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Heatgun FB Build
oldgearhead
Top  #26 Print Post
Posted on 10/12/2015 12:41 PM
I can only think of one other possibly, besides electrical, and
that would be more all flow than the heating element can heat:
1) What are the heat gun specs?
2) What is the area of your perf plate?
3) What is the total area of the holes in the perf plate?
4) How do the beans taste after 5 days rest?
No oil on my beans...
 
alexcampbell
Top  #27 Print Post
Posted on 10/12/2015 9:11 PM
I suspect you are having an airflow to heat mismatch. When I was building my roaster, I considered running with a 110V heater, but came to the conclusion that I would need mechanical agitation to supplement the blower air.
The drawback of a fluidbed roaster is the heat to airflow requirements. With so little thermal mass in the roaster, there is little "thermal inertia". As opposed to a drum roaster that relies on some pre-heating of a drum to give off heat during the roast, the fluid bed requires all of the air flowing through the roaster to be heated from room temperature to 500+ F. Think about a 1500W poppery I. It has an anemic little motor and can only roast maybe a third pound of coffee, but the airflow to heater ratio is favourable. The advantage to the low thermal inertia is that you can rapidly swing a roast profile as well as effectively cool in the roast chamber.
I think that this is why the "Corretto" builds are so popular. The airflow from the heatgun is optimal for heating the volume of air that flows through it. This, coupled with the thermal mass of the bread machines, allows a small element to roast 2 pounds of coffee. You can imagine that if you took a huge blower and circulated additional air through it, you would not have as much success.

A couple of suggestions for you. If you have 220 available, you can run up to 3300W on a 15 amp circuit. If you have a dedicated plug, you can change it at your breaker box and run 220V to that plug. Also, if you have an electric range, and an adequate range hood, you will have 30 amp 220V right behind the stove to plug into. Another nice thing with the 4 prong 220V range plugs is that the 4th wire can be tapped for 110V. I am using a 3300W plastic welder element that can roast over 1.5 pounds. Could do 2+ with a larger RC and probably 3-4 if I used mechanical agitation.

My other suggestion would be to look for a way to add in mechanical agitation to reduce the airflow requirements of your fluid bed.
 
scotthal
Top  #28 Print Post
Posted on 10/12/2015 10:57 PM
Coupla suggestions - if you have access to an AC voltmeter, check voltages at the wall plug & end of the splitter whilst under load. Should tell you if you're losing power in the cable harness, & if so, where. Alternatively, you can reduce air flow at the expense of continuous 'enthusiastic' bean circulation, or cyclically 'burp' the system.
Food for thought; coffee for concentration
 
LongLeafSoaps
Top  #29 Print Post
Posted on 10/16/2015 11:57 AM

Quote

oldgearhead wrote:

Seems kind of wide at the top. Is the lid vented?
The air that enters the bottom must come out the top.
My inlet to outlet hole total area are a close match.
Then as chaff starts to gather at the top, the outlet is restricted a bit.


Could you use a cone shaped screen for the top air ejection opening of your RC? The "point" of the cone pointing into the RC...that way, chaff could collect at the wider end of the cone (chaff would still drop down onto your beans after the blower is switched off, unless a "J" pipe is incorporated), while still allowing the narrower, pointed end of the cone to stay chaff free for air flow to pass through.

Just a thought.....
Carpe Diem With Coffee
 
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