#11  
Old 05-22-2009, 10:03 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 778
Default Re: Panting oven

Jay, the strange thing is that as the WFO heats up the panting stops and settles into a constant deep intake and the fire acts like someone was constantly blowing on it. Like I said, on a regular fire the panting only lasts for a minute or so, I managed to get this one to linger by building a smaller fire, which I suspect simply slowed the time for the oven to heat up.

Steam engines in particular steam locomotives were known for their pant. It was part of what made them seem alive. Here's a youtube of a train panting up a grade.

YouTube - Steam locomotive train 353 chugs up hill rollag engine Soo

Wiley
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  #12  
Old 05-23-2009, 02:47 AM
Apprentice
 
Join Date: Feb 2009
Location: Australia
Posts: 118
Arrow Re: Panting oven

Wiley,
an interesting comparison with the steam train sounds.
The 'panting' of the steam train changes in rhythm with the speed that it is doing. As the train goes faster. so is the panting increasing. This does not seem to be in rhythm with the steam cylinders working which drive the wheels, also I remember as a a child that once a steam loco is idle, as when in a station or when it is stationary, the panting is slower but quite consistent.
My uncle was a valued worker on and literally inside the boilers of the old locos and he would have the answers but unfortunately he passed away a couple of years ago.
Try contacting the local steam society and see if they can throw some light on the theory behind it.

Rastys.
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  #13  
Old 05-23-2009, 06:52 AM
Il Pizzaiolo
 
Join Date: Nov 2006
Location: San Antonio
Posts: 1,719
Default Re: Panting oven

Hi Wiley!

Given your additional comments... it could just be a phenomenon related to oven volume/height/door dimensions....

As the oven gets hotter the "driving force" for convection (cool air in the bottom/hot out the top) increases. The pant probably reflects an inadequate driving force to create steady flow. When the oven gets hot enough the density difference of the air is enough to provide steady flow...

Only thing that really makes sense to me...

Cool film!
Jay
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  #14  
Old 05-30-2009, 12:13 PM
Journeyman
 
Join Date: Jul 2007
Location: Los Angeles, CA
Posts: 308
Default Re: Panting oven

Quote:
Originally Posted by brickie in oz View Post
Settle down.....
Actually, brickie, PizzaPolice has a good point. Whilst an interesting phenomenon it is probably about as safe as automobile exhaust system "backfire" (remember how much fun that was... both to make happen and watch peoples stunned reactions, and later to repair the exhaust system after it splits the tubing or muffler?) and chimney flue fires. There appears to be something wrong with the combustion design that could be dangerous.

Last edited by BrianShaw; 05-30-2009 at 12:15 PM.
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  #15  
Old 05-30-2009, 03:33 PM
acbova's Avatar
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Join Date: Jan 2009
Location: York, PA
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Default Re: Panting oven

I thought you were supposed to not use the door when starting the fire?
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  #16  
Old 05-31-2009, 10:02 AM
Master Builder
 
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Location: Washington State USA
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Default Re: Panting oven

Acobova, the door in this case is a "smoke door" not a door for insulation (like baking or retained heat cooking). The attached photo has the prototype constructed of Hardibacker cement board. It worked well save that the longer it was used the more fragile it became. There was also a problem with outgassing during the first half dozen times it was used; once it reached a higher heat (450F if memory serves) it started to give off an objectionable smell. Over time the smell went away and the door became so fragile that it easily broke into several pieces and so I used it as a pattern to make this one in 10 guage plate steel (about 1/8 th inch for those not used to guage sizes).

The Hardibacker did pant although not nearly as well defined a pant as the steel door. I feel that Jay has the cause correct when he relates it to entrance area, internal volume and exit area, gas flow and gas densities.

The actual design for the smoke door is a modification of that used as a more or less permanent cast iron door as used in the "Ristorante" series of stoves. I would reference those curious to check out the pdf files available for that series on the FB website. A major difference is that the Ristorante door is between the internal dome and the chimney area whereas my door is between the entrance and the chimney area. That is why I did not include the pointed arch opening (which allows exit of smoke from the dome) just the rectangular bottom section. In my design I changed the sharp corners to a quarter round opening.

At this point the pant is a curiosity and I feel does not pose any cause for concern regarding safety. Were it to create the proper conditions for an explosion I would think it would have done so. As proper conditions for a fuel air explosion could be created in any close or semi closed (or even open un-enclosed space like the military does) it is something to be aware of but not lose sleep over. As my schedule permits I plan of messing about with different shapes for my smoke door. No need for it to be a passive experience. I have an idea of incorporating a Pyrex watch glass (3" in diameter) above the existing door thru which one could better observe what is going on inside. I expect it will smoke up quickly.

Panting of steam engines in particular of their fire boxes is a well established phenomenon. That I happened to stumble into creating the effect on my WFO is just an accident of serendipity. One that to date, I am enjoying.

Here is a photo of the Hardibacker prototype as you have watched the video you know what the steel one looks like:
Bests,
Wiley
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Panting oven-final-stucco-color-front-view.jpg  
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  #17  
Old 06-05-2009, 11:30 AM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 778
Default Re: Panting oven

Just a short update: Firing the WFO with a standard (2 1/4 x 4 1/2 x 9 inch) firebrick on each side just inside the entrance completely removed the panting. There was none what-so-ever, so shape of the internal and perhaps volume would seem critical to getting the oven to pant.

Reason for the firebricks is Im firing for buns/rolls today followed by a slow cook pulled pork shoulder for tomorrow. The bricks are to separate the shoulder from a small bed of coals for smoking and I didn't want to place cold bricks into a hot oven. Indirect heat and all that.

Hope everyone is planning on a great weekend!

Bests,
Wiley
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  #18  
Old 06-05-2009, 12:19 PM
Il Pizzaiolo
 
Join Date: Nov 2006
Location: San Antonio
Posts: 1,719
Default Re: Panting oven

Very interesting....

Thanks Wiley!
Jay
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