TomH, you must have missed this topic:
Directly to the point. We use engines to do job specific work.
Existing in thousands, hundreds of thousands, millions of get work done machines come with an existing internal combustion piston engine already.
Woodgas fueling these is the most direct way to put the work machines back to working.
External combustion systems are museum pieces. Or would need a whole supporting system re-created. Jay Leno’s Garage. His stationary historic external combustion engines get their steam from a very expensive; code enginnered, code certified, bought and built steam generator.
S.U.