topbanner.gif
Login
Username

Password




Not a member yet?
Click here to register.

Forgotten your password?
Request a new one here.
Shoutbox
You must login to post a message.

snwcmpr
03/20/2019 4:17 AM
Eth Yirg Nat Idido Gr1 today.

snwcmpr
03/18/2019 8:15 AM
1 lb roasted lasts a week. I can taste the flavor increase to peak, then drop after. Still very good, but interesting to follow the wave of flavor rise and fall.

snwcmpr
03/11/2019 4:10 PM
Roasted Panama Gesha Esmeralda yesterday. Yummy.

Beebee74
03/11/2019 3:10 PM
I seem to have lost any roasting touch I thought I had. Very frustrated to be wasting time and money. I’m hoping someone can provide some insight on roasting at high altitude. I’m at 4400ft. Thank

aicardo
03/07/2019 8:50 AM
tb

Users Online
Guests Online: 3

Members Online: 0

Total Members: 5,862
Newest Member: falllake2000
In Memory Of Ginny
Donations

Latest Donations
renatoa - 2.00
JitterzZ - 50.00
PRABHATH COFFEE WORKS - 10.00
John Despres (Scene... - 25.00
snwcmpr - 10.00

View Thread

Who is here? 1 guest(s)
 Print Thread
Heat Gun Driven Fluid Bed Roaster
coffeeforblood
I posted about my initial foray into roasting in the "First Roasters" forum and this is the follow-up. As I mentioned in that first post, I got tired of the small batch size, the individuality of the roasters and the lack of control. So, I decided to build my own. My going-in objectives were to be able to roast at least a cup of green beans per batch and in an 8-10 minute time frame with good control over air flow and temperature. I also wanted to build it inexpenively, but was willing to spend $200 or so. I had no interest in automation or computer control. I like to be very involved in the process, so I knew it would be a "manual" roaster.

I had read about roasting beans with a heat gun in a stainless steel dog bowl. I even tried it, but it was hard to do a good job and WAY too manual. However, I liked the idea of using heat guns as a heat source, so I found these Porter-Cable adjustable, two-speed heat guns for about $40. I then built a manifold out of black iron pipe and wrapped it in fiberglass manifold tape to insulate it. The base of the roaster is just 3/4" plywood covered by cement board for insulation. There are three heat gun ports in the manifold, though it turns out I really only needed two. There is also a cold air inlet that is supplied by a small Shop-vac fed through a split valve arrangement to help control air flow. There is a thermocouple in the roaster air inlet to monitor the incoming air temperature. The roasting chambers are old Uno-Vac stainless steel vacuum bottles with the bottom cut off and a coarse stainless steel screen in the neck to keep the beans in place. These work well because they are double-walled and they still have the handles on them. I also put a small 3" elbow in the top of the roaster to direct chaff and keep the beans from hopping out when they are fluidized.

The heat guns are just press-fit into the fittings in the manifold and there is a ring of gasket material on the barrel of the heat guns to prevent any blowback. There is a crude wooden fixture that holds the heat guns in place. It is functional, but really needs to be replaced with something better. The roasting chambers just sit in the reducer on the end of the manifold. There is no need to clamp them in place.

I had to experiment a bit to get airflows right. I turn two heat guns on to high blower speed and adjust temperature as needed. The air flow from the Shop-Vac is controlled with the split valve.

I can roast up to 500+ F, but I usually roast around 450 F. Once the roaster gets to steady state, it holds very constant within about 4-5 degrees which is perfectly fine. When a batch is finished, I just grab the handle on the Uno-Vac and pull the elbow out of the top and pour the beans onto a metal sheet pan to cool. I have roasted more than 50 batches so far and the results have been great. Batch times are about 8 minutes and I can easily roast 1 cup of green beans per batch. I could probably push the roast size a little more, but I am content to leave it at 1 cup for now. The only thing I would like to change is to get a slightly smaller mesh for the screen in the roast chamber to prevent any beans from falling through. I'd be happy to answer any questions you have about my roaster. Thanks for reading.
coffeeforblood attached the following images:
img_0070.jpg img_0071.jpg img_0072.jpg img_0073_1.jpg img_0074_1.jpg img_0075_1.jpg img_0076_1.jpg
 
coffeeroastersclub
That is a pretty ingenious setup. My only question is have you noticed any negative effects of the vacuums positive air pressure affecting the heat gun outputs? I would think it would reduce the heat gun air pressure output and possibly fry the heat gun elements.

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
http://www.coffeeroastersclub.com
coffeeforblood
Len - you have hit on the main unanswered question for me - how long are the heat guns going to last? This is garage engineering at its finest, so let me assure you that no fluid dynamics calculations were done in the design phase! My thinking is that "the path of least resistance" for air flow is through the roast chamber. Is there some possible back-pressure in the system? Almost certainly, but I am hoping it is low. Also, most of the Shop-Vac output is split to waste. I am using only enough cold air to supplement the heat guns in order to fluidize the beans. I'd be much more concerned if I was directing the full flow into the system. So, your guess is as good as mine. So far, I have roasted more than 50 batches and the heat guns have not shown any signs of distress, but they could just fall off a cliff at some point. I have not checked, but I would imagine that the elements are replaceable. If I can get 200 batches out of a heating element, I will be ok with that.
 
coffeeroastersclub
If you have done 50 batches so far it would seem you do not have the backpressure I envisioned. So as the old saying goes, if it ain't broke don't fix it! ThumbsUp



Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
http://www.coffeeroastersclub.com
coffeeforblood
I am also depending on a Venturi effect wherein the cold air rushing past the heat gun outlets will "pull" the hot air out. Who knows if that is true, but that's my story and I'm sticking to it. Ha ha.
Edited by coffeeforblood on 03/07/2019 2:26 AM
 
greencardigan
Interesting!

I am also curious how much air flow you are getting through each heat gun compared to it's usual air flow.

Definitely makes it easier to replace a heatgun/element.
 
coffeeforblood
The ease of interchanging heat sources was actually a secondary design criterion. Burn up a heat gun? Yank it out and throw in another one and keep roasting!
 
ChicagoJohn
Thanks so much for taking the time to post your narrative and all the great photos. What you did will be a big help to me in thinking about a design. It is always fascinating to me to see how different people approach the general objective in accord with different preferences. In my brief journey, I've learned how coffee is and area where personal preferences are prevalent. While you specifically wanted a manual system for hands-on operation, I've lately been seeking to automate so results will be as reproducible as possible and I can forget the roasting process and focus instead on single origin effects etc. But I can clearly see the issues you identified in the ways you decided to address them, and this will no doubt save me a lot of the error in the trial-and-error design process. Thanks again !

good post
So many beans; so little time....
 
coffeeforblood
John - I am even more into wine than coffee and your maxim of personal preference holds true there as well. I once met Michael Mondavi (son of the California wine icon Robert Mondavi) and he very explicitly said "drink what you like. Don't let anyone tell you what you "should" drink." Amen.
 
coffeeforblood
John - thought you would appreciate this as well:

"There are no standards of taste in wine, cigars, poetry, prose, etc. Each man's own taste is the standard and a majority vote cannot decide for him or in any slightest degree affect the supremacy of his own standard." - Mark Twain, 1895
 
oldgearhead
Nice build! Heat guns all have a flow problem and the system will require a source of pressured air,.such as your shop vac. Heat guns,typically, have 1200-1500 watts elements and in my case are rated to deliver 1000F at 23 CFM. Since 23 CFM is NOT enough flow to fluidize my bed of coffee beans (500 grams). I, like most home-roaster builders before me start with a source of air that is much higher (100 CFM) than a heat gun and install the heat gun element heater between the air source and the roast chamber.
My primary concern with your roaster is understanding the capacity. If one cup is 100 grams then you must be wasting a lot of hot air...as I have with this missive..
No oil on my beans...
 
coffeeforblood
You are probably right about wasting hot air. I know I could lift more beans easily, but the height of my column is the limitation. I would have beans reaching escape velocity if I put many more in and increased air flow at all. I could probably get another piece of straight 3" pipe to "extend" the column and roast more beans per batch, but that would undoubtedly increase back pressure in the system with unknown consequences. I might give it a try just to see how (or if) it works.
 
coffeeforblood
Out of curiosity, I weighed a cup of green coffee beans. Turns out that it weighed 180 grams. I am sure that the weight varies with bean identity, but it is a little more than we were thinking.
 
oldgearhead
Since there is .035274 ounce per gram. I assume you are using a 6.35 ounce cup. I was using a 4 ounce cup. A typical coffee maker is marked in 5 ounce cups. A cup is not always the same..
No oil on my beans...
 
coffeeforblood
Actually, I used a standard kitchen measuring cup that would be used in cooking, since this is the way I dose beans into my roaster. So, I measured 8 ounces of beans by volume and then weighed them on a digital scale.
 
oldgearhead
Eight ounces of greens, by volume, usually weighs in at 85 grams depending on %M. At least that's what I get when I fill my moisture tester..My 100 grams per cup statement, was very wrong and miss-leading, because there are four different 'cup' sizes used with coffee.
No oil on my beans...
 
ChicagoJohn
oldgearhead wrote:

Eight ounces of greens, by volume, usually weighs in at 85 grams depending on %M. At least that's what I get when I fill my moisture tester..My 100 grams per cup statement, was very wrong and miss-leading, because there are four different 'cup' sizes used with coffee.


I just weighed a level measuring cup of yirgacheffe. It weighs 160 gm. I then filled the cup with water. That weighs 238 grams, so we know my cup holds 8 oz by volume.
So many beans; so little time....
 
oldgearhead
oops! Chicago John is correct. My %M tester uses one-half cup (85 grams)..
No oil on my beans...
 
coffeeforblood
I have now roasted over 100 batches with this rig and performance continues to be very steady. The heat guns appear to be working fine and are currently showing no signs that they are having problems. I did figure out the hard way that one 15 amp circuit will not supply a heat gun plus a Shop-Vac. Oops! I figured that was probably too big of a load and I confirmed my suspicion. I am about to order some new SS screen material though because I am constantly having beans fall through or get stuck in the current mesh size. It's not a show stopper, just an annoyance, but it's easy to fix.
 
coffeeforblood
I replaced the #4 stainless steel mesh screen in the bottom of my roasting chambers with #5 screen and it worked just as I hoped it would. There was no discernible impact on roasting time or efficiency and I didn't have any beans get stuck in the mesh or have any beans fall through the screen. Happy, happy, joy, joy!

My next experiment will be extending the height of my column to see if my roasting rig can handle up to 2 cups of green beans (ca. 360 grams) per batch. This might be a little more of an issue because the back pressure will increase proportionally with bed depth and this could have unanticipated consequences. However, the only way to know for sure is to run the experiment! I just need to wait for a slightly warmer day.
 
Jump to Forum:

Similar Threads

Thread Forum Replies Last Post
fluid bed design questions Fluidbed Roaster 11 03/23/2019 8:48 AM
Transparent Fluid Bed Design Building a Coffee Roaster 68 03/21/2019 5:38 PM
TC4+ Arduino coffee roaster shield (TC4-compatible) Dataloggers/Controllers/Rate of Rise Meters 70 03/21/2019 10:02 AM
Drum Roaster on top of BBQ Drum Roasters 5 03/18/2019 10:06 AM
Fluidbed roaster build... questions... Fluidbed Roaster 36 03/14/2019 1:16 AM
Homeroasters Association Logo, and all Content, Images, and Icons © 2005-2016 Homeroasters Association - Logos are the property of their respective owners.
Powered by PHP-Fusion Copyright © 2019 PHP-Fusion Inc
Released as free software without warranties under GNU Affero GPL v3
Designed with by NetriX