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First Build - 5kg Roaster - Here we go!!
I agree Allen, I can not understand how a steep angle will let the beans spread over the drum. I only ever build 1drum in my life so I do not have much background to pull from. I think the reason for the forward slant is to unload the beans and a small mixing of beans front to back. I know on my roaster I can roast 6 pounds down to 1 pound with good results I do not think most commercial roasters have that range. When I was testing on a large load some beans would spill over the top of both veins. Is this good or bad? This short forward vein is why I can run a small batch. If it was 2 inches high I believe a small charge would pile up too much on the front. So maybe this is how commercial drum get by with the steep angle, maybe most of the beans roll over the top and spread out. Also maybe commercial roasters do not need a big charge size variation. It would be hard to make money running 16 percent smaller than max roast like I do.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
I think you nailed it on commercial roasters not needing to handle small loads. I'm sure they're optimizing the design for full batches.

On if beans spill over the vanes is good/bad? In my 1 lbr the beans are definitely cascading over the vanes which is also the case with commercial roasters. I haven't done the math on % of vane height to drum diameter on a typical 12 kilo shop roaster but I seem to remember the vanes to be around 2 to 2 1/2" tall in a 2' diameter drum or somewhere around 2' which would make them fairly short compared to most of our small home-builts.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Upate - I modeled the outer vanes based on the 4-in-a-row staggered approach for a total of 16 outer vanes. Ran at 30 degrees. The overlap on everything looks really good for solid kick of beans forward without getting stuck. Best of all is that using this method I was able to generate a flat template for the out vane cuts. Will be super easy to fab out of flat bar for a welder to just lay a bead. No helical bending on these. No crazy setup. Really simple.

The inner vanes... well... more on those later.
Separate topic... on the cooling tray... I'm very much liking this little motor for the stir arms assembly. Would be mounted just below the mesh where the beans are. Has a decent 12rpm. But it only has 2.6 in-lbs torque. Do you guys think that will be enough?


As a reminder, our cooling stir arm design is below and would spin clockwise. The overall diameter of the bean cooling area is about 19" (for reference in how deep the beans might be). The two straight paddles are the actual sweeps that are down on the mesh pushing out to the trap door. the curved one is held off the mesh and would pull the beans back to the center for a constant turn-over till the trap door is pulled.

Thoughts? Motor ok for the purpose?
2.5 inch pound is very light, I would look for something bigger. There is a place people buy gear motor from it's like surplus supply. Some one will come on here and give you the name.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Try Surplus Center:

I would read the specs and make sure it is continuous duty. Some are listed as intermittent duty. Most of these motors are used and pulled from working equipment.

I bought a really nice gear motor from them last year for a fraction of the new price.
Edited by JackH on 12/08/2014 5:58 PM

KKTO Roaster.
So... what's everyone's thoughts on torque then? For the main drum (5kg load) and for the cooling tray?

I'm seeing many options on Surplus Center and other supply outlets. But I know that torque is one of the most important factors.

I have tried to find manufacturer's and dig into their specs. Would love to get a nameplate of those motors. Just to know what specs to shoot for.

For instance... for the main drum motor... how about this one? 57rpm... 78 in-lbs of torque:

Little bit more $$ than I was expecting but if that's what we need, that's what we need.
I do not think I can help with this. I know Dan had a formula if you search his old post you may be able to dig that up. I used the shade tree method and just made them both big. My drum is a 1/2 hp and my stirring veins are 1/8 th. I found one on a scrap pile at work and one on eBay cheap.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Right on. No worries. I think at this point I'm realizing that in order to get the specs we need, for the price we need, eBay is going to be the ticket. Brand new motors are just too expensive. I'll do some more digging for Dan's thread you mentioned.

Thanks again for all of the help!!
My method for calculating torque requirements for the drum drive is to figure no more than 1/2 the maximum bean weight will be exerting a load on the drum when measured at the 3 or 9 o'clock position in the drum. So, with a radius of 6.5" x 6 lbs (half of 12 lb max load) we'll have close to 40 in/lbs of torque exerted on the gearmotor. The gearmotor you're looking at rated at 78 in/lbs will definitely have no problem driving the drum.

I'm not sure how one would calculate what the cooling tray stirring vane torque would be but I would guess you should be safe using 5 or 6 lbs for 1/2 the equation so 6 x 9.5 (radius of tray) gives you 57 in lbs which in my mind should be plenty especially considering the reduced weight after roasting. Now mind you that this is allenb's barnyard guess! limb

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Jason Field
I am the brother-in-law! Just making an appearance to make sure that I get all the leaves as they come!
Question... was planning on 3/16" wall thickness for the drum. But now realizing that if we were to go slightly bigger to a 14" diameter drum we could use stock "off-the-shelf" pipe. Either schedule 5 (approx 5/32" wall thickness) or schedule 10 (approx 1/4" wall thickness). Based on a 14" OD x 14" long drum that would math out to about 12.5 lb max load capacity per roast once you back out the wall thickness. In order for me to get pricing... what would you recommend? The schedule 5 or 10? Schedule 5 seems harder to come by. But is a 1/4" wall thickness too thick? This roaster will prolly be run for back to back roasts so how would the thermal mass of a 1/4" wall shake out?

((just not looking forward to paying someone to fabricate a 13" diameter cylinder out of flat plate... would love to just buy a simple piece of pipe.))

Thanks in advance for the continued help!
I think you would be fine with 1/4 inch. I have a thick drum and when I roast as soon as I drop the charge into cooling tray I turn the gas off and open the draft full. By the time the beans are cool and in a bag I can drop the next charge into the drum. I always keep the next charge in the funnel so it's preheating. I do think I added too much insulation to the shell and would use a loose ceramic insulation instead of dense duct board. I believe the 3/4 inch of hard insulation stores lots of heat. A thinner drum may be easier to run because you would not have to anticipate your move as far ahead but mistakes will bite you faster.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
First of all, let me say how much I appreciate this thread! Secondly, did this ever get built? I would love to see photos and an update. I would also be very interested in any finalized plans. Thanks again!
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