Clarke glass-door box stove to rocket stove

Hi, folks.
Over the last two winters, I have adapted a budget box stove garage heater (380 mm wide x 260 deep x 475 high) to a rocket design, with bulk-feeding and an internal riser tube. The idea was to keep the glass door so that the fire remains visible, use the box stove to contain an insulated feed chamber/pre-heater, and put the riser up through the existing top exit, avoiding serious re-working of the Clarke's box stove outline.


I have a 2MB word file with sketches, schematics of early developments, and photos, and a 25MB video of the system working, with a 3-D schematic at the end. Unfortunately, I'm not sure whether I can load them, or how to do it (I have never uploaded videos to YouTube, for instance). Any ideas?

yes contact me and send them via email if you want to do

and im also interested in your build as most clarke stuff is uk based

The intended design features of the stove are:

  minimal modification to the Clarke box stove, in case it needed to be converted back, or sold
  provide batch burning capability
  initially steel tunnel and riser, but well insulated to give a high temperature burn (a cast riser is definitely an option for a later version)
  swirl throat to riser, inducing a flame vortex
  pre-heated secondary air introduced into the riser above the tunnel entrance
  retain the glass door, for aesthetics, air control, and garage fire safety
  cooking plate for kettle, ‘man-cave' roasts, etc


By removing the cast flue holder from the top centre of the Clarke stove, the central steel tunnel/riser assembly can be inserted or withdrawn into the box stove for modifications/rebuilds, etc.  Sealing is by collar, fire rope, and sand.

Since the 2016 design,

I have lined the area in front of the (very short) tunnel with fire board, and created a firebox capable of taking small logs (works well when everything is up to temperature).

Behind the riser ‘wings’ the stove is filled with vermiculite.

The heat exchanger lid can be a round or square 3mm plate - the round one has a viewing hole with removable glass, for observing the vortex, and tweaking airflows during development.


I think that was also your post on a stove for a small wooden boat?  I have made a fairly conventional glass-door stove for my small bilge-keeled Westerly sail cruiser.  I am planning a removable stainless rocket stove to hang above the stove below a permanent flue.  I like the idea of a simple L- or V-shaped manual feed arrangement to get plenty of heat when you want it, and no coals or carbon monoxide when I go to sleep alongside it.





https://www.dailymotion.com/video/x67stwj

Thats an interesting design basis for a rocket stove change from a standared unit built for another purpose

Twin vortex cast combustion chamber in a box stove body

Hi again, folks.  A couple of years ago I posted mods to a simple Clarkes glass-front door box stove to convert it to a rocket mass heater with a cooking surface.  While designing it, I had been following PPotty's experience with steel risers (shown in his YouTube videos) and later cast refractory cement solution, but had stayed with welded steel construction, as development modifications were easier to make.

Sure enough, the 90 mm diameter 6 mm thick mild steel riser burned through after 2 years, as anticipated.  The hole and riser tube warping developed where the tongue of the vortex flame was hitting the riser tube (in the photo, the fuel feed is to the right, with the flame spiraling anticlockwise in the riser tube, which had been insulated with loose vermiculite chips).  I read somewhere that the theoretical wood flame temperature, assuming initial atmospheric conditions (1 bar and 20 °C) is 1980 °C.  It must have been well on the way to this figure in the riser tube - testimony to the rocket stove design and combustion performance.


For the rebuild, I decided to use a cast riser with the same refractory mix (2/3), 1/3 perlite (same mix used by PPotty).  To keep the fuel feed within the box stove and heat it to gasification temperatures, I designed a twin feed to the riser, keeping the tunnel path lengths, widths and heights the same on each side.  This was not difficult to achieve with a cast design:


For the mould, I routed the shape into a thick ply base, and used low density plastic sheet and an air hot gun to form the shapes, which easily slotted into the base.  Twin wall pipe, slit at the bottom, small pieces of cardboard, and a lot of packing tape completed the mould.  


Pouring and packing was easy, and the finish was smooth for the important bits (internal combustion passages and flue) where I was able to pack and vibrate the mix firmly into the mould; being careful at the same time to avoid crushing the perlite beads.




The height of the casting, from floor to steel pipe, was around 225 mm - the height at which the old pipe had remained intact.  This is a similar arrangement to Ppotty's Feb 2018 new build combustion chamber and riser (see YouTube video for details)



The new arrangement is up and running, with around 10 burns having taken place in the last 2 months.  It is drawing well, and the twin vortex is mixing the flue gases very effectively (the flames in the photo are at start-up, and show gas flow more clearly than further into the burn.  The refractory core glows red at full bore, and the steel pipe can be warmed to a dull red colour, though this amount of heat output isn’t required at present.  



If this helps rocket stove builders based in the UK - I ordered 1,700 degree refractory cement from Castletree Kilns, St Clears, Carmarthenshire.  It worked out at £32.40 for a 25 kg bag, including P+P and VAT.  I used around 12 kg for this build.

Ppotty - when I’m next in Liverpool, it would be great to meet and compare rocket stove mass heater combustion chamber designs and tweaking.  I’m also running and frequently modifying portable rocket cookstoves and water heaters, and could bring a few of these along to generate a some more ideas.