Tips on How to Manufacture Exhaust Taper?

[wisnoskij]

Hello all.

I am building a wood fired evaporator arch and am having a lot of trouble with the exhaust.

First off, should the exhaust be the same area as the stove pipe? So I go from ~3"x~20" = ~~~55inch^2 to 8"=~50inch^2 pipe? Abnd the taper should just be 20inch by 3inch to 8" round?

Assuming that is correct. How do you actually get that? I can weld a square tapered box, but even that will required quite a bit of precision. But I am not sure about how I will connect a round pipe to it (I have insulated pipe, so not bendable).

Any tips, tricks, advice?

Hoping to finish it today/tomorrow.


19839

[BCPP]

We went to a local HVAC supplier and had them make a section out of galvanized steel they use for stove pipes. If you're good working sheet metal you could do it yourself. Just start with a piece that is about 48" on one edge and maybe 20" on the other (depending on how steep the taper ) and then cut angles off each side so the top edge is about 27". Its easier to let them make it and not very expensive!

[maple flats]

Can you come up with a 55 gal steel drum? If yes, lay it on it's side and cut off a section at the bottom of the drum to give you the taper when cut in half. Then you will want to weld extension on to give you maybe 2' more height, weld the open face (opposite the original barrel bottom) shut. Then cut a hole the size your arch needs . The (barrel) taper will easily support the insulated stack. Good luck.

[wisnoskij]

@BCPP:

Thanks so much for your response.

What one did you go to that had that service, we live in the same area, so we probably have the same companies. Did you get it done the same day, or was it something they had to order in from the factory?

Considering that I do not understand why you would cut the corners away, and have no idea how I would crimp the sheet together, I think I would have to get the professionals to do it.

[maple flats]

Without the 2' extension will work but 2' more will work better. With that extension you can taper the width to get full width draw thru the arch for good heat across the entire arch width.

[wisnoskij]

Yes, I just am not sure how to get the 2'-4' taper.

[littleTapper]

In my gallery you can get an idea how I made mine. It's not near as tall as some others' base stack, but I see no problems with my boil in any channel especially in the rear of the pan. I just cut 16g and welded it to 1/4" plate. Flat on top and then bent some 1/8" flat stock into a circle that the stove pipe slips into. If you're using insulated pipe, there should be a "crimped" base attachment for it that looks like the crimped end of typical stove pipe. I also run a large clamp "collar" over that base ring and the stove. With 10' of pipe it's stable even when breezy (I boil outside).

http://mapletrader.com/maplegallery/2x4-arch-build/p2338-base-stack.html

[BCPP]

@BCPP:

Thanks so much for your response.

What one did you go to that had that service, we live in the same area, so we probably have the same companies. Did you get it done the same day, or was it something they had to order in from the factory?

Considering that I do not understand why you would cut the corners away, and have no idea how I would crimp the sheet together, I think I would have to get the professionals to do it. I think it was Brooms but it was several years ago so not sure! You are correct in that the crimping is the difficult part. You need to cut the corners because ultimately your sheet has to go from the ~46" perimeter of the rectangular opening to the ~25" (2pir) cicumference of the stack. But it's not simple as the distance from stack to rectangle changes as you go around! If doing yourself I'd do a scale mockup pi n cardboard first.

[wisnoskij]

@littleTapper

This looks like the most doable to me. Just do a full 20" by 8" pyramid with a cut off top measuring something like 8"-8".

Will try and make it as high as possible, was thinking something like 2.5', as but with the sheet steel laid out in front of me, maybe bigger will not seem as intimidating as it does now.