Con-vert-i-ble

Before:



After:



Distinctly different roast behavior and cup profile. No verdict yet...

Huky Motor Replacement (aka "Let the Good Times Roll")

Based on the feedback of my recent roasts, I am convinced that the increased rpm (from 43 to 52) contributed positively. The roasts are more even and the heat transfer efficiency increased. The roaster response also increased slightly as the result of the higher rotation speed.

The next step in this experiment is to replace the stock motor with a higher rpm one and install a motor speed controller so the rotation speed can be profiled throughout the roast. After watching ebay for several weeks, I finally found a unit with the right rpm and torque that is affordable as well. I quickly snatched up the motor and eagerly waited for its arrival.

Here's a quick comparison of the new and stock motors (running at 24 VDC):

Stock motor:

Manufacturer: Shayang Ye Industrial Co.
Model#: RB400150-06202
Reduction ratio: 100:1
Rated speed: 54rpm
Rated torque: 6.1 lbf-in (97.2 oz-in)

New motor:

Manufacturer: Pittman
Model#: GM8723G567
Reduction ratio: 96:1
Rated speed: 86.5rpm
Rated continuous torque: 7.1 lbf-in (113.3 oz-in)

The new motor is a much heftier unit and the construction is very solid. It is also not cheap if purchased new. The NOS unit I got is very reasonably priced. As usual, trimming and fitting are necessary to get it go into existing housing. The current coupling sleeve was drilled to accept the circular shaft. I was initially concerned about slippage and mis-alignment, but so far it seemed to be fine.

I had originally planned to purchased a PWM (pulsed width modulation) motor control unit from ebay but after conversation with a very generous co-worker (Dr. Gizmo), he designed/installed a analog motor speed control for me. Below is his schematic of the circuit:
The new motor/controller setup allows me to vary the speed from 20 to 80 rpm. At speed below 20rpm, the tachometer no longer register the speed and I do not think such low speed is necessary. The maximum rpm dropped from 83 to 80 due to the voltage drop at the transistors. Noted that in actual use, the rpm will go up 1 to 2 more when the roaster is fully warmed up.

This latest mod puts the little huky a step closer to a "commercial" sample roaster that I desired. I am very excited to start experimenting with speed profiling and anxious to see if it can solve one of the remaining deficiencies of the roaster.

Tachometer for Huky300

Bicycle tachometer modified to fit and measure drum rotation rpm. This is done in anticipation of future motor replacement (of a higher rpm unit) and addition of variable speed control. Goal is to have drum rotation as part of the profiling, in additional to gas and air settings.

I replaced the stock 20vdc adaptor with a 24vdc unit, which "restores" the stock motor to it's default speed. The "as-purchased" configuration down-rated the motor (reason unknown). Drum rotation increased from 44rpm to 52rpm.

Trial runs already showed differences in the profile. At first glance, roasts seemed to be much more even at the higher drum speed. How it affect the cup will be determined in the coming weeks...

Minor (roaster) upgrade

What? You think I am going to leave my toys un-moded?! ;-)

After some discussions with Simon, it was felt that this is the best thing I can do right now to improve the consistency of my roasts. Onto the next level...

UPDATE (4/9/07):

Did a whole bunch of roasts this weekend. This mod has turn out to be a pivotal point of my roasting experiment. I now truly have control over the profile and roasts are so consistent that the curves are practically on top of each other. Getting the profile is also much easier than before. The fun begins....

- Ben C.

New Toy

Huky300 Coffee Roaster
Capacity: 100~360g (3.5~12.7oz), 250g (8.8oz) recommended (limited by cooling)
Size: 16" x 7.5" x 14" (L x W x H)
Weight: 13 lbs
Mirror Polished 304 Stainless Steel


Perforated Stainless Steel Drum with dual agitator vanes (4.7" diameter x ~0.1" thick)
50rpm-24VDC motor (running @ 20VDC -40rpm)


Custom machined stainless steel axial/bearing (vacuum heat treated)


Bean sampler and quick release gate
Solid rosewood handle
Dual temperature probe: type-K thermocouple and analog


Exhaust vent with gate valve and chaff collector


Accessories: Storage bucket, cooling basket, cooling/exhaust fan, DC power supply, bean funnel (hand made)


High-output Portable Butane Gas Stove with ceramic element (for infrared heat)


Just about every single piece on this roaster is hand made due to the limited production number. Everything is made to last at very high fit and finish (the thing is almost entirely of stainless). The craftsmanship is amazing.

I've done two roasts with it and it's not an easy roaster to use due to its all manual nature. I never use a direct flame drum roaster, let alone one that has air-flow control. The bean probe is very accurate and the thick gauge steel drum is able to retain heat once up to temperature. There are much to learn from this setup but I believe it will teach me more than any currently available home roasters (sample roaster does not count...).


- Ben C.