Modifing the use of the rocket stove

I am wondering if the idea of collecting the wood smoke and keeping it inside one's stove piping as long as possible before allowing it to vent would benefit a typical wood stove setup?

A rocket stove proper wouldn't be what I would want in my living room, maybe some other rooms though.  You see I find the ambiance of a fire to important to our winter happiness.  So I'm wondering if the pipe coming out of the back of a wood stove could go up into a barrel encased in a cob wall and continue in the usual rocket stove fashion.  I also like the idea of piping outside air in to feed one's fire.

I bought the first rocket stove booklet, and in it they spoke of the next edition and requested people to send in their experiments with converting regular stoves much like I'm suggesting above.  But I haven't seen any such info on this as of yet.

So whatcha all think - typical fire box (wood stove, fireplace) plus rocket stove processing of fuel/heat in the smoke give the benefits of stored heat and cleaner emmisions?

Anyone have their own ideas of modifications of this system?

Darn good question. I think about that every time I see how hot my flue pipe is.

First, I would not try any of this with a typical wood stove.  The way they work depends heavily on the chimney being shaped the way it is.  And the extra pipe could make it so that the smoke doesn't leave, or that you get more creosote.

As far as not having it in your living room:  consider something that looks like a big wood bench - bit it is actually full of some sort of thermal mass.  And I've seen pictures of rocket stove combustion chambers made of flat steel in a boxy shape rather than a barrel.  Would that work better for you?

Great picture woodman.

Oh man Paul I don't want to hear that....
It's not just the ugly look, it's the open fire.  I could live with the ugly I think, but not seeing the flame I cannot live with.

I found an interesting site http://www.woodstovewizard.com/index.html
According to them a masonry heater/stove would be more what I would like -

"Masonry heaters combine the best of both worlds (rocket stoves and wood stoves) - they can be elegantly constructed to produce a valuable item of furniture while using cheaper masonry bricks to provide the thermal store."

Problem with them is the price - ouch! over $5,000 just for the parts to build your own, not counting any bricks (I would use cob anyway).  You can add an oven, water tank and additional features.  I've read about these used in old England.  They are the closest to what I want, a true fire box where I can enjoy the flames, plus the benefits of using all the heat.  Very cool. {See image}

I still don't see why one couldn't cannibalize the box of a wood stove for use inside a masonry style setup.... but then I do not know about the manics of stoves. 

~Jami

Here is what Masonry stove/heaters look like -  See the flame?  I feel happy already (maybe I'm a bit pyro).

I think that both here and in the book, ideas have been discussed for making rocket stoves look nicer than an old oil drum.  Possibilities include making the cylinder out of nicer metal, or covering it with pretty tiles or a plaster finish.  I'd like to see some discussion on this, as it's something I've been thinking about.  When I build my permanent one, I want to have a water jacket attached to the sides and back, but it would be nice if the visible portions of the cylinder (the burn chamber) looked nice, too.  I grew up with barrel stoves in the living room (cabins in Alaska and we also used a barrel stove in the house we built in Oregon years ago), and they really don't bother me too much, but they aren't the prettiest things in the world!

Kathleen

Jami I built the concrete surround in the pic. to collect heat, but way to much goes out the flue. My Quadra-Fire stove probably doesn't get as hot as a rocket stove in the burn chamber.

Have you ever smelled a wood stove overheat? It can distort metal etc. We can't get these type stoves that hot I don't think.

If a rocket stove had glass it would probably burn it out + the glass would cause insulation loss.

woodman wrote:
Jami I built the concrete surround in the pic. to collect heat, but way to much goes out the flue. My Quadra-Fire stove probably doesn't get as hot as a rocket stove in the burn chamber.

Hum....So you don't think encasing the flue in cob or mason bricks would capture that heat? 

Have you ever smelled a wood stove overheat? It can distort metal etc. We can't get these type stoves that hot I don't think.

No, but I've burned through an iron grate with my hot fires in my fireplace - I didn't smell a thing.  But I believe your right regarding a wood stove.  However, the barrel for a rocket stove is much thinner than the walls of a wood stove, as are the metal walls in my fireplace box, so something must be going on in the design and not the heat of the fire.

Thinking out loud:
Maybe it's the size of the hot fire - rocket stoves burn small amounts.  Maybe it's separating the smoke from the fire.  Maybe your flue is to close to the heat/fire in a typical wood stove.  In a rocket stove the gasses are collected and channeled around a bit before entering the flue keeping the 'extreme'' heat in the fire chamber.  The key being in the riser and drum processing of hot smoke.

If you could change around your flue around to incorporate a riser and drum I wonder if that would deal with your hot flue pipe.
By the way - I remember growing up and having my mom build to big a file in our wood stove, the pipe would glowed red hot, I thought it was going to melt - freaked us all out.  We had to be very careful, seems a wood stove could handle the heat but not the pipe.

If a rocket stove had glass it would probably burn it out + the glass would cause insulation loss.

I realize being able to see one's fire is very inefficient, and having glass brings another set if issues to deal with.  These are concessions I'm willing to make.  I don't want to add these to a rocket stove as much as adding parts (riser, drum and mass) of the rocket stove to a different burn setup...

I'm sure study of the masonry stove was part of the inspiration of the rocket stove.  Here's some information I found:
This masonry stove is based on the use of flue baffles made of brick, stone or adobe, that direct the hot flue gases in an "S" shaped pattern. The serpentine pattern slows down the air speed and also increases the length of the flow. Each additional square foot of masonry surface absorbs some of the heat from the flue gas until maximum available temperature is reached. As the fire itself is allowed to bum out, the hot bricks slowly pass their stored heat through the wall and into the living space as radiant heat. Each pound of brick will store 2/10
BTU of energy for each degree (Fahrenheit) rise in temperature. This is the reason a masonry stove is so efficient and retains heat for long periods.

On a cold day, the English fireplace will waste ninety (90) percent of the fuel that it bums on a season long basis. By contrast the masonry stove has been tested and found to deliver to the room, about ninety (90) percent of the heat generated from the fuel that is consumed. Even the least efficient masonry stove designs have resulted in eighty (80) percent of the heat delivered to the living space, compared to sixty (60) to sixty-five (65) percent for many of the airtight modem wood stove designs.

So question then becomes can a masonry stove be built out of cob (without straw of course)?
If a big masonry stove unit could be built as a cob wall in a house, with rebar as structural support of the wall, then open-fire, good-looks and efficient burn could all be achieved.

Do you think this is possible?

The net is amazing in stumbling across stuff. I found another forum where a guy built a rocket stove out of 1/4'' steel.
Here is what he discovered.(quote)

In this photo I am holding a magnet that is holding one of many large flakes that came from the steel inside the burn tunnel.  The oxygen seems to be used up before the heat riser so I will probably replace the burn tunnel with a fire brick or cob one when this steel one burns out.  At this rate I would give this 1/4 inch steel  a year.  Save yourself some trouble - use the clay tile, brick, castable refractory  or fire brick recommended in the book.  You will not want to use this on a combustible floor without adequate protection.


CountryPlans Design/Build Forum > General > Owner-Builder Projects (Moderators: John Raabe, Forum Admin, glenn kangiser, MountainDon) > Rocket Stove project

http://countryplans.com/smf/index.php?topic=2350.0

This is good stuff!  Answers some of my questions. 

The thread here on [b]vermiculite expansee/b] is interesting too.

Thanks woodman....

Seems the masonry stove was known by another name the Russian stove.

Here is an interesting video on the biggest Russian stove built.  interesting because of what we know about rocket stove/cob.

http://www.youtube.com/watch?v=Ymyg2aW3nGc&feature=related

I wonder if it might be possible to see some of the fire.

What if there were glass bricks, or maybe glass plates designed for use in wood stoves.  And rather than being flush with the burn tunnel, they were closer to being flush with the exterior and there was an air pocket between the burn tunnel and the glass?

Hey great thinking!  That's what they do in masonry heaters, move the fire back from the glass...

Here's a diagram:

The russian stoves are really cool.  Or, at least I thought they were really cool before I learned about the rocket mass heaters. 

At the workshop last winter, there was a guy there who did nothing but make russian stoves.  He said it was $10,000 minimum.  And many months.  And you really need to know what you are doing, because there are a lot of ways to mess it up.  But with a rocket mass heater, I think anybody can do it, and because it is designed to be built with scraps of stuff and rocks and mud, it can easily be under a hundred bucks and a weekend.

Yes!  I agree completely.  A stove anyone can make.  But that guy you mention, well he's a stove builder so you have to consider the source of the information.  I can talk to any construction professional about my ideas on building and they would shoot me down in a heartbeat..... So I Googled DIY masonry stoves, and found it's not just for professionals.  And it doesn't have to take thousands of dollars, one guy made his for under a $1,000 with all the nice details.

The missing link is:
I would like to find someone using cob instead of all that brick 

Thanks for the modifying idea.

~Jami

Quote by Mark Twain:

To the uninstructed stranger it promises nothing. It has a little bit of a door.. Which seems foolishly out of proportion to the rest of the edifice. Small sized fuel it used, and marvelously little of that. The process of firing is quick and simple. At half past seven on a cold morning the servant brings a small basketball of slender pine sticks and puts half of these in, lights them with a match, and closes the door. They burn out in ten or twelve minutes. He then puts in the rest and locks the door...The work is done.

All day long and until past midnight all parts of the room will be delightfully warm and comfortable...it's surface is not hot; you can put your hand on it anywhere and not get burnt.

Consider these things. One firing is enough for the day; the cost is next to nothing; the heat produced is the same all day, instead of too hot and too cold by turns..

America could adopt this stove, but does America do it? No, she sticks placidly to her own fearful and wonderful inventions in the stove line. The American wood stove, of whatever breed, is a terror. It requires more attention than a baby. It has to be fed every little while, it has to be watched all the time; and for all reward you are roasted half your time and frozen the other half... and when your wood bill comes in you think you have been supporting a volcano.

It is certainly strange that useful customs and devices do not spread from country to country with more facility and promptness than they do.

This could almost be about rocket stoves  but it is about the masonry/Russian stove.

My impression is that the rocket stove stuff took all of the best ideas from all techniques, and mixed in the need for it to be very, very cheap ... and then mixed in years and years and years of trial and error to get to where we are now. 

So, in many ways, the rocket mass heater is an improvement of the russian stove.

In the diagram of the Russian stove ,I was wondering with the air intake under the fire like that, wouldn't it fill with ash? Or am I missing something?

With this design the air is being pulled from the room at the back of the stove.  I wouldn't want that to be the case for my setup, but in this design there are two clean outs at the back for both of the air ducts.  Again, something you might not want.  Moving the opening forward to just under the door, make that a glass door please, would help.  In these stoves the fire is burned at the back of the fire box, with smaller, longer wood than you fine in a wood stove.

Since we've been posting on this I've found some interesting things on modify wood stoves, seems they can be converted into masonry stove setups.  The style you now have woodman, with air between mass and stove fire is a design used for fast heat release into a room, that's fine, but the flue coming off the fire and going straight up is the part that would have to be modified.

Seems the most important feature (missing in your setup) is the reburning of hot gasses before they travel away. 

If your interested in this let me know and I can start a new thread.

Note the reburning in this masonry design:

Jami McBride wrote:
Note the reburning in this masonry design:

The main issue with any kind of heat-exchanger working off the exhaust is maintaining adequate draft, even as the exhaust cools down. 

There are a lot of traditional masonry stoves, many types were invented in Europe during wood shortages a few centuries ago (post-plague expansion, Age of Sail, tc).

Some of these have a nifty little start-up opening or damper near the top of the woodbox, a tiny channel that lets a small amount of smoke flow directly upward toward the main chimney.  Once the draft is established, you build a bigger fire (probably the second fire in the "servant" example), and if it's a damper you close it off, so the majority of the exhaust is drawn from the firebox, through the convoluted channels, to the chimney.

Most modern masonry stoves have an inner core, an expansion joint, and then an outer facing layer.

You could definitely use cob as a surround for the masonry, instead of brick or stone.

I'd be hesitant to use cob in the hottest parts (even firebrick sometimes cracks in a rocket mass heater's firebox bridge under thermal stress; and cob erodes quickly when you're loading wood just from physical bumps and chipping).
...and definitely hesitant to use it for the whole entire thing (unless you lined it with something conventionally fireproof / gas-proof).
  Cob is susceptible to cracking if you leave the straw out, and can be difficult to repair once cracked.  (Repairing walls is fine, but in a convoluted heat-exchanger it could be problematic).
 
With masonry heaters the liner is a ceramic chimney-liner, and the structure relies on stable masonry units.

With rocket mass heater, the exhaust path is lined with metal ducting or stovepipe.  (Yes, it's better to use stovepipe or steel nearest the heat source; and yes, the fire mostly burns within the heat riser, there's not a lot of oxygen left by the time it gets to the barrel, and most barrels don't get as hot as a woodstove anyway.  But we'd love to see someone handy with metal create an improvement over the barrel.)

It's possible to do limited sections without a liner, like we built a brick corner to substitute for a ducting elbow during one workshop.  But you need someone who is going to live with the stove to be an attentive maintenance guy, who can keep an eye on the seal on that area in case any leaks develop in the plaster or mortar layers.

A chimney-sweep or inspector is not going to have the foggiest idea whether your system is sound, which means you have to know this yourself.
It would really be an experimental system, and if you wanted to pass it on (sell it, or to heirs) you'd have to be sure and train them on how to use it and maintain it.

If you have the space, the best method is to build a prototype, with a little roof over it - maybe it can double as a courtyard heater or outdoor pizza-oven, or as the first stage in a future guest-house.  If it works well, then replicate it indoors (just watch is the air pressure differentials).

...
Regarding your original stove idea - you've put your stove in a box, the radiant heat from it is being reflected back and forth by the walls of the box, and less of it is escaping into the room.  Google "Rumford Fireplace" for some ideas on how to radiate heat back into the room effectively.

...
Yes, you can cob around a stovepipe, but be careful that you don't create a pipe cool enough to attract creosote (even at the top outside the house).  Woodstoves waste a lot of fuel as smoke, especially when damped down for the night.  Smoke becomes creosote when condensed on cool metal or masonry. 

  Masonry stoves get around this by burning a short, hot fire, with more complete combustion of the wood gas and smoke.  Rocket mass heaters, and some modern stoves, also have a "re-burn" effect above the main fire area, where the remaining smoke is consumed. 

The inventor of the rocket mass heater sometimes says that if you want to watch fire, get a candle.  If you want to heat your home, without wasting fuel as smoke or polluting your neighborhood, then choose a device that is optimized for that purpose, and use it correctly.

Some of the rocketeers also suggest keeping your woodstove while trying out a rocket heater; you can have both.

Light a small fire in your woodstove for entertainment when needed, and use short fires in the masonry stove to maintain the room at comfortable temperature day in and day out, efficiently and safely.  If the masonry heater is in line-of-sight of the woodstove (I'm seeing a rocket bench here, my bias), it will serve as additional thermal mass even if you're just using the woodstove.  Like your concrete box but out in the room where it will do more good.

Masonry heaters are an improvement over rocket mass heaters for
- durability,
- time-tested design parameters,
- for watching the fire,
- can be designed for baking, with a clean, medium-temperature oven (not as hot as artisan brick ovens, but good for everyday baking or roasting)
- and for being similar to current technology (woodstoves and fireplaces) so they're less prone to operator error.  You just fill the box with wood (stacked as you would a big fire in a fireplace), start it, and shut the door.

Rocket heaters are an improvement over masonry heaters for
- cost,
- immediate availability of radiant heat from the barrel (masonry stoves take up to 12 hours to heat up, not a welcome thought if you go on vacation in wintertime; a rocket stove will warm you while the fire burns, more like a woodstove, yet still store the extra heat for later),
- fuel efficiency,
- comfort (you can sit on them)
- cooking: they simmer nicely, and can be designed for frying or baking if needed
- and probably exhaust cleanliness (they literally make no smoke for much of their burn cycle, the evidence is anecdotal but impressive).

Woodstoves are less efficient, less safe for contact, much smokier, and don't last as long without exceptional maintenance.  But they are an improvement in a couple of respects:
- quick heat and cool-down (if your weather is really variable, this can be a plus instead of a minus)
- familiar to most users
- more portable due to low weight (you have to buy new stovepipe, but you can drag a woodstove from home to home or even install it in a mobile camper-type thing.)
- cooktop gets hotter if you need to fry stuff all day.

they each have their dangers, too, but this post is long enough already

-Erica

The inventor of the rocket mass heater sometimes says that if you want to watch fire, get a candle.  If you want to heat your home, without wasting fuel as smoke or polluting your neighborhood, then choose a device that is optimized for that purpose, and use it correctly.

Excellent!  That explains why Ianto has a rumford fireplace and a rocket mass heater in the same room!  One is for watching fire and one is for heating.

Erica,

Does this mean that the idea I mention above about the glass .... would be a bad idea?  If so, why?  What happens?  Does the fire go out?  Does the glass explode? 

paul wheaton wrote:
Excellent!

Erica,

Does this mean that the idea I mention above about the glass .... would be a bad idea?

Bear in mind that Ianto is a self-declared curmudgeon, who routinely uses candles or a Rumford fireplace for fire-watching pleasure. 

The glass idea might work, and might attract a lot of people to the idea of rocket stoves who currently find them too ugly compared to a woodstove.  (Most woodstoves are in fact an ugly, black box, but seeing the fire inside gives them loveliness and charm).

So the glass idea is well worth developing, from a market standpoint as well as aesthetics.  It's not been done successfully yet, but that doesn't mean it can't be.  Someone with spare parts sitting around, or enough budget to buy some glass and mess with it, could make this happen.  And could probably sell "rocket glass units" of a door or insulated pane in a masonry-compatible frame, if they wanted to.  Or just publish the results and become mildly famous.

But Ianto is not going to do the research for you.  He's done what he set out to do with Rocket Mass Heaters, and it's up to us to develop or modify them.

-Erica

paul wheaton wrote:
Does this mean that the idea I mention above about the glass .... would be a bad idea?  If so, why?  What happens?   Does the fire go out?  Does the glass explode? 

Be sure to use tempered glass...like scavenged from a BBQ grill or old oven. The glass will get black after a while so you will have to get inside to clean it..

Looking at rocketstove mass heaters on you tube I found this video

http://www.youtube.com/watch?v=TxZazZHari0&list=PLUVwBGeHDjzItJY9pUPKy6U-XH68-xFxs&index=4&feature=plpp_video

They put a pyrex plate in the front so you can see the fire, and here are some of the comments... no design plan thought. I love to watch a fire.

My wife and I no longer live in that house because it was only temporary. If I had to change something about the design, I would have spent about $20 or so and bought real stove glass and built the front in the correct location. I moved my pyrex forward away from the feed tube about 5-6 inches so that it would not be as hot. So I believe that extra distance changed how well the stove worked. I hope you can understand what I'm trying to say. Do you have the pdf plans?

lespaul49 in reply to johnjmw1 1 year ago

How has the pyrex pan been holding out? Have you fired it full out to see how it would hold up to the heat? I'm hoping to put a window in the one I am getting ready to build also.

Hiei12345 2 years ago

I haven't used it in months, but have never seen even a hint of a problem. I should stress again that the glass is about 4inches farther from the fire than the originally designed front wall. any glass that you choose, I would burn over a good fire pit with flames touching, to make sure it will last

lespaul49 in reply to Hiei12345 2 years ago

Jami, what you're talkig abut is a bell no? Horizontal batch rocket, does that ring a bell?

http://www.youtube.com/watch?v=dM-GbmlVGXo

http://www.youtube.com/watch?v=kEiv5O5mQ7E

Someone mentioned encasing the chimney in cob, but what about encasing the entire stove in cob, except for the front where you put the wood in? Eventually I want to build a rocket stove, but in the meantime, I have a wood stove I'd like to make more efficient.

Sean

http://www.youtube.com/watch?v=2CQtKMLznHc&feature=related

Seems to me that if you lined the firebox and chimney to be similar to a rocket stove. Then add the barrel and outlet piping like a rocket. You could have the best of both. If the fire is toward the back of the stove away from the glass , the glass would stay cleaner too.
Isn't the difference between the two the temperatures and air flow which allows cleaner burns ?

I have found an old masonry version of a RMH, see attached image. Then I also found this guy on youtube: here
He uses a pyrex Pie Plate! Then at the MHA get together back in 2009 they built a Rocket Bell Combination pretty slick. Then what really looked like a great Russian Rocket, was this at MHA in 2010 when they build this Masonry RMH.

So Erica is right, Ianto passed the torch (eh hem) and we have enough system history and design out there to design a prototype that meets some of these issues head on, namely the darn ugly barrel and for me, sometimes the less than artful use of cob! SO, call me crazy, but when Paul (not Wheaton) and I are able to start on the conversion of our steel building into a house (Straw Light Clay packed walls is where we are heading we think) then I have the desire to create somethihng like THIS! And on that page is a true 2 burner rocket stove that looks awesome - and they snagged the image off of Permies.com!

Now luckily I have room to build a real prototype, and just the place I want to build it - my outdoor kitchen! So not sure if the handy little Pyrex Pie Plate is the route I will take, or cut loose for an actual tempered glassd Masonry Heater door, but Physics tells me this can be done, but it's a matter of scale, airflow, temperature and burn time. Like trying to learn that recipe from gramma when she says "just a pinch" or "put a dab in there".... the numbers will have to be worked out.