. Note the threading above the disc.

It worked.  It worked in that, the dials turned, the power went on and coffee was ground. The coffee was ground so coarse that only way you could have brewed anything out of it was boiling it stove top, till the souls of the beans scream for the fires of hell. I had missed a key element of the design.  A simple elegant and logical design.  The upper disc of the grinder nests in a plastic cup that threads into the lower half of the machine, it is also toothed along the outside. When you turn the grind selection knob you are causing a second gear to rase or lower the cup holding the grinder.  When I had put it together the first time(s) the grinder elements were far enough apart that all they could do was politely crush the beans.

So I took it a part again. And again. I recall perhaps as many as five strip downs. I found the use of the plastic cap, and where the spring went. They both went under the selection knob to hold it in place. On the most worrying test runs the machine refused to run, the lid was off, a user error.  Calibration also included several runs where I was very confident of things going great, until for no apparent reason upper plate rattled loose. The reason is crystal clear now that it is not late in the evening hours into the project. They were too close together and upper half twisted loose. It made a frightful racket.
Upper Hopper, lower grinder

At the edge of giving up I tested it yet again.  It worked, sort of.  Nothing jammed nothing rattled loose, coffee came out.  However, the knob said it was grinding the coarsest, but the output said it was grinding its finest.  Had I tried to select a finer setting at that point things would have jammed quickly. But I had a calibration point, an output close to Turkish. The fix then was simple, without moving any of the other parts I lifted the selection knob and dropped it back down inverting the settings.  That worked, it now grinds the full range as described in the manual, the knob still travels freely between all the settings.

Ideally I would have liked to strip the machine to create  a detailed photo log of what I did, but that is unwise.  The three screws that hold the upper
Upper grinder. 
half on have an aggressive thread and connect with soft plastic stocks, mess up that plastic and I won't be able have it hold together.

The end of September and first half of October saw me drinking a lot of extra bitter coffee. The first calibration runs half ground a lot of beans, I had a freezer bag full of them, there was no way I was tossing them out.

As for the camping trip. I used the inappropriately ground coffee I had saved just before I started tinkering. It was far too chewy to be worth recommending. The grounds made a plug in the throat of the thermos and the only way to get the coffee out was to get more grit in your cup.  On the second camping trip it was not chewy. Yes my cup got lined with a thick black sludge, but thats normal. It out performed the instant coffee brought by others.  Next time I might just buy the damn stuff.

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