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My 1kg Electric Air Roaster build
Ringo
Top  #151 Print Post
Posted on 02/12/2011 6:49 AM
I will just put up an idea. If before the heat chamber you had a purf plate, you could build positive back pre sure. I think this should even out the airflow to the different chambers. Air will always take the easy path so you will need some type of baffle to control it.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
Ringo
Top  #152 Print Post
Posted on 02/12/2011 6:54 AM

Quote

greencardigan wrote:
I only had 410g of beans to test. I won't drill more holes until I get some more as I want see how 1kg goes with the current perf.

I only have 3mm and 3.5mm drill bits at the moment. 3.5 could be too big.

When I built my roaster I used dried navy beans with my flow test, much cheaper and I could throw them out after testing.
Edited by Ringo on 02/12/2011 6:54 AM
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
Unta
Top  #153 Print Post
Posted on 02/12/2011 8:50 AM

Quote

Ringo wrote:
I will just put up an idea. If before the heat chamber you had a purf plate, you could build positive back pre sure. I think this should even out the airflow to the different chambers. Air will always take the easy path so you will need some type of baffle to control it.



I think that Ringo is on to something here...
http://forum.home...ad_id=1762

This post by CHAD that shows the replacement of a coil on a Sivetz 14kw machine..notice the plate @ about 7:10.
Slightly different set up because of your multiple element chambers, but I think this is a good example of what Ringo was referring to, in theory.
Sean
Edited by Unta on 02/12/2011 3:17 PM
Sean Harrington
educate.
 
Web
JETROASTER
Top  #154 Print Post
Posted on 02/12/2011 9:33 AM
+1 vote for the perf below heat. It would act as a distribution plate.
If the design above the distributor is reasonably symetrical, it would likely solve the problem.
Great build! -Scott
 
endlesscycles
Top  #155 Print Post
Posted on 02/12/2011 1:01 PM
I don't think you'll ever get them perfectly even, and it doesn't matter unless one exceeds 1600F.
-Marshall Hance
Asheville, NC
 
endlesscycles
Top  #156 Print Post
Posted on 02/12/2011 1:02 PM
With that said, the heated air builds pressure, so to a certain extent, the design is self regulating.
-Marshall Hance
Asheville, NC
 
Unta
Top  #157 Print Post
Posted on 02/12/2011 3:20 PM

Quote

endlesscycles wrote:
I don't think you'll ever get them perfectly even, and it doesn't matter unless one exceeds 1600F.

I would think balance and consistency would benefit coil life. Though I agree perfection is likely not achievable.
sean
Sean Harrington
educate.
 
Web
greencardigan
Top  #158 Print Post
Posted on 02/12/2011 4:47 PM
Thanks for the good suggestions. I might have to cut the base off the HC to add a perforated plate. I actually already have a perforated plate in the air hose just before it enters the HC. I was trying to even out the airflow after the 90 degree bend in the pipework.

But I do think the hotter elements are currently limiting my heating power.
 
greencardigan
Top  #159 Print Post
Posted on 02/12/2011 8:04 PM
And a BIG thank you to everyone who has helped so far!!

I'm continually amazed at the level of help I've received during this build.

:Clap:
 
endlesscycles
Top  #160 Print Post
Posted on 02/12/2011 11:14 PM

Quote

greencardigan wrote:

But I do think the hotter elements are currently limiting my heating power.


Nope. That's not the case. Energy is energy. If you have resistance, you have power. Doesn't matter if you end up with low air flow/high temp or high air flow/low temp...it's exactly the same energy. Watts are watts, regardless.

You can only loose energy through the walls or out of leaks.
Seriously, that's it.
-Marshall Hance
Asheville, NC
 
greencardigan
Top  #161 Print Post
Posted on 02/12/2011 11:24 PM
Yes, that's right. I still have 4.8kW but I dont think i can get the average air temp high enough without burning out the hottest element.
 
greencardigan
Top  #162 Print Post
Posted on 02/13/2011 12:17 AM
I've opened to base of my heat chamber to try installing the perf plate to spread the airflow.

www.greencardigan.com/misc/air_roaster_build/new_heat_chamber_bottom_b4_base.jpg

The rectangular tube is 136mm x 77mm. The 14kW sivetz in the previous link had a small number of large holes. I'm thinking I'll be better off with more smaller holes??
 
seedlings
Top  #163 Print Post
Posted on 02/13/2011 3:31 PM
I was thinking about this... Maybe you should block some airflow wherever the coils are dark, this would force more air across the glowing coils to evenly distribute.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
greencardigan
Top  #164 Print Post
Posted on 02/13/2011 5:26 PM

Quote

seedlings wrote:
I was thinking about this... Maybe you should block some airflow wherever the coils are dark, this would force more air across the glowing coils to evenly distribute.

CHAD

Hmm, it would be good if I could manually adjust it from externally. Not sure how this could be implemented though.
 
seedlings
Top  #165 Print Post
Posted on 02/13/2011 9:02 PM
If you put a strip of cement board to partially cover the dark elements below then the hot air would be more even.

www.greencardigan.com/misc/air_roaster_build/uneven_element_heating.jpg

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
greencardigan
Top  #166 Print Post
Posted on 02/14/2011 3:06 AM
Only the top two elements were on in that pic. The one on the left was a lot cooler, especially the left side of it.

I put a perforated plate in heat chamber tonight. It wasn't as successful as I hoped. At first I used approx 40 x 3.5mm holes but that seemed to make the problem worse.

Then I tried adding 4 x 10mm holes. One below each element. This has worked reasonably well. I'm guessing the airflow over each element varies by up to 20%.

I suspect the average air temp is getting close to 300C (572F). VC was on approx 60%.
Edited by greencardigan on 02/14/2011 6:02 AM
 
endlesscycles
Top  #167 Print Post
Posted on 02/14/2011 9:42 PM

Quote

greencardigan wrote:
Yes, that's right. I still have 4.8kW but I dont think i can get the average air temp high enough without burning out the hottest element.


I suggest trying to burn them out rather than fuss with something that you don't know to be a problem. Have you even roasted with it yet?
Seriously, 10% temp difference is not much: At failure the average air temp is over ~1500F....which unless your walls are thin and full of leaks, is overkill by double. Also, assuming that mere 10% difference is from uneven air flow is jumping to conclusions. There's instrument error and more, and I really don't think adding baffles (additional variables) is anything but bad design.
-Marshall Hance
Asheville, NC
 
SteveN
Top  #168 Print Post
Posted on 02/15/2011 9:06 AM
I was pretty worried about burning up my element when I was first firing up my roaster too. I would side with EC on this one and just get it together with a thermocouple in the flowpath and try 300g or a pound of beans. My problem hasn't been the elements getting too hot but keeping the airflow low enough to get enough heat.
 
seedlings
Top  #169 Print Post
Posted on 02/15/2011 11:08 AM
My heat gun coils glow orange while roasting, with air flow. They do in my heatgun during operation too.

Try it. If the coil burns up, then you have the freedom to get a new one. If it doesn't burn, then you're a lucky dog on the first try!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
greencardigan
Top  #170 Print Post
Posted on 02/15/2011 4:11 PM
It's not quite ready for a roast test yet. Getting there though.

I have the HC to RC gasket sorted out and have made provision for a thermocouple to be located just below the perforations.

I still have to drill out the perforations to get better bean circulation and install a thermocouple in the RC.
 
dja
Top  #171 Print Post
Posted on 02/16/2011 7:07 PM
you gotta put some beans in it and turn it on sometime might as well be now, you will either roast em or you will burn the elements out, or you won't have enough heat to roast with.

I burned out a bunch before I got mine right.

your heat and air flow is going to be totally differant with the thing loaded up and hot air flowing, and the beans constantly changing weight on you.

DJA

Just go for it!!
I pour Iron and roast Coffee BeansThumbsUp
If life seems normal your not going fast enough Mario Andrette
 
greencardigan
Top  #172 Print Post
Posted on 02/16/2011 7:30 PM
Patience :naughty:

I'm as keen as anyone else to try a roast but there's no point until I fix the perforations in the roast chamber.

In the meantime, help me decide where to put the profiling thermocouple. I was intending to place it in the bean mass opposite the perforated area. Maybe just above the high point of the sloped floor plate.

Stainless probe type thermocouple? Fixed or removable?
 
dja
Top  #173 Print Post
Posted on 02/16/2011 8:03 PM
high as you can in the bean mass to keep it away from the air stream, if your bean bed is deep enough so that you can I would put it right at the top of the sloped plate.

I run my roaster more by the air temp than the bean temp but when I do want it in the beans I have to drop it in from the top due to the pyrex cylinder.

if you are going to have to remove the roast chamber to dump the beans I would go with removable probe so it can be gotten out of the way. but thats one of the things that may end up being trial and error till you find the sweet spot for it.

or like Jim S did he used one in the heated air and one in the exhaust air stream to build the profile for his roaster long time ago. couple years ago anyway
I pour Iron and roast Coffee BeansThumbsUp
If life seems normal your not going fast enough Mario Andrette
 
allenb
Top  #174 Print Post
Posted on 02/16/2011 8:11 PM
Ditto Davids suggestion.

I ended up with the same location for my bean temp TC. About 1.5" above the bean plume off to one side so the primary hot air stream leaving the plume could not hit the TC. With only a couple of adjustments I hit the sweet spot with a 1C of 398 to 402 F.

All attempts at placing the TC in the beans resulted in wacky readings.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
greencardigan
Top  #175 Print Post
Posted on 02/16/2011 9:48 PM
Ok, I think I'll try a removable probe as high as I can away from the plume. My glass tube is going to limit how high I can go though.

I've always used the stainless probe type TC. Are there any reasons the wire type would be better other than the quicker response times.
 
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