Jake's In Mass (Started July 3, 2011)

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

OK, I'm back, new phone and recovered lost pictures. At the end of this build I'll post a full gallery of all the pictures I have taken.

Here are two pictures of the hearth and insulating layer. Like I said above the vermiculite compacted way more than I expected.

So, what did I do? Well the first two bags of vermiculite I got from my Dad. He ordered "super coarse" from the supplier he orders from. This was a very coarse vermiculite, pieces 1/4" or larger. While it was nice and very "airy" it compacted quite a bit. With this I was able to get about 2" of the 5" I hoped to get. A 60% loss was definitely more than I expected. Given, I was never exact on what I should expect in the first place.

So, my dad had surgery and I decided to hunt down vermiculite on my own. Agway was selling 20lb(4cuft) bags of "coarse". I decided I'd go for it and I grabbed three more bags. I did not look inside when I picked it up, but it felt "chunky".

When I got home and looked at it, it was significantly less coarse than my first two bags. However it was less consistent with fine material and larger material. I decided to mix it up and live with what I got. Overall it mixed much better and compacted significantly less.

So, what I ended up with when it all settled is about a 4" layer of the "chunky" stuff. Which is the right size insulating. Then about 1" of the smaller stuff, when I mixed it I mixed it wet and it naturally settled this way.

So chat away, let me know your thoughts. It looks good to me and I don't feel like I need to also include any type of fiber board too.

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

So, I am doing 5". The vermiculite compaction was evident as I mixed it and poured. No shrinking when it dried. Looks like I got about 30% of what I expected with raw 0% loss calculations.

Wow, that is a lot of compaction. I'm glad to know it doesn't shrink more as it dries.

If you are using perlite and not vermiculite you may have better luck since it is harder.

I hope you're right about perlite - otherwise my 3 bags aren't enough LOL.
-jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, I am doing 5". The vermiculite compaction was evident as I mixed it and poured. No shrinking when it dried. Looks like I got about 30% of what I expected with raw 0% loss calculations. I'll post the final "real" number after this weekend when I am done with it.

If you are using perlite and not vermiculite you may have better luck since it is harder.

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

So, a good weekend of pouring the hearth. My insulating layer needs more, I misjudged the compaction of the vermiculite..

At what point did you misjudge the compaction?
Is is evident as you 'pour' it? Or does it occur as it is drying?

How much compaction did you wind up with? 10%? 30%
I'm targeting a 5.5" perlcrete using 2x6s for the frame.

Thanks for the help,

Jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Doug,
Thanks so much for that information. Completely makes sense. I tweaked my thermocouple reader so I can easily adjust up to 16 thermocouples. The top one makes sense, though at an academic level I might like to see those temps! However, I think as I go forward 6 seems good and your placing suggestions make sense.

I left a full 3/4" core in the middle of my hearth, I used a pvc pipe so I can bore it out later(if I cannot just pull it out). Up this I will be running two thermocouples one for outside brick. The other one will actually go all the way through the brick and is itself encased in a ceramic sheath. The smallest bit of the tip will be even with the floor and there is about 1/4-1/2" of material to the actual thermocouple. It is the same idea used in a kiln. The other ones will actually be screwed into bricks, I'll use a thin nut embedded in the brick and take out only a little bit of brick material.

The ceramic sheeth and the screw access make almost all of the thermocouples easily replaceable. The air temp one will probably be anchored to my angle iron of my opening and extend into the oven a little bit. That one will be easier to tweak over time.

In the mean time, need to finish the hearth!!

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Here are some of the pictures, the insulating layer is being poured, no pics of that until I get a new phone.

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, a good weekend of pouring the hearth. My insulating layer needs more, I misjudged the compaction of the vermiculite. I would post pictures, but my phone managed to get tossed in the wash last night and isn't quite right.

Wife helped out with this pour and it went quite well.

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, in a couple of days I should know, but I reworked the design with an analog/digital MUX to use a single temperature IC to read from up to 16 thermocouples. I also dropped down from an Arduino($20) to a PICAXE($4). Overall savings of $50-$60. If it works the way I think it will I'll post some schematics. I am using Eagle PCB for the design which is free for small designs if your son is interested.

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Looks like a simple enough setup, plus my son (who's a senior in high school) is looking for project for his engineering class this year. I wonder if this would count?
Then I wouldn't have to count it as a cost for the oven either! Hmmm, I wonder if the dear wife would agree?

Jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Also, the design works with any type K thermocouple, I have purchased from Auber before and their price is good and the quality is just fine.

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Jeff,
The thermocouples themselves are not too expensive:
High Temperature Thermocouple for Kiln [TC-K-KLN] - $25.30 : auberins.com, Temperature control solutions for home and industry
Ceramic Sheath for Kiln thermocouple [TC-K-KLNSH] - $18.00 : auberins.com, Temperature control solutions for home and industry

Those I will put right to the surface with just a skim of mortar over them. I will probably put one in the center of the floor, one in the top of the dome and one 1/2 way up.

Then:
K Type Thermocouple (6 ft. cable) English thread [TC-K6] - $6.85 : auberins.com, Temperature control solutions for home and industry

I am going to drill and embed a nut into a few bricks to screw these into. Probably the same locations but these will be for saturation temperature.

They will all be replaceable.

Separate of the cost of the thermocouples themselves. I went a little expensive to make it easy, I could definitely do it with cheaper electronics. Also, I am getting everything from sparkfun.com, not the cheapest, but definitely the easiest.

Each Thermocouple IC cost $10, so that is $60, I could have made it use just 1, but that's no fun! The BlueTooth is $30, could have done a screen for $10, but it seemed fun to make it BlueTooth. Batter is $10, PCB is $10, Arduino is $20.

For me I already have a lot of these parts hanging around, so I'm only really buying $50 worth of stuff right now.

If I did it all from scratch, and had nothing on hand I am probably looking at:
Thermocouples: $150
Electronics: < $100

I attached an image of the prototype, really pretty simple and very accurate thanks to the MAX6675 IC

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Hi Jake,
It's really taking shape!
You're catching up to me!
My hearth slab is curing and next I need to go buy the portland cement and perlite for the hearth insulation.
How expensive of a setup will it be for the thermocouples and circuitry?
Where are you planning to place your t/c?
Thanks,
Jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, here is a little something different. Looking at a lot of posts about Thermocouples. While I understand the "get to know" your oven mentality, I plan on using my over a lot for bread and longer roasts too, so more data on the temperature profile will be well worth it.

So, in true nerd fashion and not wanting to pay for a commercial unit. I came up with the attached schematic and board design capable of monitoring up to six thermocouples. Could easily be less by not populating the parts, or more by changing the schematic some.

There is no interface to this, it is powered with a rechargeable LiPo battery and has a bluetooth connection. I have written a simple Android application to communicate with it allowing me to calibrate and view temperatures, as well as log the temperature over time.

If anyone else is interested in the electronics part of this let me know and I can post more information.

[rlodad]

Re: Jake's In Mass (Started July 3, 2011)

Fat? Looks like relaxed muscle to me! Trust me, I'm a doctor...

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Quick update. This weekend was spent working on a playground at our preschool. However, I am ready to get the rebar going on the hearth and I will probably pour that this weekend with the insulating layer too.

I'm the fat one in the pics and my brother Matt is the bald one. Total we had 20 people working on the playground.