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My Sight Glass FB Roaster Build
scott111000
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Posted on 09/07/2024 9:27 AM
Hi, all first post and first build. Before I take this any further I wanted to get some feedback and general impressions.  I plan to put heater elements in the pressure cooker and blow in air from a small shop vac. I'll suspend the roast chamber so that the pressure cooker can slide out.  Then I can remove the second tri clamp from the bottom that holds the screen/funnel in place to release the beans into a bowl. 

As for specifics, the sight glass is 3" diameter and the plan is 4kW heaters. I'll control the heat and blower manually at first. Then add probes, logging, eventually control. There are still so many unknowns. I'm hoping to at least roast 2 lb per batch. Any comments, questions, suggestions are very welcome. 
scott111000 attached the following images:
fb_insidesized.jpg fbsized.gif
Edited by scott111000 on 09/07/2024 12:19 PM
 
renatoa
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Posted on 09/07/2024 10:57 AM
Welcome!

Brilliant idea using a general usage cookware/pot for heater!
Any chance to see the heater placement inside ?
Do you plan to route the air through a baffle structure as a labyrinth, in order to improve heater-air contact area ?
 
scott111000
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Posted on 09/07/2024 12:15 PM
Thanks I'm already glad I posted. Here are the heaters I have 2kW each. I take it from your question that I need to direct the air flow over the heaters. I have some 2" copper pipe that the elements fit into but that seems complex. Simpler might be a perforated plate over the elements, where the air blows down onto the heaters before rising up through the holes. That would make it a lot easier to swap out or add heaters. I really want to keep every part modular so I can upgrade components as I go along.

Update : I'm having trouble attaching a photo to the reply. Maybe this works https://imgur.com/a/oUmZm0l
Edited by scott111000 on 09/07/2024 12:20 PM
 
renatoa
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Posted on 09/07/2024 2:23 PM
Be careful to not create escape ways for the air, allowing cold air bypass the heaters... we want roast the beans, not bake them Shock
 
scott111000
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Posted on 09/08/2024 10:28 AM

Quote

renatoa wrote:

Be careful to not create escape ways for the air, allowing cold air bypass the heaters... we want roast the beans, not bake them Shock


Yeah it's clear to me now that these heaters I got from ali are built to be put inside 1.5" pipe. That will force all the air to within about 2mm of the hot wire. I think what I'll do is source some copper pipe and braze it. I'm basically making a couple of 2kW hot air guns! I have to think on it more. Thanks for the insight.
 
scott111000
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Posted on 09/17/2024 8:06 PM
I got some 1.5" copper pipe and cut a strip out to reduce the diameter to better fit the heater. I'll arrange to have all the air pass through this tube.
scott111000 attached the following image:
heater_tubesized.gif
 
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