Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » David and Alchemist Roaster Building Project
Who is here? 1 guest(s)
 Print Thread
The Design - Parts 1-11
Alchemist
Top  #1 Print Post
Posted on 08/28/2007 7:12 AM
This will remain and change over time as design parameters get locked down. It is here so we can see what still needs to be designed in and what impact it might have on other components.

The Zen Beta 4.2 is a tilited drum with an open front to permit observatin and sampling of the beans. It will run on a standard 15 amp circuit, be heavily insulated and is planned to roast up to 1 kg of green coffee in 14 minutes.

1) Drum - Wire mesh. George Forman without support rod. The drum will be modified with a wire guide to allow the front to be open for sampling. The back may be modified to keep stress off the motor during dumping.

2) Control. Open for discussion. Control box will be separate but attached. Those for consideration:
Variac
Triac
Timed modual

3 Heat source. Open for discussion. Those for consideration
Tubular
Nichrome coils
Halogen (maybe as partial for internal lighting?)
Quartz

4 Drum Motor. In general needs to be compact and "light" allowing it to be attached to the drum and still be dumped with tipping. 40-60 rpm AC.

5 Insulation; Kaowool and a rigid insulation board if needed. In hand

6 Cooling system
a ) Cooling tray - round or square (or other) - Removable for bean removable or open slot for in edge?
b ) Stirring or not ( SC motor? )
c ) Fan for cooling (WB P1 maybe?)

7 Trier - Decide if one is desired. Suggestion is to make it quickly removable at EOR for dumping. The assembly could also hold TC, thermometers etc.

8 Chaff collection. With an open drum, chaff will fall to the bottom. Suggest making a removable tray with forward facing fins to keep the chaff from flying around. Access is via the tipped up drum.

9 Afterburner - optional. Bare nichrome coil. Need to decide if it will fit into the power requirements. I believe it will.

10 Convection: Linked integrally with the afterburner, a recirculating fan so heat is not being wasted to atmosphere and to provide convection in general. I have this proven out on my bench top currently. I would recommend a small metal squirrel cage blower. We should discuss a simple baffle (or two) for bringing in cool air and releasing hot air for additional control

11. View of the beans: Set of pyrex watch glasses between a pair of jumbo washers. Held in place by magnets in the face of the roaster. Washers are ferrous. Magnets facilitate easy removal and cleaning as needed.
Edited by Alchemist on 04/25/2008 9:29 AM
 
David
Top  #2 Print Post
Posted on 08/29/2007 9:42 AM

Quote

Alchemist wrote:
3 Heat source.
Tubular
Nichrome coils
Halogen (maybe as partial for internal lighting?)
Quartz

4 Drum Motor. In general needs to be compact and "light" allowing it to be attached to the drum and still be dumped with tipping. 40-60 rpm AC. RK Drum style

5 Insulation; Kaowool and a rigid insulation board if needed. In hand YES

6 Cooling system
a ) Cooling tray - round or square (or other) - Removable for bean removable or open slot for in edge? YES
b ) Stirring or not ( SC motor? ) Maybe, but SC motor is too weak for 2 kilo
c ) Fan for cooling (WB P1 maybe?)YES. not sure if West Bend is strong enough.

7 Trier - Decide if one is desired. Suggestion is to make it quickly removable at EOR for dumping. YES
The assembly could also hold TC, thermometers etc. YES

8 Chaff collection. With an open drum, chaff will fall to the bottom. Suggest making a removable tray with forward facing fins to keep the chaff from flying around. Access is via the tipped up drum. YES

9 Afterburner - optional. Bare nichrome coil. Need to decide if it will fit into the power requirements. I believe it will. YES

10 Convection: small metal squirrel cage blower. YES]


This all sounds very good to me, sir.
 
David
Top  #3 Print Post
Posted on 09/20/2007 3:04 PM

Quote

Alchemist wrote: The Zen Beta 4.2 is a tilted drum with an open front


As cool at the tilted drum is in appearance, it might end up being a PITA as far as the ductwork and other fittings are concerned.

Please remind me again of the advantages of the tilted drum.

If it is for agitation, could that be accomplish that by fixing the vanes up a bit?

This roaster should be able to to work with or without the trier, right?
So, if the tilt is for bean containment, couldn't we also take care of that by vane design?

:(

I'm all for cool-looking, but not if we are making it needlessly complicated.
 
Alchemist
Top  #4 Print Post
Posted on 09/21/2007 7:02 AM
Good point. I was just thinking about this also.

The tilt is indeed for containment. But that was before jumping into the idea (and having it fully fleshed out) of the trier. With a trier in place, there is no need to tilt the drum. We were keeping the design flexible if someone wanted the trier or not, but with the commitment to the convection system, an open front is not really workable.

I would NOT start playing with the vanes. We have a drum all in place, with the design built around it. I really don't want to start down that road. Besides, again, with the trier in place, I see no reason to tweak with the vanes. I will of course check this out 100% with the mock up.

So, think it over. Would you like to "officially" loose the tilt? We can keep the trier optional, but we would need a magnetic plate substitution if someone doesn't want the trier. No big deal I would say.

The fitting to an angle are not so much a PITA, it is as Dan pointed out. It is making it work AND be buildable by someone with basic hand tool is where the trick is. I am thinking the sinking pipes will be the way to go. But why have a complication (the tilt) if it is not needed. There is something to be said for aesthetics, but only so much.

Let me know and we can tweak the design accordingly.
 
David
Top  #5 Print Post
Posted on 09/24/2007 8:30 PM
I like the trier. It's cool and I'd like to keep it. smile

Let me consider giving up the tilt for a while.
[Of late, my thoughts keep going off into the realm of instrumentation.]
 
David
Top  #6 Print Post
Posted on 09/26/2007 9:47 AM
OK, the trier will take care of the containment.

I'm more concerned with the evenness of the roast.

I'll take a turn here at thinking out loud.

I think that it's fair to assume that any roasting vessel has some spots that are hotter than others. This would be especially true with the two different radiant heat sources we are using. There will be very little conducted heat from the wire mesh drum Plus, we're not using any heat diffusers as in a BBQ rig.

So, just to spell it out, it seems like we are tackling this in two ways. First, we are using convection to spread the heated air around. Second, we are moving the beans around in the chamber. The tumbling action of the drum will certainly give some up-and-down and side-to-side movement to the beans.

But what if the chamber is hotter at one end than at the other? We would need some end-to-end movement to take care of that. I have not ever used a drum roaster, but I have always tilted my poppers and bread machines to get better movement. I thought I got a better result.

The spiraled vanes in various drum roasters made immediate sense to me for this same reason.

The "stock" George Foreman rotisserie basket has a tab arrangement that serve as "vanes" and I would guess that they give a good mixing movement. But then you would actually know. How do they move around in your Zen II? Do the roasts come out nice and even?

If so, then I'm OK with eliminating the tilt.

It seems that in the worst case we could give a little twist to a few of the vanes to get some north-south movement of the beans.
 
Alchemist
Top  #7 Print Post
Posted on 09/26/2007 4:19 PM
First off, I like this kind of out loud thinking. So I will just answer. Don't take it as defensive.

We are not going to have any evenness problems. None. Why? I can't even begin to describe the amount of mixing and agitation that the vanes provide. They are nothing less than amazing. Recall I have been roasting in one for years now and my roasts are extremely even, regardless of profile. The beans are in a constant blur of motion all over the drum from combination figure eights. And that is in a drum with two heat sources and no convection. Maybe I can get Les and his recorder to get a short video. Still photos just won't do it justice.

And just to answer it, I can't imagine one end being appreciably hotter than the other, especially with the bean motion and air movement. No way.

I will take that that we are going to go for flat (no tilt). I will see about getting the drawing revised. That saves me a little prototyping work, but I will still test out the front bearing and dumping ability.
 
David
Top  #8 Print Post
Posted on 09/26/2007 10:53 PM
A most excellent answer! s:2 Just what I needed to hear.

So, no tilt needed. B) Grin

Onward!!
 
Alchemist
Top  #9 Print Post
Posted on 04/22/2008 5:50 PM
I noticed we didn't have a way to view the beans designed in. I have a little quick removable sight glass designed up. Virtually all off the shelf parts. It will require opening the front of the drum a little more, but that actually fixes a construction problem I was having. More hand room now.

I will probably amend a #11 - Sight glass/port hole and toss a drawing up at some point.

Basically a pair of watch glasses (two for insulation properties) sandwiched between a couple jumbo washers and a little padding held in place by a couple magnets on the front panel. Pop it out every roast or two for very easy cleaning.
 
David
Top  #10 Print Post
Posted on 04/23/2008 9:06 AM
That solves the sight glass problem.

Regarding the positioning: :(
Since we have a light source on the inside, will we be looking down on the beans? Or, if the sight glass is lower, will we have the light passing through into our eyes? (Halogen, ouch?)
 
Alchemist
Top  #11 Print Post
Posted on 04/24/2008 8:07 AM
Here is a rough mock up of the front.

Trier off center high. View port off center lower left in the flow of beans (motor runs CW as seen, beans will be left of center). Halogen light will be at the top as shown, or at the very bottom front as shown. I have not decided which. Either way there will be no direct line of sight from it to the sight glass so no blinding issue should occur.
Alchemist attached the following image:
front-rough[905]_1.jpg
Edited by Harly on 01/04/2009 7:31 AM
 
Jump to Forum: