How to Build a Backpipe

Does anyone have any past experience building a replica backpipe? With a tee, a solid mpd, and pipe with divider in it?

Yes. Last winter someone made a back pipe using steel plate as the vertical baffle inside the pipe and an MPD plate inside stove pipe and a tee.

I was going to do similar for my first Modern Oak 118, by mounting a tee on top of the back pipe. One end of the straight-through legs connects to the pipe collar at the back of the stove barrel with a short length of pipe to span the distance. The other straight-through leg of the tee connects to the stack. The right-angle leg of the tee connects downward to the back pipe.

Then, make a 1/8 thick plate steel baffle plate that extends from up inside the tee to the bottom of the pipe where it rests in the back pipe support casting at the rear of the stove base casting.

Then, cut the baffle near the top to fit up to the curvature of a regular MPD plate installed in the middle of the tee, that is used to switch from direct to indirect modes.

The baffle plate would have a hole near the bottom for the flue gases to circulate through when in indirect mode.

With the MPD open the pipe is in direct mode with the flue gases going directly to the stack. With the MPD closed, the flue gases must travel down the front half of the pipe, though the hole in the baffle plate and up the back half of the pipe to reach the stack.

For stoves without a base support casting, the back pipe bottom can be closed off with a clean-out cap. Support can be provided by making a steel support to the stove base, or supporting leg down to the hearth.

Easy-peazy !

Paul

Yeah, there is a thread and are some pictures of the re-built back pipe posted here somewhere.

Awesome, how good are these? Would it be worth making?

Here are some ideas bro. I have not built one yet as I re positioned my stove and barely have a foot of vertical room in back of the stove.
Indirect Back Pipe on Any Hand Fed Stove
Sunny Boy's example is very thorough and doable.

Alright thanks, I just can't visualize how to set the mpd up to be able to switch from direct to indirect..

hotblast1357 wrote:Alright thanks, I just can't visualize how to set the mpd up to be able to switch from direct to indirect..

I will try.....hmmm put a shot glass in front of you, now first drink the contents it's 4 o'clock somewhere. The shot glass represents the top of the vertical pipe behind your stove.....visualize a silver dollar standing on edge atop of the shot glass and Susan B. Anthony is facing you. The coin is the mpd and it is closed facing you and open looking up or down, any luck?

Visualize standing behind the stove, off to one side facing the back pipe, with that side of the back pipe and tee cut away.

You'd be looking in at the edge of the vertical baffle in the back pipe. You'd also be looking edge-on at the MPD plate located halfway between the straight-through legs of the tee - sighting along the MPD plate's axle like a rifle.

The MPD plate is directly above the baffle plate and in indirect mode, it's lower half fits into a semi-circular cut out in the top edge of the baffle plate. The upper half of the MPD, being the same size as the tee, closes off the upper half of the tee.

In the indirect mode, the bottom edge of the MPD plate lines up with the top edge of the baffle plate, thus only allowing flue gases to come out of the stove, through the front half of the tee, tuning down into the front half of the back pipe, then through the hole in the bottom of the baffle, up the back half of the pipe into the back half of the tee turning away from the stove into the stack pipe.

Paul

Edited for more clarity.

michaelanthony wrote:

hotblast1357 wrote:Alright thanks, I just can't visualize how to set the mpd up to be able to switch from direct to indirect..

I will try.....hmmm put a shot glass in front of you, now first drink the contents it's 4 o'clock somewhere. The shot glass represents the top of the vertical pipe behind your stove.....visualize a silver dollar standing on edge atop of the shot glass and Susan B. Anthony is facing you. The coin is the mpd and it is closed facing you and open looking up or down, any luck?

Haha I understand that, I ment where to put the mpd so that it can seal against the T and the baffle plate. Exactly center of the T?

Yes. Right at the middle - the intersection of the three legs of the tee.

Paul

Ok I've never paid much attention to the actual size of the inside of a T compared to a mpd, I didn't think a mpd would fit snug, but now I see.

Yes center of the T and tight to the top. I would have the top of the baffle plate right behind the center of the mpd just below the pivot rod. You can cut a half moon out of the top of the plate slightly smaller than the radius of the mpd. It will create a nice seal and stop the mpd when verticle. I would cut approx a 5" hole an inch or so from the bottom of the baffle plate to allow for a place for fly ash without it blocking the passage way.

Ok perfect, I'll probably do it with some thicker galvanized first to keep it cheap and because my Franco belge is 5" and if it works great this season I'll make it out of black pipe for next year, I should prob run for at least a week first to see how efficient it runs the way it is

I found a pencil and paper. This is what I was going to make until I found another 118 with a back pipe.

Paul

Ohhhh see I want the T turned 90 degrees to exit straight up, will that still work?