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first BM/HG mod
Hi All,
I'm still getting the hang of the forum setup. Is this forum for reflecting on a first roaster or just your current and first with developments?

My first roaster was fired up last night. I'ts a BM/HG as stated. I picked up the BM at Savers for $6 and a bunch of odds and ends there as well. I'll post some detailed pic's later as i need to organize the setup a bit. It's pretty normal except i have extended the bean chamber with a pot of the right size and used it to mount the HG and chaff exit. I am using the cheapest Harbor Freight heat gun on II but modulating with a router speed control. I have attached the profile from last night (derived from hand notes). I used a kitchen thermometer probe and didn't realize it maxed at 400F. This will be remedied soon. The result is that i have no idea what the profile is like after 400. I used my IR temp reader but the machine isn't designed for it and i got some wacky numbers. You can see one number plotted showing 495F @12mins. I don't believe it. So in the future i have some better ideas for the dial control and temp metering. Oh, this was 2 cups of green. and the "ideal" is just for my ref.
AMAC attached the following image:
I'd be interested to see what it looks like! I've heard of people drilling holes in the back for chaff and hot air to exit through and I'm hoping to figure out how to mount the heat gun easily. Good luck and thanks!
Thanks for moving this, sorry, the sticky guide was clear.

Tried the roast, prepared as espresso. i'ts far too gone. I need to get this temp probe figured out pronto. I bought a IR meter that i was going to dedicate to this project. The thought was to drill a hole in the lid for the sensor eye and mount it there. On the package it states the environmental temperature max is 120F. So now i realize i cant do it with IR. I suppose everybody has come to this conclusion already and just use a probe/TC in the bean mass. Omega has some IR temp devises that can handle the temp but there quite costly $350 or so.

pic's to come, i need to spruce up a few things and then i'll post
Here is the roast chamber. This is the bread machine bottom grafted to a pot top. The pot top just so happen to be the right diameter, it has a handle and a top. More pic's to come but here you can see the side hole for chaff exit. Obviously the bottom of the pot has been removed. The HVAC duct work seen taped to the side carries chaff from the chamber to a collector. Here i'm gluing a silicone seal to the fish mouth cut on the duct work and taping it to the pot side just for curing against the correct shape. The duct will be stationary and the vessel will drop in and index the hole location with the duct. I didn't need the silicone seal but i had it and thought it might provide a great seal and a bit of compliance between parts.
AMAC attached the following image:
For your temp sensor check out img_1480 in an old thread of mine. A simple K thermocouple snaked down a pipe strap provides excellent results and is cheap and easy.

Honey badger 1k, Bunn LPG-2E, Technivorm, Cimbali Max Hybrid, Vibiemme Double Domo V3
Some pic's and problems:
I've attached pic's of the roaster. I'ts certainly no beauty and it's not producing good results right now. I need some help!

Firstly, the HF heat gun only draws 5A max rather than the 12A stated on the gun. I verified this with a multimeter. Quite strange but i expect such things from HF. I'm not able to ramp as fast as the example profile i've been using and the weak gun must be the reason. Although, the problems i'm having seem to be too much heat? I did two roasts this weekend, the first gave strange results so i changed the way the thermocouple interfaces with the beans. The second roast nearly duplicated the first. The thermocouple is twisted but it's pretty neat and the exposed twist makes contact with the bean mass.

Here is the process as done:
1)I warm everything up to about 80 C using the BM heating element. I just thought this would be a nice way to do it compared to the heat gun.

2) The heat gun is on a HF router speed controller and set to max (5A unfortunately). I keep this setting until i hear first crack. For some reason this happened at 174 C or 346F ?!

3) It's first crack and we want to slow the roast so i reduce power to the HG. The first roast i reduced it way too much and stalled the roast. The second roast i reduced power just a bit so as to slowly climb. The second roast happens to be power at 4 amps.

4) wait for a slow climb to about 430F but i am experiencing rapid second crack, billowing smoke and my the thermocouple is reading about 197F or 387C.

5) pull the roast and sadly stir my oily black beans in their cooling tray.

The second roast of the weekend was pulled right as first crack started rolling. this was too early and the coffee is not developed at all. I was scared. on the plus side i am mixing the over and under roasted beans and producing not garbage espresso, but close.

I thought my TC was reading high because it was sometimes exposed with green beans, but after the beans expand the TC is completely submerged in the bean mass. I suppose it could be a reading issue i have not compared the TC to another measurement tool at elevated temperatures.

Please help!
AMAC attached the following images:
img_20140223_185008_719.jpg img_20140222_210155_765.jpg img_20140223_184849_903.jpg img_20140222_210143_311.jpg img_20140222_211451_251.jpg

Edited by AMAC on 02/25/2014 12:21 PM
How long have your roasts been lasting? As long as your thermometer is consistent you just have to change your expectations for when roast events happen. For example fluid bed roasters can see FC start at 385F, but in a drum it may not be until 410F. I suggest you focus on time and roast events to "calibrate" your thermometer.
"Grind it like it did you some great injustice!"D.L.Clark


Airhan wrote:

How long have your roasts been lasting?

oh right, sorry see attached. The roast that was too far gone(first roast) went for 10 minutes.


As long as your thermometer is consistent you just have to change your expectations for when roast events happen. For example fluid bed roasters can see FC start at 385F, but in a drum it may not be until 410F. I suggest you focus on time and roast events to "calibrate" your thermometer.

It's a good point, thanks, although the killed beans from the first roast showed a max temp of 387F this seems so wrong. That's why i'm so confused and feel like there is an issue with my setup. such as if the heat gun is giving the TC direct IR and causing funny readings?
Problem solved!

I fired up my griddle and set it to 400F. I got my IR thermometer and a meat thermometer and compared them to the meter on my roaster. Firstly my griddle is way off, but that's another matter. The IR and meat probe will read quite close, about +- 3 C. Here is the kicker, when my griddle is 160C the TC on my roaster was reading 105C! I also submerged in an ice bath and I cant' recall what the reading was. So it was either my TC or the PID controller. (BTW the controller is not controlling just reading temp, it was one i had around). So i got another K type probe and it was working fine. The culprit was the twisted end making poor contact. I wanted to use the original wires as they are in a sleeve which interfaces with the BM just right so i cleaned them up with sand paper and crimped one of those electrical wire end effectors on the pair and snipped it way down. Now the TC reads perfectly. In retrospect the twisting may be ok but clean wires are critical.
That's interesting, I would never have thought cleaning the thermocouple wires would make a difference, but It does make sense. I'm glad you figured that out!
"Grind it like it did you some great injustice!"D.L.Clark
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