Hi Everyone
In persuit of geeting a good freshly coffee roasted and since I can't find a good local Roaster I dicided to built my own.
As some of you know, I'm from Tucumán, a small city at northwest in Argentina, and there is too difficult to find fresh and quality roasted beans. So i'm starting to home roasting and what do i need first? A coffee roaster.
Home roasters are difficult to find here and buy one from Europe or the U. S. is not an option. the customs are restricted and nothing gets in. So what I'm gonna do? Like every other Argentinian I'm gonna solve it any way I can.
I am a Mechanical Engineer and i'll desing and built an Electric Drum Roaster. I PMed sversimo asking for use his desing as a model and he agree.
Ok, why I'm typing this? Because I want to share this experience and to ask you about recomendation on the machine specs because this is a new subject to me.

First on the list is:
What is the amount of coffee do I want to roast? I'd like to roast about 300Gr to 500gr maximum (abount 1/2 to 1 pound)
What is the heat do I need? I don't know... I was thinking in two heating element 800w each 1600W in total
Drum size: I'm thinking in a 1.5mm thick stainless steel rolled sheet soldered each side together (1 inch = 25.4mm) 160 mm Diameter and 250 mm long

The case will be constructed with same thick of sheet as the drum
I'm gonna make a drawing of the prototipe and upload it latter

Well this is have till now. What do you think? would it have enough power and size to roast the 500gr of beans?

Please comment

PS: Sorry for my bad english I hope you understand

Sounds fun! You will have enough power to roast 500g, but perhaps not enough power to make very quick temperature changes, but than again, if you plan your roast you dont need to.

Do you think that i need more power? i can use a higher resistance. How much do you think?
I didn't bought anything yet, everything is on paper stage
I was thinking to make a 50% reculating flow that wold result a better thermic performance and the heater controled by a dimmer

Hi everyone, it's been a while since I made this Post so i don't know if it's Ok to revive it, if not i'm sorry

Ok, I made some progress with the design. It will a 6" carbon steel sheet rolled drum that can roast 500gr of coffee, Two heater elements, 800w each, on the lower sid of the drum and a fun to produce air flow. Now my problem that i've got are the vanes, the beans have to move foward and back while the drum is turning so I have to make a set of vanes that moves them foward and other set that moves them backward. Ok, now I reached to two options this ar the pictures:




The first is simetrical. Two helicoidal vanes that moves the beans Fowars and two that moves backward.
First this was my first option but the I saw other designs like the huky 500 and became with this:





This is the second, asimetrical two that meves foward and three that moves backward. I tough into this because in the first, maybe the beans get stoked at the front and with this confuguration the bean will go back before avoiding that to much beans get stocked at front and alloing them to spread more evanly over the drum

What do you think? would be the first option enoght to distribute the beans evenly over the drum getting a more even roast? or i should use the second? Or Other?

Plese let me know your opinion.
Thanks a lot

Hy..nice design from the vanes.What CAD software you use?
Me I made a gas roaster, but same from 500 grams green coffee.The dimensions is very same.
A few observatios:the CAD model is one, reality is different .Is good to have a good circular shape from drum.In final whit all mounting tollerance will be a +/- 2 or 3 mm roundaround tollerance, not bad but not very good.The rolled procedure to do drum is....more os less imperfect.Try a tube , you find sure.My thicness is 3.5, but is good 5.
From me , only a 4 vanes, simple shape appear to be enough.The dimensions is small , the agitation wil not be a problem.Your shape of vanes is nice, but difficult to obtein, and difficult to weld.
Try to think a method to adjust axial position of the drum relative with frame, and think 2 minutes from thermic dilatation.My ax have 12 mm, but if is a little more is perfect.I dont put bearing, is only antifriction material, but made a little noise.
I have only 60 holes in bottom of drum, D5, total area near to exhaust tube area, to not create negative pressure inside the drum.
I used in the past electric, not drum roaster, SCTO, but I understand only now why gas is champion here.
In final important is to think a little from total price, and to try to not be very imaginative, to use very practical and simple solutions.Opion from design engineer

hadriano wrote:Hy..nice design from the vanes.What CAD software you use?

Hi! Thanks for answer! I use SolidWorks 2011

hadriano wrote:the CAD model is one, reality is different .Is good to have a good circular shape from drum.In final whit all mounting tollerance will be a +/- 2 or 3 mm roundaround tollerance, not bad but not very good.The rolled procedure to do drum is....more os less imperfect.Try a tube , you find sure.My thicness is 3.5, but is good 5.

I know that the real product will be diferent but my idea was build all the parts on 1.6mm carbon steel sheet and make a cnc plasma cuting including the fiting holes to avoid most imperfection on the construction. the rolled sheet will be fixed with rivets to another small sheet on the edges that would allow some thermic dilatation as well, but maybe I try to use a tube if that doesn't work. I think that 3.5 mm is too thick and will have a big thermic inertia that may dificult the roasting profile, maybe i'm wrong but that's what I think.

hadriano wrote:From me , only a 4 vanes, simple shape appear to be enough.The dimensions is small , the agitation wil not be a problem.

Thanks for the suggestion, i was thinking that 2/2 will be ok as well but when I saw other models with the 2/3 configurations the doubt came.

hadriano wrote:Your shape of vanes is nice, but difficult to obtein, and difficult to weld.

Not really... The cad software make a sheet template for plasma cutting. Is like an incomplete circumference and then you only have to strech them to make a helix. For the soldering i was thinking to fix with and epoxy adesive first and then oxiacetilene soldering that works well thin sheet

hadriano wrote:Try to think a method to adjust axial position of the drum relative with frame, and think 2 minutes from thermic dilatation.My ax have 12 mm, but if is a little more is perfect.I dont put bearing, is only antifriction material, but made a little noise

The axe will be made from a 1/2 inch bar and then turned in the front to 8 mm to fit the 3 arms support that you see in the picture. and then supported by bearings. Do you think I should make it bigger?

hadriano wrote:In final important is to think a little from total price, and to try to not be very imaginative, to use very practical and simple solutions.Opion from design engineer

You're absolutly right that's why decided to use carbon steel sheet. Is relatively cheap, It has really good thermal transmission and I already have some remnant in my workshop and I have the access to a cnc plasma cutter as well. I'm a mechanical engineer too and i'm thinking all the posibilities here

Regards

Ps: Sorry my bad english

-1.6 mm maybe is ok from electrical, but from me, gas, appear to be too little.More simple is to find a tube.
Make all weld drum assembly, ax, etc, and in final turn again ax with fixing point exterior of drum,to be sure the radial dimension runout tollerance is little.Is important, because in the front plate of roaster, the eject door is very near with drum, and, if the drum make a movement radial up down, this space became big and is posible to lose coffee,ecc.Is important to have a precise aseembly between front plate and bottom plate, to be sure in final your drum have a small runout tollerance.This became more difficult if you try a solution with all chassis mounted and posibility to insert drum after.I will put a few photos with my idea ,not now.I used more or less same chassis with sversimo.
Very good if you have posibility to use plasma/laser cut.
I know the software posibility to make development view for sheetmetal, is ok if you belive is posible to bend helix after.Be atent to remain a space between th vane corner and front drum face, 15-20 mm, because in this space will be thermocoupling.This diameter of drum is little, and all component will be here .
1/2 inch diameter is big ,half is enough, in my opinion.Important is the front plate to be min 4 mm thick, 6mm is more good.
Try to make a complete CAD, and you will see all.I have mine, I will put a few photos in future.

Hi! Your idea looks quite similar to an old coffee roaster that I posted here...under number 317632, mine has 2 elements, 600W each at the bottom of the roaster. I used mine with 300grams, but it is supposed to hold 500gr. Let me know if you need any pictures of it. I am really frustrated now because the 25w broke and I am no electrical/mechanical engineer, I sent it to an appliances repair center, but since the roaster is from the 50's/60's I am sure there will be no parts available...I hope it is easy to change the motor.

German roaster G.M.H. Any good?