rocket mass heater riser - the five minute riser

Mike Haasl wrote:What about using a SS insulated chimney pipe to hold the high temp wool?

Mike Haasl wrote:What about using a SS insulated chimney pipe to hold the high temp wool?

Chris McClellan wrote:Thomas Rubino’s 5 Minute Riser made from the new less toxic Morgan Superwool he carries on his website
https://dragontechrmh.com/morgan-superwool-plus-non-ceramic-fiber-blanket/

Andrés Bernal wrote:Some images of 5 minute risers from the rmhj!

Coydon Wallham wrote:

Mike Haasl wrote:What about using a SS insulated chimney pipe to hold the high temp wool?

The wool already provides the insulating qualities so wouldn't insulation in the pipe be redundant/extra expense?

Mike Haasl wrote:Yes, but it's a metal cylinder that might be able to handle the temps in there.  Don't know if it would work and you'd probably need an 8 or 10" pipe for a 6" riser.

Phil Stevens wrote:Mud's remark about them "getting wobbly" over time makes me wonder if I could prolong the lifespan by putting a skim coat of fireclay slip on the inner (and maybe outer) surface from time to time. Gonna try it and see. I replaced a clay and perlite riser last year with one of these and I really like the performance improvement.

As I think about it, the coating would also very likely improve the laminar flow of the superheated combustion gases in the riser by reducing the roughness of the wool. There's another motivation for trying it.

Chris McClellan wrote:Mud: The metal exoskeleton of the 5 minute riser can be hardware cloth or steel remesh (generally used to reinforce concrete) or my favorite is to use a piece of the next larger stovepipe. (Caution, hardware cloth is galvanized so it could offgas zinc at you). Life span has been about 3 years with the hardware cloth before needing a rebuild, longer with the stovepipe surround.

William Bronson wrote: This is a great report Tristan!
I'd thought to use a parge of refractory cement, but this just works.
Considering clay with perlite failed, but clay over fiber did not, perhaps the fiber is making the difference.

Tim Osborn wrote:...

It appears from the picture that you use 2 layers of 1" superwool. Is that correct  and if so, would you start with an 8" stove pipe to build a 6" riser? Would stainless steel stove pipe work for the outer layer of the core?

Thomas Cleman wrote:What if one were to tile the susceptible area at the bottom of the riser with these?  Graphite tiles.

You will get a very hot burn, once. Graphit burns like coal in the presence of oxygen.

Tristan Vitali wrote:

Phil Stevens wrote:Mud's remark about them "getting wobbly" over time makes me wonder if I could prolong the lifespan by putting a skim coat of fireclay slip on the inner (and maybe outer) surface from time to time. Gonna try it and see.........
Maybe rename it the 10 minute riser, as it takes a couple minutes to coat the wool, then a few more to pull the failed hvac ducting "form" out when it gives up. 10 minutes for 3 seasons of heavy use certainly ain't bad in my book!

loved it, did it last week, could not! finish yet new version (4th in 6 ys! same stove) of rsmh, will try to post info on how it works. planned movable cooking plate to monitor this too. not the original motive.
thanks a lot, carlos at casa verde montevideo, uruguay

Nico Poeta wrote:How are you guys connecting the 5 minute riser to, say, firebrick?

Gerry Parent wrote:

Nico Poeta wrote:How are you guys connecting the 5 minute riser to, say, firebrick?

I can’t answer how Carlos did from his pictures, but a 5 minute riser generally has a flat bottom that can just sit upright on the firebrick (or other) levelled off surface at the top back end of the burn tunnel. A little sand/clay ring can help seal the gap and also help support the riser to keep it from shifting over time.

Phil Stevens wrote:
As I think about it, the coating would also very likely improve the laminar flow of the superheated combustion gases in the riser by reducing the roughness of the wool.

Tristan Vitali wrote:

Maybe rename it the 10 minute riser, as it takes a couple minutes to coat the wool, then a few more to pull the failed hvac ducting "form" out when it gives up. 10 minutes for 3 seasons of heavy use certainly ain't bad in my book!

Eric Lyle wrote:

Tristan Vitali wrote:

Maybe rename it the 10 minute riser, as it takes a couple minutes to coat the wool, then a few more to pull the failed hvac ducting "form" out when it gives up. 10 minutes for 3 seasons of heavy use certainly ain't bad in my book!

How about using an 8 inch carboard tube (concrete form or mailing tube) as the form and just let it burn off?

Phil Stevens wrote:
I run a 4" J-tube in my glasshouse and it is very sensitive to any impedance in the burn tunnel or riser thanks to the low ratio of cross section to surface area in the system. Larger rigs are more forgiving.

paul wheaton wrote:
Because the interior of the riser has more texture, the inner diameter of the riser must compensate by being a little larger.  If you are building an 8 inch rocket mass heater, your riser would normally have an inner diameter of 8 inches, but with the 5 minute riser, it should be 9 inches.   And a 6 inch system would need a 5 minute riser with an inner diameter of 7 inches.