Switches on hot air popper coffee roaster

switches

The Poplite popcorn popper I’ve been using as a coffee roaster lacked even a simple power switch.  I ordered a couple of suitably-rated toggle switches and wired them in to control the power to the whole shebang as well as to switch off the heater while allowing the fan to keep blowing.  This should (1) allow for cooling of the beans in situ and (2) help cool the device between batches to prevent the thermal cut-out from kicking in.

The wiring inside the popper is really simple (check out the diode bridge around the DC blower motor) and I managed to wire the switches correctly by just eyeballing the scene.  Looking forward to using it.  By the way the chimney extension I made out of sheet metal works nicely.

Amazon appears to suggest caffeine for kids

amazon bigger

On Amazon today this image caught my eye:

Pretty interesting organic molecule, I thought. It looks kind of familiar.  I resized and sharpened the atomic drawing to make it easier to see:

Some of the N and H characters are hard to distinguish if you don’t know any organic chemistry, but if you do it’s clear which is which.

Anyway here’s a caffeine molecule (unlike the Amazon drawing it doesn’t draw out all the carbons and hydrogens):

The molecule on Amazon isn’t shown complete, so there’s plausible deniability, but it sure looks like Amazon thinks caffeine is a “school essential” for K-12 students. I wonder if it works as well as ritalin.

Popcorn Popper Chimney for Coffee Roasting

chimney installed

As noted before, I’ve been using a hot air popcorn popper to roast coffee. The tin can “chimney”I was using to keep the beans from flying out was a little short. For a while I had it extended with some metal foil tape, but the tape was not holding up well.

I had some extra sheet metal around and a Pop brand riveter from a yard sale so I tried to extend the can a bit.

I wound up with an extra drilled hole where one of the rivets didn’t take (a poor artist blames his tools, but really that rivet gun is lousy). It looks relatively durable.

It doesn’t add a lot of height to the can itself, but because the added diameter keeps the can from extending deep into the popper it effectively adds a good amount of height to the chimney. The week’s roasting was already complete when I made the thing, so operational testing will have to wait.

Rancilio Silvia Portafilter Gasket Replacement

old portafilter gasket

Poort Miss Silvia was still laboring with the original brew system gasket that seals the portafilter against the body of the machine.  After six years of almost daily use, a replacement was in order as it was prone to leaks.

I knew the old gasket would be difficult to remove but I had a few dental pick style tools ready.  This is what it looked like after removing the diffusion screen:

You can seen a channel worn around the diameter of the gasket where it was crushed by the portafilter.  The diffusion screen was badly grunged up and there’s a stained pattern of holes on the brass behind where the screen was.

The old gasket was hardened and brittle in spots.  I wound up using a chisel at times to cut the material.  Here’s the remains of the old gasket next to the new gasket:

The cheap Harbor Freight tools didn’t stand up to the job very well – the dental picks bent easily and the chisel was damaged too:

Once the old gasket was out I ran the machine before reassembly to make sure no old gasket material would be trapped behind the diffusion screen.  I didn’t expect it to shoot a stream in a forward direction.

Getting the new gasket in was relatively easy and it was nice and squishy compared to the old one.  I won’t wait six years to do the next replacement!

Rebuilding the Rancilio Silvia steam valve

wand o-rings

I’ve had my excellent Rancilio Silvia (“Miss Silvia”) espresso machine for seven years now and the steam wand developed a dribbling leak.   Time to rebuild that sucker!

I ordered replacement o-rings and seals from 1st line and was happy to get the parts just the day after ordering them, despite just using ground shipping.  Most of the work in rebuilding the steam valve went as described here, though there were a few things worth pointing out.

It is important to back up the flare nut fitting when removing the steam valve from the solid copper tubing connecting it to the boiler, to avoid twisting and kinking the solid tubing.  Here’s a photo with blue-handled wrenches (the top one is out of focus):

I used a couple of cone wrenches that had previously seen service in rebuilding bicycle wheel hubs (a side benefit of having too many endeavours is having a bunch of related tools that could serve other uses).

The steam wand itself was stuck hard and it took a lot of force to remove it.  It has an odd plastic bit where I expected an o-ring.  This photo shows the degraded plastic bit alongside the o-ring I replaced it with:

I removed the degraded black plastic bit when I rebuilt it.

Here is a test before I re-assembled the housing.  The PID controller I’d added years ago for temperature control is resting at the bottom left – I had to pull it out to access the steam valve.  The boiler has wooly ceramic insulation installed to try and protect the electronics in the PID

No leaks!  Hopefully Miss Silvia will provide many more years of service.

Roasting Coffee

roasting

So Mrs. Nerdly called me saying she found a hot air popcorn popper at Community Forklift for $5 – should she buy it for roasting coffee?  Why not!

Years ago I’d used a Zach and Dani’s roaster (now Nesco) when I lived in an apartment – that roaster had a nice feature of an “afterburner” to reduce the inevitable smoke from roasting coffee.  But it crapped out as the belt driving the auger started slipping, and I junked it after stripping out some parts for my junk salvage box.

This new device is a Presto Poplite model 04820 (or as it says on the bottom of mine, 0482007) and fairly powerful at 1440 Watts.  I guess there was a glass top or something at one point for popcorn, but no matter that it was missing.

I started with some green coffee beans from the fantastic Sweet Maria’s: Espresso Monkey and another espresso blend, “Espresso Workshop #21 -The Satpura Fold.”

I did four batches, two of each blend, each using about a half cup of green beans.  I put an open-ended food can on the top of the roaster as a chimney

With about half a cup of beans, I lost a few beans blown out the top, but I like to think they were mostly sickly light dried-up beans.  It did a nice job blowing the chaff out.  Definitely something to be done outside!

The end results looked nice and I look forward to tasting them tomorrow.  I got about 11 ounces by weight of roasted coffee from the four small batches.

Incidentally, I would swear I got a caffeine buzz from being near the coffee as it roasted.