Top's A10 furnace Project

I don't know if my exact setup needs emulating: I had just one butterfly valve which needs a lathe to make ideally. A slide valve would be easier to make. I had a capped off short length of pipe that allowed the fuel nozzle to be positioned and also withdrawn from the furnace on shutdown to prevent the brass parts from melting. It was on a short length of hard drawn straight 1/2" copper tube. So I ended up with a short stub of PVC heat shrunk onto the metal tuyere pipe that allowed a PVC 'Y' shaped fitting, a 45 degree elbow, a stub of pipe with the butterfly valve ( you can see arrows in black feltpen for settings ), a 90 degree elbow, straight pipe and then a 15 degree elbow into the air blower. The Y has a cap on the end with a 1/2" hole (far left) for the fuel pipe to exit.

Having a lot of direction changes can significantly slow airflow and cause resistance to flow as the direction changes add up.

 

Since you already have air-control for the most part, what about simply disconnecting the blower or switching it off? Likely simpler than worrying about the cooling air in your output.

 

I ended up getting a pair of bought-returned-marked down 2.5" aluminum slide gates of Amazon for only a couple dollars more than buying one new one. So between the rotary baffle on the blower and the slide gate I hope there is some air control. I still need to figure out how the particulars of hooking it together...

 

I went to a local auto parts store to get flex pipe, a connector, some clamps, and some ideas to string it all together.
There are three choices of this brand's store, depending which direction I want to drive the 10 or 15 miles.
Furthest away seemed to be best stocked so I set out.
I get there and that connector (that was in stock according to the interwebs) was not in stock. My project laying out on the counter drew the attention of the rest of the staff and one of the customers, a regular, who does, among other repairs, exhaust and custom fabrication. One of the clerks said his shop is a great place to visit, museum-like in its presentation. So after buying three clamps and returning a piece of pipe that would not work, I followed his SUV in my SUV (same make and model, he works on those too) out into the countryside. Longer story made a bit shorter, the shop is amazing (neat/equipped/stocked/decorated), the gentleman is skilled at what he does, and I left there with two custom pipes with better than store fits and a bit of scrap aluminum, and an offer to come back if I ever needed more work done or scrap aluminum. I can't imagine a more providential chain of events...

 

He certainly did! He took his time creeping up on the expansions, to the point that we think self tapping screws will be enough to keep things in place versus the u-bolt and saddle clamps. I think there are some intangibles (cleaning up my shop, helping others, being helped by others) that I am supposed to take away from this too. It all made for a great day.

 

Here is the burner and piping assembled to the furnace. The plywood platform is about 3 & 1/4" (8cm) high off the concrete.

To-do list (and here I thought I was going to test run it today...):
-add shutoff valve to propane after regulator and gauge and before burner entrance
-re-attach lid to lift mechanism
-mount blower to base, attach pipes w/ self-tapping screws to blower and both sides of slide gate
-fire Kastolite 30i hot face (Q: should I do this with the burner from the small furnace instead of the 'Brute' on propane and blower?)
-order crucibles
-make tongs and shank
-finish sheet metal 'beauty ring' to protect/hold the disk (the one on top of the bore and under the lid)
-calibrate liquid fuel drip
-replace epoxy patch around copper fuel line on burner with a pipe nipple and cap (compression fitting?)

 

I met up with a gentleman associated with our maker space to have some parts cut via CNC plasma for the furnace.
-parts to make a 'beauty ring' to hide the poorly trimmed shell and support the outside of the upper refractory (the part that mates with the lid)
-parts to finish the lid lift mechanism
He did a great job on the parts. Today I assembled the beauty ring. Everything fits nicely but I need to make a couple changes to the outer shell to get the beauty ring and refractory disk parallel to the top of the bore. There is also a 'bump out' in the shell in the back, I might work that out while I am in there.
Once those changes are done I can attach the lid with the new lid brackets (will post separately as is not yet completed).

 

That looks pretty good, even if the ring cracks it'll still be retained in place. At this rate you'll be using yours before I get my furnace online.

 

Thanks Mark. Looking forward to hearing about your progress.

I forgot to mention that he rolled the 3 vertical pieces for me, saving me much time and effort in wrapping them around the circular forms. There was maybe 2" (5cm) on each end that was not quite rolled but I was able to add curve to those with a ball peen hammer, using the slot on the table saw table as a die of sorts. It did not take much force or time to adjust those portions. I did that and the fit up of the circular sections the night before so I could get straight to welding the next day.

If I were to make a second one, I'd made the flat pieces a bit narrower (they barely fit the roller) and a bit longer. Tack weld them flat and then roll. Trim off the one flat end, wrap, mark, trim off the other end to fit.

 

I got a little closer to done today. Shell trimmed under beauty ring, miscellaneous pieces primed, brackets welded to lift mechanism.
I moved the sliding portion of the lifter 'up' to allow for taller brackets by moving the pivot bolt hole. This change seems to make the action less smooth, it hangs
in the up position and no longer has enough travel to make it to the locked up position. I may put the cam back to the original position and add a 'slug' between the cam and original mating surface and see if the the longer tail on the slider makes it work any better.

 

I burned in the Kastolite today with my small burner and tested the new burner briefly on propane+forced air. I set up the drip rate for liquid fuel but did not try it either. I was wishing I had one more set of hands to work valves during testing or at least to call 911 and/or shoot me with the fire extinguisher... One spot got hot in the front and the upper ring cracked in half (as Mark predicted...).

 

That hot spot is like a full 90 degrees around from the burner. That third photo had my sleepy morning brain fooled by the illusion, if that's all the crack you get, you'll be doing well.

 

If only those were it...I am still pretty happy with it all. Once I get the lid to stop sticking up and subsequently banging down I can mortar those back together. I was wondering if a bead of mortar around the bottom between floor and bore would be a good idea too (?)

 

That would be a idea, especially if flames are leaking there

 

I probed the joint between the bore and floor with a bent nail. The joint is not that good, especially towards the front of the furnace, and there appears to be a void in the ceramic fiber insulation at the 'hot spot'. My mortar is intended for thinner joints 1/8" (.3cm) so I am thinking about using Kastolite after adding insulation behind the burnt area. Trying to decide if I need to remove all of the insulation to fix the insulation, or partially remove, or just go after the problem area from the inside through the generous gap I have before it get filled...? Next time I imagine I would want bed the hot face components together with something gap-filling during installation and use smaller pieces of insulation to make sure the lower sections are better filled.

 

I had similar issues with the top ring sealing on the bore cylinder and grouted it with clay I use to patch the furnace. I also used to sieve the dense castable refractory to remove the larger aggregate chunks for patching holes.

 

Slowed forward progress due to rain and snow.
I pulled out all of the insulation and patched the joint from the inside with Kastolite 30i. My plan is to refill it in smaller pieces so I know it's all in place without gaps. I also molded a couple plinths so I could make a reasonably-sized small batch instead of a super small batch. No pictures for these items at this time.
I also started planning out how to replace the epoxy patch on the burner tube with a pipe nipple and a brass cap.
I dd some CAD to make templates for cutting and a 3D printed hose clamp jig to help me get both pieces in position to tack weld.
I got in a #15 (close to an A10) crucible in off Amazon. I need to make tongs and a shank for it. Also messing around in CAD to see how that would look as well.

 

I worked on the burner some yesterday. I am confident that no one will confuse me with a real pipe fitter... I only used the small pipe template and the 3D printed part with hose clamps.

 

I cut the tab loose that holds the needle valve to the burner tube and moved it to correct the alignment between those and the run of the new pipe nipple/drip tube combo..