e61brewski wrote:she has a gas stove, and this idea seems almost absurdly simple. why not rig some sort of machine that uses a stove burner for its heat instead of a dedicated element? the rest of the machine, roughly speaking, would need little modification.
but does such a thing exist?
Begin searching German, Italian, and French Ebay - Conti, Astoria, Wega, San Marco, and Rancilio all made single-group 'Gaz' (Butane in France, LNG elsewhere) powered lever machines which would work well for her.
Since there's no pump or electronics required for a lever machine, the only bit of design cleverness is the choice to use either a boiler pressure relief valve and allow the burner to operate without external control - or rig up a mechanical connection from a pressure-driven diaphragm or bellows that operates a gas-flow valve to regulate the flame.
I've seen both systems, the older Gaggias used this monster steel ball in a captured race to release the boiler pressure, while my two-group Futurema uses a nifty bell-crank and 1/4-turn valve to regulate the gas flow.
These machines do exist, some of the older Conti and Faema machines are works of Techno/Deco Art, and because of their limited appeal these days can be had quite cheaply.