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renatoa
03/25/2024 12:38 PM
coffee drink, Ramper?

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Heat + Airflow -or- Airflow+Heat
CharcoalRoaster
In a FB, if using propane as a heat source, does the propane heat source (torch/burner) need to be placed underneath the airflow inlet? or above the airflow inlet? If below, how do you direct airflow upward toward the RC?
 
BenKeith
Depends on your blower.
If using one that can handle the heat, you can have the burner at the inlet and going through the blower.
If you are using vacuum blowers, or similar, the heat will need to be between the blower and the roast chamber.
 
CharcoalRoaster
Currently, I have the propane burner feeding directly into a steel tube. I have the vac motor blowing into the tube through a VERY short piece of steel pipe so the airflow inlet is about 8" above the burner. However, once I place the RC on top of the steel tube the backflow from the air goes out the bottom and doesnt loft the beans.

So, I guess I am asking, if I have the burner below the airflow inlet is there a way to direct airflow upward so it doesn't start coming back down toward the burner if its flowing into the vertical steel tube via a perpendicular steel piece of pipe from the vac motor?
 
BenKeith
How many air leaks do you have around the burner?
Sounds like you have too much air leaking or too small of vacuum motor or both.
You have a couple of options. Fix any leaks, leave the heat off, with the blower running. Start pouring beans in until you start losing most of your lift/agitation. Then make sure it will start up with that load. That amount will be your roast limit.
If that's way less than you were wanting, you need to upgrade to a much stronger vacuum motor, or a second vacuum motor, or blower unit. You've got to be able to agitate the green beans or the heat is going to be way too uneven the first part of the roast.
Like mine with the old iRoast2 blower I'm using, I can agitate 300 grams and once they get some heat and dry some, they agitate fine, I actually turn the blower down some near the end. However, I've tried 350 grams and it won't agitate that much green beans, so 300 is its limit.
 
CharcoalRoaster
That's part of the reason I'm asking. Under direct airflow - vac motor blowing straigt up into the RC I can easily agitate 1.5lbs of beans. I'm thinking I see the issue though as the steel pipe isn't enclosed around the propane burner. It's open on the bottom to allow the burner to send heat up through it as the burner sits about 1" from the bottom of the pipe.

If I understand correctly, I need to seal the burner inside the pipe so that all air is forced up through the RC?
 
BenKeith
Seems like some of these guys that run propane burners would jump in and help out.
If the pipes/burner is not sealed so the air can escape around them instead of being forced through the beans, It's not going to lift them.
Now, since I have not tried a propane burner in one, I can't reply to how it will burn with one. Different types of burners respond in different ways when placed in a forced air stream. I build my own forge burners and know exactly how they respond, too much air will blow the flame off them.
So, what I'm saying, once you get it sealed so you get your bean lift, if the burner wants to act up, I can't help you with that one. Hopefully it will burn great for you.
 
Mustang967

Quote

CharcoalRoaster wrote:

That's part of the reason I'm asking. Under direct airflow - vac motor blowing straigt up into the RC I can easily agitate 1.5lbs of beans. I'm thinking I see the issue though as the steel pipe isn't enclosed around the propane burner. It's open on the bottom to allow the burner to send heat up through it as the burner sits about 1" from the bottom of the pipe.

If I understand correctly, I need to seal the burner inside the pipe so that all air is forced up through the RC?


Hey, I'd love to help but I'm having a hard time understanding your burner setup. Could you take a picture of your roaster and your burner setup? Just a general note, you will need to seal any holes or openings that don't directly lead to the roast chamber. Any holes, even tiny ones can cause issues with heat and airflow.

Thanks

Royce
 
CharcoalRoaster
Here's an image that will give you a rough idea of what I've assembled so far. I can get airflow up to the steel tube outlet but not at enough CFM to loft the beans. Once the RC is placed on top of the outlet is decreases even farther and I can feel A LOT of air escaping out of the bottom of the tube under the burner.

Sealing everything up makes a lot of sense to me so I just need to figure out how to fabricate it together with no ability to weld!

https://www.dropb...1.jpg?dl=0
 
BenKeith
That setup is totally wrong and has no possible way of ever working. The vacuum motor has to go where the burner is at. The burner has to be located inside the pipe between the vacuum motor and the roast chamber, with no leaks around the pipes and burner where they inter the pipe. Other than figuring out how to mount a burner inside the pipe, you should not need any welding. Even then, bending and screwing brackets should work, just may not be a show piece when done. You should be able to arrange the burner above the piping so the heat source is far enough up that, other than some conductive heat, the pipe should not be too hot to use some type of tape that can stand a little heat to seal them. If you have to, buy you some muffler tape, but that stuff can be expensive.
Also, if that's you typical fish fryer/turkey roaster, that burner probably won't be very practical to try using. It's so large, you will probably need a 4" to 5" pipe to mount it in and have the clearance for enough air to get by to the roast chamber. I've seen some of the guys use the small propane camp stove burners or torch tip type made for your application. Since you have it, you can try it with a large pipe to see if you can make it work.
Edited by BenKeith on 01/10/2017 8:17 AM
 
BenKeith
Look in your local builders supply or hardware store and check out their metal stove/heater ducting. That stuff comes in all sizes and is easy to work with. You can probably find a piece that will work. They also have a fairly good assortment of reducers that might get you close to what you need.
 
CharcoalRoaster
Yeah, that's sort of what I figured once I turned the blower on and didn't get any lift in the bean mass. I'll play around with the configuration this week and see what I can't work out.

Thanks for the insight.
 
Mustang967
Yeah I completely agree with BenKeith, the air supply must be below the burner. Your current setup will just blow air out the path of least resistance. I'd suggest a box below the burner that your vac can be in or be mounted to blow air into the box.

Royce
 
CharcoalRoaster
Ok, so I've redesigned to mount the blower below the burner and am almost ready to fire it up and try out a test batch of coffee. Hopefully, tomorrow. Typically to seal air gaps and connect some pieces together I have been using the high temp copper caulking. However, I found some stuff at ACE today and thought I'd give it a shot. Its fire barrier sealant caulk that can withstand temps of 2000*, remains flexible, and expands slightly under extreme heat.

I'm sure there's something wrong with using this since I can't find anyone utilizing it for sealing there roaster on here... just break it to me... what's wrong with this stuff regarding roaster use?BBQ grill
 
coffeeroastersclub

Quote

CharcoalRoaster wrote:

I'm sure there's something wrong with using this since I can't find anyone utilizing it for sealing there roaster on here... just break it to me... what's wrong with this stuff regarding roaster use?BBQ grill


The fire barrier sealant I am aware of is latex based, made by 3m, and expands to a minimum of 3 times its dried volume at temps over 1000. I would be concerned with expansion below 1000, and fumes released from it when heated.

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
snwcmpr
I can't add to the upper or lower placement question.

But, it would seem the box that the burner is in has a leak. I assume that the only way air should have to get out would be into the RC. Maybe turn on the blower, no heat, fill with beans to the 'limit' then check for leaks around the box. Where all the screws, joints, and etc are. I have a couple of very small leaks, but not worth fixing. I can feel a little bit of air out of the box.

Ken in NC

roar
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
 
CharcoalRoaster
So after leveling out the roast, securing it so it will be safe with the RC on top I ran a test load and I can EASILY circulate/agitate/loft 640g of greens at 30% blower power. Almost threw em out of the RC!

That was all i tried and it doesn't seem like I could go more than 750g without maxing out the bakearound RC. I've attached some pics so you can see the roaster design. Once the fire barrier sealant cures completely and when I have time to get back to the roaster I'm gonna install a thermocouple at the top of the burner chamber just below where the RC will sit to measure some temps with the propane running.

https://www.dropb....jpeg?dl=0
https://www.dropb....jpeg?dl=0
 
BenKeith
Not too sure about your sealants. I ALWAYS us food grade, high temp sealants. Some of that stuff can get pretty toxic.
As a minim, before putting any beans in it, run it at least a 1/2 hour at temp to try and cook off any fumes etc, it might generate.
 
walt_in_hawaii
Nice job, Charcoal Roaster! I'm curious; can you show the label or tell us what kind of 'firestop sealant' you used? I'm trying to toss my own roaster together, similar to yours (but uses electric heating element) and a Bake-A-Round pyrex glass, and the caulks I see say it will 'expand when heated' which is sort of scary as I don't want it expanding too much and breaking the glass. Does your expand noticeably when heated?
 
CharcoalRoaster
That's a good suggestion to run it at temp for a while to burn any fumes off. I will have to let you know how much it expands under heat as I just applied it and am waiting a few days to ensure it cures properly before turning on the gas. For the seal at my bakearound I used the high temp copper RTV silicone caulk.

I did take some of the dried fire barrier caulk and put a torch directly to it to see how much it would expand before I loaded up a bunch of beans and it sort of just turned to ash with maybe 100% expansion but I couldn't quite tell if it was because of direct flame application or if that's how its supposed to react...

After I run it at temp with an empty bean load for a while I'll update this thread and if all is well I'll post a pic of the caulk tube.
 
BenKeith
I've always used this. https://www.amazo...B0114AERBM
Even with this stuff, it smells pretty strong and actually smokes a little until its run at temp for a little while. I've got one roast chamber I've had it on a couple of years and still holds fine though.
 
walt_in_hawaii
Thanks BenKeith! I've just ordered one.
CharcoalRoaster, you may want to think of swapping your RTV silicone... copper is poisonous, and although we are probably talking a tiny trace amount, I dunno about accumulation over time.
 
snwcmpr
You might consider running at 'less than temp' for a while to cure, then run at temp for a while. My wood stove sealant says low/medium temp at least an hour before using at full temp.

As for capacity at 30%, the beans will swell, will they blow out the top?
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
 
CharcoalRoaster
Thanks for the heads up Walt - I'll see how things go on firing up the heat.

snwcmpr - I think I'll take you up on that suggestion and run it for a while at lw/med before cranking it up. As far as bean expulsion I guess we'll have to wait and see!beachcross fingers
 
CharcoalRoaster
Well, I ran into a problem and propane + problems isn't the best mix.

I drilled a small hole (large enough to fit a match through but not large enough to significantly decrease pressure) in order to light the burner. If I barely open the propane and stick a match into the chamber I get combustion that bursts backward through the venturi of the burner instead of igniting the burner and producing a healthy flame. If I run the motor the ariflow puts the match out.

How can I SAFELY light the burner inside the combustion chamber without blowing myself up?
 
BenKeith
Electronic igniter.
Might try a long reach butane lighter. Make you a little cover held by a screw over a hole you can slide open to light. Stick the butane lighter in, light it and then ease the gas on might work. Then see what happens when you try turning the air on. Just be ready to turn the gas back off, because that turkey roaster burner might not stay light in that air stream.

Like this
https://www.amazo...BD6YT2Z64S
 
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