An Idea -building An Oven From Cement Board

[boink]

Thanks for the info... I'll be putting a floor in it very soon.

I tried it out Friday and without any insulation and the top not sealed yet ( I need a steel plate in top to hold the weight of whatever is hanging on the hook).....it will hit 300 degrees in 2 minutes... 400 in about 10 more. Tops out at 425... without insulation and not fully sealed.

I think it will probably top out at 475-500 when insulated and air movement is controlled.

attached is the first piece out of the oven.

[Noob2PC]

Wonder if that would work well for insulating a big metal box im building?
Do I put it inside or On the Outside?? hmmmmm?

[wamontgomery]

Originally Posted by boink

Thanks for the info... I'll be putting a floor in it very soon.

I tried it out Friday and without any insulation and the top not sealed yet ( I need a steel plate in top to hold the weight of whatever is hanging on the hook).....it will hit 300 degrees in 2 minutes... 400 in about 10 more. Tops out at 425... without insulation and not fully sealed.

I think it will probably top out at 475-500 when insulated and air movement is controlled.

attached is the first piece out of the oven.

That frame turned out great. Keep us updated with new pics/info you have.

[pickleboy]

Originally Posted by Noob2PC

Wonder if that would work well for insulating a big metal box im building?
Do I put it inside or On the Outside?? hmmmmm?

it should work either way but if you already have the box built i would put it outside that way the metal will reflect/ radiate the heat better. just a thought.

[boink]

I'll have to remember to take a couple more pics.

I got the back insulated today with fiberglass duct board tonight, nice fit. Later on I think I will put some sheet metal on the outside of the duct board. The concrete board would help to serve as a heat sink with the insulation completed.

As of the last fireup, the concrete board on the outside gets around 200 deg F near the top at the end of the curing process.

I do, however, have a nice square in the middle of my garage when I did that last piece... there will be an insulated bottom on the oven on the next set of pieces.

[bluegiller]

WOW, I signed up last week when I came across this thread but my reply was vaporized?

Anyway's, I was asking about specifics about the propane heater used.?

I'm looking at a construction site tube type that has 150k btu's?

Is this the same type you are using boink?

thanks a lot

[boink]

Yes, except mine is a 125 btu propane unit... 150 btu would probably work a little better. I haven't insulated it yet fully to test the max temp of the oven. but I suspect it will be around 450-485 range with the 125 btu unit. Without the insulation it ran about 425 deg.

I rigged a type of "deflector" to keep the air stream away from long parts that come close the the bottom of the oven. Seemed to work good.

[wso]

I have built my 5x7x3ft oven from cement board and angle iron about 3 years ago. It has worked flawlessly, however due to so many heat cycles over time it has become brittle and has cracked in several places. You really cannot beat it for the price and it will last a few years if done properly.

[kd5sfq]

I checked out the cement board prices at Lowes and Home Depot.

A 3' X 5' sheet is $9.95

At a local steel shop, a 3' X 10' sheet of 28 gauge galvanized steel is $11.32.

[bluegiller]

I wish I could get a little more information about using propane heaters to heat ovens.

I used Boink's design with durock and steel studs and its just about finished. (sealing up cracks etc.)

I've attempted a couple of dry runs just to see how effiecent the heater I have will be.

When I put the heater right up against the oven opening for the heater it trips at about 260 degrees. (flame cuts out, some kind of safety feature..?)

So I backed it out away from the opening about 4-5 inches and it worked much better in fact with some makeshift wood and scrap durock, semiplugging the holes, I was able to get it up to the 360's pretty easy. I figure when it is sealed good, 400F shouldn't be an issue.

The Heater I have a LP forced air 175k-350k, Boink only has a 125k and his comes up to temp within 12 minutes, so I'm kinda wondering how I can fix my problem with the flame going out when it's located against the oven hole..?

I haven't had a chance to make an extension tube for the end of the heater or a deflector for the air control for the inside of the oven, this is my next step.

Thanks in advance for any help.