Overview: New Quest M3s Sample Roaster
Quest recently released their new M3s roaster, a revamp of the original M3 model, but with a couple of new features. At 7 1/8" across, on it's face, the upgrades appear to be minor. But a closer look reveals a chaff drawer at the bottom, an extra analog thermometer for measuring bean temperature, and perhaps the biggest but least visible changes are the improvements to both the airflow and the drum insulation. Another improvement is that you can now thoroughly clean the roaster without removing the outer shell. We'll break down these new features as well as share test results of side by side comparisons.
If you're not familiar with the Quest M3, then I've probably already confused you. They're snazzy little hand-made stainless steel drum roasters. The Quest functions great as a sample roaster, but is more "kitchen appliance" in size than your typical single barrel setup. Heat is delivered by two electric heating elements to the bottom right and left of the drum. Both heat and airflow are controlled manually, and the roaster has a built-in cooling compartment in the rear that effectively cools your roast batch completely in less than 3 minutes. For all intents and purposes, this roaster is ideal for shops who need to assess a handful of coffee samples at a time since you're still looking at 8 - 10 minute roast time from start to finish.
Airflow on both roasters starts by pulling outside air in through access holes at the back of the roasting chamber. This ambient air flows across the drum, up the front "batch input" duct, through the top tube, and finally out the back of the machine via a variable speed fan in the cooling tray (the above diagram illustrates M3 airflow). On the old Quest M3, the air inlet is a quarter-sized hole just behind the drum that doubles as a cleaning access hole. One potential problem with this design is that the large hole creates little air resistance, significantly reducing suction for pulling chaff. In addition, the air coming in is ambient (in my case, 70 degrees today), and the more you pull across the coffee, the higher the risk of reducing roast charge and stalling. That said, finding potential weak spots design-wise is all part of figuring out how to use any roaster new to you, and we found these to be fairly easy to work around.
The design of the new M3s addresses the airflow inconsistency. They've done away with the large access hole, replacing with three steel air-inlet tubes, approximately 3" in length, and 1/4" in diameter. They are positioned between each of the two heating coils at the sides of the drum, and one along the top of the drum, naturally heating up with the roaster. Much like a heat exchange water heater is reliant on a small reservoir, the small diameter of the tubes rapidly warms the incoming ambient air, appreciably reducing the risk of a stalled roast. The intake holes that feed into these tubes are even smaller in diameter, which also promotes suction by creating greater resistance. These tubes provide added thermal mass as well, taking on a significant amount of heat, helping with overall heat retention.
Heat retention is also reinforced with an extra layer of metal attached to the exterior. If you've removed the outer shell on your Quest, you've probably noticed a lack of insulation altogether. While the new model doesn't include insulating material, the extra layer of metal adds to the overall barrier, helping to minimize heat transfer between inside the drum and the outside air. The outer layer rests approximately 1/16" above the pre-existing outside of the chassis (which has not changed), the air space in between facilitating some thermal resistance as well. It also affords you the opportunity to make a simple modification, adding an insulating material like fiberglass, or silica to the cavity in between.
I did a side by side comparison of heat retention in both machines, and was surprised by the difference in cool down times. The test was rather simple, and I imagine there will be some variance if run multiple times, however I expect the M3s to always outperform the M3 because of the aforementioned modifications. First I brought both machines up to roast temperature by roasting three 100 gram batches. After cooling the final batch, I closed the front door at 400 degrees, cut the heat and turned the fan to high, tracking the drop in temperature over a 6 minute period. During that time, the M3s lost 78 degrees, compared to a 125 degree loss from the M3. I imagine you could widen this divide significantly with the addition of insulation between the two outer metal layers.
Both Quests are incredibly simple to take apart, requiring nothing more than an allen key set and about a half hour to fully disassemble. This was especially handy for the first generation model in order to clean out chaff that collects under the roast chamber. The chaff tray on the new model nearly eliminates this need, catching much of the wayward chaff, and giving you access to vacuum anything that hasn't collected in the tray.
The extra analog thermometer in the front just above the door is supposed to be used as a bean probe. I imagine beans might make contact if roasting larger batches (150 grams or so), but with 100 grams, it still seems out of reach. I find the analog thermometers to be pretty clumsy, and not entirely accurate. I would ditch the lower position thermometer right out of the box in favor of a digital thermocouple, in order to be able to more accurately track roast development.
- I prefer a 100 gram batch size, because in most cases, importers send us 200 gram samples so this gives you two chances to get the roast right! I warm up the machine with the amps set to 7.5 - 8, and airflow at 2.
So how does it roast? I've logged a couple dozen roasts on the M3s over the past month or so, and find that like the M3, once you figure out the best settings to achieve a desired roast profile, you won't stray far from them trying to replicate results from one batch to the next. But finding them can be a bit tricky, and so I've included a few tips to help set you off in the right direction.
- The first batch roasts fairly quickly, in most cases finish times will be in the 4 - 6 minute range. It takes a couple roasts for heat to stabilize. That is, batch 3 is usually the precedent for the roasts that follow.
- I keep the heat right around 7.5 amps, and air at 2 for the majority of my roasting, switching the air to full blast just before dropping into the cooling tray in order to remove chaff. This gets me 1st crack somewhere between 6 - 8 minutes depending on bean density, moisture, etc., and finish times between 8 and 10 minutes.
- The temp readings read a little low on my digital thermometer; around 385 for 1st crack, and I'm pulling City roasts right around 405 - 410 F. The analog seemed to read within a couple degrees of this as well, but as stated earlier, it's hard to track incremental change on the analog.
- Try cutting the heat while cooling the roast, which with the M3s takes about 2 minutes (about 1 full minute faster than the older M3). After cooling I return the heat and air to the initial settings and start roasting the next batch.
- The heat range on these machines is fairly tight, meaning I don't generally wander outside 7 - 8.5 amps period. In my experience, below 7 amps won't push 100 grams to 1st crack, and anything above 8 gets the coffee popping well under 6 minutes.
The M3s's upgraded air flow and added insulation greatly assist heat consistency and retention, allowing you to make fewer adjustments to keep the roast progressing. As a matter of fact, other than cutting heat when cooling a batch, I like to pretty much keep the heat locked in at one setting all the way through from green to finish, much like how I use our electric Probat 3-barrel sample roaster. That's how I think this machine functions best: as a small-batch, single-barrel, shop sample roaster. Additional information is provided on the Quest M3s product page, along with detailed photos, and ordering info.