Drum roaster electric conversion -

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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Chert

#1: Post by Chert »

I went out to our favorite local junk store and found some things to use for my planned electric huky heater. And already questions for the coffee roasting hobbyists.

How do the Probat, Dietrich and other electric drum roasters regulate heat? Duty cycles seem to make too much fluctuations as I imagine it but also experienced it in my long gone bread maker convection top roasting days.

As to the junk I acquired: would a mid century hot plate necessarily have asbestos so I should avoid dismantling it for parts?

LMWDP #198

baldheadracing
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#2: Post by baldheadracing »

A Variac/auto-transformer might be the easiest way to control heat.
- bigger flat burr makes always better grinding result than smaller one - H. Lee

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Chert (original poster)

#3: Post by Chert (original poster) »

Is this a Variac? I've dismantled the Dominion Oven_Broiler and it appears I can reconfigure the 800 watt element fairly easily to take the size dimension I need to become Huky element. It comes with little ceramic pieces to elevate and separate the element coil above the metal housing.

I don't expect that control - however it works- will
do the job. Heck, I don't even know if 800 watts, what like 2650 BTU / hr tops (?) matches the propane burner I'm replacing. But maybe I can preheat the unit with clean electricity the move on to propane .



Clips removed for reconfiguring. ~~~>
LMWDP #198

baldheadracing
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#4: Post by baldheadracing »

That looks like a thermostat to me.

A variable autotransformer varies the voltage that will be going to the heating element, and so offers infinite adjustment of heat. (Variac is a tradename for autotransformers made by the Variac company. https://www.popsci.com/diy/article/2009-10/what-variac/) You may still be able to find surplus Variacs on eBay, as well as new production from other companies. (New Variacs are expensive.)

As for wattage, for comparison: a Quest M6 (550g capacity) is around 1500w; an M3 (200g) around 1000w; and a Hottop (~250g) around 750w.
- bigger flat burr makes always better grinding result than smaller one - H. Lee

luvmy40

#5: Post by luvmy40 »

Be very careful reconfiguring those heater wires. They become brittle with use/age.

The control in your picture looks like an adjustable bi-metal T-Stat. On-off control with quite a wide dead band, probably.

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Chert (original poster)

#6: Post by Chert (original poster) »

Thanks for the tips. I bet you're right. If I arrange the ceramic buckles and t stat to function but wire coil fails, might it be available off the shelf without purchase 1,000 yards? Well junk yards and stores abound too I guess.
LMWDP #198

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Chert (original poster)

#7: Post by Chert (original poster) »

Getting into this cheap test of my conversion I looked at the Quest M6heater elements which consists of two elements , solid, not coiled wire. I'm guessing the resistance wire lies inside a solid tube in those.
I bet small bits of chaff - despite my solid drum - and chaff collector set up - could shorten the life of the coiled resistance wire I sourced in that old broiler.
LMWDP #198

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Chert (original poster)

#8: Post by Chert (original poster) »

So while I sit back from this project to find a more suitable element, there are many threads on PID of heaters to study like nunas' Quest M6 one.

Next time I roast, the Dainty Maid will be tasked with heating the Huky to 200 C charge temp. I'll compare that heat RoR under different fan settings and time to heat up compared to my usual propane heat up. Once hot, after unplugging the Dainty Maid - older than me , no doubt - I can lift the little roaster by the handle and take away the electric pre-warmer, open the gas valve, and roast as usual.



A stove top 240 volt element would be one choice, but 6" diameter for the smaller size is a bit wide for this purpose.
LMWDP #198

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Chert (original poster)

#9: Post by Chert (original poster) »

I did my first test heating with dainty maid pictured above.

Okay anyone interested in a wee contest?

How much time did it take for the roaster to reach 100C from ambient temperature of 19C , when I turned on the heater and started recording?

If you can guess within 2 minutes of it the closest gets free 200g bag of my current espresso blend.

If that same winning guesser can give peak RoR (within 1 deg C /min)during heating, I'll throw in 50 grams more.

Contest ends when I post the preaheating curve tomorrow evening.

To clarify: your entry would state minutes .... And RoR ....
Teaser image of the test run:




*In case of a tie, first guesser takes the prize.
LMWDP #198

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SAS
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#10: Post by SAS »

It never got there. :P
LMWDP #280
Running on fumes.