Post By artman
Behmor 1600+ temperature and drum speed questions
I have a few questions about what is happening inside my machine when I am roasting.
Firstly, when I increase the drum speed, I believe this makes the roast more even as the beans are moving more, does it also effect the overall temperature of the beans, or have any other effects? There must be some reason faster is optional not standard, but I am not sure what that is.
I regards to the temperature readouts given by the machine, I have realised the exhaust fan kicks in during the roast, causing the temperature given for the drum wall to drop. Is this an actual temperature drop effecting the beans? Are these temperature readouts actually useful in controlling the roast? I have only just started looking at these temperatures, not sure how to deal with the change once the fan starts.
I have just gotten to the stage where I am comfortable with how the machine works and can make a decent but not exceptional roast. I am wanting to start improving the quality, so any other tips you can give me for this machine would also be great
The drum speed will affect the extent to which the beans receive direct heat from the element (and the basket I guess) or from the airflow within the roaster. So increasing speed (particularly after you hit first crack) reduces the chance of scorching and/ or tipping the beans.
Originally Posted by leoniedukes
But will it have any other effect? Is there a downside to the faster drum?
Given that the new Behmor AB has increased the drum speeds to 16/32 - The faster drum speed on the 1600+ is my preference.
my basic method is a 70deg C preheat and then i let the B temp come up to 100 deg C and then i double speed the drum.
and with respect to the A- temp. the afterburners and exhaust kick in at the 10:30 on a 400g roast, I use the A-temp to gauge rate of rise trying to hit somewhere around the 10deg/min after it has reached 130degC and you can also hold it at certain temps along the ramp up until you hit your final temperature.
Temperature readings with the A and B buttons on the Behmor plus are like thermocouples on coffee machine boilers -- they tell you what is happening somewhere else away from the place of interest.
In a coffee machine the place of interest is the water temperature at the shower screen...in the behmor it is temperature in the rotating mass of beans.
So when the B button says 140 degrees C and first crack starts, I have no idea what the temperature is at the beans.
I do know that at this point, playing wih the buttons to raise or drop the temperature, while that will work and I do do it....it is with the understanding there will be an appreciable lag before it all happens.
A faster drum rotation will speed up the roast. Think of it from this extreme analogy:. If the drum is not turning at all, the beans closest to the elements will be heating up...while those on the far side will be relatively cool, insulated from the heat.
But start the drum spinning and every bean gets exposure to heat.
If you want to play with temps you really need something meaningful like bean temp. You can do this easily on the behmor by drilling the cetnre spindle of the drum at the lid (non drive end) and bending a thin thermocouple then using whatever readout you want, preferably something like the heat snob and roast monitor software where its an easy to follow graphic.
The thermocouple setup info is around here somewhere, i think it ended up getting called the wiper mod? Because I used a wiper blade stiffening stainless strip to attach the thin bead thermocouple to. Its very effective and reversible.