Author Topic: FGM Raised Dome long awaited Modified Throat  (Read 5182 times)

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Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #20 on: January 31, 2013, 05:31:48 PM »
I'm not eating my hat quite yet  ;D

It can take a long time for heat to penetrate 2" of firebrick.  Because of the insulating nature of the brick, it may delay the impact of the reduced throat. I know I'm asking a lot, but I'd like to see some dome temps, and, if not dome, then the same spot on the back wall.

I would much prefer you eat good pizza, hats are for head warmth!

Scott123.  I am not sure how to meet your request.  If you could tell me more, I will certainly give it a try.  

Aside from the fact that my particular laser gun maxes out at 932, I think it is hard to understand how that will help.  The dome and walls, during heat up, max out.  As I think Antoine described, I can get my floor and dome really hot, much faster than the times I posted.  They are not sustainable in that the temperature of the floor drops pretty fast after the coals are cleared and then even more when you put in a pizza.  I have not played around with that much to find out my minimum heat up times, etc for one or two pies.  I have been, for the sake of benchmarking, learning and also big parties, seeking the sustainable temperatures.  I have found that the FGM thermometer is a pretty good indicator.  For example the temperature of 460C / 860 F corresponded pretty nicely with my floor temperature.  The first pie was probably at 900 or thereabouts and the second at 875.  Of course, near the coals it was over 900 and at the furthest point it was probably 850.  I could tell it would probably be easy to maintain these temperatures just from the lack of drop off between pies and after.

One thing I can do is something like floor readings at the same exact spot(s), 30 minutes after clearing coals, after having tried  parallel heat ups with and without the insert.  Scott, does something along those lines sound like what you are thinking about?

I was thinking that, this weekend, I would not go all the way up to an interior temperature of 460C.  Insteady, I may heat up for a much shorter time, let the coals soak heat into the floor, clear them out and cook a pizza soon thereafter.  Since I will only be making one or two pies (which is what we do 80 or 90% of the time), then if I get all my needs met (fast heat up, less wood, high temperature) for one or two pies, then the longer heat ups only matter for parties.

Having said that, that does not add any insight into the performance with or without the insert...........This may end up taking many weeks of comparison testing since I only fire up once a week on the weekends.

- Mitch
« Last Edit: January 31, 2013, 05:33:54 PM by mitchjg »


Offline shuboyje

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #21 on: January 31, 2013, 06:14:18 PM »
I'm actually pretty surprised by your numbers, reducer or not Mitch.  My first oven was a 30" low dome brick oven with 3" of mass.  I could get that little oven to nuclear temps in under an hour.  By an hour and a half I could have it nuclear, saturated, and cook countless pizzas for huge groups no problem.  Thats the one thing I miss about that little oven, firing my 42" oven with 4.5" of mass is a totally different story.....

On paper your oven is very similar to my first oven, I wonder why it is taking so long to get up to temperature?
-Jeff

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #22 on: January 31, 2013, 06:29:24 PM »
I'm actually pretty surprised by your numbers, reducer or not Mitch.  My first oven was a 30" low dome brick oven with 3" of mass.  I could get that little oven to nuclear temps in under an hour.  By an hour and a half I could have it nuclear, saturated, and cook countless pizzas for huge groups no problem.  Thats the one thing I miss about that little oven, firing my 42" oven with 4.5" of mass is a totally different story.....

On paper your oven is very similar to my first oven, I wonder why it is taking so long to get up to temperature?

Jeff:

I was hoping your guys would tell me!!!!!!!!  My specific hope, of course, has been that the insert would do the trick.  One concern Antoine has expressed is that my wood may not be fully seasoned and that almond may be a wood that produces an over abundance of coals rather than producing more flames.  I will not address that for a couple of months. 

But, there is no way mine would be that ready in 1 1/2 hours.

- Mitch

Offline shuboyje

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #23 on: January 31, 2013, 06:50:17 PM »
How are you firing?  In my opinion the reason I was able to get the little oven hot so fast was that I could completely fill it with wood.  My best results came from building a cabin in the middle AND a ring around the perimeter of splits stacked like fallen dominoes if that makes sense.  I could light it and walk away.  The perimeter wood would burn last and once it was done it was ballistic.
-Jeff

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #24 on: January 31, 2013, 07:12:55 PM »
How are you firing?  In my opinion the reason I was able to get the little oven hot so fast was that I could completely fill it with wood.  My best results came from building a cabin in the middle AND a ring around the perimeter of splits stacked like fallen dominoes if that makes sense.  I could light it and walk away.  The perimeter wood would burn last and once it was done it was ballistic.

I have basically used three different approaches:

1. Start with a fire in the center.  I stack 4 logs in a square, each leaning on the next, so that one end of the log is raised up, and the other end is on the floor (like falling dominos).  Put some kindle on top of that, put 2 or 3 logs on top of that.
Once the fire is up and running well, say 20 minutes or so, start adding logs so that I build a large blazing fire.
2. The same as what you described.  Same as number 1 in the center, but also a semi-circle of logs around the perimeter.  Also, stacked end to end with one end resting on another log, the other end on the floor.
3. Same as 1 (or 2 - does not matter much) - stuff the heck out of the oven with logs and keep stuffing.  This is the way I did the last two the same as each other.  It did heat up the fastest, but left the most coals.

I have started all of the fires with one of those little Weber fire cubes.  They seem to work nicely.

So, when I followed number 2, it did all burn well and the like.  It was just that the oven, (as measured by the FGM thermometer) was no where close to "ballistic."  Roughly speaking, except for the last 2 firings where I really stuffed it, the oven would heat up by about 130 degrees C in the first hour and the 100 per hour thereafter.  Since I was striving for a minimum of 425 (about 800 F), this takes somewhere around 4 hours.  Then I need to get the coals out, bank it, throw a log or two on the banked coals, and let it stabilize.  Now it is 4 1/2 or so.  The last two times, where I cut it down to 4 was "fast".

After the last bake, I filled the oven to the brim with logs (the oven was over 200 C) and put the insulated door on.  So, they should be nice and dry when I fire the oven.  I also have a small load of oak (bought a bit to try it out instead of the almond).

Any ideas on an approach this weekend?
« Last Edit: January 31, 2013, 07:15:16 PM by mitchjg »

Offline TXCraig1

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #25 on: January 31, 2013, 07:23:30 PM »
How are you firing?  In my opinion the reason I was able to get the little oven hot so fast was that I could completely fill it with wood.  My best results came from building a cabin in the middle AND a ring around the perimeter of splits stacked like fallen dominoes if that makes sense.  I could light it and walk away.  The perimeter wood would burn last and once it was done it was ballistic.

When I talk about it taking 10 hours to get mine ready, I'm starting with about 4 medium-small logs and then burning 1-2 medium-medium-large logs at a time for the balance of the 10 hours.

I need to try your way sometime and see how it goes.
I love pigs. They convert vegetables into bacon.

Offline TXCraig1

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #26 on: January 31, 2013, 07:26:38 PM »
3. Same as 1 (or 2 - does not matter much) - stuff the heck out of the oven with logs and keep stuffing.  This is the way I did the last two the same as each other.  It did heat up the fastest, but left the most coals.

I'm not surprised #3 left the most coals. You probably didn't have enough oxygen for that much wood.
I love pigs. They convert vegetables into bacon.

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #27 on: January 31, 2013, 07:33:28 PM »
I'm not surprised #3 left the most coals. You probably didn't have enough oxygen for that much wood.
I was guessing that was the cause.  My thinking was to try 2 again but not be as aggressive in feeding it as before. - M

Online JD

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #28 on: January 31, 2013, 07:36:38 PM »
Jeff:

One concern Antoine has expressed is that my wood may not be fully seasoned and that almond may be a wood that produces an over abundance of coals rather than producing more flames.  I will not address that for a couple of months. 

Not sure where you are located but why not head to your local Lowes/HD/supermarket and buy a couple bags of seasoned firewood? Seems well worth the $10 to rule out under-seasoned wood.

Seasoned wood makes a tremendous difference in efficient firing as unseasoned wood wastes so much potential energy by changing water to steam.

My $0.02  :pizza:
Josh

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #29 on: January 31, 2013, 07:40:56 PM »
Not sure where you are located but why not head to your local Lowes/HD/supermarket and buy a couple bags of seasoned firewood? Seems well worth the $10 to rule out under-seasoned wood.

Seasoned wood makes a tremendous difference in efficient firing as unseasoned wood wastes so much potential energy by changing water to steam.

My $0.02  :pizza:


I am in the SF Bay Area (Oakland).  I have no big allergy to trying that.  In theory, the place I purchased the wood is a reputable firewood dealer.  If I go to Lowes or someplace, I am not sure how I would know that their wood is seasoned any more or less?

Do I need to add some sort of moisture meter to my pizza oven arsenal?


Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #30 on: January 31, 2013, 07:44:39 PM »
Mitch- Do you remember which way you fired in reply 12 here? I don't have near the experience as others in this dept but that looks like a lot of coals which would corroborate the poorly seasoned wood theory.

Again I have cooked in a WFO about a dozen times, but have had a wood fire place etc so I'm making a guess.

Sure do.  Both firings, with and without the insert, were number 3 - basically started with a pile as described in number 1 but followed up pretty shortly by stuffing the heck out of it and keeping it that way.

- Mitch

Online JD

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #31 on: January 31, 2013, 07:48:52 PM »
I am in the SF Bay Area (Oakland).  I have no big allergy to trying that.  In theory, the place I purchased the wood is a reputable firewood dealer.  If I go to Lowes or someplace, I am not sure how I would know that their wood is seasoned any more or less?

Do I need to add some sort of moisture meter to my pizza oven arsenal?

Last time I purchased a bag from Lowes it had right on it "Seasoned for a year" or something like that.... marketing or not, it was very dry and burned quickly.

My experience with burning wood is from using a wood-fired fireplace (stove), not really a WFO. The difference between firing seasoned wood and "nearly" seasoned wood is night and day.

Best part is if you find out your almond wood is a little wet, you know you'll have some great wood for next year. Absolutely nothing wasted.

I like to try simple solutions first... probably cause I'm cheap  ;D
Josh

Offline shuboyje

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #32 on: January 31, 2013, 07:56:34 PM »
When I talk about it taking 10 hours to get mine ready, I'm starting with about 4 medium-small logs and then burning 1-2 medium-medium-large logs at a time for the balance of the 10 hours.

I need to try your way sometime and see how it goes.


In my second oven I found it did not scale well...I had to totally relearn how to fire it.  I think the ratio of door size to oven volume makes oxygen the limiting factor.  Small ovens have proportionally larger doors, and because of that can burn a proportionally larger quantity of wood.  I had to think a lot more to learn to fire my large oven, and I implement ideals I learned from reading about wood fired kilns.  I personally start a small fire in the middle with the sole goal of producing a pile of coals.  The coals then go to the back of the oven where I begin slowly adding wood.  As the coal pile at the back of the oven builds I start racking it forward until eventually the entire oven floor is covered by a thin layer of coals.  As the cool air comes in the oven it is at the bottom where it is preheated by the coals on it's way to the back.  By adding the wood at the back it tends to pyrolyse and produce a lot of volatile gases.  The volatile gases then combust with the preheated air and make for an intense fire as the heat moves back towards the front of the oven and eventually out the vent.    With this method I can get the oven to Neapolitan temps and fairly well saturated in about 3 hours.  I haven't done any big parties with the new oven so I'm not sure how well saturated it is, but I have cooked Coal oven style pizza in it without a live fire and actually get frustrated having to wait for the oven to cool.  
-Jeff

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #33 on: January 31, 2013, 08:03:26 PM »
Last time I purchased a bag from Lowes it had right on it "Seasoned for a year" or something like that.... marketing or not, it was very dry and burned quickly.

My experience with burning wood is from using a wood-fired fireplace (stove), not really a WFO. The difference between firing seasoned wood and "nearly" seasoned wood is night and day.

Best part is if you find out your almond wood is a little wet, you know you'll have some great wood for next year. Absolutely nothing wasted.

I like to try simple solutions first... probably cause I'm cheap  ;D

That makes sense, I may call around.  We have a Home Depot and Ace Hardware close by.  The Lowes is more of a trek.  I do love your point about the wood not being a waste - just needs to be rescheduled.

Given, I stuffed the oven to the brim with almond when the oven was at about 200 C / 400 F , put the insulated door on it, and left the damper open - wouldn't you think that load of wood is now dried out?  It probably took a full 24 hours to get down to under 70 degrees.

- M

Online JD

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #34 on: January 31, 2013, 08:20:16 PM »
That makes sense, I may call around.  We have a Home Depot and Ace Hardware close by.  The Lowes is more of a trek.  I do love your point about the wood not being a waste - just needs to be rescheduled.

Given, I stuffed the oven to the brim with almond when the oven was at about 200 C / 400 F , put the insulated door on it, and left the damper open - wouldn't you think that load of wood is now dried out?  It probably took a full 24 hours to get down to under 70 degrees.

- M

I'm sure the surface of the wood is dried but I have no clue whether the core of the wood would be. Lots of factors involved and I'm certainly not an expert on kiln drying wood

If you find your almond wood is tough to get started, even with a lot of kindling, then I can almost guarantee its too wet. If it stays lit pretty easily then it's probably not the wood. The fact that you hear hissing is a huge red flag though.

Josh

Offline breadstoneovens

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #35 on: October 25, 2013, 09:30:59 PM »
After quite a few month of testing, and so on 3 different sizes ovens, we can safely say that the throat reducer doesn't improve the heat-up time.
Sorry Scott  :P

I guess we can say FGM knew what they were doing after all those years.

That said, with the help of some of my customers, we have developed a draft door.

The original idea was to create a spark arrestor door to help prevent any spark from jumping out of the oven. Pretty much just giving enough space to let the air in.
We noticed that this device served it purpose but also actually helped with eliminating the smoke when first firing the oven and improved the heat-up time.

I just got the first batch back from the welder today, let's paint them and  it is time to start a new thread.

Antoine



« Last Edit: October 25, 2013, 10:49:48 PM by breadstoneovens »
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Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #36 on: October 25, 2013, 11:16:27 PM »
Sorry Scott, Antoine is right.  The throat reducer was very ineffective impacting heat up time.  I tried it several times.  It did have a small impact on more top heat, but not a lot.

On the new door, I will start a thread since I am one of the experimenters.

- Mitch

Offline nickr

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #37 on: October 31, 2013, 01:01:43 PM »
After quite a few month of testing, and so on 3 different sizes ovens, we can safely say that the throat reducer doesn't improve the heat-up time.
Sorry Scott  :P

I guess we can say FGM knew what they were doing after all those years.

That said, with the help of some of my customers, we have developed a draft door.

The original idea was to create a spark arrestor door to help prevent any spark from jumping out of the oven. Pretty much just giving enough space to let the air in.
We noticed that this device served it purpose but also actually helped with eliminating the smoke when first firing the oven and improved the heat-up time.

I just got the first batch back from the welder today, let's paint them and  it is time to start a new thread.

Antoine

Hello Everyone,

I've been following this thread closely as I have been looking at the 950BR but was concerned about the door to dome ratio and the possible inefficiencies there.

I am a bit surprised how quickly this device was deemed not to work. I only see one set of incomplete data. The fires were built for different reasons and it appears that a laser thermometer was not even used? There was also no mention of wood consumption (unless I missed it somewhere). Even in that test you can see a difference in temperature and it is stated that the smoke goes up the chimney.

I feel that if I bought this oven I would want the throat reducer. It's just a feeling but so much of it seems to make sense. Is there any actual full tests with data to support this as "not working".

Online mitchjg

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #38 on: October 31, 2013, 10:07:16 PM »
Hello Everyone,

I've been following this thread closely as I have been looking at the 950BR but was concerned about the door to dome ratio and the possible inefficiencies there.

I am a bit surprised how quickly this device was deemed not to work. I only see one set of incomplete data. The fires were built for different reasons and it appears that a laser thermometer was not even used? There was also no mention of wood consumption (unless I missed it somewhere). Even in that test you can see a difference in temperature and it is stated that the smoke goes up the chimney.

I feel that if I bought this oven I would want the throat reducer. It's just a feeling but so much of it seems to make sense. Is there any actual full tests with data to support this as "not working".

Hi:

Antoine mentioned in his post that testing was done on 3 ovens.  One of them was mine.  I do not know who else was testing and on what ovens, so I cannot speak to that.  I can tell you that, although I only "published" data from one heat up, I have heated up several times with the door (perhaps a 1/2 dozen) and it did not make a meaningful difference.  I am pretty clear on how fast a heat up I will get under various conditions/approaches and I am confident that, for me and my oven, there was nothing about it that was particularly impactful.  No worthwhile difference in wood consumption nor in heat up time.  As I mentioned, I think I did get a little better top heat.  But, for me, it all seemed a bother.

Regarding the laser thermometer, I do not understand.  I have one and use it.  But, it is pretty useless while a fire is going.  With all the flames, the readings are off the scale.  And, for measuring heat up temperatures, I used the thermometer that is part of the oven - it measures the temperature in the core of the oven which is much more stable/objective than a surface reading.

Anyway, the whole matter was disappointing to me but I have moved on. I love trying new things like this and do not regret giving it a go.  But, no dice.

On the other hand, the use of the draft door has clearly made a difference to me.

You may want to ask Antoine about the other 2 folks if you think that will help you be convinced one way or the other.  In terms of the 950 BR, I have no experience or comment that would help you decide one way or the other.  There are many very knowledgeable experts on this forum and perhaps they can help guide or advise you.

best of luck,
Mitch


Offline scott123

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Re: FGM Raised Dome long awaited Modified Throat
« Reply #39 on: November 01, 2013, 07:55:12 AM »
Sorry Scott  :P

Sorry Scott

If by saying 'sorry', you're congratulating me on being right, then thank you, it does feel pretty great finally having my ideas on this subject being fully vindicated  :P

Seriously, though, Antoine/Mitch, you do know that the indisputable success of the draft door thoroughly proves everything I've been saying, right? What is the draft door other than an extremely low throat?  My calculations were obviously a bit off in terms of the necessary height of the throat opening required to reveal a tangible difference, and, for that, I might need to nibble on a corner of my fedora ;) but my theory that a lower door shortens pre-heat times and saves  wood is, thanks to the draft door, no longer a theory, but proven fact.

It's quite simple, the opening in the throat prototype was too large to produce a discernible difference.  The draft door proves that it needs to be smaller.  Now, the total size of the opening in the draft door, when visualized as a single hole, isn't viable to work through as a throat, obviously, but you can certainly split the difference between the prototype and the draft and end up with time/energy savings and an opening that will allow the necessary access.

A prototype throat opening reduction of half the size should be perfect.  I don't think it's a coincidence that what I'm describing is pretty close to the opening size of a Stefano Ferrara.  I hate to sound like a broken record here, but the Italian oven builders have been doing this thing for quite some time and seem, for the most part, to know what they're doing.  I think it also reveals that door sizing, as Jeff (shuboyje) and Tom have pointed out on more than one occasion, is about more than just arbitrarily picking a height of 63% and expecting it to be perfect. A particular oven might perform better with a higher or (in this case) lower door, and you can't avoid taking the shape of the opening into account as well.

Rather than looking at doors just from a perspective of the ratio of their height to the height of the dome, I think it might be prudent to look at doors the same way we look at chimneys by calculating the total surface area of the opening. This would take shape into account a bit better and give us a much better idea of proper door sizing than the, imo, far oversimplified 63% figure.
« Last Edit: November 01, 2013, 08:23:38 AM by scott123 »


 

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