Top's A10 furnace Project

Thanks Mark.
The doughnut came out without incident.

 

The solid disk is 8.24# (3.75kg), the doughnut is 6.92#(3.15kg) , and the cylinder is 22.8#( 10.36kg) [measured on a different scale].
The disk and doughnut are pretty close to 100 PCF which is mid-range for Kastolite 30i if I compare weight to CAD reported mass.
The cylinder is coming in about 5% higher weighed versus calculated, which could be the 'knockout' as drawn versus as it turned out molded.
I do not have a weight as cast for the lid insert, quick math (55# bag-22.8 cyl -8.24 disk -(-6.92*2 doughnuts)-1 plinths) = 9.12# (4.15kg)-ish.
I found something in CAD that looks like what I made and threw it in as reference.


Too bad on the ruined doughnut, probably enough material to have made the tuyere...in that vein of thought, is this really an opportunity to make the tuyere from heavy castable or something better suited? The tuyere I original planned is sort of a 'blob' that fills between cylinder and shell, hemmed in vertically and surrounding the burner pipe.

 

Thanks Kelly. I went for a test fit and discovered a few things:
1. Plywood cam for the lifting arm is broke. Time to make one from something better. If only I knew how to cast one out of metal...j/k
2. Doughnut is too 'robust' in comparison to shell by about 1" (2.5cm) of circumference. Not sure how this happened. Thinking to add 2 or 3 triangle cutouts and weld in gussets. As can be seen, I am not much of a sheet metal guy...
3. Burner was placed coming out side, I think the original reason was to keep it cooler when the lid was open. Now I think it will be less of a tripping and storage hazard to have it go out the back. The shell is welded to the stand so I may opt to cut a new hole instead of 'clocking' the barrel 'out of time' with the lid.

 

I founds some CAD I had started for the cam, looks like my plywood one may have been a test run that stayed in place as it worked.
The two piece pattern is 3D printed in PLA+ at 10% infill, set up for 1/8" (3.17mm) pins, primed, and coated with graphite. I was not concerned about filling in all the layer lines from printing.
I also made a template for moving the burner hole in the shell.

 

I packed and cast the cam and got it into place today.
Even though air temps were nice, I needed to set the Petrobond out in the sun for a while to get it warm and sticking to itself.
My cavalier attitude about the pattern (roughness, fillets,etc.) was rewarded with some extra breakout and flash. I also forgot the holes for extracting screws...
It did not take too long to fettle and the handle end turned out a good size.
The cam is perhaps a bit small and/or I will need to adjust the joint between lid and lifting mechanism to get a little more lift. . The lid also sags a little so I will need to work on that as well.

 

I decided to cut off the 3 tiny tack welds barrel to the frame and the welds off the lid to the lifting mechanism so I can clock the barrel and lid to put the burner in the back and adjust the handle position and play in the lifting mechanism.


PS: moved to next post 24.Oct

 

All said and done so far, the shell is maybe only 3/8 to 1/2" (9-13mm) above the top of the cast cylinder.
Since the cast doughnut is known to be larger than the shell...wondering if I should just cut the shell (green) off even with the cast cylinder, cast the tuyere, add the doughnut, and trim it with a metal ring (red) at the end.

 

Having the steel retaining ring a little higher than the refractory ring would give some protection from knock and bumps cracking the refractory ring. I'm fully supporting the refractory ring on my furnace with sheet steel in case of cracking.

 

Thanks Mark. Thinking about this, it would certainly hide alot of the 'ugly' so far if I did a neat job of it.

 

That's a "belt and braces" approach to retaining the refractory in place. It could reduce cracking due to the extra support of the steel.

 

I cut about 1/2" (12mm) off the top so the doughnut lands on the cylinder. The project started with a homemade jig to get the height of the cylinder marked on the outside of the barrel. When I got the barrel, it had olive oil in it and the cuts that had oil involved went smoother than those without. I smeared some grease gun grease along the inside along the path of the blade . I still had one of the cradles I had made to help handle the shell previously which helped stage the cut. I have not addressed the diameter mismatch and out-of round thing going on with the shell, it seems to carry down the entire shell where I thought at first it was more along the upper edge. I probably should have sprung for a barrel or shell the right size...We have a couple nice days coming up, hoping to cast the tuyere among the various outdoor chores to prepare for fall/winter.

 

Checking CAD to as-built, the tuyere/burner tube hole was 1/2" (13mm) lower in elevation as-built. 1/4" (6.4mm) I can account for with the thicker floor hot face, the rest is ???

Decision was made to raise the holes back up to plan. On the inside this was just an adjustment to a new cardboard pattern that became the mold surface and tube hanger, cut with a CNC laser and hot glued into place to be removed afterwards from the inside. On the outside is a revision to the hole in the shell, a remake of the scissors-cut paper template. The outside will get a laser-cut pattern/gasket/mold surface as the bottom of that hole is now 1/2" too deep/large. I wiggled and jiggled the shell and hot face cylinder and shimmed the pipe, I think the outcome is reasonable. I also have a slight down angle going into the furnace as mentioned by Razortoe as I have plans to try liquid fuel in this one.



I ran out 3 material estimations for the tuyere, messing first with the sweep angle and then the depth. I am leaning towards the smaller version. Plan is to wedge polystyrene foam (Styrofoam or Formular) to make the sides of the form. Then I will grease (Crisco) and place and seal the exhaust pipe. Finally I will mark a line so I know when I have achieved the depth I want. The it will be time to mix, place, and vibrate the Kastolite 30 into place.

 

I made another cardboard plate for the outside of the burner tube form. I cut it in half to make it easier to hot glue into place.

The exhaust pipe is one size bigger than my burner. The part exposed to the K30 is covered in Crisco along with the cardboard. The pipe is hot glued to the carboard. Where I could not /did not get hot glue I used butyl tape to add a seal.

I re-measured the tuyere after everything was in place and realized I was 10% under on my size estimate so I adjusted the mix to be +15%.
I dumped a bag into a bin, mixed it all up, and sampled it back into 5 x 2.5 gallon bags. Then I mixed my batch approx 7.75# (3.5kg)


I blocked up the cart with foam and used the air chisel and wood to vibrate the shell and frame. I put a screw into the side of the shell at 1" (2.5cm) above the burner tube form and my batch covered it with about 1/4" to spare. Tonight it is sitting misted and covered loosely in plastic, tomorrow we have a warm day and after that I will apply heat.

 

Wow, really nice job. And good catch on the height mismatch. I'm convinced that the ghosts of dead garden-gnomes occupy the space between CAD and reality

I'm really impressed at your sealing job, I would have been terrified of the water weakening the cardboard. I think the low-density castable, your mixing on the dry end, crisco, and all the other sealing you did were probably really important factors in success. I'm super happy you pulled this off, nice work.

 

Thanks Razor. We'll have to see how I did once I de-mold, probably in a couple days. This is the last refractory casting bit.

 

Well...I got the exhaust pipe stuck in the tuyere hole it was supposed to form. The thin layer of Crisco was not enough.

I was able to move it some, tried twisting and pounding out from the inside, adding slits with the Sawzall (reciprocal), etc. and now it is really stuck with a fair amount inside the furnace and the whole bit going through the casting.

Exploring and open to options to solve the situation.
Current thought is to cut the external excess off pretty close to the outside of the shell shell and try to slit it either with a long Sawzall blade from the outside or a cutting torch from both sides.

In retrospect, the form should have been something that could be more easily removed or in worst case demo'd, like taking the pipe and slitting it into 2 pieces and taping it back together, or could have been made from foam or cardboard. The hot glue I used to seal it made rotating it during drying a non-option.

 

Can you just leave it? Cut it off flush on the ID.
Both of my furnaces have a steel tube welded to the shell that I slide the burner into.

 

The exhaust pipe's ID does/did fit over the original burner tube's OD... so, yes. That would be easy and keep me going. Thanks!