Auto exhaust/muffler pipe as parts for RHM/ rocket stove?

I heard someone talking about using this stuff for a rocket stove. thinking of getting some more from the muffler shop. I got a few bits of 4", I think 3" and less is more common, but the walls are much thicker, thinking it might hold up better to the high heats as that's what it is designed for. It welds very well, and I have a basic wirefeed welder.

The way I see it, the alternative is it gets sent somewhere far off to get melted down for scrap, using more energy before it can be used for something else.

reconfiguring it would be a bit harder as it would need to be welded, but it could be tacked in a couple spots for testing.

would 4" be big enough for a heat riser if I were using a 55 gallon drum?

Its not enough of a vacuum, I've done it but into a smaller drum, allot smaller. You can do it with forced air, but that manks with the economy of the heater. But your auto exaust system idea sounds great from a component durability salvage point of view, so it might be worth the trade off. I use the rocket mass heater design to run a drying room so I'm trying to create bleed off into a small room so I can lower the humidity. All the moist air sucks into the stove, the design of my piping coils under the deck floor so I have to force air in exchange for all the turns i had to make. If not a rmh i think those retort kilns could certainly make use off the parts, I'm not into making biochar, but I am into charring bones for potash and calcium so a nice small one could use the smaller piping from the muffler.

i answered your identical question on reddit ;p
4" exhaust is massive. is it off a big truck or industrial machinery?

It's probably a big truck part. From a muffler shop...

So twin stacks would be ok you think?

Just a re-bump to ask a related question:  Would a large-port truck muffler mated to stove-pipe provide good heat exchange between the muffler and the surrounding air to be worth doing for a small space and short burn time?  The burn chamber (wood-fired) would be a few feet away from the muffler and a damper possibly installed above the muffler (i.e. downstream from the muffler in the exhaust flow).  Just looking to heat a small space for less than an hour and do not want to leave any fire unattended.  Thanks!

Hey John;
If I understand correctly, do you want to place a large-bore diesel truck muffler on the riser of a rocket stove?
And have a damper beyond it?  Just to give it more heating area.
Well, it could work just fine!
Or it could try to vent back out the throat of the feed tube.

I think it will work fine, but here, hold my beer and watch this... :)

thomas rubino wrote:Hey John;
If I understand correctly, do you want to place a large-bore diesel truck muffler on the riser of a rocket stove?
And have a damper beyond it?  Just to give it more heating area.
......

More heating area, yes....but not on a rocket riser.  More on a quick-n-dirty rocket stove concept.  Photo below.  The twin-walled burn chamber would be loaded from outside the building so animals (mostly chickens) living inside would not have to put up with my crappy attempts at fire starting.  Moreover, all 'open' smoke and embers would remain outside the building if not in the burn chamber, muffler or stove piping ending at the standard chimney cap.  The burn chamber is horizonal like in a j-tube or rocket cookstove and draft from the heated stovepipe would provide air current to the fire.  The muffler would need some research....some have some pretty good baffling that would slow down the exhaust whereas others (racing mufflers) apparently are less resistive on flow rate.  On a cold night when I make sure these chickens are secure, it would be nice while cleaning up a bit by headlamp to have a short heating burst in there that felt pretty safe, making sure the burn is complete by the time I leave.  (Building is too far from electricity to use a space heater.)  The idea would be to used light scrap/cardboard to heat up the muffler and stovepipe for a bit, the warm air of which would rise into the rafters where the chooks resided.  Already there is some brick thermal mass against the north wall on the inside that heats up a bit on sunny days from the south-facing windows.  The muffler heater would be part supplemental, part curious brainstorm.  If stovepipe alone (without the muffler) would transmit as much heat, I would just go with that alone.......but was thinking a muffler may have some useful properties that may make it a better choice....??

Hey John;
I think this will work fine!
How long that heat lasts is debatable but it will give a burst of heat to the egg layers!
I wonder if some form of insulation could be up above to help hold heat a bit longer.
Pictures and a post please if you try this idea out.

I have been looking at your drawing.
You have a basic L-Tube rocket design. They work great.
Ash cleanout can be accomplished from the outside with no need for an interior cleanout.
I like the proper collars thru the wall and roof.  I wonder if you want/ need a double wall pipe at all.
I think a regular stove pipe with a 90-degree will last quite a while.
With a cap on the outside after your fire is out, it will help hold the heat longer.
You are only building small quick fires, not hot enough to spall.