Help with penny stove

Posted by: Budric

Help with penny stove - 08/03/09 05:53 PM

Hi,
I've tried making the penny stove as described:
http://www.csun.edu/~mjurey/penny.html

I'm not getting anywhere near the performance described. I haven't even got to boil any water, not to mention simmer it for any length of time. For example >30ml of alcohol, I get burn time of about 6 minutes (the site has results of 6 min for 20 ml). And have yet to boil any water (tried 500 ml and 1 L with 30mL fuel and 60 mL fuel respectively). The pot is about 1.5" above the stove. The support is a round sheet of aluminum that acts as a wind screen with some vents to let air in. I'm using methyl hydrate as fuel.

So what am I doing wrong? Anyone with experience like this when you made your alcohol stove? What are the common mistakes?
Posted by: phat

Re: Help with penny stove - 08/03/09 09:02 PM

Your pot support sounds like it's very constraining to the airflow, which might make it not work as advertised.

I get approximately what is claimed on the site with penny stoves made about like he says. I use a small pot stand made of coat hanger wire, two "U"'s with one set of uprights wired together. I then use aluminum flashing or an msr windscreen around the pot, but the pot support might be what is causing you grief.

Here's my setup in action:


You can see how my windscreen is not the pot support. That morning is below freezing (you can see the frost) and it boiled up 3 cups of water on about 3/4 of an oz of alcohol or so. If you look carefully you can see that's a canadian penny smile




I think my pot is about 2cm (slightly less than an inch) above the stove:



Posted by: Budric

Re: Help with penny stove - 08/03/09 09:54 PM

Thanks for the response and your pictures.

Well I can put more holes on one side of the wind screen to allow for more air. However I think reduced air would just put the fire out not make it less efficient? The pot height from flame and pot material may be impeding the heat transfer/boiling, but at the end it's just not burning as long as the site says.

One thing I do notice is the simmer ring doesn't burn like in the picture: http://www.csun.edu/~mjurey/jpgs/simmerburn.jpg
It's just a huge flame coming from the center (not 6 distinct smaller flames. Perhaps too much vapor is coming out? Maybe if I can seal around the can somehow...

P.S. Where did you get such thick coat hangers? I've been trying to find some sort of aluminum rods, but so far no luck.
Posted by: phat

Re: Help with penny stove - 08/03/09 10:42 PM


The coat hangers are just regular wire ones from the dry cleaners..

I don't seal around my cans.

simmer ring burn for me doesn't look like the picture either, more of a sterno can thing.

Try the stove without your pot stand. make sure you made the right size holes in the stove.

Posted by: thecook

Re: Help with penny stove - 08/05/09 10:47 PM

One possibility not mentioned is that the stove may be running too hot in a confined space. Alcohol stoves work on burning the vapor. If you heat the alcohol you get more vapor. If you heat it too much, you boil the alcohol and can get run away in which you burn off your fuel too fast and never get a boil with your water. The Trangia is known as a 'stormcooker' because the higher the windspeed, the faster the stove cooks. It has been finely engineered, however, to prevent run away, by decoupling the stove from the support and the pot.
Posted by: ohiohiker

Re: Help with penny stove - 08/20/09 12:56 PM

What are the pot dimensions and metal?

What is the stove sitting on?

Are you using ice water??? grin

Ethanol is probably the best fuel which doesn't produce soot (based on BTU's listed on the penny stove site). The denatured stuff from the paint section is cheap.