I had no idea these were actually made in significant numbers.
>even a modern woodmobile requires up to 10 minutes to get up to working temperature
That was my first question, and I can't imagine it would be great to have a parking garage of these things warming up / outputting gasses for 10 min each.
You don't run these inside enclosed spaces, because the carbon monoxide would kill you.
It's nowhere near as convenient as gasoline--there's plenty of minding and care required--but during hard times it's much more efficient and convenient than hauling a truck load of stuff by horseback, or walking. A wood gas spark engine runs much more efficiently than an equivalent steam engine, for example.
The difference back then is everything was carbureted and switching over to wood gas was relatively simple. With today's extremely complex fuel injected vehicles it will be a whole different story.
Converting the wood to charcoal before use has been found to be the most reliable method of burning wood by most users, with lowest contamination/fouling risk, although the owner of the http://www.driveonwood.com forum (a guy from Springville, Alabama) runs his truck on straight hardwood and has put many miles on it like that.
When in good tune, a full size pickup truck will go about a mile per pound of wood.