Karangi Dude's 48inch Oven

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey All,
What to do with all these tools?
I was just noticing all the tools that I use for the oven and I probably need a couple of others as well, like something to lift those 2 foot logs that I sometimes use. Here are a few, 2 Brushes one brass one soft, 2 Shovels one for ash one for moving the fire around, 2 Scrapers one wide one narrow and the list goes on.

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey Lee,
That was my third firing after the initial long curing, I think the oven is most likey cured and do not think there is any moisture under the floor with the low temp showing under the insulation bricks.
Lee my oven was completly build under cover so it was not effected by rain at all and there was a fair gap in time from when I closed up the dome to when I first started to cure it. Tests over the next few fires will tell I suppose.

[Lburou]

Interesting data Doug!

Doug, how many times have you fired the oven since your curing fire(s)? Do you think the oven is completely cured?

Celebrating the milestone with you and laud your success Doug

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey Paul,
Good to here from you.
I agree wholeheartedly that the oven needs time to heat up and saturate, I always start with a small fire and slowly build up from there.
I will be doing a lot more tests both heating and cooling.
Paul, I did notice though that after you put the door on, the oven equalises completely the air temp is the same as the rest of the oven and the thermo couples all read within 5c of each other except the one under the insulation. I am not sure how long it takes but the next morning after I have had a fire and placed the door on the night before that this has happened. (I don't take the fire out I just spread out the coals and ashes over the floor and put the door on) some times 8 to 10hrs later the coals are still glowing a little when I empty them out to bake bread.
So for all the people who put a thermometer probe through their door to measure the air temp this will actually be the equalised oven temp given the door is placed on and that the dome and the door are satisfactorily insulated.

[Alter ego]

Re: Karangi Dude's 48inch Oven

Doug,

It is interesting to see these tepm readings.

When I use my oven I always try to burn for at leats 3hrs so that I fully soak the bricks, this way it retains the heat much better and I can use it for 2 days after. If I only burn for 1 to 1.5hr before cooking pizza I find that the oven cools off too quickly.

If you are able to, please let us know a few readings about the rate the oven cools down.

[Bert]

Re: Karangi Dude's 48inch Oven

Ooops! Didnt see the diagram. Take you point re overall temps considering the overall heat within the oven.


Bert

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey Bert,
I think I have mislead you the temp at 65mm is inside the floor brick.
Did you look at the diagram referring to the placement of the thermo couples.
The insulation fire brick works extremely well with the bottom of the insulation brick at only 66c, that is not very hot when there is a 240c fire brick sitting on top.
Remember boiling point is 100c.

[Bert]

Re: Karangi Dude's 48inch Oven

G'Day Doug.

This is interesting from my perspective...the fact that the temp at 65mm below is quite high and on the outside of your insulation (from memory you used 75mm insulation refractory bricks?) is much lower. What concerns me for my build is if I use those 300 x 300 x 50 floor tiles + the insulation bricks my slab temp will be + 70 degrees Celsius. Given the proximity to the neighbours I am paranoid about excess heat. Good food for thought! Thanks for the data!

Bert

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey All,
The planned monitoring of my thermo couplings was interrupted when I was called away for 1.5hrs just after I lit the fire so I will have to do it again at another time. I do have some results but I did not take any laser readings to compare with.
The most significant reading was the difference from inside the fire bricks to the outside and how long they take to saturate.

See Diagram Below for Placement of Thermo Couples

3.00pm
Lit fire all readings @ 17 / 20c

4.30pm
1. 10mm under floor 537c
2. 65mm under floor 56c
3. 10mm iside wall 282c
4. 10mm outside wall 244c
5. Air temp 547c
6. Under insulation 25c

6.00pm
1. 10mm under floor 623c
2. 65mm under floor 147c
3. 10mm iside wall 436c
4. 10mm outside wall 265c
5. Air temp 352c Note temp dropped as I had moved the fire to side
6. Under insulation 40c

8.00pm
Let fire die down left door off

9.00pm
1. 10mm under floor 302c
2. 65mm under floor 240c
3. 10mm iside wall 290c
4. 10mm outside wall 305c
5. Air temp 294c
6. Under insulation 66c
Note at this stage the oven was starting to equalise.

These readings may not mean a lot everybody, but it does show that even when the carbon starts to burn off, inside the bricks the temps are a lot lower than expected.

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Bert, these things are over engineered by a long way.
It is surprising to see how well they do hold there temperature though.
Once you put the door on it takes a few hours and everything starts to equalize all the 6 thermo couples read about the same and they all read the same as it cools down, a big difference to when it is heating up.
Yes the thermo couplings are expensive along with the digital display and the hand held laser thermometer that takes an extra thermo coupling, it will be good though and good for the forum I will be posting results as I get them.

[Bert]

Re: Karangi Dude's 48inch Oven

See your point re the floor, I guess it always good to over engineer!

Hows your thermal coupling going? I expect its not cheap but great to have a good accurate and easily obtained thermal reading.

Bert

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey Bert,
Thanks, I don't think I am that clever I just like to do things right I guess I am a bit anal.
Bert the reason I went with fire brick for the hearth instead of the tiles is I wanted a bit more thermal mass, the bricks are 75mm while the tiles are only 50mm the tiles are probably all you need, but I do a lot of baking, roasting, curing (drying) so I went with the extra mass.
At some stage My wife and I might look at a B&B but I would really like to start a small Eatery like Russel Jeavons in SA but that is a couple of years away, our daughter is in year10 so when she goes off to Uni we will get a bit more serious, we also have 2 businesses that need to be sold before then.
Bert thankyou for your offer re: a web site but my wife is a graghic artist so we have that one covered.

[Bert]

Re: Karangi Dude's 48inch Oven

You?re a clever man Doug! I enjoyed very much your step by step guide of your experience. I will certainly have you on speed dial once I get momentum with my project. I also found the refractory place in Wetherill Park. One question: any reason you used the smaller tiles for the floor? During my initial research I sourced 300 x 300 x 50 from the same place, which would give a smaller chance of your paddle sticking to any edges. Your process of bedding them down with a notching trowel probably stopped this from occurring anyway.

Slightly off topic?I also note you are looking at starting up a B&B. My in-laws are running one out of Taree and I assisted them in creating a web site. Would be happy to provide you with info on that when you are ready.

Kind Regards Bert

[Karangi Dude]

Re: Karangi Dude's 48inch Oven

Hey Lee,
It is interesting to observe oven temperatures, most members measure oven temps with a laser thermometer that only gives you the surface temp as we know. I noted that my oven took a long time to get the temp up 10mm inside the wall bricks let alone the outer of the bricks these ovens do need time to saturate. The carbon burns of at about 350c but 10mm inside the wall brick is still about 230c these temps are pretty rough though that's why I plan on doing this study, I will have more detailed data nest week.

[Lburou]

Re: Karangi Dude's 48inch Oven

Hey All,
....snip.....I plan on taking regular temperature readings (from start up through to cool down) from the 6 thermo couplings I put in the oven and from a laser thermometer, I will post results next week.

Cheers Doug

Doug, you are continuing an oven worthy of our study

I would be interested in the data from each of your sensors during this Sunday firing, then on subsequent firings, on out until the oven is fully cured. Such a chronological record would be interesting and give future builders a data point on what to expect in a perfect situation.