deleted.

The only thing I would add would be the insulation (shown in purple)

The book also talks about the insulation.

My understanding is that it is the insulation that makes it so that there is a powerful push one way through the whole system.  Without it, the system would be wimpy.

    If at first the smoke cools down too much then it wont burn that may be one reason for insolation.

    The other is if a toungue of flame is going through there because these heaters burn the smoke then your children or furniture might burn if the place the smoke was burning in wasn't insolated.

    The cans in this type of stove have to be the secondary combustion chambers, no secondary combustion chamber, no clean burn and these stoves have this clean burn that is one of the good things about masonary stoves. in other types of masonary stoves this part is covered in masonary or stoen clay or adobe like the rest.
    I think these metal tanks exist because of the debt to hobo stoves of his particular variety of masonary stove. This is reflected in their name rocket stove.  Rocket stoves are hobo stoves.

I thought long and hard about rocket stove water heaters... and the real difficult part is in the sealing of the surfaces between the water and the hot gasses.

You really need to be a boilermaker  to guarantee the welds/seals

I got around this by creating a dedicated heat exchanger from an old chip water heater (called a donkey around here)

If you are interested checkout the page on our blog

http://www.milkwood.net/content/view/80/49/

cheers
Nick

Milkwood Nick wrote:
I thought long and hard about rocket stove water heaters... and the real difficult part is in the sealing of the surfaces between the water and the hot gasses.

You really need to be a boilermaker  to guarantee the welds/seals

I got around this by creating a dedicated heat exchanger from an old chip water heater (called a donkey around here)

If you are interested checkout the page on our blog

http://www.milkwood.net/content/view/80/49/

cheers
Nick

Nick's design is one of the better ways I've seen suggested to do a rocket water heater. 
Any boiler-type design carries a high risk of explosion.
Any heat-exchange coil design also can boil, vapor-lock, and explode.
Any design which puts the water near/around the combustion chamber itself, cools the fire and reduces combustion efficiency, creating a smoky, polluting fire.

The heat riser needs to be insulated, not only to burn clean, but also to draft properly in the first place. 

Nick's design puts the water to be heated above the insulated heat riser, avoids interfering with combustion, and uses a big enough jacket and tank.  Thermo-siphoning keeps the water moving water through that jacket and hopefully avoids boiling.

The only thing I don't see specified is a pressure-release valve - if it were built exactly as drawn, if the water ever did reach boiling, it would have to vent through the shower as super-heated steam!

Good job Nick, I imagine you've got a couple of pressure-relief solutions tucked around back where they can't be seen in the drawing.

-Erica Wisner
http://www.ErnieAndErica.info

Dead right Erica. 

It' got a pressure release valve at the top of the storage tank (where any steam should collect) and also a tempering valve on the hat water outlet of the storage tank.

We should be showing it on the diagram too

Just letting you know the link for the rocket stove article on our blog changed

http://milkwood.net/2009/07/12/the_rocket_powered_shower/

Milkwood Nick wrote:
Just letting you know the link for the rocket stove article on our blog changed

http://milkwood.net/2009/07/12/the_rocket_powered_shower/

Thanks for the update.  I followed the old link again today, and nosed around a while - the rocket shower is not easy to find from the menus, but lots of other interesting things are.  I have to compliment you on the gorgeous pictures you have on the rest of the site. 

The rocket shower, by contrast, is a more purely functional article, with clear but messy drawings and construction pictures.  Maybe you should lead off with the steamy bloke and the burning sticks.

       I found this site when I was studying stoves that use the principles that Paul Wheaton talks of when he talks of rocket stoves.but I came to rocket heaters from a different direction than Paul Wheaton’s.

       The hobo stove has a different design than the rocket stove but there are many version of the rocket stove that are not mass heaters and are made with old tins suitable for quick construction with no money, such as for the homeless and that appear among hobo campers tin can stoves, the hobo stvoes and the wood gassifiers.
           These stoves that produce little smoke and dont leave ash on the ground, ash  can be kept in the can til you can put it in a waste papre bin, mean that the homeless can cook withless likelyhood of getting into trouble for building fires, the homeless are usually pretty closely whatched by the police.  You can see plenty of these rocket stoves that are rocket stoves but not mass heater ones on you tube. Rocket without being mass heaters, which  is to say with the rocket desing tha tmeans a strong draft to whip up the fire but the rocket effect in this case is used to cook on, using  the heat at the end of the combustion chamber. This means making use of the efficiency of the system  to allow them to cook with a very small amount of wood, rather than using the system to heat a mass of masonary, be it clay or brick or rock that later heats a house.  When i say made with tins i mean those that your peaches or Campbells soup arrive in.

        One of the main reasons for mass heaters is that the quick burn of the wood that is the result of the efficent combustion methods of rocket stoves, the good draft of air and the enclosed spaces beyond th efire box that keep the smoke hot enough for it to burn, is the use of masonary to store that heat so that though  the burn is too quick to keep you hot for a long time the heat is stored in the clay stone or brick tha tsurround th eflues and chambers of secondary commbustion and the thermal mass lets out the heart bit by bit later so it keeps the house hot for a long time, some say even a whole week end.  One owner of a masonary stove says that he lights it up for the weekend and then gets by for the rest of the week on the stored heat, things getting a bit chilly towards the next weekend. agri rose macaskie.

   

just a note that our rocket water heater is still rocking it, 2.5 years on

http://milkwood.net/2011/08/03/our-rocket-stove-water-heater-2-5-years-on/

I've been thinking of a design similar to Nicks but using a pair of 40 gal gas water heaters for the heat exchangers. The gas heaters only have a 3" flue running through the middle, so I figured I would fabricate a manifold box to distribute the heat equally between the two. That would give me 14 sq. in. flue area and 60" of height for heat exchange. Of course, this will require a stout stand to support the 700 lbs. of water and tank. Whatcha think?

     Here's a super low tech way to heat your bath water. A cast iron tub embedded deeply into a wide portion of a cob bench would absorb heat from the surrounding material. Water could be added to the tub after each use to allow time for it to heat again. When it's time to use the tub test the water. If it's too cold, run a quick fire and heat some water on top of the riser. If it's too hot add some cold and have a deeper bath. Clawfoot tubs which are missing their feet are readily available and have very little market value. The drain of the tub should not be cobbed over. This setup would be more suited to an en suite spa situation than it would to a living room by the picture window arrangement.

    The tub and any water it contains adds to your thermal mass. By leaving the tub uncovered you have a humidifier or cover it to prevent excess moisture from entering the air. Extremely long soaks could be had without the normal problem of the tub cooling off since it is well insulated and being heated from below and from the sides.