creating draft on fire in oven

[leff1rj]

First time I built a fire in oven, it seemed like a slow process. Several times that I used oven, I would build a fire with kindling and wait for this to build into a nice fire so as to add more and increasingly larger pieces. I finally figured out that if I injected some air into oven fire would build faster. So I rigged up my shop vac on blow and used various items to balance the vacuum wand tube pointed into the oven opening. I would place kindling, some larger pieces, and then some firewood on top, start fire on kindling. I would wait until kindling was burning nicely and then turn on the shop vac. Now that made a fire! Wasn't pretty with this contraption set up in front of oven and was noisy but sure did make a fire burn nicely and in pretty short order. And made it burn hot more quickly. Heated dome nicely and more quickly.
I bought a used furnace blower assembly and some various duct fittings. Started with a 6" fitting at blower and tapered down to a 3" pipe. Blower ass'y will be placed underneath oven with removable 3" piping coming out from under oven, turned up to oven opening, and then turn back into oven. I can't wait to try this out. Be much more quiet, a lot prettier, and with 1500 cfm capability fires should burn hotter faster.
You may ask what is faster. My first fires were taking 6+ hours to reach hottest temperature which I think was in excess of 700 degrees. (My infrared thermometer only read up to 650. Next major purchase is infrared temperature gun that will read over 900 degrees) With the shop vac, I could reach in excess of 700 in about 3 hours. In the words of Tim The Toolman Taylor, "More power!" with a few grunts. ha ha.
I'll let you know how it works.

[GianniFocaccia]

Re: creating draft on fire in oven

Wow! 3 hrs? How big is your oven and what kind of wood are you using?

[PizzaPolice]

Re: creating draft on fire in oven

My 60 inch takes every bit of 4 hours. Try a propane weed burner. No flying ash.
Try to heat the flue first. The smoke will be pulled out rather than billowing about the mouth.

GianniFocaccia: Is your avatar from the Monte Carlo's restaurant, Diablo's Cantina in Vegas?

[dmun]

Re: creating draft on fire in oven

Lets see. Residual moisture in oven? Lack of insulation? Undersized flue? Wet wood? Something isn't right.

[brickie in oz]

Re: creating draft on fire in oven

I use an electric heat gun on high to get the fire going, the oven is hot and ready in under 2 hours from blow to go.
The heat gun does show signs of melting in the front area though...

[david s]

Re: creating draft on fire in oven

I tried an old hair dryer which worked admirably, alhough my oven is way smaller. CAUTION too rapid a rise in temp is a major cause of thermal shock failure a resulting cracking. Better to be slow and safe. The materials you use might be very refractory and able to withstand temps three times that to which we fire but no refractory likes to be heated too fast. Potters use 100 C rise as a standard. We fire from ambient to 400C in 1.5 Hrs That's really too fast for the materials. Take it slow and safe and give the thing a chance to expand evenly.

[DrakeRemoray]

Re: creating draft on fire in oven

leff1rj mentioned in his other post that he used the Rado Hand design. I believe that calls for a huge heat sink of concrete under the hearth without any insulation...enough said...

[GianniFocaccia]

Re: creating draft on fire in oven

PizzaPolice,

Correct! I took it last December peering into the restaurant window from Las Vegas Blvd just outside the new Aria shopping center. The sign struck me as really funny, having worked as a waiter to get through college.

John

[Spunkoid]

Re: creating draft on fire in oven

Start small and build big, use dry wood, and split it lots so you have more surface area to weight and it will burn quicker and release more heat quicker too. Put your door in the front, partiall turned in so there is lots of space for draft and make sure it is still in front of the vent.
Adding more oxygen with a fan seems like overkill and you may overheat the oven if not carefull. Basically you are creating a powered version of a bellows for a forge. Add more oxygen and the fire will burn hotter, just make sure your wood is DRY.
My oven is 39" across and about 23" high, should have went lower, but I can bring it up to temp in 2 hours or less. No extra fan or oxygen.

[Tscarborough]

Re: creating draft on fire in oven

One match and 2 hours max to 1000 degrees. I guess being a Boy Scout paid off in the long run.

I take two 2-3" diameter by 18" long logs, wad up 3 or 4 pages of non-glossy newspaper, cover that with a layer of twigs that are a 1/2" or less by 6" laid cross-ways on the side logs, then put a layer of 1/2 sticks 18" long perpendicular to the twigs, then 3-4 2-3" diameter logs across, then one 4-6" diamer log on top. I light it and walk away, and 20 minutes later start feeding 3-4" logs in to get it to clear.

[BackyardPermaculture]

Re: creating draft on fire in oven

I am a big fan of top-lit fires, especially after doing a fair bit of experimentation with top-lit updraft stoves.

The top-lit fire has the bigger wood on the bottom, then smaller wood, then a layer of kindling, then tinder on top and a fire starter on top of that. It has two advantages:
1. Much less smoke
2. More heat with the same amount of fuel

The idea is that as the wood below heats, it gives off gases which are burnt as they pass through the flames above. So long as the fire is assembled well to begin with, it should burn on its own for long enough to heat the oven. When I have to add additional pieces of wood, I always place a smaller kindling-style piece on top of any larger piece.

Cheers,
Mick