Easy build penny stove (the potstand)

The penny stove needed a potstand/windbreak, the improvised wooden one would not do, so I fashioned a simple one from some sheet aluminium I had in my workshop. The design is so simple that I didn't draw it out first. Its simply a rectangle bent in a curve with three prongs to support the pot. It is open at the front to allow access.

Before filling with fuel

I have drawn the potstand in Solid Edge 2D. Please note the shallow triangular cut-outs on the base which perform two functions.

1. Three points of contact with the ground act as a tripod, and are more stable on uneven surfaces.

2. They allow airflow to aid combustion.

The design could be refined with some tabs for the feet at the bottom and by drilling some additional vent holes, but in keeping with the 'easy build' nature of my penny stove I wanted something simple and easy to cut.

The material was 1.5mm aluminium sheet and I cut it with straight tin snips.

Priming

Boiling water

The potstand is quite stable and will prevent soot marking my cookware. I also noticed that it was quite difficult to blow out, so it should be quite wind resistant.


Here is the stove and potstand operating at full boil.

I hope you enjoyed my short trip into the world of penny stoves.

Easy build penny stove (part two: using the stove)

This is part two of a two part post. I am assuming you have read part one.

100ml of fuel on the left, the stove and the bottle of fuel that I purchase from a local DIY store.

For fuel I use methylated spirits, specifically formulated for camping stoves. It burns at the correct temperature, burns cleanly and is easy to obtain. I have previously tried many other spirit based fuels and rejected all of them. This is the correct stuff!

The 500ml bottle retails for around £6. I don't carry this large bottle, I carry either a 50ml bottle or a 100ml bottle of fuel. I get four refills from the 100ml bottle. Each refill will boil approx 500ml of water from almost freezing.

To use the stove, I first fill it so that the fuel does not come above the large pressure vent hole. When the fuel is just below the vent hole the stove is full.

Next I put a penny over the vent hole.

Then I fill up the dish above the vent hole to the top with fuel.

This is then lit, the heat of it burning off will vaporise the fuel inside the stove turning it to a gas jet that will be ignited. If you listen carefully during priming you can hear the alcohol starting to vaporise. I had to prime this stove twice, because it was so cold. I should have also put the stove in a dish to catch the overspill.

I have been asked by a friend from T&TTT to explain the priming process again:

Here is how I primed my stove:

1. I filled the cold stove with fuel making sure it did not fill above the pressure vent hole.

2. I put the penny over the hole.

3. I filled the dimple up to the rim with fuel.

4. I lit the fuel in the dimple.

As the fuel in the dimple burns (for about two minutes), it heats the fuel below it in the stove turning it into a gas that will eventually come out through the burner holes and ignite.

I have on occasion had to repeat steps 3. and 4. one or two times, checking carefully each time that there was no flame coming from the stove before refilling the dimple. I do not need to do anything to or with the penny.

When it catches it is obvious and is often preceded by gaseous hissing noises. (From the stove not me!)

This very short video show the process at step 3.

I should have put the stove in a dish or lid to catch the overspill. :-/

So with the stove going I decided to see just how fast it would boil 250ml of water that is just above freezing. Today the temperature is hovering around freezing point. This is a good test of the stove operating in extreme conditions (for leisure camping).

Poorly improvised pot stand :(

Unfortunately I forgot to arrange for a potstand, so I improvised with some wood, which covered my cup in soot!

However only four minutes later my water starts to boil...

You can really hear it roar like a jet in the video. Within 30 seconds of taking this video I had a rolling boil.

A nice rolling boil, time for tea.

After extinguishing the flame and allowing the stove to cool, I noticed that I had use around half of the fuel.

That's it, thanks for reading.

p.s. I have now made a potstand from aluminium sheet.

Easy build penny stove (part one: building)

Following a discussion with my sister where we were bemoaning the power outages in a Scottish Highland Winter, I decided to make her one of these penny stoves as she has no alternative energy source to electricity, and could not make a cup of warming tea or even fill a hot water bottle.

At a rolling boil

Penny stoves or Pressurised Jet Alcohol Stoves to give them their proper name are easy to make and very efficient in operation. i.e. You can heat a lot of stuff with very little fuel. They work by heat from a flame causing alcohol fuel to expand in a pressure vessel (the stove). That pressurised fuel escapes through holes and ignites, keeping the flame (and the whole cycle) going.

I generally have one of these in my camping kit as a backup stove. They are small and light and very practical.

Right now my lawyer (Mister Lionel Hutz, AKA Miguel Sánchez, AKA Dr. Nguyen Van Falk) will want me to say do not try this at home. Building and using the stove involves some risk(s). Some of those risks are obvious, such as sharp edges, burny flames, others less so like carbon monoxide poisoning, death, etc,.

There are several versions of penny stoves out there already however, I have my own method (explained below) that takes some of the difficulty out of the process which may be of academic interest to stove heads and ultralight backpackers.

The components and tools

1. Two aluminium drinks cans (one FULL, one empty). These will become the stove body.
2. One penny coin. This will become the essential safety valve.
3. Two drills (one 1.5mm the other 6mm), and a hand drill.
4. An ink marker for marking on the cans.
5. Household scissors for cutting the cans.
6. Very fine sandpaper for buffing the paint off the cans. (optional)

Note there is no ruler, everything was 'eyeballed'. The cans must be identical to ensure a good fit.

Marking a parallel line approx 40mm (1 1/2 inches) on the empty can.

After marking a line parallel to the workbench I cut the can with scissors. It cuts very easily as the can is extremely thin, and it was important for me to cut a perfectly parallel line as this will be the edge that my stove sits on. This is the first difference in my technique, I cut with scissors and not a craft knife. It is way easier.

A nice clean cut

Next I drilled out the pressure vent hole using first the smaller drill followed by the larger drill.

I could have used a power drill/driver, but a hand drill is up to this job.

I had to drill the pressure vent hole before this next step where I press the full can (bottom first) into the cut can. If you don't drill this hole first, trapped air will prevent you from pushing the cans together permanently and both halves will soon part company.

Gently pressed to fit

I pressed the bottom of the full can into the cut can approximately 12mm (1/2 inch). This is another difference from the 'usual technique'. Usually you cut the bottom off two cans and press them together, cut edge to cut edge.

Keeping the can full means that it has enough rigidity to stand this process and it stretches the cut can by acting as a form to make a good enough seal without glue. No need for slits or shims if you are not trying to press one cut can into another cut can and the added bonus of less chance of cut fingers.

I then emptied the full can, drank it (mmmm, burp!) and cut it down to the edge with the scissors.

Both cans cut and pressed together, bashed can quality control failure!

Then I marked out the burner and drilled out the jet burner holes with the smaller drill.

Look carefully to see the marks

After a short time the drilling is finished and the stove is essentially complete. It is a good idea to buff off the paint with some fine sandpaper.

Note that the drilling does not have to be precise

The total build time was lest than 10 minutes.

"WTF is Irn Bru anyway?"

Irn Bru is Scotland's "Other national drink" after whisky of course! It has been used for decades as a traditional folk remedy if you drank too much whisky on the night before. It tastes of raw magic, and is made to a ancient druidic recipe, that is still kept secret by the Barr family who make the draught in nearby Cumbernauld.

Continue to part two