[Stoves] Heat / cook stove - proposed design

[Darren]

Hello Stovers,

Finally got the stove finished enough to test fire it on Thursday.

I ran it for an hour and a half.

Things I noticed.

I put some  5cm x 5cm lumps of wood, then some smaller pieces then some 
paper in the combustion chamber side of the stove and top lit.  This 
worked well and there was little smoke.

I threw some more 5cm x 5cm lumps into the fuel hopper.

Through the window I could see that once the wood in the combustion 
chamber burnt away the flames died right back down.   I opened the 
hopper up - it was full of smoke.  I closed it again, leaving it open a 
crack and blocking the primary air inlet at the bottom of the stove, 
which allowed the smoke to get sucked from the hopper, it also 
reinvigorated the fire.  I tried pushing the wood through under the 
bridge so that some was further down the grate. This was difficult as 
these pieces of wood would readily jam together blocking the throat 
(space under the ceramic bridge).

Once wood/embers were pushed through under the bridge the fire would 
again burn vigorously.

I chopped some smaller pieces of wood but found that I still had to push 
them through under the bridge to get the fire burning with more than a 
few licks of flames.  This was not easy to do.

When wood and embers were across most of the grate the whole combustion 
chamber would be full of flames that would disappear into the heat 
exchanger.

Other points to note.  I tried covering/uncovering the secondary air 
inlets at different times which had a limited effect on the fire.  I 
could see the flames being blown away from the main secondary air inlet 
at times.

My attempt to have secondary air wash the glass apparently did not work 
well.  I guess this may be due to the poor combustion at times - there 
was noticeable amounts of smoke from the chimney at times.  I may 
attempt to fit some further piping/jetting to send the air more directly 
at the glass.  Wood ash and a little water does clean the glass quite well.

The ash draw was not sealing well.  The front of the stove is not flat 
(much of the stove is not flat or square - the scrap metal I used was 
not all flat and not enough care was taken during the construction of 
the stove).  I set the ash draw so that the gap was under the hopper 
rather than the combustion chamber.

I managed to bend the front of the ash draw today with a hydraulic press 
so that it now has a reasonable fit against the fire rope/tape that is 
stuck to the front of the stove.

I guessed that the reason the fire was dying back when the combustion 
chamber part of the grate was empty was due to excessive primary air 
passing up through the uncovered (by embers and wood) grate and cooling 
the combustion chamber burn. (I'm now not entirely sure that this was 
what was happening)

Yesterday and today I did some more work to try and remedy this...

I made the hopper slope in from 3 sides onto the grate, rather than just 
one, to direct the wood onto the grate and to give less places for the 
wood to jam.

I made another grate out of 10mm bar that sits on top of the original 
grate and can be moved backwards and forwards with a handle.

I did this in the hope that moving the grate will encourage wood under 
the bridge and across the grate.

Since doing this I noticed that Crispin said that the grate would not be 
completely covered.

Still the moving grate gives more variables to play with.  I can also 
easily lift it higher.

I moved the stove today from my workshop (which is 50 miles away from 
where I now live)

When loading it into my truck I took the doors off.

Despite twice noting that I had done so and telling myself not to forget 
I unfortunately left the combustion chamber door sat on the bed of the 
truck and it slid off the truck as I was driving!!!! Luckily I heard the 
glass break and realised what had happened and went back to get the door.

I've still got to make the choke for the stack pipe and the air 
regulators for the secondary air inlets.  Also got to order some new 
glass for the door and burn the paint from the outside of the stove (I 
made it from scrap plate that was painted) so that I do not poison 
myself when I fit it in my home.

Hopefully I'll get a chance to do some more test fires later in the 
week.  I may temporarily fit some plate metal where the glass should be 
while I await a new piece, although the window has been very useful for 
assessing what is happening.

Best

Darren
-------------- next part --------------
A non-text attachment was scrubbed...
Name: stove-test1.jpg
Type: image/jpeg
Size: 279698 bytes
Desc: not available
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20120109/56f38d0b/attachment.jpg>