Mullins Luxy Build

[cobblerdave]

Hello,

I posted this on Sunday, but it obviously did not post...

I have shut my build down for the winter after having two nights with ice and frost in October (very mild since however!). I went to the builders suppliers on Saturday to investigate my under hearth insulation. They never heard of ceramic fibre board, and could only suggest autoclaved aerated concrete. The blocks would be 10cm tall and are made by a company called H+H. The builders suppliers do not have the technical specs of the product and it comes in at euro 2.50 ($2.75) for measurements of approx 4.5"x20"x10". I understand aerated concrete is similar or the same as Hebel? The guy told me they are insulating blocks used to build an insulated house.

The price alone makes me wonder if this is suitable, as if it was any good, I would assume everyone would be buying this product instead of the other more expensive options as outlined by Russell, Gulf et al.?

Has anybody used this product? Any feedback?

Thanks,

Eoin

Gray
Ytong or ACC is. Swedish invention. Been around since the 1930s as a building material. Very popular in SEA as a building material so it's possible you local product is an import. Nown in Australia as hebel, like I said in Europe as Ytong and in Britain as thermolite block.
Not as well known in the US.
Ive only got 50 ml of hebel as the hearth insulation but it's done my well enough over 5 years now. The ovens not sunk into the insulation layer and I seem to have a good heat retention
Regards dave

[Mullins]

G'day,

Considering doing Hebel and then Fibre Board, and hardibacker board (to distribute the weight), and putting the floor on top of the hardibacker. Any thoughts?

It looks like I will have to buy the fibreboard online from Germany. I won't have a chance to see it before I buy. I think it was Libouru or SableSprings whose fibreboard compressed from the weight of the oven. I want to avoid this at all costs, and thinking hardibacker would distribute the weight (and give me a nice even base to start the oven on)....

Thanks for your thoughts/feedback...

[UtahBeehiver]

What is the compressive strength of the fiber board, I used Themogold 12 which has a compressive strength of 650 kPa @ 5% compression, FB's board has 500 kPa @ 10% compression. I laid the floor bricks directly on the Thermogold with no issues and I am going on 5 years. So see what the compressive rating is for the fiberboard you are looking at and it should be similar in either the ThermoGold or the FB board and you should be good without the handi board. CF board does get soft when it gets wet so you need to protect board while constructing or until it is enclosed.

[Mullins]

I found this product on a German website.

SILCA 250KM Color gray
- Dimensions of the panels: 1250 x 500 x 40 mm
- Building material class: non-combustible A1
- Maximum temperature: 700 ? C
- Building authority approval: No.Z-43.14-117
- Pressure resistance: 1.2 N / mm? <- Guessing this is it?
- Density (standard EN1094-4): 250 kg / m? <- Or this here?
- Porosity (EN1094-4 standard): 90%
- Thermal expansion: 0.2% at 500 ? C
- Thermal conductivity (standard EN993-15): <0.1W / mK at 200 ? C

This product is relatively cheap at E24.04 a panel (about $28-$30). Max temperature is only 700C. Is this enough?
That is on www.ofen.de and I am using google translate to translate it. Spec sheet is here in English http://www.silca-online.de/pdf/silca_20-6_en.pdf

The same company also recommend on their own website for weight-bearing uses to use a product they call SILCAPAN 845
http://www.silca-online.de/pdf/silca_12-6_en.pdf

This product appears to be able to hold three times the weight and up to 1000 celcius instead of 700 C (but I cannot find a price per panel...)

I will keep looking for a supplier, and see, but any thoughts?

mullins

[Gulf]

According to this pdf for Silca 250KM, it is Calcium Silicate board.

SILCA? 250KM The established calcium silicate insulation board for fireplace and tiled stove construction

The 700 degrees centigrade rating is very close to Thermogold 12. Actually, it is a little better. I can't find the proper conversion charts to compare the compression strengths and thermal conductivities. You may could use this pdf for Thermogold 12. I would call a local distributor and ask them to compare the two.

[Mullins]

Thanks Gulf,

According to this website the SILCA product has double the compressive strength? http://www.translatorscafe.com/cafe/...5BN/mm%5E2%5D/

1.4mPa is 1400 kPa, so the SILCA comes in at 1400 kPa, and the Thermogold is 690 kPA, SILCA is therefore a better product in terms of strength (or worse?). I am thinking better?

I cannot translate the thermal conductivity on a like for like basis…. there is another spec page there that gives a broader range if it helps? http://www.silca-online.de/pdf/silca_20-6_en.pdf

[Gulf]

Yes, I saw that 1400 kPa. That is about 200 psi I thought that was a very broad range from the Thermogold 12 and the ceramic fiber board. And, not being able to convert the thermal conductivity, is why I think that it would be good to talk with a distributor. Maybe, Russell (Utahbeehiver) will jump in. I like to punt all "pie r square" type questions to engineers .

[Gulf]

I looked again at your last link for Silca 250 km. Although, it is calcium silicate, it seems that it is specially manufactured for a thermal backing behind heaters. I also noticed that under Special Characteristics, it describes it as "very light". The industrial calcium silicate board that I am familiar would not be described as "light weight". I also see at the bottom of the page that "For load bearing protection structures we recommend SILCAPAN 845". That tells me that they make different grades of calcium silicate board.

I'm retired from the pulp and paper industry. That is where my first experiences with calcium silicate came from. I know that your part of the world is big player in that industry. I'm just guessing that your local supplier is primarily for residential construction. If your local supplier can't get you what you need (at a reasonable price), check with/search for "industrial insulation" suppliers. They supply pulpmills and the like that have industrial boilers.

I hope this helps.

[UtahBeehiver]

Mullins,

SInce the Silca product has higher compressive strength than FB board or Thermogold 12, not sure in Insblok, a comparison of the thermal conductivity is important, The Silca cut sheet units are in Watts per meter Kelvin vs the Thermogold in Watts per meter Centigrade. To get Kelvin, you add 274 degree to the Centigrade number. This way you can compare apples to apples. High compressive strength does not necessary mean good thermal properties, ie concrete handiback is high in compressive strength but not so good in thermal properties. But at a glance the Silca may work for you but again, need to do comparisons of products that have worked for WFO ovens in the past,

[Mullins]

Hi Russell,

After doing a bit of research on this The size of one unit kelvin is exactly the same as that of one unit degree Celsius. This means that a change in temperature of 1 kelvin is equal to a change in temperature of 1 degree Celsius?the scales just start in different places."

So, based on the above, and the fact that a lower number in thermal conductivity is better, it would appear the Silca conducts double the heat through it (based and the spec pages photos). My question now is, is the 250 Silca sufficient for using in my WFO? I am thinking probably yes. It's being sold on a German site that sells it for this purpose, and is probably still better than vermiculite/cement...?

I appear to slowly be getting there through this groupthink workshop!

I will call (instead of emailing the distributor tomorrow) to confirm

Eoin

[UtahBeehiver]

Eoin,

If everything checks out (compressibility, thermal conduct, price) then you are golden. We are always on the look out for newer and better materials for the next generation of ovens.

[JRPizza]

Hi Mullins, over on your thread now. I had visited earlier but forgot
I see you have a corner build, so my cad model really won't take too much modification to be useful. You can update the stand size and oven diameter then you will be able to play with fore/aft placement to get the amount of clearance you want along the sides. Then you can place your inner arch and think about what kind of landing length you want and what your stand will accommodate. Just save copies with different names when you make changes so if you really mess something up you can just go back to the previous version. I'm speaking from experience here as before I got good at editing I had lots of 'do overs".

[Mullins]

Hi JR,
Thanks for the file. I was away for a few days with the missus and kids and looked at a couple of tutorials on Monday night. I was able to amend easily enough a number of the components i.e inner diameter, outer diameter, hearth and dome. At that stage I was flying and thought this was much easier than I thought it was going to be. I was able to measure all the measurements from outer diameter to edge of hearth (a small bit tighter than I thought at 3.12 inches before insulation!).
I can change views and navigate around a bit, but as I am on a Mac not everything works that way it was designed to work on a PC or in Linux! One thing I cannot do is pan/rotate the view so that I can get in/around/behind the vent arches. I don't have a mouse and am using a mac with a tracking pad. Is there a button or drop-down that you are aware of that I could do this? That would make adjusting/measuring easier for me?
Also, there are a few components greyed out which I cannot click on/adjust and see if they are in the build. I'm not sure if they are incomplete, or if there is another issue? Specifically "Blanket", "Shell", "First Row Brick" and "insulation Board". Any ideas?
I am reading up on the FreeCad forum on the website, and checking out some tutorials on YouTube, but fantastic to be able to have a starting point and adjust than try to build this from scratch!

Thanks again,

mullins

[JRPizza]

Mullins, for changing the view/perspective I use the cubes in the menu bar shown below. If they aren't visible to you the bar needs to be turned on. The first one is an isometric view, the rest are side, top, etc. As for the greyed out components, just select by left clicking on them , then hit space bar, which toggles their visibility. You can turn off elements so they aren't distracting, and if you want to take a snapshot of part of the build without any clutter. I found the measurements to be pretty accurate. At work, I never trusted a model until I verified it with actual measurements. I made a full size cardboard oven shell and it was spot on with the model when I moved it around on my hearth.
Glad to hear the model is helping and you are getting the feel for Freecad.

[Mullins]

Thanks JR,
Yes, I can see the view/perspectives and can use those, but have seen there is another way to "pan" the view which basically rotates it to whatever angle you want as opposed to the generic pre-set views. I can't do that myself (yet!) though. I have just seen FreeCad 0.16 is out 3-4 weeks, and functionality on that is improved. It was suggested to a few other Mac users to try that. Currently downloading it ;-)

Thanks for the tip on toggling the visibility, I can add those items back in, but that means I can also remove the strip back the chimney, concentrate on the inner dome and those pieces, and build it out piece by piece. It will be far less cluttered, and easier to concentrate on specific pieces!

I have a full size cardboard made, and a full size inner diameter made in plywood (i may trim that in a half-inch or an inch based on the measurements in FreeCad). It's easier to visualize the dome and scale up or scale down components on the screen than doing it in real life first?once I am happyish with the CAD I will finalize the cardboard and plywood and then build the real bad boy!

thanks again for the tips

mullins

mullins