Insulated door design...

[mrchipster]

Re: Insulated door design...

Very nice design, I may implement it instead. The only direct heat transfer would be through the bolts and minor radiation.

It all kind of depends (for me) on how heavy of a gauge sheet metal I can pick up at the local 'big-box' hardware stores that I can still successfully cut with tin-snips. If the sheet metal will be thin, then maybe the rigidity of 3 sheets may work better for me; if it's heavier gauge, I like you design better.

thanks, Dino

I found a 4 inch angle grinder with a thin curf metal wheel 1/16 inch. Works great for cutting sheet goods.

Chip

[mrchipster]

Re: Insulated door design...

Hi Chip,
I have a similar drawing as you with the same idea. I've yet to make my door but that is what I had planned on.

The only thing I would change on your design is the internal layer could be metal lathe and not a solid piece of sheet metal. Removing extra material on that internal piece would also aid in reducing heat transfer.

Chip

[Dino_Pizza]

Re: Insulated door design...

Very nice design, I may implement it instead. The only direct heat transfer would be through the bolts and minor radiation.

It all kind of depends (for me) on how heavy of a gauge sheet metal I can pick up at the local 'big-box' hardware stores that I can still successfully cut with tin-snips. If the sheet metal will be thin, then maybe the rigidity of 3 sheets may work better for me; if it's heavier gauge, I like you design better.

thanks, Dino

[Laku]

Re: Insulated door design...

Here's my version of the door. Idea being that inside and outside surfaces have very little contact area with each other. Kind of a heat break build into it.

http://www.fornobravo.com/forum/44/c...tml#post138419

What I haven't drawn in the picture is a plywood cover to attach the decorating wood to at the front. Between the plywood and ssteel front there's also glassfiber rope to keep them appart.

[Dino_Pizza]

Re: Insulated door design...

Hi Chip,
I have a similar drawing as you with the same idea. I've yet to make my door but that is what I had planned on.

I have left over FB blanket and it compresses slightly so 2 isolated layers will work and I was thinking that since there is less heat transfer, I can bolt (or even glue) a thin wood "facade" to the outside of the metal door and even replace it every few years if needed.

This is a good thread, thanks Russell and Chip for some fine ideas on door building, possibly the hardest part of the wfo process at least for me

I've been using a temporary door made of 2 pieces of duroc (cement board) with oven mortar inside it and it's HEAVY and of coarse brittle and chipping like crazy so I don't recommend EVER doing it except as a quicky door after you've just finished your oven and you have scraps laying around.

[Aussie Pete]

Re: Insulated door design...

thanks Chip, think i've got the idea.

[mrchipster]

Re: Insulated door design...

Pete and Russell,

Sorry about creating confusion by jumping in on your post.....

I have an idea for and thermally isolated door.

The concept is quite simple.

The door is made up of 2 layers of ceramic board encapsulated inside of some type of metal sheathing ideally this would be a reasonably light gauge stainless. Each layer of the ceramic board would be attached to the front or back respective plate with bolts with washers large enough not to pull through the expanded metal internal sheet that is between the 2 layers of ceramic board.

This would allow minimal heat transfer due to the expanded metal yet strength because of the bolt ties to the inside and outside.

An additional level of safety from burning of the decorative outside layer could be provided by mounting the decorative layer to the outside sheet by having small risers preventing direct contact with the potentially hot outside sheet. I would make the decorative outer layer (think wood) a little smaller than the sheet that is directly in contact with the oven as I had one door burn up because it was exposed to the hot gasses escaping the oven at the top. Making the decorative door a half inch or so smaller would not take away from the way it looks because most of the time the door will be inserted into the flue opening and deep into the tunnel.

The piece of metal that wraps around the edges of the ceramic board could maintain a small gap between the outside sheet and the wrapper sheet to prevent any thermal connectivity from the interior the oven to the outside. This would also be the location where a glass rope could be placed to better seal the oven.

As you can see from the drawing the bolts are offset from each other and because there are 2 layers of insulation heat transfer would be minimal.

Other materials could be used in place of the expanded metal but I believe this would be strong and still conduct a minimal amount of heat.

The expanded metal would not go out to the edge of the door but be fully encapsulated between 2 layers of ceramic board. The ceramic board could be of any thickness from half-inch all the way up to 2 inch thick depending upon the insulation needs of your door and the 2 layers could be of different thickness. If so desired.

Chip

[Aussie Pete]

Re: Insulated door design...

geeezz..i got a little confused then, when chip posted up after my post, i had a look at the pics he put up, and thought...."thats not your door you posted earlier Russel". Then i realised it wasn't your post Russell....d'oh.
I like the idea of the cladding on the front, it seems to finish off the door nicely, i might possibly use something like Merbau (not sure), get that nice dark red colour. I'm trying to think of a way to make the door so theres no heat transfer through at all (as in no bolts through the plate), can be done i'm sure, just have to think of an idea for design.
if i was to use the wood cladding on the front, what glue or silicone sealer would hold it on ok....(liquid nails be any good), after all, hopefully there wont be much heat after the insulation....right?.
I wont be making for a while yet, just trying to get ideas worked out, so i know what to do when i come to it.

[OzOvenBuilder]

Re: Insulated door design...

Hey Russell, love the door, i think i'll end up doing one very similar, a few questions:

I was going to make the front plate, then weld the 50mm sides & top to the back, then wack in the silicate board, then weld the back plate on, any reason you didnt do this, it looks like you have your handle bolts going all the way thru the board to the back and nuts on holding back plate. Did you just use fire silicone to seal the back plate around the edges.
Also , the silicate board, what do you use to cut it with, have never seen it before.

Also, with this type of board, do you have any real time temperatures to see how well this type of board & set-up works. Say an inside high temp, and the temp at the front of the door.
Is your door very heavy, would you try & make it lighter if you had to make another one.

Hi Pete,
I didn't weld the inside plate to the front & kept the gap to try & reduce the heat transferring from the inside. You can see the glass rope fills this gap, and the only thing that transfers the heat to the front should be the bolts and a bit through the temp probe.
I didn't use fire silicone fill where the rope is as the rope covers this well. I did fill the gap along the bottom with silicone where there's no rope.
Just cut the board with a jigsaw or similar, but make damn sure you wear some kind of breathing protection as the fibers are very nasty to inhale.
re the weight, I'm quite happy with it, & realistically I'm not putting on / taking the door off very often so it's not an issue for me.
I don't have any real temps, no thermocouples or anything like that. I just use the door probe as a guide to 'learning' what this particular probe says and how it behaves in my oven with whatever it is I'm cooking at the time.
Here's some pics of another I built with timber cladding, just used stainless screws to hold the timber.
Please put up some pics when you get it together, would love to see it!

Cheers,
Russell.

[mrchipster]

Re: Insulated door design...

I am very happy with my insulated door and it required no welding and is holding together very well..Strictly stainless steel pop rivets holding it together, Interior is stainless and outer sheet is aluminum because I ran out of stainless.

It maintains heat like you cannot believe. Last night made a roast and temp up to about 750. This morning 12 hours later temp average 550F. Even in this Minnesota winter average temp has been about 20F degrees right now. Last night it got down to 16F.

I can maintain heat for a while and usually still have 200F - 95C after 5-6 days.

Door is 4 inches of FB Board between stainless and Aluminum.

My Temp Probe does not work very accurately as it does not extend in to the oven it just barely reaches the back of the door (See last photo) and I made a small hole to allow heat to reach the probe. but it always seems to register about 150F degrees low.

I will eventually get a probe that is about 2 inches longer but for now it is fine I just need to add the 150F degrees. The nice thing is I will never whack it on anything.

Total weight of door is 17.5 pounds.

in a very high heat oven 750F+ the outside aluminum gets to warm to hold your hand on but it can be touched briefly without burning the skin. So I am loosing some heat to the outside by conductivity of the metal.

As you can see I used up about 40 rivets to hold the skins in place. One of my goals was to have very little of the ceramic board exposed so it did not shed fibers.

I will be building a lighter blast door that will have no insulation and also a lighter and thinner door for use when actively baking, I do need to use both hands to remove and place this door and would like one that I can put in and out with one hand.

Chip

[Aussie Pete]

Re: Insulated door design...

Hey Russell, love the door, i think i'll end up doing one very similar, a few questions:

I was going to make the front plate, then weld the 50mm sides & top to the back, then wack in the silicate board, then weld the back plate on, any reason you didnt do this, it looks like you have your handle bolts going all the way thru the board to the back and nuts on holding back plate. Did you just use fire silicone to seal the back plate around the edges.
Also , the silicate board, what do you use to cut it with, have never seen it before.

Also, with this type of board, do you have any real time temperatures to see how well this type of board & set-up works. Say an inside high temp, and the temp at the front of the door.
Is your door very heavy, would you try & make it lighter if you had to make another one.

[OzOvenBuilder]

Re: Insulated door design...

Gudday Russell

Re the probe don't have it fixed in position on the door.Mine"s loose so I just draw it out and pop it on the brick shelf at the front of the oven then remove the door and do whats got to be done. Just slide it back when the doors back on....been doing it for a good 6 mths...no probs no bent probe.
By the way neat door...wish I had the metal working skills


regards Dave

Well I'm happy to report that the door works well! Whacked it on the other week after pizzas & it's keeping the heat in nicely.
Also did a slow beef roast the other day, fired the oven in the morning, last wood at about 10am and let this burn down with no door. Whacked the roast in after the oven had cooled at about 2pm, door on about an hour before this to even out. 3 1/2hrs turned a crappy bit of topside into sheer joy!
Glad it works well, I'm making one for a customer now!

Russell.

[Ken524]

Re: Insulated door design...

Great looking door! Mine is very similar and works a treat!

[cobblerdave]

Re: Insulated door design...

Gudday Russell

Re the probe don't have it fixed in position on the door.Mine"s loose so I just draw it out and pop it on the brick shelf at the front of the oven then remove the door and do whats got to be done. Just slide it back when the doors back on....been doing it for a good 6 mths...no probs no bent probe.
By the way neat door...wish I had the metal working skills


regards Dave

[OzOvenBuilder]

Re: Insulated door design...

Hey Russell, very cool door. I only wish you posted this about 1 month ago. Mine is very similar to yours but my face is made out of hardwood floor boards. I used PVA glue on my insulation rope. Whish I had of thought of the fire rated silicon. Still holding together after a few firings though.

Mick

Yes Mick, I wish I had made the door alot more than a month ago, but to be honest I've only recently decided to have a crack at some breads. I've been strictly pizza and roasts in iron pots etc...

My neighbor (who is very jealous of the oven & homebrew) likes to try breads but only inside, we're both very keen to have a go in my WFO.

The hardwood boards sound like a great idea. I'm a big fan of Australian woods!

Cheers,
Russell.