New Cart mount and other modifcations for chaff avoidance

I developed a cart mounting for my Bullet.

My goals for this cart:

To have a ‘Clean’ setup.

Be able to run the bullet without the chaff screen filter in the chaff collector so that the air flow through the Bullet would not be impacted by a clogged filter and I can run back-to-back roasts without making any ‘on-the-fly’ adjustments to the roast.

Not clean out the chaff and fan components as often.

Have no smoke from the roaster exhausted into the garage.

Be able to roll the cart out of the way when not in use and have a small footprint.

Basic description of my modifications:
I removed the screen filter, and the chaff passes through the Exhaust fan and is drawn through a cyclone filter where 99% of the chaff is trapped. I am using a Shop Vac to pull the chaff, steam, and smoke through a funnel above the exhaust port. I am controlling the speed of the Shop Vac with a Router speed controller. I run the speed controller at ~40% during the roasting cycle and take it up to 100% during the cooling phase after dropping the beans into the cooling bowl. The installation of the speed controller was very easy. Plug the speed controller into the wall and then plug the shop vac into the speed controller. The speed is then controlled by a rheostat.

I printed a baffle to go inside of the chaff collector housing to keep the chaff from filling up the bottom of the collector.

The baffle is the red part.

I may have to design a new baffle. A few flakes of chaff puff out occasionally from some chaff that collects in the nooks and crannies.

I printed most of the fittings for this setup.

I made a new bucket for the Cyclone DustTopper that I bought from Home Depot by cutting a white bucket in half and then printing a new bottom for it and gluing it in place with silicone caulk. I needed the cyclone to be shorter.

It is hard to tell from the photo, but the chaff is around 2.5 inches deep in the middle of the bottom of the bucket. That is the chaff from ~10 kilos of roasted beans. most of the roasts were Naturals with heavy chaff.

None of the chaff made it out of the cyclone filter into the shop vac

I expect that I should be able to roast 100 kilos before emptying the Cyclone filter.

I mounted a touch screen tablet on an articulating arm so that I can move it out of the way for storing.

Here is a photo of the exhaust fan after roasting 10 kilos.

I have a 2.5 inch diameter hose for the exhasut from the shop vac which I am currently just running under the garaqe door.
I will drill a hole in the wall and put a quick connect fitting for the exhaust hose.

There was no smoke in the garage.

The only downside is that this setup is a little loud when running the shop vac at 100% during the cooling cycle after dropping the roasted beans into the cooling bowl.

The last test that I ran was to roast six 750g roasts, back-to-back without stopping to clean anything. That test went very smoothly.

I think that this could be a great setup for doing commercial roasting.


Wow!! My head is in overload trying gather all the changes you’ve envisioned, tried, tested, modified and incorporated. That’s overwhelming. And you documented all of the changes. Impressive Bill!!!


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Looks great. Just so I understand the only change to the bullet itself was to remove the basket & let everything pass through the fan. If that is right did you have to make any fan adjustments during or after the roast. Also did you remove the filter in the bean cooler.

Edit: I missed the baffle. I need to get me one of them thar 3d printers.

I removed the screen basket. I removed every other blade of the fan. I re-calibrated the fan. I couldn’t detect any difference in the amount of air velocity from the fan. I did make some adjustment to my recipe to add a bit more fan to help remove the chaff earlier. very minimal adjustment. I probably didn’t need too.

Regarding the filter in the bean cooler.

Yes, I removed it. I haven’t used that filter in a long time. I had an earlier hack that worked very well. I bought a 300 mesh nut milk bag (like for making almond milk) and attached it to a printed flange on the back of the fan on the cooling bowl. I removed the filters before the fan and have an electric stirrer.

The Stirmate knocks loose most of the chaff in the bowl and without the filter it all goes right into the 300 mesh sack.

I found that the filter in front of the fan was getting clogged with chaff and really slowing down the cooling of the beans in the bowl.

The bowl housing without the filter does not get caked with gunk

I’d be happy to share the STL file for the baffle. It is an easy print.
There are several people on this forum that can print things for you.

The Stirmate is availabe from Amazon. You need to get the additional wire stirrers to go with it. It works really well. I tried the Saki stirrer, but I can take the Stirmate on and off with one hand.

Now, the chaff goes throught the cooling fan, helped by the shop vac, into the cyclone filter where it gets trapped.

If I wanted to, I could remove the baffle, replace the exhaust fan with a new one and I would be back to the original configuration for the Bullet.

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How long have you done the cooling tray without a filter?

Over a year.

It is a very simple and effective hack.

I’m surprised that it doesn’t gum up the fan, but consider my curiosity piqued.

The second photo without the filter is after a year and no cleaning other than vacuuming every other month. I very seldom go into second cracks. I had bought an extra fan to have it on hand “in case”
but never needed it.

I think that one of the reasons that it doesn’t get gummed up is because all of the moisture in the beans was expelled as steam during roasting of the beans and therefore the residue coming from the beans during cooling is not as sticky. Also the velocity of the air moving through the fan without the chaff slowing it down is very fast.

Ya that makes sense. I will try this :slight_smile:

This photo is after capturing 5 or 6 kilos worth of chaff.


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I can vouch that the nut milk bag hack from Bill works really well. When he posted about this eons ago I switch to this and it really helps to not having to vac the cooling tray when sometimes I’m roasting 4 to 6 kg a session. No issues with that fan gumming up because the beans are already dry by the time you dump it out. Like Bill I rarely go into 2C.

Hi billc
Thanks a lot for your post. It’s a fine solution and gives me some ideas for the planned solution of an own cart mount, equipped with my temporary exhaust system (just fumes ventilation to outside). I’m also thinking about a elegant solution for the chaff collection (which is quite a weak point of the bullet

Any chance I could snag the .stl files for the baffle as well as the flange for the chaff bag?

i’d be also interested in the .stl file/s … :slight_smile:

Very cool! But wait, so the smoke from the roast itself goes below into your chaff cyclone as well ? I have my ventilation going outside, and my roasting area still gets a bit smokey from the beans cooling in a similar manner as you, even though I have this part separate from main exhaust.

I have tried to draw some arrows to show the air flow. The red arrows are warm or hot air from inside the bullet. The Blue arrows shows cooler air entering the funnel.

In the first photo, the chaff filter screen has been removed (not shown).
Without the screen filter the chaff would be expelled and make a mess around the Bullet and on the floor.

By running the shop vac at about half speed, the chaff is collected and sent through the cyclone where it is separated. There is no influence on the draw of air from the exhaust fan (F1-F9). Therefore there are no changes needed to the recipe.

Another view without the Bullet. The horizontal chrome pipe is sealed to the flange adapter going to the cooling bowl. During the roasting phase, air is drawn through the cooling bowl and into the cyclone. The air flow going through teh cooling bowl at this phase is not doing anything and has no effect of the roast.

During the cooling phase, I turn the shop vac up to full power to help cool the beans. any chaff that is left on the beans is knocked / rubbed loose at this phase by the stirrer and is sent to the cyclone where it is separated and left in the cyclone.

The air is passed through the Shop Vac and is expelled through another sealed tube to a fitting in the wall and the outside world.

The last photo shows the Shop Vac exhaust tube going to the wall

No air from the Bullet is exhausted into the garage… It all goes to the outside world.

The amount of air from the roasting phase is minimal and the cyclone does not have to work hard to filter the chaff. the steam is passed through to the Shop Vac exhaust.

While roasting, I don’t have smoke or steam in the garage. After turning off the Bullet and letting it cool, There is some residual roasting smell from the Bullet and tubes. It dissipates quickly.

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I think I would miss the smell of fresh roasted coffee in the back corner of my garage. My wife loves the smell when she goes into the garage. However, as a roaster with some history of prototyping new systems in the medical field I really like what you have done. I just have a simple ducting system powered by a 100 cfm fan over the Aillio air exit. I move the air outside through a nearby window. My neighbors don’t seem to mind. My roasting volume is much lower than your though, approx 1-3 kg every 2 weeks.
Great work and the fantastic description of your modifications with pictures was excellent.

Thanks for the compliments.

I love the smell of roasted coffee, but the smell of roasting coffee not so much. My neighbors love the smell of roasting coffee and get excited because they know they will get some…

I love the smell of certain fresh green beans. Some of them are very sweet smelling. some you can smell the spice.

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Same here. Not to mention if one is roasting frequently and smelling a lot of roasting coffee, then it’s time to look into a better ventilation solution, for the sake of long term health.

I like this solution. Simple. Has anyone mounted a nut milk bag inside of a 4" hose (similar to what I now use to assist in cooling (and to vent the hot bean air outside))?