Peter van den Berg

Yes, I am participating in a workshop during the AFPMA (French mass heater builders association) annual gathering, held from 14th through 18th of May. The venue is a campsite close to the village of Montendre, north of Bordeaux. I did the design, a Shorty core coupled directly to a voluminous (although not very long) bench. It will be a quick build, meant as a proof of concept as opposed to a finished heater.

OK, you don't have the Sketchup application. By the way, the Shorty core isn't published on the site as yet, so much to do before I am getting too darn old...
But I can provide you with jpegs, of every layer of the core and you can work with that. I understand you are in Australia, the firebrick sizes might be different.
So, what are the firebrick measurements you are able to buy?
Is a Shorty sidewinder core the type that you want, or just the straight one like Thomas has built?

thomas rubino wrote:Shorty's riser is actually 6"x 6" for the first 10.5", and then it becomes a 9" x 6" rectangle.

Thomas, are you sure about that rectangle? As far as I know, you've built the thing to specs, which means the upper part of the riser box is also square.

Madeleine Innocent wrote:I'm finally ready to start looking at plans and building a RMH. I don't have any fire bricks, and if I don't have to have them, as you mention, then I won't. I really like the look of your shortie. Can I buy the plan to compare with the plan I have?

What size do you want to build? Straight one or sidewinder? I am able to provide you with the core drawing in ISO or Imperial measurements. What do you prefer, pictures of every layer, drawn out brick by brick, or the original SketchUp file? Free to use, no charge.

Small donations are appreciated, although not mandatory in any way.

The design of the bell is done  by Thomas Rubino and Gerry Parent, ask them for guidelines.

Regarding the development of the Shorty and DSR3 cores: both were done for a large part with kiln shelves. The top of the riser box and firebox were as thin as 10 mm (0.394"). Sidewalls of the firebox were mostly 15 mm (0.591") and the rest was a hotchpotch of 30 mm (1.18") slabs and thinner leftovers that were laying around. The core that was in the EU approved DSR3 was done entirely in kiln shelves, bar the riser tube, of course.

I don't know about the DSR3 development model, but the Shorty one is in daily use since the last week of November. The top of the Shorty's riser box is still closed with three strips of 10 mm shelve material.



All shelve parts are still in one piece as far as I know, have seen it Januari 31rst last time.

The neighbors of a friend living in a yurt were complaining about the smoke of his steel box heater. The development model of the Shorty core was lent out to him in December. We did some repairs on it lately, the thing wasn't meant to be in use all winter anyway. He's now getting the hang of it, the upper barrel has a bypass now, and the liner inside the riser box was replaced by a sound refractory one.

This evening he sent me a short video, showing the Shorty running like mad after starting with really dry fuel and the bypass open. The video was shot 10 minutes after startup, the chimney is just a bare pipe of 4 yards long, rising two yards above the yurt. Not much wind, about 4 degrees C above freezing point.

https://pberg0.home.xs4all.nl/pictures/dev2023-2024/VID-20250209.mp4

Pretty hefty for a mere 5" ish core, I'd think!

Burra Maluca wrote:Maybe something like this?

You might like this thread if so - shorty core gets a bell

Hi Burra,
The link you provided doesn't lead to the thread but to the picture only.
Just to let you know.

Coydon Wallham wrote:Is a clean burn associated with an absolute temperature? IE, if there is a thermocouple at the base of the riser, will that tell you at what point you've obtained an optimal burn with an indexed reading?

The short answer is no, not in a reliable way.
Long answer: years ago, I checked this with a thermocouple and the Testo analyser. It turned out clean burning (in a batchrocket) started much earlier than could be explained from the temperature readings. Most people know that in order to get a clean burn, the three T's (Temperature, Turbulence and Time) are all-important, and they are. But... with one of the factors increased, one or both of the others could be decreased. In my specific case, while getting turbulence up to new heights during development, the earlier the clean burn started. Even while the temperature opposite and halfway up the port, and one inch sticking inside the riser was about 300 ºC (572 ºF), the proverbial miles (km's) ahead of the 1000 ºC (1830 ºF) some sources mentioned.

Coydon Wallham wrote:More to my interest here, without dedicated instruments, what are reliable indicators of a clean burn?

Lots of turbulence in the riser and a lighter colour of the flames as compared to the firebox.
And the exhaust should produce nothing more than just water vapor which should vanish within 3 or more yards. Much like a high-performance natural gas burner would do. But you have observed that yourself already.
And third, smelling the exhaust should be like a laundry vent, lots of water vapor and a hint of ammonia. Most of the time there's also a faintly smell of wet charcoal (9-methyl ketone) or wet socks, absolutely nothing like the penetrating stench what most of us would recognize as wood burning.

Coydon Wallham wrote:Are there other passively observable indicators that reliably show a clean burn?

Not that I am aware of, sorry.

Coydon Wallham wrote:Hmm, I'd come to think that the excess creosote from my old conventional wood burner was from damping it down to extend the burn as long as possible before going to bed, and associated that phase with a long coal-out. I guess that was usually right after a refill of the box, so somewhere between startup and the top of the burn, it having coals from the last batch? Or is the creosote in that case simply more of a product of limited air flow?

My definition of coaling out in a masonry heater is when all the fuel is turned into smokeless charcoal, at the end of the burn. So that last question is the correct one, limited air flow. With other words: starving the fire of oxygen, so the stove is turned into a sick smolder generating lots of smoke that is condensing in the flue, waiting to be ignited into a roaring chimney fire. Mass heaters are run differently, with hot and booming fires, at least I hope so.

But I'd think you knew this already, don't you? Please, say yes!

Coydon Wallham wrote:There are definite signs of creosote in the exhaust stack, though I haven't taken it apart to see how much. This would be building up any time I let the box coal out, no?

Creosote will build up in the chimney during startup and less so during the top of the burn, assuming the thing is running well. During coal-out however, there aren't any tars formed which as a consequence, can't build up in your chimney. All carbons during that latter phase are released as CO. In free air, this decays to CO² and water very quickly, plus... some heat.