Tag Archives: wood heat

385 – Uncle Mud – part 3

Paul continues his conversation with Chris McClellan aka Uncle Mud about Rocket Mass heaters. They start this podcast talking about the Minnie Mouse, who now lives in the Love Shack. She’s a rocket mass heater contained inside a barrel, inside a wooden structure. Peter cleverly lined the back of the barrel very tightly with bricks, so that the stove doesn’t radiate a bunch of heat backwards to the wall. Thus, the heat shield is built in – no metal or brick had to be put over the wooden wall. Mud points out that this heat shield is also functioning as thermal mass, which is awesome double function action.

Minnie Mouse throws off a lot of heat quickly, but she also holds onto some heat, making her sort of a hybrid stove. She has a metal core – a metal wood feed and a metal burn tunnel. The heat riser is not metal. The reason this works is that the wood feed and burn tunnel are both air cooled. Steel will spall at 1600 degrees F and melts at 2600. You need to keep steel around 1400 degrees. This is done by having a smaller system – a 4 inch J tube system (4 inch batchbox would probably get too hot). The heat riser is vermiculite and can take a bit more heat. Paul thinks that if it was a 6 inch system, you couldn’t have a metal core.

Mud notes that “mild steel” will become challenged at 906 degrees F. You can use metal for a rocket cooker, but that’s because it never runs for very long. Peter uses metal to test various designs, because he’s just seeing how things work, he’s not going to put it into someone’s house. Metal cores tend to fail.

Mud says that although you can “hook” people into RMH with the economy of heating with less wood, and cheaper wood, the real value is in the increased safety. Paul agrees “Hey, you wanna save some money?” is the calling card of the RMH. Heat your home with 1/10th the wood *and* you don’t burn down your house with a chimney fire.

The Liberator is UL listed, so that should make your insurance company happy. It is a fully steel system that uses fins to dissipate heat. It’s a 4” system, another reason it works. (It’s not as efficient as ceramic cored rocket mass heaters for this reason.) Paul is still hoping someone will develop a non-metal shippable core. When he’s seen rocket mass heaters made with metal cores, they don’t seem to last. If something was made of ceramic, then you can have a 6” or 8” system. You can’t do a larger system in metal, it will get too hot and then it will fail. Paul has seen many people build 6 or 8 inch systems in metal, and they work grea… until they fail.

Rocket mass heaters with basic firebrick cores do great – they heat a home for years, no problem. We need more videos of the good builds, to compete with all the flaming freak shows of death that you can find on YouTube.

Moving on to the tipi. The rocket mass heater there was no longer working well. Ernie went up there to check it out. He thinks the core had some silt (instead of clay) and over time, this led to breakdown and holes in the core. Where the burn tunnel met the riser, there were holes leaking into the manifold, thus bypassing the heat riser. Ernie opened it up and rebuilt it with insulated firebrick and now it works great again.

The double shoe box is a batch box system that doesn’t have a heat riser. Instead, it has another box above the batch box, with a slot in the top of the bottom box. The fire goes up through the slot and does the cool ramshorn thing in the upper chamber to mix the gases and get the secondary combustion. They’ve built one up at Allerton Abbey. It’s got a glass cooktop, so you can see the curlicue flame path (and cook on it as well).

Having two chambers solves a problem that batch box heaters often had. People would overfill the batch box and it would interfere with fire leaving via the back wall. Then the fire wouldn’t burn cleanly. Now, the flame leaves via a slot in the top, so it’s much harder to block. The stove in Allerton Abbey has a heating bench attached to it, an open stratification type bench. The batch box has a casserole lid door, and once they built a bit more cob to get the glass further from the fire that’s working well. The thing burns really cleanly. The exhaust has no smell “not even like socks.”

Mud says there are lots of new designs showing that the secondary combustion doesn’t require a barrel with an insulated heat riser. People are making really interesting designs, especially with cooktops. As long as the system moves air well, multiple forms can lead to secondary combustion of the wood gases and thus impressive efficiency. Paul feels that the key factors that make a heater efficient are that the gases move through an area that’s over 1400 degrees (up to 3000 degrees) and that the exhaust is not nearly as hot as that of a conventional wood stove. He’d like to see how efficient these stoves can become – there is still room for optimization.

Mud says efficient is cool, but we’ve got to get people to use the things. Lots of people hate the idea of feeding a J-tube system every 20 minutes, so having the batch box system can help. The usefulness of the cookers may help these appeal to different people as well as the different aesthetic (no barrel). When he proposed building a rocket mass heater in his home, his wife said that saving $150 in fuel was not worth tearing up the living room. More designs, more choices in shape and function, this is how we get lots of different people using this better technology. Burn the fuel in your stove, don’t let it build up in your chimney to later burn down your house.

Paul says we’re getting to the point (in design) where a person might heat their house with sticks from the yard, plus garbage. If you pay for garbage hauling, now you’re saving money a couple of different ways. One idea for saving energy was to plug the chimney at the roof line, but Paul is here to say – don’t do this. Humans being fallible, somebody’s going to build a fire when the chimney is blocked, and it takes too long to figure out there’s a problem.

The last item on Paul’s list is the bun warmer. They already talked about it, but Paul wanted to note a couple more things. The original ring of fire used half barrels not as stratification chambers but sort of as ducting. Over time the ring of fire pulled sand into the barrels. Mud took over building the bun warmer from Ernie (whose leg started to trouble him and he had to take a break). He saw this as an opportunity for students to build a basic thing with their own hands. They made it a little harder than it needed to be, trying to bend barrels. In retrospect, it should have been built as a long bench, but having it bent in a U shape allows folks to sit and talk amongst themselves. Having it set up as a stratification chamber allows the heat to equalize all over. Paul says yeah, the surface was 85 degrees anywhere you might choose to sit – very nice. Mud says the fundamentals of the bun warmer are very cool, and he’s thinking of building an herb dryer using a similar design. (He also mentioned constructing a clothes dryer using a rocket core, and that sounds cool -JW)

Paul wishes that a thousand times more people knew about rocket mass heaters. Why would anybody buy a conventional wood stove when you could have a rocket mass heater?. OK, some of it is backlash from the lame so-called rocket mass heaters that people see. Still, there’s still a mystery here – come on, they are cleaner than natural gas heaters!. How do we get this information into more brains. We need to have more rocket heating jamborees – all over.

Credit: Julia Winter

Support the podcast on Patreon

Relevant Threads

2018 Appropriate Technology Course in Montana
2018 Permaculture Design Course (PDC) for Homesteaders
384 – Uncle Mud – part 2
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)
Rocket mass heater forum
pebble style rmh – in the fisher price house
Better Wood Heat: DIY Rocket Mass Heater Videos
Podcast 315 – More on Rocket Mass Heaters with Ernie and Erica Wisner Part 1
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)
The Liberator.

Discussion

You can discuss this podcast on this thread at Permies.

This podcast was made possible thanks to:

Lisa Goodspeed
Keith Kuhnsman
thomas adams
Jocelyn Campbell
Julia Mason
Dominic Crolius
Josh Phillips
wade L
Suleiman ALAQEL
Ash Jackson is The Scrollbard
Jason Hower
Bill Crim
Full Name
Doug Barth
Miroslav Ultrama
James Tutor
David Ingraham

Get all of the podcasts in convenient, giant zip files

384 – Uncle Mud – part 2

Paul continues his conversation with Chris McClellan aka Uncle Mud about Rocket Mass heaters. He talks about the cottage style RMH. Paul describes a J-tube type system with a vertical feed system. Heat hits the barrel and then goes down the sides of the barrel. It acts like a standard 6″ J-tube system. There are a few exhaust tubes through the mass and allows for quicker heat response. These tubes lead to a manifold that eventually leads to the exhaust. It is possible for this to be a shippable core. The efficiency of this unit is close to 65% because of a shorter riser. With a short chimney, the cottage rocket is insulated with cob and it performed more poorly than expected near 70% efficiency. Once placed in the workshop it had a 20 foot chimney and it began to perform much better but time did not allow for testing. RMH’s built since then, building the heat riser with split insulated fire brick (instead of cob) which created a chimney effect and this increased efficiency above the one in the workshop. This removed the need to preheat the exhaust. This design benefits from a well insulated chimney and allows it to burn extra hot. Paul likes the idea that the cottage heater could have mass added to the top of the barrel rather than trying to heat a large cob mass alongside the barrel the mass would sit on top of the barrel. A clean burn and of course the concept of the mass giving off heat for a long time. Heating up a large mass takes time. The cottage heater would be used to generate heat quickly. It does not burn all that clean but it is much smaller so there are advantages to the smaller footprint. Paul likes the cottage style heater for tiny houses.

Next they do a comparison of the cyclone design and the cottage design. Paul likes the cottage style and sees it as a possible shippable core. UPS will ship the barrel as long as it does not weigh too much. This is an advantage compared to heavier designs.
Cyclone is a 4″ system with a matchbox. This would use kindling. The interior is only 4×4″. It is a tiny tiny wood feed. This will require burning it for a while before it heats up. This system was nicknamed mini mouse and took less than 20 minutes to heat up. It also does not have a large amount of mass. The need for mass is important in the cabin because of gaps in the floorboards. The cyclone has a casserole door. It sits at a 70 degree angle. The lid sits on the angled side and this allows for a larger wood feed. This allows you to load up the wood feed with about 4 times the typical wood feed. The temperatures for the cyclone run at about 1800 degrees. The size is about the size of a 55 gallon drum. It is narrower from side to side but deeper. It is also a little taller. It has a nice arched top and a cathedral roof of sorts. The riser goes up into the chamber to hold all the gases. The 4″ stove pipe takes the gases out the exhaust. There is some sand and clay acting as mortar. All the masonry gets heated up. The heat only gets to the room after the bricks are heated up and this can take a few hours. If the red cabin were better insulated it might only take 40 minutes. Once the bricks are at 160 the heat continues to pump heat out. RMH’s are designed to provide consistent heat through the night. The cyclone may heat things up even after the fire goes out. The cottage style takes about 8 hours to build nicely, but could be done quicker if aesthetics are not important. The cottage took about 2.5 days including the chimney install. The cyclone heater took more like 6 days and there was a lot of masonry done and it is a slower build. The cyclone has a lot more mass than the cottage. Each style has different missions the cottage RMH is good for heating a workshop versus the cyclone which is good for heating a cabin.

A discussion follows about using the clear casserole lids for doors and some problems of them breaking. Paul talks about different kinds of glass that could be used with better results. Some types of glass work better than others. The cyclone has a casserole lid as a door. Pyrex is a brand name and it used to be fairly high temperature resistant. The newer lids are no longer capable of handling the higher temperatures. When the cob is fresh and wet it tends to generate steam which cracks the lids. Moving the door away from the fire will help reduce the issue with cracking. The trick seems to be keeping the door farther away from the fire. There is a thread on permies about the casserole door. Pyrex has changed to soda glass and it does not hold up as well and it tends to explode when it gets too hot. Amber cookware seems to tolerate warmer temperatures. A conventional wood stove runs at about 1000 degrees. The amber glass can handle about 1300 degrees where soda glass maxes out at about 450 degrees. Paul reminds us that we are trying to get to 2600 degrees with a RMH so none of these glasses work well for that. The glass also works to cool the fire which is not what we want. Paul thinks that using the glass lets some of the heat escape before the secondary burn. Do not use too much glass and it is something to use with caution when designing a RMH. Paul loves the idea of using the casserole lid instead of the metal frame door. The door fabrication alone takes several days. The casserole idea is a magnificently simple solution. One thing to note, the cyclone heater has no barrel. If you wanted a RMH that does not look like it has a barrel, you have a trade off because it has not barrel. You have to be careful if you add to much cob then the RMH will not work properly. Kirk (aka Donkey) has come up with a good design that strikes a balance using a stratification chamber. This design is slow to heat up but once started it stays hot, maybe even too hot but it does keep the space warm through the night. The cyclone does provide a stable temperature over a long period of time because of the large mass. Knowing the benefits of thermal mass is important when using the cyclone. If you are only looking to use it for one day, then it may not be the right solution. There are some Rocket Mass Heaters coming out of the Ukraine that are square instead of round. These are batch rocket based masonry heaters. These may be acceptable to insurance companies because masonry heaters are pretty well defined in the codes.

A discussion of the season extender is next. This was built with seven barrels laid end to end to create a giant Pringle type can under a hugelkultur mound. Paul hopes he can use this to plant tomatoes earlier in the spring. This giant can is perfectly level and is very wet tolerant. Inside the barrel they started with a basic 8″ RMH J-tube. The core is made with firebrick and insulated firebrick around the heat riser. The riser is two drums welded together so it sits about six feet high. The riser is insulated with perlite and ceramic wool. There is an exhaust tube that goes down into the Pringles can that sits under the hugel bed. There is some discussion that maybe five barrels would probably have worked better than the seven unit design. The barrels are the radiant surface with the ends are exposed for cleaning and inspection purposes. This design also has a small seat where you can sit and feed the fire. The exhaust goes back up and out through the manifold where the exhaust leaves the heat riser. The chimney needs a little heat to help it function better when it is very cold. The heat is being pulled from the bottom of the stratification chamber. The design of the chamber size is also an important factor. A discussion of the Facebook group versus the permies forum on RMH’s comes up. Paul is NOT a fan of Facebook and thinks it is better to have the information at permies because Google search will not include Facebook links.

Credit: Kevin Murphy

Support the podcast on Patreon

Relevant Threads

2018 Appropriate Technology Course in Montana
2018 Permaculture Design Course (PDC) for Homesteaders
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)
Rocket mass heater forum
pebble style rmh – in the fisher price house
Better Wood Heat: DIY Rocket Mass Heater Videos
Podcast 315 – More on Rocket Mass Heaters with Ernie and Erica Wisner Part 1
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)

Discussion

You can discuss this podcast on this thread at Permies.

This podcast was made possible thanks to:

Lisa Goodspeed
Keith Kuhnsman
thomas adams
Jocelyn Campbell
Julia Mason
Dominic Crolius
Josh Phillips
wade L
Suleiman ALAQEL
Ash Jackson is The Scrollbard
Jason Hower
Bill Crim
Full Name
Doug Barth
Miroslav Ultrama
James Tutor
David Ingraham

Get all of the podcasts in convenient, giant zip files

383 – Uncle Mud – part 1

Paul talks to Chris McClellan aka Uncle Mud about Rocket Mass heaters. Chris was one of the innovators at the Innovators Event and will also run the appropriate technology course Jul. 9th – Jul. 20th (tickets available on website from Jan. 1st). They talk about the Cottage Rocket, The Butt warmer, The Ring of Fire and a Season extender to put into a green house which can withstand wet conditions. They discuss the advantages and disadvantages of using pebble vs. cob as the mass in the Rocket Mass Heater, and touch upon the use of a glass casserole lid as the door in a batch box. The discuss the “Minny Mouse” heater used in “The Love Shack and the modifications they made to it and how it improved the heat retention in the leaky shack.

Credit: Dawn Hoff

Support the podcast on Patreon

Relevant Threads

2018 Permaculture Design Course (PDC) for Homesteaders
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)
Rocket mass heater forum
pebble style rmh – in the fisher price house
Better Wood Heat: DIY Rocket Mass Heater Videos
Podcast 315 – More on Rocket Mass Heaters with Ernie and Erica Wisner Part 1
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)

Discussion

You can discuss this podcast on this thread at Permies.

This podcast was made possible thanks to:

Lisa Goodspeed
Keith Kuhnsman
thomas adams
Jocelyn Campbell
Julia Mason
Dominic Crolius
Josh Phillips
wade L
Suleiman ALAQEL
Ash Jackson is The Scrollbard
Jason Hower
Bill Crim
Full Name
Doug Barth
Miroslav Ultrama
James Tutor
David Ingraham

Get all of the podcasts in convenient, giant zip files

382 – Heating with less wood – part 2

In this episode Paul and Jocelyn continue their talk about how they heated their house with 0.6 cord of wood. They talk about the things that contributed to them using more wood than would have otherwise been necessary: e.g. no curtains on the windows and the windows not being able to close properly because of ice on the sills. They also talk about things they do to reduce the amount of wood needed – e.g. using incandescent light bulbs, dog bed warmers not using vents in the house and cooking home made food.

They discuss why rocket mass heaters are not more known in the world and why people who have no experience with RMHs are so quick to dismiss their efficiency.

They refer to the YouTube series about common misconceptions about RMHs:

Credit: Dawn Hoff

Support the podcast on Patreon

Relevant Threads

381 – Heating with less wood – part 1
Rocket mass heater forum
pebble style rmh – in the fisher price house
Better Wood Heat: DIY Rocket Mass Heater Videos
Podcast 315 – More on Rocket Mass Heaters with Ernie and Erica Wisner Part 1
all of the rocket mass heaters and rocket stoves at wheaton labs (with pics!)

Discussion

You can discuss this podcast on this thread at Permies.

This podcast was made possible thanks to:

Keith Kuhnsman
thomas adams
Jocelyn Campbell
Julia Mason
Dominic Crolius
Josh Phillips
wade L
Suleiman ALAQEL
Ash Jackson is The Scrollbard
Jason Hower
Bill Crim
Full Name
Doug Barth
Miroslav Ultrama
James Tutor
David Ingraham
Michelle Martin

Get all of the podcasts in convenient, giant zip files