Malm Imperial Carousel - Making Refractory Lining Great(ish) Again

[ExWrench]

Finally got done redoing the refractory lining in our Malm Imperial Carousel fireplace, and wanted to share my ~saga

WAIT - WTF is a Malm Carousel? Fair question; I didn't know either until we bought a house containing one.

Vijayo is the best way to 'splain it:

It's great for rapid heating and fun to watch, but it's the antithesis of a wood stove - as much a curse as it is a blessing. Think of a Diesel engine w/ unlimited turbo - any wood you put in it will get beer-bonged into heat + ash in ~ an hour. Once it's going, you don't pile wood up w/ air space unless you want a 550*F stack temperature & an honestly scary amount of combustion going on indoors - and all that wood will be gone in well under 2 hours.

The air inlet is a 1/2" gap on the right side of the door, so the air swirls clockwise as viewed from the top. Fire is constantly agitated w/ fresh air, and the swirling keeps ash and smoke off the glass (it's 360 degrees of glass). Ours is about 50 years old, and it's been out of commission for about 1.5 years now. One glass pane broke in early 2023 and we have a wood stove in the dining room, so we were OK.

Last summer (yes the one a year ago), I ordered the replacement glass piece and pulled all the glass panels out.

Note: this is the OG first generation of Malm Carousel, and FYI it's a yuuuge PITA to disassemble.
Note 2: I've had that janky folding table + fireplace parts in the family room for well over a year now

Upon looking at the inside, the refractory lining was not only shot, but done completely wrong:

That^ is after I dislodged the lining to start taking it out about a month ago.

Supposed to be 2" everywhere:

Whatever hippie did this last got over 3" on the bottom & way less than 2" on the sides:

. . . and now I know why - details to follow.

December 2023, I ordered up castable refractory cement & planned to fix it before last Christmas. That didn't happen because other emergencies

Anyway, that's all the intro. "Tech" is up next & will be photo-heavy so bail now if you have a slow connection (or just DGAF ).

 

[RusM]

In

 

[SomeGuyFromOlympia]

awesome
but not in my house

got good insurance?

 

[ANGRYBLACK]

Um Yeah. stop being a Bitch. Try a holding furnace the size of a 28 foot trailer and 14" of that to pound in. Or carry 15 Pallets of the stuff down 6 flights of stairs then into the boiler.

Enjoy your fire pit

 

[surpip]

Those are super cool.

 

[ExWrench]

Trigger Warning: hackfuck ghetto-rigged tools may occur randomly in this thread.

Wanted to make a guide line so I knew where 2" off the floor fell on the walls. Turned out a cat food can, scrap of PEX, and some hot glue will place the tip of a Sharpie 2" off a flat surface.

And the reason the hippie ended up with that nonuniform liner? The castable refractory cement slumps too much once you get barely enough water into it to be workable. Or at least it did when they did it . . .

. . . and also when I did it

After mixing material for the floor, I realized it wouldn't stay up on the walls like clay so (in a quick, fast, desperate hurry) I made this:

Large, cheap stainless salad bowl of the "close enough & we're desperate" size sitting atop 3 each 1/2" stainless rods (axle shafts from grenaded conveyor rollers) put the bottom of that bowl exactly 2" above the floor of the steel fireplace pan (7" from fireplace deck to floor, salad bowl is 5.5", SS rods spaced salad bowl up 0.5", leaving a 2" gap). 25# bucket of mix held the bowl down in place.

That came out better than OK, and I was happy:

Needed to visualize where 2" from the 40 degree inclined walls was, so ^another hackfuckularly expedient tool was made (compass + Sharpie + zip ties + hot melt glue + rubber vacuum cap = SharpieCompass2000®

Thinking I could get the mix perfect when doing the walls (& slam dunk on the hippie that fucked up last time - yeah, let's call that hubris ), I made a wire form to keep track of that precious 2" wall dimension:

The toothpick-looking thing to the right of the small tape measure is a nail w/ a couple pieces of heat shrink on it to give me a 2" depth gage when I flawlessly do the walls like a master craftsman in crafts class w/ the refractory cement miraculously acting like clay . . . instead of . . . well, cement.

Made a second form gage out of a scrap of 1/8" x 1/2" aluminum strip leftover from (I have no idea, but it was free):

And here is the workpiece with all the forethought forethought, and this is just gonna' go awesome:

And here is the scene of the motherf_cking sonofabitch boondoggle disaster after I pulled 50# of refractory out by the handful, piled it back in my mortar tub, and stormed out into the yard to pack that shit into gopher holes before it set up completely:

 

[Sluggy]

Never knew about this kind of fireplace but it looks cool and who doesn't like heat when you want it hot.

 

[ExWrench]

So . . . yeah . . . Wile E. Coyote time

We're making a core for this casting job (AKA, "mu'fugger, your only option is to do what I tell you" ).

I had made a Solidworks model of the liner to finger out how many cubic inches of material I needed, so I cut off the already-poured section to get dimensions of the cone section I need for a core.

Not opening SW just to get a better pic - it looks like that^ but more enginerdy

Then, I lazy-assedly found an online metal cone calculator & plugged in my dee-menshuns:

. . . and back into Solidworks to draw out my flat pattern for a 2-piece sheet metal cone:

Printed that^ from Solidworks to a PDF, printed the PDF onto 3 sheets of 11x17 paper, stitched them together, and:

. . . either Adobe or Xerox had a wonky setting that printed it out at 90% scale

. It was honestly comedy at that point.

Made hacktastic tool #3 (not counting those 2 precision form gages ): a jumbo compass consisting of shelf bracket channel scraps + #10 hardware (overtightened for stability) + zip ties + 1/4" steel rod ground to a point + #2 pencil. At least this tool didn't have any hot glue . All the angles were good, so I just re-drew the 2 radii & other dimensions that were fucker'd.

Oh, here's a better view of my precision compasses:

This is a good break point. Time to stop planning and laying shit out, and go do some damage in the shop

 

[ExWrench]

Galvanized flashing was my material of choice, 12" width worked well for the 2-pc. cone sections w/ 1" tab ends.

Strong mini magnets kept me from moving the template & losing my shit while tracing.

Yay - we have 1 cut out.

After doing the 1st w/ snips, I did 2 more w/ nibbler style hand shears like this (innanep photo).

Only needed 2, but the spare gave me peace of mind. On IBB I heard someone say, "I'm not superstitious, but I'm a little stitious"

Sheet metal pieces needed forming to become the cone shape for which they were conceived:

At left, the shell of a conveyor roller (that those 1/2" stainless shafts came from) served as a hand-forming anvil.
Pipe clamp at right was for tighter forming, and it worked great . . . but only for fucking up and kinking the sheet metal

Now, we need something to hold those formed cone sections in place and hopefully in shape.
Cut two identical pieces of plywood out of some random 3/4" scrap, then drilled dowel holes w/ a jig:

Chucked my 5/16" dowels in a drill motor & spun 'em against a sanding belt to make one side a tight slip fit:

Screwed my newly unified board pieces down to a bench top for some router ensculptulation:

Idea was to go 11/16 down at 14" diameter, then step out 1/16" and go to full depth, leaving a lip for the flashing to butt against.

Key word there^ is "was"

Shitty old router chuck and shitty old router bit decided to part ways mid-reacharound

Probably close to a post pic limit here - to be continued . . .

 

[ExWrench]

So, to hell with the sexy milled registration lip - it was fragile anyway.
If the base plate was metal, the idea would've been badass. No biggie, FISHDO.

A window sash latch that came "free" with the house was perfect to hold my core halves together.

Core is 2 pieces because the complete cone won't fit through any openings in the fireplace.

And enlatchinated:

Fender washers for temporary registration points to make up for the sexy rim ledge that wasn't meant to be:

Those are so I could get the cone to the bottom of the plywood w/o going past the bottom.

Needed something to hold the top in place (using flashing structurally made her a bit of a wiggly beesh )

One side assembled. Had to grind relief for the sash latch to move under the top spider.

And here in all its glory is the thing I hope to only need one time:

That^ got taped on the underside & hot-glued from the top side for sealing, but mostly for structure.
Purty, it ain't But it's just a fookin' core.

We're done fucking around in the shop now; time to go fuck around back in the house.

 

[ExWrench]

This was where it finally started to get fun - there was a light at the end of the tunnel and maybe it wasn't a train

Test placement was promising - fuck yeah! Also, no pic, but my wire form fit the bottom of the core like a glove

- that nerdy math shit is handy some times.

Showing the ship in a bottle reason I dicked around to make this in 2 pieces:

Masking tape covering the 2 side seams + Kreg screw heads, and foam insulation to conform to the irregular floor.

All latched, placed, and weighted (bucket's full of water), flashlight checking for air under that bottom gasket:

No light leakage, she's ready to participate in the suckage.

Flashing is a wee bit wiggly, so I added masking tape to hold form out between top spreaders where the weight of the refractory cement wanted to push it inward.

Annnnnnd . . . here:

That's all I was trying to accomplish. Pretty fucking anticlimactic, huh?

 

[ExWrench]

got good insurance?

Yes, it's required by our mortgage lender.

 

[ExWrench]

Um Yeah. stop being a Bitch. Try a holding furnace the size of a 28 foot trailer and 14" of that to pound in. Or carry 15 Pallets of the stuff down 6 flights of stairs then into the boiler.

Believe it or not, I've done shit like that before.
But thanks for assuming otherwise

Enjoy your fire pit

If it weren't part of the character of this 50 year old mid century modern house, I'd rip this mu'fugger out & put a badass woodstove in its place for half what this fireplace would cost new. However, we're doing it the hard way because reasons

Also it's from before red porcelain was outlawed so you can't even get this exact same piece of shit new. We're "lucky" I guess.

 

[ExWrench]

Those are super cool.

If I get it back together & can burn wood in it, it'll be super hot

Never knew about this kind of fireplace but it looks cool and who doesn't like heat when you want it hot.

It's like owning a dragster - great for exhibitions, badass, cool toy, etc. . . . but you can't load it up & slow it down like a wood stove, so it sucks as a practical heating appliance. Great for parties and ridiculously rapid house heating, just needs more frequent feeding than I'd like.

 

[gt1guy]

That thing is bitchen.

Stupid questions.

Can the door close all the way?

Could you not put a few holes around the outside of the concrete and have it act like a normal fire pit?

 

[ExWrench]

Can the door close all the way?

I've considered modifying it to make the min. gap 1/4" instead of the 1/2"-5/8" it is now. Wouldn't want it to close all the way because it could be a brutal smoke bomb w/o positive draft. Also, the chimney is 20+ feet of 8" pipe (it's in the only room of our house that's an open two stories inside), and I'd rather not give it the opportunity to create creosote that requires me to spend time or money to address. Right now, zero fear of creosote or a chimney fire because she burns ridiculously lean.

Could you not put a few holes around the outside of the concrete and have it act like a normal fire pit?

I could, but definitely wouldn't want to. While reducing minimum airflow seems like it could help, the vortex is what keeps the smoke and ash off the glass, and swirls all the heat out against a heat diffuser built into the hood.

TL/DR: I may screw with the air volume, but the routing is already optimal - I could only fuck it up by changing it

 

[SomeGuyFromOlympia]

does this thing serve a purpose other and the kool factor?
I see it is neat, but the burn rate, and crazy temp, I guess I am trying to just understand the angle
I haven't seen one before

 

[ExWrench]

does this thing serve a purpose other and the kool factor?

Uh, yeah - it's a fireplace

I see it is neat, but the burn rate, and crazy temp, I guess I am trying to just understand the angle

The crazy temp. is only if you forget this thing acts like a forced-air burner. If you don't overload it and don't leave big air gaps under any logs, it's reasonable. You just have to constantly remember not to build a loose or tall stack, then it's manageable . . . and will need a recharge in an hour or less.

"Practical" uses:
I have a bunch of walnut firewood to use up (which is poor firewood compared to the almond and oak we feed the wood stove) - the Carousel is a perfect place to rip through all of that this winter. Also, if the house is freezing, you can drop a Duraflame + two oak logs in the Carousel (side by side in a single layer) & walk away knowing the house will be comfy toasty within half an hour. If you think "normal" fireplace & cant your new logs up across the established ones, you're getting the "show"

I haven't seen one before

It was a new concept to me, for sure. If all goes well during reassembly, it'll be "new" for a long time once again.

 

[gunracer1]

ok i'm thinking an ice pick to set depth, and just keep working the mix till it stiffens up. but i always try to take the easy way out.
looks good

 

[pdangerp]

Have you seen moldable refractory? I think it’s called ram. Also I’ve seen people weld wire stubs to the metal pan to hold the refractory in place.

 

[Splib]

When is the first burn ? Srry if I missed that but I glazed over eyeing all this on a cell screen.

 

[ExWrench]

ok i'm thinking an ice pick to set depth, and just keep working the mix till it stiffens up. but i always try to take the easy way out.
looks good

It's been 15+ years since I did any refractory relining, and maybe I just plain fucked up or this material was finicky, but I swear it took less than 1/4 cup of water to change a 50 lb. mix batch from not fully wetted, to more slumpy than peanut butter. After duplicating those results on two separate batches (floor pour and 1st wall attempt), I fell back on metal casting mold experience & made a core to yield an end result that exceeded my apparent talent .

Going into it, I expected to ram a dry-ish, tacky, clay-like mix into shape & babysit it for ~ an hour tops, but got my ass handed to me twice, so this was my overcomplicated route to a result that wouldn't frustrate me further. All later versions of the Carousel look like they can be disassembled down to the bottom pan, but on this one the verticals are welded and I had to work through the window openings. No doubt this could've been easier w/ different material or technician, but I'm just glad to be done with it.

 

[Ditchrunner]

Damn, looks like it would have been easier to fill it up and mill it out
I hope it was worth all the effort.

 

[ExWrench]

Have you seen moldable refractory? I think it’s called ram. Also I’ve seen people weld wire stubs to the metal pan to hold the refractory in place.

Yeah, I was trying to duplicate the manufacturer's intent, and ended up rewriting the script to get an acceptable result with what I had. Definitely not trying to sell my approach as optimal, just sharing my journey to 110% of "fuck it, good enough, we're done"

 

[bad zuki]

Dang that is cool. The parents had one until the floods came through and wiped the foundations out.

How much heat does it put out with the glass windows?

 

[ExWrench]

When is the first burn ? Srry if I missed that but I glazed over eyeing all this on a cell screen.

At least a month away, based on weather expectations. I'm going to drop a heat lamp in there for a few days to drive any excess moisture out, and will start with a few small fires before recreating the "firenado in a bottle" events.

 

[ExWrench]

Damn, looks like it would have been easier to fill it up and mill it out

Probably

I hope it was worth all the effort.

Me too

 

[ExWrench]

How much heat does it put out with the glass windows?

A lot. The radiant heat is enough to paralyze a house cat 10 feet away and the chimney makes a ~15' run vertically indoors before penetrating the roof, so it's actually pretty efficient, not just decorative fire.

 

[RusM]

Please post of video of the first Trogdor burninating this season!

 

[Clb]

This place located in Bodega?
I rented a house with one of these once...
Nice work.