Quest M3 exhaust vanes mod

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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#1: Post by Peppersass »

I'm about to install a Quest M3s drum and a new fan in my Quest M3. I'm wondering if while I have the machine open it would be worthwhile to enlarge the exhaust openings in the rear panel.

In the Quest M3 Mods thread, TomC describes removing the vanes, though mainly to reduce cleaning frequency and to better feel the airflow during the roast. But in a later post he refers to the mod improving airflow, as does at least one other poster.

The only reason i would do the mod is to improve airflow. I'm OK with cleaning frequency and I can't feel the airflow during the roast because my exhaust opening is completely covered by a flexible hose and adapter screwed to the rear panel.

So my first question is whether the airflow improves enough to make the mod worthwhile? If so, my second question is what's the best way to do the mod?

I can think if three alternatives for enlarging the opening:

1) Remove all the vanes (probably with a Dremel too). Given that the opening is completely covered during roasting, there's no safety issue. But If I resell the machine the next owner might not want to use a hose, perhaps creating both safety and aesthetic issues.

2) Remove every other vane. I think this will provide as much improvement in airflow (if any) as removing all the vanes, but would be more appealing aesthetically. However, I think the openings would be large enough for fingers to get through, creating a possible safety issue on resale.

3) Cut or file the ends of the vanes so they can be turned 90-degrees from vertical to horizontal. I think this would address the airflow, safety and aesthetic issues, but looks like it could be tricky to do without damaging (bending) the rear panel.


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#2: Post by Nunas »

My opinion is to leave it as is. I have not had much trouble cleaning after hundreds of roasts. As for airflow, the air comes in that weenie little hole under the roaster at the back; this restriction trumps cannibalizing the discharge side, which already has a more open area than the little intake hole.

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#3: Post by another_jim »

I think Maurice is likely to be right. The back hole is one major restriction. There is another at the front, when the air has to go over the gap. Finally, I have to run the air's power higher with chaffy DPs, so that is also a barrier. The Quest isn't really designed to be a convection roaster, the fan is just for spreading the heat evenly over the drum area

Going somewhat off topic ...

I find it interesting that a lot of the mods for the Quest have been made to get faster roasts with higher loads, in essence, they are productivity rather than quality mods. Moreover, a lot of the posts on this forum have been about managing the thermal momentum (all those crash & flick posts) of larger batch sizes on machines that, judging by their external dimensions, are pushing the limits on how filled their drums are.

In the mean time, the manufacturers of the Quest have kept reducing the recommended batch size as they've focused on marketing it as a very robust and inexpensive sample roaster.

For me, the bottom line is that the batch size is a major control for the Quest. If I'm doing a medium-dark Brazil blender for espresso, I can go up to 200, even 225 grams, and do a 12 to 13 minute roast. If I'm brewing a light roasted Central, it's 125 grams, and a 8 to 9 minute roast.
Jim Schulman

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#4: Post by TomC »

The squirrel cage fan, even in it's enclosure, pulls air from any point of least resistance. The small entrainment hole under the drum being one of them. But it will also pull air thru the various spots around the roaster that air can leak in. I cut the vanes in the rear because they still create an air flow obstruction leaving the roaster. Do you have to? Nope.

The limitation on the Quest isn't the heating element (although it's slow to respond), it's the management of airflow and the limitations of it's original design. Quest copied my own development of the drum to have at least a perforated rear wall and air gap, allowing for some improvement of hot convective airflow drawing across the beans and to my knowledge, that is now how they call come stock. The little tweaks and mods over the years have made it behave more like a small drum roaster rather than just an agitator over a hot element. Air, does very little for the beans mid-roast, when it isn't heated.