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Gas burner design for hot air roaster
Dan
Air going past a burner is traveling very fast and is bound to disturb the flame, leave some gas unburnt, or extinquish the flame altogether.

What are some burner designs that work? Do they use a burner with dozens of small flames, or one large one? Pictures or drawings anyone?

Dan
 
RayO
My folks had a natural gas clothes dryer years ago, that had a burner similar to a furnace burner- several small flame ports in a burner manifold in a heat exchanger. Did I mention- Old?
Subsequent dryers have always had a single flare flame feeding into a cone receiver, flame stop, and into the drum. A blower draws air/ combustion products/ moisture out of the drum, through a lint filter and exhausts out the dryer vent.

Now I have a surplus dud water heater with a 62,000 BTUH burner. Everything's in good shape but the tank. Leak! I may miter cut the thing to make a Tee shape out of it, or just cut it down and use a Porta-Power or 16 pound Persuader to reshape the tank to accept a horizontal RK Drum- an AO Smith or RayO Roaster!
Cheers -RayO

Got Grinder?
 
Dan
Ray-O, What do you mean by 'flare', as in single flare flame? Did that flame feed into the small or large end of the cone?

I'm completely new to this subject. I do own one of those huge 1 million BTU 'weedburner' propane torches and it is very simple. I also have a turkey fryer burner that must be around 100,000 BTU.

187, Yes, I recall that discussion. A simple on-off with maintenance heat would work.
 
Javadude
I just tried a 55,000 btu adjustable propane torpedo heater in a bbq application. After stuffing foil all around the grill and closing off every air leak that I could, the best temp I could reach was 450 outside of the drum. Inside the drum I could not get it to second crack. However a larger btu should have got the job done. I think using this type of application would work if you could get the temp about 75F. hotter. The reason I tried the forced air was because my roasts had a smoky aftertaste that was horrible. What I ended up with was a traditional bbq drum roaster, then took a air popper apart, cut a hole right behind the roasting drum, and mounted the whole air popper to the lid, so that there is about 1/8th inch clearance between the roasting drum and the air drum. right after 1st crack I turn on the popper and the temp spikes up a bit and the chaff blows out along with all of that unwanted smoke.
 
David

Quote

Javadude wrote:
I just tried a 55,000 btu adjustable propane torpedo heater in a bbq application. After stuffing foil all around the grill and closing off every air leak that I could, the best temp I could reach was 450 outside of the drum. Inside the drum I could not get it to second crack. However a larger btu should have got the job done.
....What I ended up with was a traditional bbq drum roaster, then took a air popper apart, cut a hole right behind the roasting drum, and mounted the whole air popper to the lid, so that there is about 1/8th inch clearance between the roasting drum and the air drum.


Wow! s:1

Pictures please.

c:2
 
Dan
That's a good idea. I'll look at the burner design on torpedo heaters. :)

I checked out owners manuals for a couple propane construction heaters and the designs for these direct-heat, fan-forced units are encouraging. I think something similar could work for a hot air roaster.

Like I expected, they use a hurrican shield to prevent the fast moving air from blowing out the flame.

I prepared an image, but it is too large to post here. You can download it from our Downloads section or here: http://forum.home...nload_id=4

What is especially nice about these designs is that they use a single orifice burner. A person could make such a burner using black pipe fitted with a brass cap in which a small hole is drilled. Vary the hole size for the BTU and pressure required. HINT: the gas pressure must be appreciably higher than the blower pressure. Use a pressure regulater on the propane bottle to control heater output.
Edited by Dan on 01/28/2007 9:31 AM
 
Javadude
After work and rework after rework the grill has patch after patch all over it, and I feel a bit embarassed. I will draw up some blue prints and a pic or two asap kinda busy with the wifes car at the moment, its froz:@. The design is a bit unorthodox and needs a revamp to make it more user friendly, but it works as is. Now I will show both, with and without torpedo, like I said would have worked with, but not hot enough for app. So I reverted to older design that worked so I could get coffee done for customers.

Yup, looked at your illustration, and thats the puppy. The one I bought as a 30-55,000 BTU by Remington. The biggest one that they offered would have done the trick I think!! This model is too small.
Edited by Javadude on 01/28/2007 9:07 PM
 
Dan
I saw one 170,000 BTU heater, so heat shouldn't be a problem. :)
 
Javadude
OK FIRST MY DISCLAIMER: s:3 DO NOT TRY THIS AT HOME WE ARE TRAINED AMATEURS.B). NO ONE CAN BE RESPONSABLE FOR YOUR HOUSE FIRE BUT YOU!! SO DON'T ATTEMPT THIS IN ANY WAY SHAPE OR FORM s:3 . Now as I said before I have patches all over this roaster and it is UGLY but it works very well. After all types of drums and devices to release the beans into a cooling tray faster, I have came up with a design that copies a Probat-Burns sample roaster (of sorts). But it retained too much smoke in the roasting process so I looked into moving the air inside the roasting chamber. A regular fan dropped the temp way to far, so I installed the air popper in the back as shown in the pics, now this does not move vast amounts of air. BUT it does aid in the smoke AND chaff extraction. which blows out though the front orifice fairly well. This design will exceed 700F., But I dont let it get that hot s:3 . You can see in one of the side views where I cut the giant hole in the base and lid for the torpedo, but patched so I could get some roasting done. OK enough of that, in the spring I will get a new bbq and rework all the uglyness out. This roaster works very well and I have hopes for a torpedo design on the same bases. Side Note: the Torpedo WILL work standing upwards, so my suggestions for this design is to research mounting from the bottom to blow upwards. But it MUST be mounted far enough away for the heat and air to mix properly, this may have been my problem I am not sure yet. I will research farther. Well Here are the pics.............
Javadude attached the following image:
roaster1[139].jpg

Edited by Javadude on 01/31/2007 9:47 PM
 
Javadude
more
Javadude attached the following image:
roaster2[140].jpg

Edited by Javadude on 01/31/2007 9:48 PM
 
Javadude
and more
Javadude attached the following image:
roaster3[141].jpg

Edited by Javadude on 01/31/2007 9:50 PM
 
Javadude
and yes still more
Javadude attached the following image:
roaster4[142].jpg

Edited by Javadude on 01/31/2007 9:52 PM
 
Javadude
and one just to show my favs
Javadude attached the following image:
bags[143].jpg

Edited by Javadude on 01/31/2007 9:54 PM
 
Javadude
forgot one
Javadude attached the following image:
roaster5[138].jpg

Edited by Javadude on 01/29/2007 10:25 PM
 
Dan
Your real name wouldn't be Javarube, and in Goldberg, would it? This is a marvel of ingenuity and using available resources. You da man! s:1 Tilting the top half of the roaster taking along the drum and gearmotor is the same setup I use on my sample roaster. In a Javez sample roaster the gearmotor stays behind in the bottom half.

You concern about high temps near the torpedo heater exit is justified. A hurrican shield of perforated metal should help a great deal. It will generate a lot of turbulence. The other name for turbulence is mixing.
 
Javadude
Thank you for the kind words, but as always (at home) its a work in process. When I can afford it, I want to fab a housing and use some perf stainless for the drum. I respect all of the guys out there that are fabricating home roasting drums. But I know that cooling those little gems fast mean alot for the taste and aroma. So after using several versions of the traditional grill drum including my own version, with a spring loaded dump gate, I decided that a open faced drum like the jabez was the way to go. Fast to dump AND you can get the probe right into the bean mass. With the other versions I would need welding gloves and it would take a bit to long to pull the drum from the roaster and pull the pin and lid then dump, by that time you have went from a city to a city ++ or a french s:3 . With this version you can get a roast that is close to a pro-roaster. Now with that said, I am NOT claiming to get the same results as a P-Roaster, however all of the components are there, heat, air, spinning drum and a cooling bin, all in a ez to use setup. I only hope that someone take this idea and runs with it. And improves on it Grin . The store I got the heater from will take it back so s:2 I can get a bigger one and continue to chop away at the grill s:4 s:8 ....Roast away
 
Dan
I have a trite phrase I like to use from time to time. "What people want is a sample roaster."
 
Javadude
One word of caution:Shock With the larger torpedo's you might need a 100lb propane tank as required with several of the larger models. So there will have to be a larger investment. I can do a 2.2lb batch in 16-18 mins,(I can do it in 14 min, but I think that is too short) depending on the roast, with the roaster as is. This weekend I will attempt a 3 lb batch, I know the drum will hold that and more, but do I have enough energy to accomplish it, I am hopeful. Before I stuffed foil all around the grill, the temp in the grill area was around the mid 600's but now after the foil I can go in the mid to upper 700's. (I WILL HAVE AN EXSTINGUISHER ON HAND WHEN ATTEMPTED)s:4 The need is there as I am getting orders that will be hard to keep up with at 2 lbs per batch, but still managable. I will be replacing the air popper with a adjustable heat gun, the box says it will reach 1000 F. and some nice air pressure, I think this will inprove the ability to curve the roast profile much like a pro-roaster. We will see, but the 55,000 BTU is going back to the store. Roast happy...............
Edited by Javadude on 01/31/2007 10:23 PM
 
Javadude
Just aquick update. I installed the heat gun, and it produces a lot more heated airflow but, the first roast went south, as I now turn the burner down at first to compensate thenew heat source.
 
Javadude
OK I have put the new heat source through the mill, and with the roaster "as is" I got it up to 3 whole pounds per batch it 17 minutes. And the roasts are very even. Tonight I did 5 lbs Colombian, 2 lbs Braziliain, 2lbs Tanz PeaBerry all in just under 1.5 hours. Not bad for a roaster from stuff lay'in around the garage. (Mostly ;) )
Now with that said I had to push the heat all the way open towards the middle, but it made the 20 degrees/min to get the roast. I dont think I should push any more in the drum, even though volume wise, it will hold more. I also mounted a new digital 3 foot probe thermometer inside the drum. Now, much better tracking. Just cuppedtonights roast and each one was a nice cup. Has anyone tryed the torpedo yet, I am afraid to buy a bigger one, maybe when the taxes come in ;)
 
Dan
You've been a busy boy! Your next challenge will be maintaining your roaster now that you are putting some significant volume through it.

I've not tried a torpedo heater. From the schematics I've seen it wouldn't be difficult to cannibalize one. You may even be able to put one vertically underneath your roaster. These things induce lots of air to cool the exhaust. That temperature is well below roasting temps, so you'll have to reduce the fan speed or turn it off completely and let convection help out. The problem will be that the combustion chamber will get hotter. You might want some fan-forced air moving between the combustion chamber and the torpedo housing.
 
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