|
Post by foxtatic on Sept 22, 2020 10:37:58 GMT -8
Hi all, I'd like to bounce a design idea off you. I am planning a heater build based on Peter Van Den Bergs DSR2 riserless core and exploring the idea of building the core entirely out of ceramic fiber board like Matt Walker does. Of course, the problem with building a core entirely with CFB is keeping it sturdy and secure. Another problem is supporting the core within the bell. To accommodate these two issues, here is what I'm thinking: Build a pedestal of red clay bricks on the floor of the bell (integrated into the front wall of the bell itself.) Make it just high enough to raise the core to a comfortable height. On top of this pedestal, continue building bricks up as a three sided stall. The front is open, the core slides into the "stall" and I add a some feature (bricks or iron) to lock it in and attach a door to. Here's a crude example image from sketchup. drive.google.com/file/d/1P5J7rlTSMaicYGPYa_FuLqOCs3H5Fwhu/view?usp=sharingI would make the CFB core sturdy enough that it doesn't need to attach the the stall, just sets in there able to expand/contract as it likes separately from the brick. The intention would be to keep cost down and materials simple, just CFB, red brick, and refractory mortar. Maybe some hard firebrick splits to line the firebox. Can red clay brick take the heat of being so close to a CFB core? Am I overlooking any part of these design elements?
|
|
|
Post by peterberg on Sept 22, 2020 11:48:48 GMT -8
Yes, it can be done like you describe, my early experiment model happened to be one out of CFB and insulating firebricks. The inside of the firebox tended to become soft and prone to abrasion. The riser stub's walls became black and crumbly as if the first half mil of surface was melted a bit although it stayed firm. Lining the firebox with splits would be really sensible. In case you want to do that, remember that the top box' inside need to be as wide as the lined firebox. Wouldn't be much of a problem to make it like that. The firebox could be placed on the red bricks, no problem expected there. There's one thing that could easily be overlooked though, the bell's walls above the core's top box need to be lined with firebrick or other refractory material with superwool in between. In general: along the lines of the Mallorca build and the larger (5" and up) heaters built by batchrocket.pt.
|
|
|
Post by foxtatic on Sept 23, 2020 5:47:14 GMT -8
Peter, thanks for the reassurance. It's so nice to have you out there to confer with as I dial in my plan. Admittedly, I am getting a bit ahead of myself on the bell. The plan right now is to build a core and get it running in my shop over the winter with minimal housing (likely the two stacked drums.) Then when I'm confident enough I can work on a more refined design with masonry in my home the following year.
When you mention the riser stub wall becoming black and crumbly: Would you still line the riser stub with superwool like your sketches show, even if the stub itself was made of CFB?
|
|
|
Post by peterberg on Sept 23, 2020 7:19:42 GMT -8
When you mention the riser stub wall becoming black and crumbly: Would you still line the riser stub with superwool like your sketches show, even if the stub itself was made of CFB? Simply put, I wouldn't. But the riser stub need to be less wide as compared to the firebox and top box. I tried it without this liner about two months ago and the results were meager to say the least. But then, you could use the same CFB to make this liner on three sides of the stub. The sketch is how the proportions of the thing should be in order to get the right results. This design is even more tight as the original batchrocket.
|
|
|
Post by foxtatic on Sept 25, 2020 10:05:49 GMT -8
The most cost effective CFB I can find is rated for 1200C but with a "working temperature" of 1149C. Most manufacturers just say 1200C without specifying a working temperature like this. I saw on an old thread that you measured a max temperature of 1173º C (in 2012 developing the batch rocket.) Have you recorded any higher temps in the DSR2 design? Do you feel like this material I mentioned would be safe to use? Specifications can be found here: ceramicfiber.com/wp-content/uploads/2013/11/Ceramic-Fiber-Board-Data-Sheet.pdf If not, I also found 1426C rated material that bumps my cost up $100.
|
|
|
Post by peterberg on Sept 26, 2020 0:14:13 GMT -8
Have you recorded any higher temps in the DSR2 design? Do you feel like this material I mentioned would be safe to use? At the time, I borrowed a high temperature measuring device from a Dutch guy living in France. He got his device back about three months later, I never bought one of those myself. I had to push the development model very hard in order to reach this 1173ºC. That said, reaching 1000ºC was a piece of cake, 1100ºC seemed to be quite common, 1150ºC relatively easy. That last 50º up to 1200ºC proved to be very hard to reach. Also because during the burn the highest temperature point shifted to roughly halfway up the riser. And came down again as soon as the hottest moment was over and done. I use two thermocouplers at the same time, so I could watch it going up and down. No measurements like that done on the DSR2. But... if you are not much of a dare-devil, go for the higher specc'd material. Inside the riser at least unless the riser liner is easy to replace.
|
|