However, in speaking to my neighbour again this afternoon, he said that,
in his experience, full length - 1 metre or so - logs were inserted in
the gazogènes, the length depending upon the height of the gazogène
; a practice in line with that mentioned by "renertec" in respect of stationary
equipment. Maybe the design of gasifier had something to do with
it? Imbert gasifiers were the most common, and the most highly thought
of (according to my book on Imbert gasifiers) but they were not the only
ones. My neighbour has no idea of the internal construction
of those he saw. But he mentioned again that it was said in those
times that "beech produces the best gas".
I realize now that the moisture in wood cannot produce water-gas (H2
+ CO) in an updraught gasifier, since the evaporating water will be carried
away from the hot coals, and not through them. Imbert appears to
have taken out a patent on a downdraught gasifier in 1933 - French patent
#765369 - so it is not clear to me why his firm continued making updraught
gasifiers.
By the way, I see from the book "Le gazogène à bois Imbert"
that in Sweden in the early forties there were several hundred motorcycles
fitted with gazogènes. There are photographs of them.
Am still trying to contact the person whose family (name: Chevet) built
gazogènes.
> The logs were approximately 10 to 15 cm (4" to
6") in diameter and from 1
> metre to 1 metre 80 (3' to 6') long. The gasifiers were very
tall,
> making possible insertion of long logs, and usually mounted just
behind
> the cab.
But this was not plain Imbert gasifiers? The form of the fuel
vessel
allows sticking small logs in it, but I can't imagine the regular Imbert
hearth operate properly with logs. A V-hearth would be even worse I
should
think.
Later during the war, around 1944 or so, they begun modifying the Imbert
gasifiers by turning the upper half of the outer mantle into a condenser.
(Actually, this was invented earlier, but for some obscure reason,
ignorance perhaps, or patents? it wasn't put to practise in the early
40's.)
Now, if we stick a metre long log into such a gasifier, the log will
be
heated from the lower end, near the hearth, and release water and steam
by
the upper end, near the condenser. Why then the gasifier burns sticks
in
roughly the same way as when I put green sticks on a camp fire then.
;)
And just like the man says, the fire on a dry log would perhaps spread
across the length of it too fast, while on a damper log the oxidation
zone
would stay by the nozzles.
I've never heard of small vehicle gasifiers running on logs before.
It
could be something worth developing further. It could also be that
they got
better operation with green logs than dry ones, when using logs, but
would
have gotten even better operation with regular block wood. Slicing
up logs
to block wood is a lot of work though, particulary if electric circular
saws aren't available (or too expensive to use). Maybe they were
too shorthanded to have block wood as an option in the fuel economy.
I'm
sure they must have been aware of that block wood was used elsewehere.
This doesn't explain why `my reference' suggested green birch though.
I
tested it, and the gasifier runs on it, but poorly. The fuel consumption
goes up significantly (about doubles), and I can't put too much load
on the
gasifier or I get problems (fuel hangs, poor gas -- have to stop and
let it
rest with the lid open and charify for a while). Green fir is worse
though.
I think that must be the worst possible gasifier fuel there is. But
one of
these days...
A friend of mine, another gasifier tinkerer, told me some time ago he
had
had a weird dream were I and him were firing up a gasifier we had designed
that ran on full length logs (whole tree sticking out - hilarious).
In the
dream, it had some sort of turbine whizzing down the hearth. He thought
that was a big laugh. ;) Wait till he hears of this.
