Stack Base Plate w/Collar on Home Built Evaporator

[Ghs57]

I had a stack base plate with a 1 inch collar made for my evaporator by a local fabricator. They did a great job, but it did not work out so well. It was made out of 1/4 steel plate, and once it heated up, it warped so bad it pulled out all the anchors around the edge. I had to use pipe clamps to keep things together for the rest of the season.

What should we have used? I was thinking it would be easier to secure something made out of thinner material. There would then seem to be less force on the anchors when it expands or warps.

[maple flats]

When I bought new pans for my arch I ended up needing to make a new base stack bottom support plate. I did not measure, I just read the tags on the old pans and ordered the same. It seems leader is like the lumber yards. When I got my 3x3 syrup pan and my 3x5 flues pan I tried to set them on the arch. The old ones fit fine, and there was a 1" thick insulation piece between them, about 1/2" support exposed in front, the 2 old pans (with the 1" insulation seal between them) and at the rear frame that supports the base stack I again had about 1/2".
When I set the new flue pan on, rather tight to the back, put the 1" thick ceramic insulation between the flues pan and the syrup pan, I was about 1.5" too long. First I removed the 1" insulation and put in a 1/4" woven one. Then I had to make a new base stack support that would accommodate the base stack but use 1.5" less space from front to back. I made it out of 1/4" x 1.5" angle iron and the sides and rear rest on the arch so they only got the 1/4" angle, under the forward facing I added another angle with a lip also facing down. This has not warped and I've used it for 6 seasons. However, my stack temps do not run real hot as I have air over fire (AOF) which puts much more of the heat farther forward under the pans rather than sending it up the stack. Before I added the AOF I had stack temps that at times ran as hot at 1400 F, since that it seldom runs over about 800-850 and more often it's between about 700-800.

[DocsMapleSyrup]

I just finished insulating my chimney base plate. I have no experience like maple flats has as far as performance. This is just another idea. I did oversize the arch bolt holes compared to the bolt holes in the base plate in case there was some warping. I too have AOF so I'm hoping my stack temps won't be 1400 degrees.

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[Ghs57]

I'm not running any air on my rig. It's my impression that a good deal of heat is heading up the stack, and overheating the base plate. I don't have a stack thermometer either yet. I'd like to add at least AUF this season.

I'll post a picture of the situation. I should add that I was running a 2x6 rig with a 2x4 pan, so my stack base plate was actually two and half feet long. I used one inch arch board for my insulation. Since I have to resize this plate, now that my 2x6 pan has arrived, i was curious as to what others have used, and whether I should work with what I have or start over. 1/4 inch seems to work for you guys.

[lpakiz]

Mine is made from 3/16 plate, with a 1 inch lip turned up, front and back. The flue pan rests against the front lip.
1 inch tall lip around the hole, to position the base stack.

[Sugarmaker]

Most of the old stack bases were cast iron and they took the heat better than steel. Thicker is about all I can think of to help the warpage issue.
Regards,
Chris

[Ghs57]

Here is a picture of what I have now. I noticed now that I did not use enough fasteners, but I'm not sure that would have prevented the plate from bending up when hot. There was about an inch gap around the edges toward the back.

I like Dave's method of using angle iron across the long edges. When I cut this back, I will run some on the underside pointing down and against the pan, and also run some on top facing up and against the pan. That should reinforce that area. I will also run some across the back edge pointing up to help reinforce that edge. The collar keeps the stack area flat. I don't weld, so I may take it back to the guys that made it for the refit. Either that, or I will drill and bolt it together.

We are having some warm temps here today, and everything is wet with condensation. There were more clamps on this when I was running. Probably about ten total.

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[maple flats]

My original base stack support was indeed cast. If I ever have warping issues on what I made I might get a cast one made. There is a foundry less than a mile from me and they will do custom work. I have not gotten a price however.

[Ghs57]

Dave and Chris, cast would be nice. Just think of the abuse and temperatures a cast iron wood stove contends with non-stop during the heating season. I'm thinking of my own. I wonder if Vermont Castings ever thought about building an evaporator....

[BeeRay Farms]

We built our own plate/ collar on 4x12 setup at my fathers almost 25 years ago now and it held up well. Used 3/8 plate steel base. Had a ring rolled from 1"X 1/2" stock to match the sides of taper stack when cut in half. Skip/ Stitch weld those half rings on each side of plate and stitch weld 2 more pieces of same dimension flat stock to plate. Burn out center of plate once welding is complete. If more warp resistance is needed one could take channel iron and place groove up around outside perimeter of plate and again skip weld it around in a few spots. When you burn out center and it's still red hot make sure it lays flat by beating it with a hammer if need be. If you could clamp it down while it cools to a flat surface or back of
Your arch itself it probably would never see as much heat stress again and stay flat.

Hope this helps..

[Ghs57]

BeeRay, that's exactly how they made the one I have, except they cut it on a cnc plasma cuter. I'm pretty sure I can save this one by reinforcing the edges with 1/4 angle. I just have to cut it back to the new length.

[maple flats]

I have questions about AUF only. My guess is that it would raise the stack temp. This is because before I had AOF I did run a blower 1 season with AUF and I had a stack thermometer. It ran as high as 1400. Before I put in the AUF I had no stack thermometer so I don't know how it may have affected stack temp. All I knew was that it boiled a little faster but burned a lot more wood. I stopped using the AUF mid season that year because I was afraid I might run out of wood.
Then, when I added the AOF I put AUF in again, with a ball valve to regulate it. Then my stack temps were usually 7-800 with both AUF & AOF.

[Ghs57]

Dave,

I just got the fan I'm using for AUF/AOF. My plan is to install both and I've drawn the AOF manifold. Now just to get it made.

I don't know what my stack temps were last year, but the tags on the new pipe did not burn off, or even brown. I set my air damper and never touched it again all season. There was a good deal of suction at the damper.

I'm hoping to meet the expectations i've read about with the forced air, and hope that the temps don't play havoc with the stack base.