Arch Collar

[xyz5150]

I am building my first 2x4 arch what do you use for collars, collar plates? I was thinking of using a 3/16 plate with a 8" collar, should i weld it in air tight or gasket and bolt it to the rails? or does someone make a reasonable cast collar plate?

[DanE.]

I am building my first 2x4 arch what do you use for collars, collar plates? I was thinking of using a 3/16 plate with a 8" collar, should i weld it in air tight or gasket and bolt it to the rails? or does someone make a reasonable cast collar plate?

last year I did as you are thinking about. but I did not have a boil on the edge of the back of the flue pans. most of the gasses went right down the center and up the stack.

this year I made the stack base like you see the the manufacture arches. it was real simple to make. 4 pieces welded together. I made it out of 18 gauge steel. actually a old computer case. the front and back was a trapezoid and the sides were a rectangle. I was able to get a lot more heat to the sides with this style base than the other. I screwed it down to the rails with pan gasket in between. just something to think about......

1611.


Dane.

[Big_Eddy]

Here's what I did. I simply wrapped a piece of 1 1/4"x 3/16" bar stock around a heavy 7" pipe, then tack welded it to a piece of 3/16" flat plate with a rough hole cut out.
I cut the hole with a 4 1/2" grinder and a zip wheel. It isn't round, but it is close enough.

I just place this on the block behind the pan and drop in the base of the stack. I use 3 guy wires on the top of the stack to hold it in place - no screws or anything holding the base into this plate.

Works well enough and withstood a mini-tornado that ripped roofs off sheds and silos all up and down the road.

[SeanD]

Dane,

I'm planning the same thing you did, but I haven't figured out how to transition from the square sides to the round stack without gaps. What did you do?

Sean

[DanE.]

SeanD,

The pipe I'm using is 6". so the circumference is 18.8". I already knew what I needed for the width of the stack (it just happened because of how I made the arch and pans), 4", 8 total for the sides. that leaves me 10.8 inches for the front and back. divide by 2, and it leaves me with 5.4 (~5 7/16) Because I wanted a tight fit also I tapered it. starting at 5 3/8 to 5 1/2.

For the pipe I marked the measurements on the pipe 4, 5.4, 4, 5.4 and start to squish the round pipe square. once I started to get close to the right shape, I used a couple pairs of pliers to square up the corners.

Dane.

[SeanD]

That's smart. Thanks for the advice.

Sean