[Stoves] Heat / cook stove - proposed design

[Darren]

On 20/10/12 02:35, Crispin Pemberton-Pigott wrote:
> Dear Darren
>
> Good to hear your project lives. Are you really going to stack the fuel across like that? It should work really well if the orientation can be maintained.
>
I have had a chance to try this now.

I cut lots of ash (fraxinus excelsior) branches into approx 9cm long 
sticks, up to about 3cm diameter, and stacked them up in the hopper -  I 
cut the branches from a tree about a month ago and they have been 
sitting in the woods since then.

I decided to use ash as it has a low water content and can be burnt when 
freshly cut, although much better when properly seasoned.

In the combustion chamber I stacked up some well seasoned and dry pine 
getting progressively smaller and topped off with some newspaper which 
was soaked in some vegetable oil I spilt the day before (I dumped my 
heavy mechanics tool bag on a full 1 litre bottle of rapeseed oil - 
which emptied instantly all over the floor of my truck. I use it to 
lubricate the chain on my chainsaw)

I lit the paper and watched... as the pine burnt away the fire started 
to die.  As the ash had been out in the rain I decided to throw more 
pine into the combustion chamber to heat things up/dry things out a bit 
more.   I had to do this a lot of times before I could see down in the 
hopper that the fire had spread onto that side of the grate.

After I noticed this I fell asleep on my sofa, so warm and cosy....

When I woke it was cold.... I looked in the hopper and all the sticks 
were gone :)

The next two nights I tried again but the fire would not really spread 
through into the bottom of the hopper, despite last night adding some 
lengths of split pine mixed in with the ash sticks at the bottom of the 
hopper.  One night it was getting there but didn't appear to quite catch.

Tonight I built a fire with longer pine pieces stacked the same way as 
the bars of the grate.

On top of that I added some cut willow sticks that had been hanging dead 
in the woods for 2 years, mixed with some split pine  Then on top some 
of the ash sticks

All burnt well.  I refuelled with ash and this all burnt as well.

To make the hopper thinner I placed a few engineering bricks to either 
side of the grate, not ideal as there are big gaps which could 
potentially induce the sticks to twist and stick rather than feed in a 
fairly orderly fashion (I have yet to fill the hopper right to the top, 
although I did have quite a load in there at one point).  The sticks do 
appear to feed reasonably well.

Interestingly only tonight did I see the hopper fill with smoke, but the 
smoke was not as thick as when I was running pine squares or ash 
woodchip at the beginning of the year .  Other nights it was completely 
clear of smoke.

I'm thinking that the water content of the freshly cut sticks is a bit 
high until the heat has really built up in the stove.

A picture of after the first night.  A few sticks didn't burn as they 
stacked up on the hopper slope, rather than sliding down onto the grate 
and into the fire (this was repeated with the burn tonight)


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