Build a rocket stove

Introduction

The internet is full of various designs of rocket stoves, from the simplest and smallest utilising a coffee can, to large sophisticated heating units for a living area.

We have dabbled with the rocket stove before.

Rocket Stove – the first attempt

The idea to provide the CradleArk community with a quick, efficient, reliable heating source. The biggest drawcard the ability to quickly heat using very little material. Version one was fine for the odd weekend camper but did not meet their requirements on a day to day basis. The rocket stove did use a little fuel but the size of the burn chamber meant that it had to be continually topped up with fuel. Easier to go back to a traditional fire? We doubled the burn chamber but following the initial excitement the test rocket stove was stored and stopped featuring in the daily usage. Rocket stove upgrade -part one

The original idea for the Rocket stove made with available scrap
Version 2 Rocket stove still with a split air/wood intake and a doubled burn chamber

Rocket stove upgrade-part two

Bigger brother Rocket stove Version 3 with a few bells and whistles

A bigger burn chamber

I had a suitable scrapped gas bottle which was relatively thick steel plus 76mm square tubing off cuts. I had some 50mm steel pipe, some off cut expanded metal and some 20mm flat bar. By adding a couple of latches , some heavier flat bar and a 5mm steel plate, I now had enough material to tackle the build. Just the time factor was always lacking.

Cutting the gas bottle

Not wanting to feature in the Darwin awards and to meet my Lord earlier than absolutely necessary, I opened the gas bottle and filled it with water. (A slow process using a small funnel but very necessary for peace of mind) I left it for a couple of weeks, topped it up and then summonsed all my courage, to tackle it with the angle grinder.

Cutting the scrapped water filled gas cylinder along the centre seama
Rocket stove basis: a scrapped water filled gas cylinder cut at central seam

I wanted to be able to access the burn chamber for making the initial fire cleaning and easily adding an expanded metal burn platform. This meant cutting it in half horizontally

More cutting

Once this was done without incident, I then used a 50mm hole saw to make a hole for the air inlet pipe.

To show how the chimney slot removed the brass fittings and rusted handle
Initial cutting of gas cylinder completed for rocket stove

I drilled this to allow the air to be directed to the fire and welded it in place. I then welded small brackets into the bottom half of the bottle to support the grid.

Grid support and air intake pipe in Rocket stove

The grid was made with a ring roller just undersize of the gas bottle.

Latches, food and grill in place in Rocket Stove

An inlet for the wood chute (made of two joined 76mm square tubes) was then cut in the top half and a spot for a vertical chimney.

As I was impatient and wanted to get it running asap, I added a foot and the pressure latches to hold it together. A quick test burn saw it functioning nicely.

Rocket stove in action with fire visible as flap open

The purpose of this prototype was to heat a kettle for tea and coffee at the church services. I thus needed a stable flat top for the kettle to rest on and this was fashioned using some small angle offcuts and flatbar.

The flat top for the Rocket stove with airflow to the side but no holes in the plate

I decided not to drill through the plate to minimise cleaning of the base of the kettle.

As I had a plough shear that was donated I added handles and a fitting so it could be used for frying food or as a large wok?

Skottel (Plough shear) in the making for the Rocket Stove

Some modifications

I removed the drilled pipe and replaced it with 76mm tubing to allow greater airflow.

Old air intake removed from lower half of Rocket stove
Bigger air intake fitted to Rocket stove

I also added a flap to the opening of the wood chute with handle. I then added a carrying handle which consisted of square bar plus a recycled trampoline spring as the grip.

The final stage was to grind off the ugly welds and excess paint that had not blistered off completely and then to paint it with a heat resistant paint.

I would say the rocket stove prototype no 2 is ready for testing on a daily use basis.

The “final” Rocket stove. What about insulation?

A further improvement would involve insulating the burn chamber and chimney and this will probably happen at a future stage when a suitable steel drum is found. This will add to the weight and portability of the stove so may there may be a trade off?

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