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Weird question #2 - Ovens

5-90

5-90

NAXJA Forum User
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This should be a fun one - I'd like to make an oven, preferably gas-fired (propane/LP/NG,) that I can make large enough to handle several wheels or an entire axle for powdercoating (or other heat-cured finishes)

I can handle the idea of fabricating metal, I'd just like help on picking a good insulation, gas metering, temperature control, and suchlike. I've got some half-assed ideas, but I'm getting stuck on temperature regulation.

I'd prefer to use gas because it's quicker and more efficient.

Anyone have a hobby or a habit of gas ovens, think you can help me out? I'd probably only need a maximum operating temperature of 400*f or thereabouts - I'd have to check again to be certain (most of the coatings I want to play with cure in the 300-350* range...)

5-90
 
I toured a potter's house a couple of years ago and found his homemade kiln quite interesting. It had to be homemade, because a commercial one that size would have been tens of thousands of dollars. Its internal dimensions were 6' tall, 8' wide and 10' deep. The entire structure was made of dry piled kiln bricks with a mortared ceiling. It ran on LP, and was plumbed with steel pipe. He had what he called 'firing nozzles' inside that acted as burners. His was obviously meant to get much hotter than what you want (2500+ degrees) but the principle is the same. The nozzles entered the oven through spaces in the bricks. He said he got the idea from websites, so I'm sure there is lots more info out there...
 
I powder coat using radiant heaters running from propane. I monitor using a non-contact IR thermometer. For axles, I hang them and and slowly rotate them while they heat. It has worked great other than smoking like hell if you don't get them cleaned out completely.
 
Yes the hand held IR temp gun is cool. Cerwool prolly would be a cheap insulator(we use it to cover molten iron to keep the temp from the furnace to the molding deck)
 
A real heat treat funace has a timer that will kick the NG off after reaching a certain temp. It gets alil deeper than that but for coating, it shouldnt be to bad to get a timer and temp sensor set up.
 
MMM back to back post, my bad just thought of something. What about a cooking stove temp/sensor setup, you only need like 350 right. Tell your wife its time for a new stove lol, and gut it and build a big ol oven.
 
Yeah - I've used heat treat furnaces at school. Only problem is, they were about the size of lunchboxes when you opened the door - probably couldn't get a ring gear in there unless you leaned it in the corner!

That, and I just don't need 1800* or so!

The biggest dilemma for me will be figuring out the temperature control (a timer should be kid's play,) and next is figuring just how much burner I'll need for max temp. Then insulation...

Of course, the whole thing will probably be on wheels or a low-boy cart so I can shove it out of the way when I don't need it.

5-90
 
could you find a couple of used and operating electric ovens,(that have some other problem than temp. control) and then use the bake heaters and themostats(240v in parrallel) from each inside your "homemade oven cavity". i would recommend hydraulic type thermostats for ease of hookup, electronic boards can be fussy and costly.
 
I'd considered electric, but my garage doesn't have a 240 circuit, it would be a fair amount of work (pull wiring, change subpanel, ...) and we rent, so I'd have to get the landlaird to sign off (which I'd sooner not have to bother with.) Besides, Professional Gouging and Embezzlement already loves us - I've got a small lead pot that sees a lot of use, we've got an electric dryer and stove (dammit!) and my mother-in-law has a LOT of medical devices that just love electricity.

Besides, the advantage of gas (beyond efficiency) is the potential to make it portable, and the near-instant response and light-off time.

I did find a temperature control from an outfit that does - of all things - turkey fryers for about $25 - I've got to email them or look for tech data on the thing, and see if it can be adapted to my needs. It would work with propane, but that's what I'd been hoping to use anyhow (probably from a bulk tank - or at least a BBQ tank...)

I'm still digging, and I'm sure I'll have to get my hands on - or access to - a largish box and pan brake before I'm done as well. This might take a while...

5-90
 
I think the simplest and easiest route would be to grab an old gas range. It'd already have everything you'll need. You could even add the top burners into the oven and just plumb them inline with the regular oven burner. The range would have the thermostat, ignitor, and everything else you should need to make it work.
 
That's a thought - but it would be calibrated for natural gas instead of propane, woudn't it? I'd think there would be a metering issue due to the difference in gasses and I'm inclined to think the burners are a little different (or are they not? Just wondering - most of the burners I'd been looking at for another project are designed to make temperatures more like 2500-3000 degrees Fahrenheit.)

If the gas range burners can be adapted, it's a viable option - I'd just like to make sure (it would be even more work to pull a gas line out to the garage than to get 240VAC. I'd do it if it were my own house - but it ain't. Damn.)

I feel like we're making some progress here - I'm just not sure exactly where we're going yet... I'm hoping we can come up with a workable idea - I'm more used to high-temperature projects than stuff like this. It seems easier to melt the metal, rather than coat it...

5-90
 
What about commercial kitchen equipment like the ovens that bake trays of bread stacked a dozen or so high (the appliances themseves are around refrigerator size and some a half refrigerator). Gas fired, have the thermo-control installed and I do believe some have wheels. If you only need 350 degrees, should be adecuate right, maybe w/ some modification? You could check places that sell used commercial kitchen equipment (yeah there really is a lot of trade in this). Also, at municipal auctions (where confiscated and police property is sold) I have seen them cheaply, from school cafeterias.
 
Converting an oven to LP is simply a mater of changing the orifice. Any appliance place should have what you need, just tell them you need to go from nat gas to LP, the burner and temp controls are the same.

Rev
 
Rev Den said:
Converting an oven to LP is simply a mater of changing the orifice. Any appliance place should have what you need, just tell them you need to go from nat gas to LP, the burner and temp controls are the same.

Rev
Click to expand...
what he said, i did it on the appliances at my dad's river house.
 
most ovens are totally convertible to l.p. as they are. you are just goin to use the bake parts so you can adjust most of those quite easily to l.p., switch the regulator over to l.p.(or install an external one) and adjust the bake orifice clockwise all the way down, adjust the air shutter and viola, you should be "cookin with gas" as they say. i would still try and get an old hydraulic style t-stat set up though. new glow bar styles are fussy and won't take much shop abuse, i.e., something dripped on it or banged around, etc. just a thought......
 
Really? Shows how much I play with gas - I'm usually working with metal...

That can greatly simplify things - I can use the guts of a gas oven, and then I just have to build the box to stuff it all in. I've got most of it designed already - I'm thinking either 2" or 4" of a high-R insulation, and I've got a baffle figured for redirecting the heat to make it more even so I don't wreck my coatings...

Anyone know where I can find a BTU/temperature/volume formula? I need to look again - but I just got back from taking a batch of teenagers camping (yes, I'm certifiable. I should probably be committed...) and I'm getting my bearings again. And, someone here should have this to hand - we've got pretty much every trade and profession represented here, don't we?

5-90
 
Rev Den said:
Converting an oven to LP is simply a mater of changing the orifice. Any appliance place should have what you need, just tell them you need to go from nat gas to LP, the burner and temp controls are the same.

Rev
Click to expand...
Like he said.


Seriously, all RVs and travel trailers use standard appliances converted to LP.
 
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