BeanAnimal's 42" build - Pittsburgh PA

[fhausback]

Your pyrometer looks very familiar. I totally agree on the coolness factor.

I did try K type thermocouples in mine, and they do work once you adjust the little screw under the 4. Before I buy more, I do need to experiment with the accuracy over the full 1200 degree range. But they do seem to be reasonably accurate up to 450.

my plan is to install thin stainless tubing up to the fire brick locations, and hope a short thermocouple can be replaced in the future. I still need to experiment. I figure I can push the new TC thru with a fish tape. If that doesn’t work, I’ll skip the tubes and install 2 or 3 thermocouples at each inaccessible location. And as they fail, switch to the backup TC.

i like you, am debating the install. Knowing I probably won’t use them much after I learn the oven, it’s only for cool factor.

[BeanAnimal]

Your pyrometer looks very familiar. I totally agree on the coolness factor.

I did try K type thermocouples in mine, and they do work once you adjust the little screw under the 4. Before I buy more, I do need to experiment with the accuracy over the full 1200 degree range. But they do seem to be reasonably accurate up to 450.

my plan is to install thin stainless tubing up to the fire brick locations, and hope a short thermocouple can be replaced in the future. I still need to experiment. I figure I can push the new TC thru with a fish tape. If that doesn’t work, I’ll skip the tubes and install 2 or 3 thermocouples at each inaccessible location. And as they fail, switch to the backup TC.

i like you, am debating the install. Knowing I probably won’t use them much after I learn the oven, it’s only for cool factor.

Unfortunately - Your are not going to get accurate readings by just shifting the scale via the adjustment screw.

A few notes: The "cold junction" (the wiring in the meter) for both probe types are different. I am not sure how this affects the actual reading.

More importantly - the outputs, both being linear, are not the same slope. So you can get it dialed in and accurate at a single reading voltage, and as the temp moves away from that point, so will the accuracy.

Your options

- live with error - dialing in the crossing point where it is most important to you
- print a new scale and install it in the meter - there are plenty of online resources you can use to do this. I have done it with some older simpson meters converted from their original purpose.

I threw a quick spreadsheet together for you with what I would expect the readings to be if you want it.

I will post a screenshot here

First image is millivolt readings to degrees for BOTH types. Kind of useless to compare, as you can't see the effect of adjusting the meter zero point. It does show you how much they differ in output though.



The second chart - I picked a zero point in Degrees F to align the scales (~500 F). So adjusted to match near 500, the error is at the high end, and grows larger the further from 500 you get. So heat Type-K to 500F and adjust meter to read 500F at that voltage.


Third chart is the same as above, but row shifted to match toward the end of the scale instead. No idea how you would accuratly hit 1200 or 1400 to calibrate at that temp. I guess you can pick a cal point near the area you are most interested in. Clearly if you choose near 200F then 1200F is going to be way off and visa-versa.

[fhausback]

Wow, thanks for the great info. The differences over the whole range was much more than i was expecting it to be. I went with the K because they are so readily available, and i have extras in the garage for my smoker.

Sounds like i need to find a bunch of J type thermocouples. They aren't as cheap as Ks, i probably need to prioritize the install for replace-ability.

Also, a custom designed scale does open up more cool options. Names, icons at target temps, Oh S**T! temp, etc...

[BeanAnimal]

I was able to get another hour or so in this evening and complete the first full ring over the inner arch.

Simple geometry dictates that if the trammel is used to set the distance from the center (a constant for every brick), then for each brick on the same course, the leading edge to floor distance (cord length) would be the same. I know many folks struggle with setting this course of brick, but keeping it level and circular is not really that hard if you simply measure. Place the brick in the trammel, pad the joint with mortar and bed the brick until its leading edge is the same distance from the floor as the other bricks in the course, you will end up with a perfect circle to build the final courses on.

[BeanAnimal]

Forgot to upload,

Anyway rained out today and likely tomorrow unless I setup the ez-up (wind dependent)

starting narrowing down veneer stone choices and am looking at natural and some faux stuff like eldarado.

[GreenViews]

Looking good! I've been deciding on my outer house design also.... and as I prepare to put up metal studs, I'm feeling remorse at the thought of covering up my precious round shape. To the point where I'm just considering making a roof and doing a stucco finish over my insulation, but I probably won't... Just feeling sad about covering up the masterpiece. Maybe this is unique to my experience? But looking great!

[BeanAnimal]

Looking good! I've been deciding on my outer house design also.... and as I prepare to put up metal studs, I'm feeling remorse at the thought of covering up my precious round shape. To the point where I'm just considering making a roof and doing a stucco finish over my insulation, but I probably won't... Just feeling sad about covering up the masterpiece. Maybe this is unique to my experience? But looking great!

Yeah - I am with you, but at the same time, I am fond enough of the igloo shape to leave it and certainly don't want to see or tend to the inevitable cracks and waterproofing issues.

I need to wrap my head around a prep area also. I have limited space and aesthetics are going to be tough. Because I am putting a tiber frame over this - I think the house will have a flat sloped roof. A peaked roof under a peaked roof will look odd I think. Not sure if I want to use metal, concrete, or something else.

[BeanAnimal]

I was able to get a bit of work done between rain showers on Saturday.

Course 9 completed! it went so easy that I got excited that 10 would be a breeze. The course 9 bricks stuck like they had magnets in them. Course 10 is nearly vertical and umm... it is going to be slow going. I got 3 of the ~15 bricks set and did a lot of swearing.

The kit came with a fiberglass inner form that can be raised up (small bottle jack or scissors jack, etc) to set the last few courses. I just can’t bring myself to use it because I want control over the brick face and mortar joints that will be visible. Not that anybody but me will ever crawl into the oven and look up at the last few courses.

The kit also cam with refractory castable cement to be used as a dome plug instead of a tiny course and keystone brick. I am not there yet, but it looks to be maybe 10” on the outside. Like the form, I can’t bring myself to use it and instead feel that I need to custom cut the left over brick for a last course and a for a perfect fit keystone.

Rain intermittently forecast for today.... for now here is yesterday’s progress. Going to try to close it off today, weather permitting.

[BeanAnimal]

I talked to a local sandstone quarry on Friday. They can cut me a custom landing area 12” deep and the width of the stand. 6” thick is not a problem, but I am afraid something that heavy is sure to break by the time I horse it into place. I need to call back and ask them if they can possibly make it “L” shaped 3” thick, but have no idea what kind of saws they use. I am guess a band saw, meaning that the answer is a flat “no”.

FWIW sandstone weighs roughly 150 pounds per cubic foot. 6 feet wide, 1 foot deep, 6 inches tall = 3 cubic feet = 450 pounds. 2-3 people can lift this into place, but it will be awkward. Cribbing under it a few inches at a time, engine hoist rental, diy pivot lever, good ol’ brute force. Still working this out.

[BeanAnimal]

Just beat a very heavy rain shower, hopefully they will pass and I can finish the dome and outer arch this afternoon.

I decided to skip the fiberglass form and hand place the final rows. The trammel s somewhat useless on the narrow brick. I did keep it in place as a gauge and used the top of the holder as a support when needed. I basically threw the in as fast as I could and fenangled previous bricks into final position as they began to stiffen a bit. I cut a few support sticks, but did not have to rely o them except for every. 3rd brick or so. They helped to prevent the whole row from wiggling lose as I set new bricks.










Sorry, the iPhone is turning some of the photos sideways when I post them.

I am happy to have ended up with a circle instead some weird ovoid or football shape.

As you can see, I gave up trying to stay on bond on this course. I did not want t start trimming bricks and obsessing about it.

[BeanAnimal]

The sun came back out and I was able to pick up where I left off. The dome is complete, as well as the entry arch. Next up is then flue gallery and insulation. I had a lot of mortar left over after the arch so I spread it over the top of the dome. I do t know if this will help anything with regards to cracking, but I do t imagine it will hurt either.

They keystone pieces for the dome were not that hard to cut, I just eyeballed them and took a few round trips to the bridge saw. The little table top junker slings water everywhere and I dislike using it.

[JRPizza]

Awesome - another milestone completed!

[BeanAnimal]

Pulled the arch form this morning and am extremely pleased with the result. I am going to let it sit for part of the day before moving on to the flue gallery. I don't want to bump the arch and have to start over!


Kit Deviation:

The kit is supplied with 2" of insulating blanket that is to be set under 2" of pcrete.

I have ordered an extra 1" of insulation blanket and am considering skipping the pctrete render - as I am enclosing the entire oven in a house. What is the consensus here, given that it will be enclosed under roof?

1) more blanket and no pcrete
or
2) just 3"blanket and the 2" pcrete?

One way or the other, I am going to get started in the blanket today.


Second Question:

The kit calls for fully completing the oven before the small curing fires. If the consensus is pcrete over blanket, is there any reason to cure the insulated dome before the pcrete render?

Is there any benefit on placing a small heater in the dome now - while I work on the insulation layers?

[BeanAnimal]

Spent about 30 mins at lunch and got the flue gallery set and mortared into place.

[david s]

I think it's safer to cure the oven after doing the vermicrete layer and before doing the outer render, because the vermicrete contains so much water the steam pressure can crack the outer shell. However as you are doing an enclosure you don't really need any perlcrete. Many builders have just placed dry perlite or vermiculite over the blanket, or as you've suggested another layer of blanket and skip the perlite.