A Hot-Air Engine Powered Gramophone

Updated: 24 June 2021
New video added.
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This remarkable gramophone is powered by a hot-air engine instead of the usual clockwork. It was found at the National Gin Museum in Hasselt, Belgium. The link is that the engine is heated by burning alcohol, though not, I assume, gin. It was called "The Maestrofoon", and according to the label on the case, was made by Paillard in Switzerland, around 1915. It is amazing when a manufacturer's label remains in place on an antique item for over 100 years. Label printing today is done by digital printing machines but who knows if those labels will last 100 years!

Left: The Maestrofoon in all its glory.

The engine compartment has a hinged door to allow access to the burner, which is the boat-shaped brass object in the foreground. Fuel consumption was about one pint of methylated spirit per hour. The wick (missing its vapourising cap) is on the left and the filler on the right.

The black funnel to the left is not a tweeter. It is presumably something to do with cooling the cold part of the hot-air engine, or it may simply be an exhaust for burner fumes. Or both.

The cabinet is of polished oak.

You can now see and hear The Maestrofoon for yourself; Rene Rondeau has put a video on Youtube.
Go to www.youtube.com/user/ReneRondeau (external link) and select the "Antique Phonograph with Stirling Engine Hot Air Motor" video.

There is now another video available at www.dailymotion.com/bdeschabis which shows a great deal more about the internal construction and operation of these machines, and reveals that the the hot-air engine is of the gamma Stirling type.

Left: The engine-room of The Maestrofoon.

I have to say that it is not very clear to me what kind of hot-air engine this is. (there are several configurations) It is however quite certain that it is a hot-air engine.

Having said that, hot-air engines typically have two cylinders, and only one is visible. The vertical iron plates appear to have a cooling function, but what they are cooling is not clear. The red arrow points to the centrifugal speed governor.

Note the brass pillars that create an air gap in the casing, to let the heat escape from the engine compartment. There is a substantial flywheel visible just above the crank; this is 7 inches in diameter. Hot-air engines are not self-starting, so a tug on this was required to start it moving. The crankshaft had ball-bearings, and the drive train consisted of spur gears, then a belt driving the main turntable spindle. A friction-clutch operated by manipulating the central spindle of the turntable connected and disconnected the engine.

Left: The enigmatic funnel of the Maestrofoon.

The discoloured metal in the middle looks like the end of a cylinder which has clearly been heated at some time, and the burner flame is visible through the bottom of the funnel.

My research into hot-air engines is continuing. There's more to learn than you might think.

I have found a source of information which states that the hot air engines were made in Liège, Belgium, and were originally intended for driving shop window displays. This also states that the engine had 3.2mm bore and 3.1mm stroke, which is clearly wrong. A 3.2cm bore and 3.1cm stroke seems to be what was meant, but since hot-air engines tend to have two pistons, this is still not too helpful.

As I said above, the exact kind of hot-air engine used in the Maestrofoon is somewhat enigmatic, as hot-air engines usually have two cylinders, or two pistons working in one cylinder; either way there are two cranks, and it is pretty clear in the photo above that this engine only had one.
The classic Stirling hot air engine uses a displacer to move air from a heating zone to a cooling zone and back, and a power piston driven by the resulting expansion and contraction of the air. These are mechanically coupled so the power piston can drive the displacer.
However, it is possible to configure an engine so that the displacer moves by itself; this invention is usually credited to Ossian Ringbom. This may be what we have here, but it seems unlikely.

Left: Another Maestrofoon.

A lot of searching has revealed that there is at least one more of these devices around. This one was built by Paillard in 1910.

The air-gap for cooling betwen the top and sides is clearly visible.

The Swiss company of Paillard was established in 1814, and began by building musical boxes, before producing their first cylinder gramophone (the Échophone) in 1898. In 1904 they began building disc gramophones.
The Maestrofoon was first displayed at a fair in Liepzig in spring 1910. Several models were marketed, including the Benvenuto 206, the Polecute 205, and the Appolo 10. Production seems to have ceased in 1914, so they had a short run. These gramophones cost about £5:00, which was a great deal of money at the time and considerably more expensive than a clockwork version.

Bibliography: Hot Air, Caloric and Stirling Engines. R Sier.

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