"Harold and Susan Vordos" fired this volley
As I recall, they are relatively simple devices,
gasoline being the fuel.

"Relatively simple" goes way beyond the complexity of them.

They're a "doughnut" shaped burner/heater that goes in the bottom of the
can. There's a single baffle that seals off the gallery in the doughnut
between the downdraft tube and the chimney.

A drip of gas falls onto a grate in the down tube, burns, and shoots the
flame all the way around the doughnut to the chimney side, where the
updraft keeps the action going.

The ones I worked in 'Nam didn't have any moving parts except the spigot
valve to control the gas drip. This "new" one has a swing-out igniter
pot in the chimney designed to help establish the updraft.

We just threw a wad of burning paper down the chimney, dripped a little
gas in the down tube, and after about a minute of heating the chimney,
threw a match down on the gas. It turns out that's a LOT easier way to
start the beast than the documented method in the manual.

Yeah... no moving parts, all welded construction, plain old merchant
stock steel sheet metal so you could fix them in the field, no 'custom'
parts -- all stock pipe fittings, etc.

LLoyd