Segmental Thin Plastic Refractory/Wool Furnace Build 14" Dia Bore

I have a new design for my lid in mind that will be a somewhat non-segmental cone of Blu-Ram similar in shape to the prior lid but without true full segmentation of the refractory. I'll score it to produce contolled (I hope!) cracks. But it will be laid up in one piece using a temporary steel internal form and a permanent steel shell.

Here is the grey lid shell nested lifted out of the support pan. The lid shell will sit down into the pan and refractoy built up inside it. Then the whole works will be brought up to around 1000 deg F to set the refractory. The support will be removed and the lid insulated, supported and placed into service.

This is the lid. It has lugs to hold it off the pan by a half inch or so. That way the refractoy will protect the otherwise exposed metal lower rim.


The pan from above. It will be made from 20 ga with lots of ribs for support to allow poound in of the refractory.



The lid from below showing rigs to be made of 1/8" flat bar stock 3/4 wide. In reality the ribs will be open in the center, though, if Ihad a good shear and could set it up spot-on, I'djust shear the wedges. As is, I'll make a fixture and just tack them up.


Getting started today.

Denis

 

I made some progress today on the refractory form. And I welded up the lid ring yesterday. I used 16ga 303 aluminum for the lip of the lid as that part does "see" flame/gas/heat if and when the gasket between the body and lid leaks. The heavier ga and more resistant alloy should help improve longevity of the part.

Today I focused a couple hours on cutting the pieces and welding up the triangular-shaped supports for the refractory form shown in yellow above.

I made them from 3/4 x 1/8" flat bar. Since there were 16 to do, I did not want to fiddle around trying to freehand square up and align parts and then tack them. Instead, I made an outer triangular frame into which the cut parts would fit. That speeded up assembling parts for tacking and helped ensure uniformity of size. I've not used this technique before. But, it seemed to really help produce uniformly-sized parts with minimal fuss.

Here is the outer frame tacked together with three fitted pieces not yet prepped for welding set inside the frame. For actual welding I clamp them into place with over-center clamps after cleaning off scale. The tacks hold poorly if the scale is not removed.


Since there were 16 x 3 frame pieces to make I tacked 5 flat bars in a stack and cut them to size finishing them to length using my belt grinder. After cutting and grinding, a few hammer blows broke the intentionally-weak tacks and the parts were ready for cleanup and install.

I've got 11 triangles tacked together (five more to go) and they ARE nice and uniform in size and shape. By the time I am finished I'll have the process down pretty well. ;-) Tomorrow I hope to make the pan and maybe even lay up some Blu-Ram.

Denis

 

Sixteen wedges are tacked together. That’s all the welding they will individually need. I am liking the fixture as the resulting wedges are more uniform than I could have achieved using my “free-form” tacking method. And setup was much faster

Denis

 

Very nice Denis. Are you going to keep this mold so you can make replacement refractories for the lid in the future?

 

I sure hope it is reusable. If so, it will really reduce downtime.

Denis

 

Some progress today. I had about a half ton of iron returns to saw up and put away as I picked up a load at a foundry an hour away on Friday. So, that consumed a fair bit of time as many of the pieces are too large to fit into my crucible. My little 4x6 saw made a big pile of iron filings cutting over-size chunks to manageable size.

I also have the ribs tacked onto the pan base ready for covering first thing tomorrow. I used 16 ga for the pan base to give it some substance. I plan to cover the ribs with 20 ga even though I know it will dent in some between ribs. That really won't matter. With the ribs tacked to the base and the locating ring everything feels quite solid and attaching the cone skin should really firm it up solid. I think I'll just drill 1/4" holes over the ribs and use the holes to allow welding access to tack on the skin.



A paper template drawn in Onshape and printed on paper made layout of the ribs a lot easier. I put the paper under the ring andplaced a rib on a printed rib outline (Vertical projection) and zapped it to the ring. That was pretty quick and accurate enough.

Denis

 

Here is the skin plan for the cone-shpaed portion of the pan. It is nice to have online calculators for truncated cones!



When I actually cut this out, I will leave a little extra along the straight edge so that I'll be welding a lap joint rather than a butt joint---lots easier in 20 ga.

Denis

 

Today the foundry mostly took a back seat to being a grandpa and other family activities—-good stuff. But I was champing at the bit some…

I did first make a paper test cover for the cone ribs and the calculated shape did work just fine.


So I cut the shape out of sheet metal and started seeing how easy or hard it might be to wrap around the ribs.


I can see this is going to work out fine. It is not hard to mold the metal especially with the help of a few clamps. I'd like to convince everyone, myself included, that I designed in the open centers of the ribs realizing how handy they would be as clamp-holds. But the truth is that was just good luck. They really are handy for attaching clamps, though. I think this will all weld up in an hour or so tomorrow. I'll post a progress report tomorrow.

Definitely plan to instal some Blu-Ram tomorrow.

Denis

 

Just came in from welding it off. I was surprised at how easily the skin bent around the ribs. I just tacked the edge of the skin lightly to a rib and started pushing it down and tacking every 6 inhs areound the perimeter. It laid down nicely. I did a bunch of tacks on the periphery and at the inside edge popping litttle welds to the rib points. Everything was good to go. So, I started laying down 4 to 6 inch beads around the outside edge. Everything behaved itself and then I got out the grider to make a non-catching relatively smooth transition form cone to flat face. Finally I removed the extra metal off the flat face and opened up the centeer so heat will be able to circulate up from the bottom when I pre-fire the rerfractory. Next step is to line it with parchement paper to keep the BluRam from sticking to the form, fill it with a layer of refractory and pre-fire it.






Ready to line and then mold BluRam.


After that I have to rebuild the chimney support for the new lid shell and finish the shell.

Denis

 

Well I got the lid and pan assembled and ready for refractory as soon as I line it parchment---in the AM.

You can see that the lid is raised off the pan by 3/4" standoffs tacked between lid and pan. That will allow refractory to be worked under the edge of the metal lid and, it is hoped, protect the metal bse of the lid from flame. Once the refractory is pre-fired, I'll cut the lid free from the pan and place it inito service.


I plan to used double-sided tape to afix the parchment paper to the conical pan hoping that will help it stay in place when I pounding on the BluRam.

Denis

 

So if I understand correctly, you'll remove the cone mould form work and retain the band around the circumference in service?. Will there be any metal tabs on the band to key-in and retain the refractory?.

 

If you look up into reply 81 you can see that the grey lid rim has a welded-on 3/4" wide horizontal lip that will key in the refractory. I do want the refractory to hide that lip from fire, though. So it will extend below the level of the lip as dictated by the stand-offs. After the refractory is in and pre-fired, I will weld tabs to mount the lid to the lift mechanism and onto which the chimney will rest. I have the parchment paper in place now. So, the next step is to lay in the refractory.

Denis

 

Ahh, I see....

 

I put the plan to ork today and laid up the BluRam and fired the lid to about 1100F It was uneventful. I did have to use my diesel burner rather than the propane weed burner. I had figured the weed burner would have enough power to do it. But, that proved not to be the case. I was abe to get the furnace and lid to about 800 but at that point propane was burning and the temp was rising slowly. So, I drug out the diesel burner and ran it as slowly as I could --- about 1/5 normal fuel burn rate. That quickly got the metal form glowing a low red and brought the refractory itself to about 1100 degrees as measured with a infra-red temp gun. From prior exerience I know that is hot enough to set the BluRam quite hard. I did not want to damage the pan form as I hope to use it again when this lid gives up.

Partially laid up.

Ready to fire and scored into three segments. Icut about1/2 way through to form segments hoping that if/when it cracks, those will be the seams the cracks choose.


Here is a peak under the barrel lid I put over the new lid. I felt any hotter might cause damage to the form. Along the lower edge you can see the BluRam has lifted off the pan form. I like that as one thing I do NOT want is for the BluRam to stick to the pan. The parchment paper is supposed to provide a layer of carbon to prevent bonding. You cna also see that the lower lid margin is about 3/4" above the lower marging of the BluRam. How durable that edge will be remains to be seen.


Once the lid cools a bit, I will bring it into the shop to be fitted with the lift/pivot gear so it can be placed on the furnace. Chimney attachment points will also be applied to the lid.

Denis

 

Today was the first actual use of the lid (and a somewhat redisigned chimney). The lid did just fine. NO cracking and the outside surface remained cooler than the prior lid. I measured the temp as 350 over most of the lid.

The furnace ran great as I melted 55 pounds of iron using 17.5 liters of diese;l in 85 minutes with a 2550 pout temp. I'll find out tomorrow if the castings are good or not.

Denis