You could inject controlled hot air to the inside of the drum directly. It is not perfect but it may help.

Heatgun upgrade for Quest M3 roaster

Cheers

My point was that there's no hot air entering thru the back of the drum like a traditional drum roaster.

Agreed. Air does come in at the back, as the drum is open, just like the front. But, the air is not super hot, as the makeup air comes in at the lower back. The air being sucked into the drum at the lower front of the drum, on the other hand, has had a chance to come past the heaters and the heated drum, so it must be much hotter.

Regardless of what the fan does or does not do, IMHO, once one gets used to the Quest it is possible to turn out some dandy roasts. At first I was nearly temped to dump it and go back to my air roasters, and build a new air roaster for which I've collected most of the parts. But, as I've gained experience I've been turning out really good roasts. At the risk of going somewhat off-thread, a few things I do on my new-style Quest are:
--Charge of ~450 g (half a pound)...I've given up on trying to roast lesser amounts as the results were too variable. I've not tried more than 450 g, but will.
--At least 200 C pre-heat, but no hotter than ~210 (depending on bean density) to avoid burning the exterior of the beans on charge. I pre-heat at 10-Amps/low fan, but it would probably be better to back off the heat a bit and get the roaster more evenly hot...too impatient .
--keep the heat on the high side and the fan low at first but watch the elapsed time (I shoot for about 4 minutes to dry ~150 C).
--Drop the heat and or increase the fan after drying but well before 1C, monitoring BT to ensure no negative ROR. I shoot for about 7 or 8 minutes from dry to 1C with most beans.
--Ride the heat and/or blower to keep the Delta-MET steady at a modest rise (say about 3 C) after 1C but watching the overall elapsed time to 2C. If it looks like more than about 4 minutes, I'll pop the heat up significantly and drop the fan to avoid the roast being too flat. I generally dump on the first sounds of 2C, but do use colour in the window and smell from the trier as my primary indicators.
--I've given up watching and smelling the vapour and smoke coming out the back vent as indicators...just did not work for me.

I've been thinking about drilling some holes through the drum near the very back. Basically making the back 1/2 inch of the drum perforated. Anyone do this? The upside is that you'll get air into the drum without doing too much metal work. The downside is that the back 1/2 inch of the drum will be at a different temperature (the drum temperature itself) since there will be significant airflow through it. However, I'm not sure how much that will affect the roast, since i'm sure that most production roasters deal with drum hot spots anyway.

I've been thinking about drilling some holes through the drum near the very back.

Why would one want to do this? If my theory about the air flow (see above) is correct, the air being sucked into the drum will be mostly ambient air coming in from the hole at the bottom/back of the roaster, not heated air. I'm not clear as to what folks wanting to change the air flow in the Quest want to do. What am I missing?

Holes anywhere near the rear of the drum will entrain air that is super hot. The drums rotating and there's going to be incredibly hot air up at the top of the outermost shell of the roaster as well ( heat rises). It's not just going to suck in cool air from the rear hole and drag it thru. I think tweaks to the drum would be a fun experiment, but like I mentioned before, I'd likely combine them with some form of enclosure that allows the ambient air to be pre-heated somewhat.

wrakocy wrote:Don't get discouraged Mark. It took me months to get the knack of roasting on the Quest.

For what it's worth (and at the risk of steering the thread toward a Quest "recipe" discussion), I've found on my 2014 build that aggressive application of heat during the drying and ramp phases of the roast nearly always gets me better results in the cup. For kicks, try experimenting with higher charge temperatures (something closer to 401F/205C) and more heat input up to and even through the first 15 to 30 seconds of first crack.

By way of example, on my 200 gram batches, I typically charge at 401F/205C and apply between 10 and 10.5 amps (with fan set at around 2) up to around 365F/185C, at which point I briefly *boost* my amps to between 11.0 and max to get a good vigorous first crack going. At around 390F/199C I cut heat to between 0.0 and 5.0 amps (and boost the fan to around 4) and drop between 406F/208C and 422F/217C, depending on the roast degree I'm looking for.

Obviously, there are many (many) different ways to skin the cat here and I'm by no means claiming that this is the best approach. Just wanted to throw it your way as, based on the graph you posted, it's bound to get you something different to ponder

Hope that helps!

Thanks, I'll give it at try soon.

TomC wrote:Holes anywhere near the rear of the drum will entrain air that is super hot. The drums rotating and there's going to be incredibly hot air up at the top of the outermost shell of the roaster as well ( heat rises). It's not just going to suck in cool air from the rear hole and drag it thru. I think tweaks to the drum would be a fun experiment, but like I mentioned before, I'd likely combine them with some form of enclosure that allows the ambient air to be pre-heated somewhat.

I was thinking something like this too.

Would a small shield by the rear hole that pulled the ambient incoming air over the bottom of the drum into the roaster work? I thought I remembered a mod of Arpi's that did something like that.

Nunas wrote:Why would one want to do this? If my theory about the air flow (see above) is correct, the air being sucked into the drum will be mostly ambient air coming in from the hole at the bottom/back of the roaster, not heated air. I'm not clear as to what folks wanting to change the air flow in the Quest want to do. What am I missing?

If warm air was pulling through the bean mass, the Quest would perform more like a traditional drum roaster. And may be able to be used as a sample roaster for profiling on a larger roaster.

The others in this thread may be able the correct me if I'm wrong.

markmark1 wrote:I was thinking something like this too.

Would a small shield by the rear hole that pulled the ambient incoming air over the bottom of the drum into the roaster work? I thought I remembered a mod of Arpi's that did something like that.

You need the air to come in relatively unobstructed. With the back of the drum perforated, air will be simply drawn thru, pulling heated air in the space surrounding the drum. It shouldn't take a complete re-engineering of the whole thing in order to accomplish this.

markmark1 wrote:If warm air was pulling through the bean mass, the Quest would perform more like a traditional drum roaster. And may be able to be used as a sample roaster for profiling on a larger roaster.

The others in this thread may be able the correct me if I'm wrong.

I said exactly this a few posts up.