Wood gas?
 

Has anyone built a wood gas system? :turtle:

I've been toying with powering a small tractor with a FEMA-type wood gasifier (with a cyclone and a filter system for the tar)

What did you want to power with it?
Something like a wood stove or boiler or something like a piston engine?

a small piston engine.

That the same idea as the coal-gas engine conversions the brits did back in the war or whenever it was?

not only brits, a lot of countries had wood gas at the time of the war.

the engine would be a 10-something hp engine.

One thing I do remember is people saying that wood gas roughly cuts the engines power output in half.

exactly. That's why I need a 10-something hp engine.

The gearing will be super-low though, as the top speed only needs to be about 9Mph. It will pull a small trailer :)

but I can't make my mind if should build a updraft or a downdraft (or a sidedraft) gasifier. The fuel is going to be very inconsistent in quality and size.

The gasifier system also needs to be small in size.

Well, there's a problem. https://www.google.com/search?q=wood+gas+ca Looking at the Images of presumably successful installations, compactness is not apparent. Most successful seems to be VW, with a 'power bulge' on the hood and the filters underneath the floor.

And if the fuel is 'inconsistent in quality and size' you could add a chipper/shredder render it consistent.