Ultimate Arch Design for Waterloo 2.5x8 Raised flue ?

[ibby458]

I just got home with the evaporator that I bought from FK. The arch is in quite good shape (The pans are like new!), but I think I'd like to build a new air tight one.

My thinking so far has gone like this:

Move the sides out a bit so I can use arch board behind full bricks, and still not block much of the pan bottom.

Make the grate space just the right size to fit 3 of the leader forced draft grates. (8x30 inches each) I LIKE forced draft, and will definately use it in this arch.

It has a 14" stack, so I need about 150 square inches of smoke space. 12 flue channels 6.5 x 1.5 means I should bring the arch bottom to within one inch of the flue pans to maintain that capacity.

Make one large air-tight door to fire it, and another on the ash pan. Mount the blower under the arch, with a deflector in the ash pit to force the air up the front and into the fire.

For materials, I have 60' of 2x2x1/4 SS angle, 120' of 1x1x1/8 SS angle, several sheets of 1/8" SS 24x48, and a lot of 20 gauge SS sheeting. I got 25 lbs of SS welding rod, a portaband saw, Sawzall and a friend has a plasma cutter.

My thought was to use the 1/8 plate for the front, back and stack connection plate, using the angle on the edges and around the doors to stiffen it. It's a bit light, but If I insyulate the front and doors, it should work OK.

I'd build a frame with the big angle at the top, and the smaller angle on the bottom, filling it in with the 20 ga. sheets, riveted in place. I'd use the rest of the heavy angle to make 3 sets of legs with leveling screws, to raise the top rail to 36" high so I don't have to bend over so far to fire it.

My question is- How far back to bring the angle from the firebox to the smoke shelf under the flue pan. I think a gradual rise might be better than a steep one, but I also see that getting those flames up into the flues as fast as possible would have advantages, too. Any suggestions, or does someone have an arch like this that they can measure for me?

[saphead]

A few sugestions: The forced draft grates are hollow,so basically you attach them to a plenum on the rear bottom of your fire box and your blower is hooked up to the plenum.You won't need an ash door because what little ash is left is in the firebox.Some arches have a plenum that goes all the way to the front to provide over fire air,use cast iron pipe fittings for nozzels so they won't burn out. Spend the money and buy a cast iron stack base,steel won't last and it will warp and flex the back of your arch.As far as the angle @ the rear of the fire box goes ,I'd do some more homework (and field work),see what's in other rigs and crunch the flue gas area numbers.When I get around to building my arch I will build it wider to accomidate ceramic(KAO wool),arch board and fire brick in the side walls,I don't understand why manufacturers waste so many square inches of heating surface with the present designs.Most newer designs of air tight arches have moved the fronts out to keep them from warping at the door closures,a cast iron air tight front would be the cat's meow!

[ibby458]

I see your point. SS DOES tend to warp like crazy under extreme heat. I'd really like to keep it all Stainless. Maybe if I insulated the bottom of the stack connection plate with ceramic wool, pinned in place with SS bolts, SS sheeting and fender washers, that might do the trick.

The primary reservation I have (and others have pointed out) is that 1/8 is awful thin for the front and doors, even beefed up and insulated. I'm now thinking maybe I should stay with the cast iron front and rear, just replacing the existing sheet metal with Stainless, and build a new air-tight door(s) to hang from the existing hinge pins. I have stove door gasket (3/4" rope style) that I could use to seal it to the front when closed.

[WESTVIRGINIAMAPLER]

You can use plate steel on the front for the airtight front, but 1/8" is probably too thin. Just insulate it with a couple of layers of ceramic blanket and it would be fine! :) Go with cast for the base stack, the blanket could fall off and you would never know it until it's too late. :?

[Fred Henderson]

Ibby, What I did on my homemade arch at the stack end to protect the mild steel, was I sandwitched a 2" thick piece ceramic blanket with pipe spacers(to keep from compressing) and a 1/4 piece of SS to it. I normally run a 650 drg stack temp.

[John Burton]

leader uses 18 on theres but I went with 3/16 on mine worked fine you can buy inconel pins and washers from leader along with blanket. use square tubing for the air jacket around the door..

[ibby458]

I was looking over the arch again, and came up with another plan. How would it work if I used arch board or ceramic blanket on the OUTSIDE of the existing sheet metal, and covered it with another layer of light gauge stainless? That would allow me to rebrick it in the normal fashion without losing firebox space.

I found this material on the web

http://www.mcgillswarehouse.com/ItemDetails.aspx?ItemID=109140101

Is this the same as arch board?

I can seal the existing ash door and bring the forced air in the back. THe loading doors swing on a set of bolsters with pins on either side. I can take the doors off, and replace with a single door, swinging from the original hinges. If I extend a cross bar top & bottom to cover both sets of bolsters, I could switch the hinge pin from side to side, reversing the door swing everytime I switch draw off sides.

The heavy SS angle I have can be used to build a platform with leveling legs to raise the whole thing up enough to make firing it easier.

This is a fair amount of work, but a lot less than building a new arch!

[Fred Henderson]

The inner sheet metal will become so hot that it will lose all strenght.

[mountainvan]

That's how my dg is insulated. metal, arch board,metal, and then bricks. works great.

[ibby458]

I think a plan is coming together here. Fred came over and suggested putting it up on cement blocks instead of building another base. That's a lot easier, and I think I'll do it.

This arch looks to have been originally designed for a drop flue. I was planning to bolt in a set of angle irons (and sheet metal) to raise the smoke shelf to just the right distance under the raised flues, then brick it. (No blanket or arch board) Will that be OK, or should I insulate that area too?

[mountainvan]

you should use ceramic blanket under the flue pan. insulates as well as brick, but does'nt hold the heat. instead it reflects the heat back up into the flue pan giving a stronger boil. new intensofire rigs have it in the back and I've used it for 10 years. much easier to install too.

[ibby458]

Are you saying JUST ceramic blanket, no bricks? It sure would be easier and less expensive!

[Banjo]

I've been pondering arch and pan designs as soon as I realized my little pot wasn't going to cut it, fueled by reading everything I could find here.

If I've got this right, you only seem to need the firebricks next to the firebox part, and it helps to have some ceramic behind them to keep the heat in. For the ceramic under the pans, I'm assuming that you don't get any creosote build-up on it since the surface stays warm? Would a thin metal cover help at all, I'm thinking along the lines of the insulated wood stove chimney?

The grainy picture of the "Intens-o-fire" arch in the latest CDL catalog seems to just have blanket under the flue fan, and it seems to have a metal firebox lining too (although maybe you put some bricks in there too)? Does anyone have any more info on this arch?

This topic has been a great source of info so far.

cheers, Andrew

[mcmp]

A few years ago, I put some new ceramic blanket under the flue pan on my wood arch converted to oil. I found some ceramic blanket rated at 2600 degrees that had a aluminum foil face bonded to the blanket. I figured this would be great and keep the blanket much cleaner. A few weeks ago when I sold the evaporator , I saw that the aluminum foil face had taken a terrible beating. The foil was shriveled, cracked, broken in areas. Of course the 2600 degree blanket was fine. The blanket in the flue pan area sat on a layer of vermiculite between the arch and the blanket.

Paul

[mountainvan]

yes, just ceramic blanket. brick is needed in the firebox because the wear and tear of burning with wood. I would recommend to stay away from vermiculite, it may contain asbestos. as for metal on top of the ceramic it is not needed. creosote does not form on the surface, but a fine layer of ash will, it does'nt hurt a thing.

[ibby458]

I think that's settled. Just ceramic blanket under the flue pan. Will 1" be thick enough? I figure a few pins to hold it in place wouldn't hurt, right?

Next question - THere is no door in the back for brushing the flues. Can I get them brushed adequetly from the front alone, or should I install a rear access door? A raised flue is so different from what I'm used to.

[mountainvan]

You want to have about 1-2" between the bottom of the pan and the ceramic, so you may need more than one layer. A clean out door is a must as far as I'm concerned, the intensofire I boiled on didn't have one, so to get to the back of the flues you crawled in or didn't clean the back and lost evaporation capacity. You can try and use a long pipe to reach the back, but will probanly mess up the nice ceramic. Also use the web gasket betweeen the arch and the rails, I have mine set in place with high temp. silicone and I can pressure wash it!Sounds like you're getting it right.

[ibby458]

I haven't seen the web gasket in any of my catalogs, just strips of ceramic blanket, which doesnt hold up well. (It does seal well, until you disturb it) Where can I find the web gasket?

I'm going to put a false bottom in the arch under the flue pan, so I can make it any depth I want. Will 1" blanket be enough there?

Sounds like a rear access door is a must. (Wonder why they didn't put one in to start?) It also looks like I'm going to have to bend my flue brush into a different shape to get up in there as much as possible.

[mountainvan]

web gasket for lapeirre, page 30 #ebtpro21. It' in maplepro catalog too, gave mine away. I would suggest 2 layers, just in case you tear it with your brush. always good to have a backup! They make brushes for raised flue, the white nylon. I've had to trim it a bit to fit in between the flues. Yes a few stainless pins with stainless washers will help hold it down but they're not completely needed.

[ibby458]

I have a Lapierre catalog, and found it just where you said. I just missed it. Reasonable price, too. I wonder if the Maple Guys carry it. I'd like to order from them.

I worry about the ceramic blanket under the pan getting pushed out of place while brushing the flues. Once it gets rippled or an edge lifter, the blower might push it up or back. I'll put pins and washers in for sure.

[WESTVIRGINIAMAPLER]

Anything in the Lappierre catalogs, the maple guys have or can get. I have used the ceramic blanket as a gasket for several years. I just buy a big roll cheap off ebay and cut a 1" strip and it works great and at the end of the season, throw it away and use new the next year. There is no way you should be able to damage it brushing the flues unless you put several inches in and let it hang down into the firebox. :D

[ibby458]

I've hit another speed bump in my journey to the ultimate arch. I was planning on using the Leader forced draft grates in the firebox, but I measure my grate space to be 23" wide. Since they're 8" wide (according to the catalog), 3 of them won't fit.

I asked my local dealer, but he didn't have any in stock to measure, and just shrugged and said to grind them down. I imagine I'll want a bit of wiggle room for them to expand, that means taking off about 1/2" per side. Is that excessive?

The catalog pictures look to show a good lip on each side. I also considered just overlapping them. I could put the outside ones out as far as possible, and set the center one with the edges overlapping.

The alternative is to raise the grate rack up a couple inches. Since this Grimm arch is rather wasp-waisted, that would give me the room I need, but at the cost of losing fire space.

Any suggestions?

[WESTVIRGINIAMAPLER]

Give Randy Gaudette or Brad Gillian a call. They can give you an answer quickly. :D

[ibby458]

Calling Leader directly does seem like the best solution. Maybe I can negotiate a better price on them, too!

Under the grates, the arch sides flare out quite a lot. I was planning to lay it on it's side, and pour that dead space full of concrete on each side to concentrate the air from the blower. I think the forced draft would keep it cool enough. Will this work?