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BM / HG Roasting Starting Point
I just roasted my 3rd batch of coffee (sumatra aceh mandheling) from Sweet Marias. I'm roasting 1 lb at a time and I have a pid to register temps (in C), keep the top of the BM covered, and put a vent in the lower back of the machine to get rid of chaff. I got to the start of first crack in about 8 mins and my temp probe registered 180 C/356 F. This seems about right from what I've read.

This is where I'm having problems. I was shooting for City+ or Full City but on my first 2 batches it went so quick into second crack I kind of missed my window. This batch, I cut the output of my heat gun roughly in 1/2 once 1st crack got going, but the roast stalled. Temps slowed to a stop then started going down. I jacked the heat back up and then went into second crack when the temp read 208 C / 406 F. The roast probably finished around the 12/13 min mark.

I feel like I'm flying blind. Does anyone have any recommendations for a good starting point for settings on a BM/HG setup like mine? I'm trying to get better at controlling the roast with a current setup after first crack? I really want to be able to shoot for City+ / Full City for most of my roasts.
Half power is too low.I use hg bm setup. I use a router controller for heat control. I toggle the switch to variable at first crack. I have measured the voltage at the heat gun after the controller and I'm getting an observed reading of 65 volts or so. Maybe a little more. Any lower and I get stalling. Hope this helps.
Bad coffee prevails when good coffee roasters stand by and do nothing.
Thanks, that's a HUGE help. What size charge are you roasting at a time?
My breadpan limits me to 400 grams. It yields exactly3/4 lb. My prior roaster had everything the same. Showing me that this setup is capable of 536 grams, which will yield1 lb. If I can replace the bread pan. This may be possible. But I will probably leave it like it is and get it all completed. That way I can post a few pics in the roasting station forum. And get on to my next build. :)Grin
Bad coffee prevails when good coffee roasters stand by and do nothing.
What about your pan limits the charge, do beans fly out of the bread pan because it is it just too small? I've been roasting 1 lb and am tempted to shrink that to 1/2 lb but am not sure how much less heat I'll need. Do you think that a smaller charge would be easier to roast?
Yes. My pan is too small. You can roast a half pound. But you will need to practice. Try to hit150 at the four minutes point and 1st crack around 8. Keep logs. Refer to them for any adjustments in those temp/time frames.
Bad coffee prevails when good coffee roasters stand by and do nothing.
I normally roast 500 gm and will react slower compared to your case therefore requires changes in advance.
Try dropping by 50 deg celcius at the first sign of first crack so that the exothermic reaction does not cause it to run away.
One minute after end of first crack drop by another10 deg to avoid the "flick".
Sorry for the gram and celcius due to me from oz.
Another member of the KKTO rider's club, together with coretto, FZ-RR700 Baby Roaster and a sad sack of less than 20 kilograms of greens.
For example, my heatgun is showing 500 centigrade til first snaps first crack.
Turned down to 450-460 til end of the roast.
By all use it as a guide.
Your set up will differ by batch size, heat gun nozzle distance, environment temperature etc.
Over time you will achieve better results after adjustments.
I can recommend taking samples out every 15 seconds , log the times and cupping.
Do it a minute after first crack ends.
Another member of the KKTO rider's club, together with coretto, FZ-RR700 Baby Roaster and a sad sack of less than 20 kilograms of greens.
Lawnmowerman - I picked up a router speed control from Harbor Freight and tried it last night for the first time. It seems to be very sensative in that if I decrease the "power" even slightly it reduces the head significantly.

I also tried to monitor the voltage of the outlet with a multimeter and oddly enough it always read about 122V regardless of the setting on the dial. I made sure that it was on variable mode :)
That is strange. Something isn't right. I've consistently been able to observe wide voltage swings at the output of a router control. That's where the heat gun plugs in. It MAY be the voltmeter because the router controller distorts the sine wave and voltmeters are designed to read a pure sine wave to get an accurate reading. The router controller clips off the leading edge of the sine wave, but the PEAK voltage of the signal will still be the same. The power delivered is averaged out. My voltmeter is also harbor freight. It is the one they give away when you make a purchase. I'm only guessing, but here's an explanation: if your voltmeter reads the PEAK voltage then calculates rms volts from the peak, a router controller would display no change.
Bad coffee prevails when good coffee roasters stand by and do nothing.
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