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09/28/2020 9:48 AM
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Drum Roaster Advice and Discussion
slaserj
Hey guys! New here, but trying to find my way to a well-engineered home-built roaster. I'm a custom motorcycle builder by hobby, and cloud engineer by day, so I'm no stranger to design and fab. However, I understand there are nuances to things like this, and would like to stay on a budget. Trial and error can be substituted for the wisdom of those who have walked this path before me in many cases. With that, here's my plan so far, tell me what I should change:

Heater: Propane, maybe a "sheet burner" like this:
i.ytimg.com/vi/A9J6XUxASv4/maxresdefault.jpg This is a Deidrich burner, where would I even begin?
Valving: Needle bypass and solenoid for high-low function control
Drum: Stainless, 8". Could this work? https://www.amazon.com/San-Jamar-L360C-Large-Stainless/dp/B003UUTMQ0/ref=sr_1_4?keywords=stainless+trash+chute&qid=1570725795&sr=8-4
If not that, where can I find a stainless pipe for something like this? Aiming for 1/8inch or a little thinner for profiling.
Front and Back: 8mm aluminum plate, laser cut and beveled by contacts at a local machine shop
Inlet: Stainless plate hopper, with tube to cyclone behind the roaster
Motor: Nema46 LARGE stepper motor with controller: I had this lying around, this level of speed control should be fun
Other things to be figured out later on.

Glad to be here, looking forward to learning!
renatoa
Welcome

Are we talking about a ceramic burner like this?

http://www.induceramic.com/industrial...rner-plate
slaserj
Yep, after some research I’m finding that they’re pretty generic grill-dear infrared elements. Would this be suitable for a solid drum? My other option is a pipe burner, or a pipe with 3-4 small Venturi heads tapped into it and pointing up.
renatoa
Infrared seems like a gentler heat transfer method than a direct flame...
Edited by renatoa on 10/11/2019 2:43 AM
slaserj

Quote

renatoa wrote:

Infrared seems a more gentle heat transfer method than a direct flame...


That's what I was thinking. May go with a mild pipe for the drum for more heat conductivity. Seems like that would provide a nice middle ground without being too costly.
slaserj
Here's a new one: Has anyone used a LARGE stepper motor for the motor drive? I have a very large stepper that I'd love to include in this project, for no other reason that it gives an obnoxious level of drum acceleration control, plus it's on my shelf. The torque curves show it will produce at least 5 Nm during a fairly aggressive acceleration curve. I think I may go for it!

In other news: burner control is nearly done. It's pressure tested for leaks, and ready to attach the burner. I'll post up my burner details soon.
slaserj
Here’s the burner idea! Still a proof of concept till I can get thicker square stock, but these are “jet burner” replacement nozzles. Less than a dollar at a local restaurant supply. And they burn HOT! I’ll put about 10 of them in a row, then weld an end cap on the square tube to thread into.
slaserj
i.imgur.com/vdPhz50.jpg
slaserj
i.imgur.com/zxvBY5Q.jpg

Finished! Very happy with it, on to the rest of the roaster.
allenb
Wow, nice burner results! This is a top shelf burner!
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
San Franciscan Roaster Co
Hey man,

Just chiming in here... have you finished?

Seems like you got the fab down pat, however the results of roasted coffee will vary depending on heat source and direct contact with drum. Ultimately, like coffee, there are objective and subjective aspects to roasting, but allowing more flame contact with the steel drum will provide more effective conduction contact with beans on drum while roasting. This will significantly aid in the sugar carmelization phase. So, all that to say I'd definitely choose options creating more efficient heat exchange to the drum.

Stoked on your project and look forward to following along!
slaserj
Great to hear from you guys! I'm planning on having the flame lick the drum, with about 1/2" overlap at full length. Obviously the flame will be adjustable by needle valve, and I'm also adding in a height adjustment for the burner so that this can be changed if needed. The drum comes next, and I've been fabbing up the trier. Just waiting on my stainless tig wire to come in :)
slaserj
Back with a motor question! As I posted first, I have a BIG stepper motor I plan on using for the drum, for extremely precise drum speed control. According to the torque curve here:

https://www.oyostepper.com/images/upload/File/34HS46-5004D_Torque_Curve.pdf

It has plenty of oomph. I have gears available for: 1:3, 1:2, 1:1, and their inverses. Has anyone used a stepper for a drum? It will be outside of the enclosure for heat isolation, and connected by a chain to the drum. Anyone see any red flags in this setup?
slaserj
Here's the first iteration of a 3d model! Criticism greatly appreciated!

i.imgur.com/j1UDWf5.png
baldheadracing

Quote

slaserj wrote:

Back with a motor question! As I posted first, I have a BIG stepper motor I plan on using for the drum, for extremely precise drum speed control. According to the torque curve here:

https://www.oyostepper.com/images/upload/File/34HS46-5004D_Torque_Curve.pdf

It has plenty of oomph. I have gears available for: 1:3, 1:2, 1:1, and their inverses. Has anyone used a stepper for a drum? It will be outside of the enclosure for heat isolation, and connected by a chain to the drum. Anyone see any red flags in this setup?

I don't know anything about motors, but with a chain drive, you will want to add some kind of a release mechanism like a clutch to prevent castastrophe if the drum jams. Depending on the size/weight of the drum, a belt drive might be a less complicated solution - the 1kg roaster in my avatar uses a generic v-belt.

Good luck!
slaserj

Quote

baldheadracing wrote:
I don't know anything about motors, but with a chain drive, you will want to add some kind of a release mechanism like a clutch to prevent castastrophe if the drum jams. Depending on the size/weight of the drum, a belt drive might be a less complicated solution - the 1kg roaster in my avatar uses a generic v-belt.

Good luck!


Great idea! I might add this in electronically. I can limit the torque of the stepper motor, and tell it to cut out if its too hard to turn. Might require an encoder, but shouldn't be hard to add. The motor has a spot for one. This is fully feedback-enabled, so it could theoretically even stop the entire roast if it jams, and sound an alarm! Steppers are cool.
slaserj
Drilled about 500 holes today! The cooling tray is done, and turned out pretty good! Tested with pinto beans.

i.imgur.com/aXCuYDH.jpg

https://imgur.com/a/rtoXpQV
San Franciscan Roaster Co
Love this... How much volume is in the drum? Looks like you could easily roast 5kilo of coffee into that cooling tray!
slaserj

Quote

San Franciscan Roaster Co wrote:

Love this... How much volume is in the drum? Looks like you could easily roast 5kilo of coffee into that cooling tray!


Drum is setup for 2kg, I was aiming to match the outside diameter of the roaster itself with the tray. Hopefully the larger area of the tray will help with cooling. Plus, aluminum should draw the heat away very well. I have a 12" 80W electric radiator fan that will be installed beneath it, that thing is POWERFUL. It about launched off of my workbench when I tested it. $20 for 2 of them on amazon, gotta love open box deals.
slaserj
Sorry for the silence guys and gals! I've finally gathered materials, and will be getting the steel plate laser cut this weekend! Super excited to finally have some progress. As much as I love this burner, the flame won't jump from jet to jet, making it pretty useless for an auto-ignition setup. May go a different direction with it, but the rest of the design should allow for a plug and play burner swap.
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