The Dolgorouki Rotary Steam Engine

New page: 15 July 2008
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Dolgorouki Engine pic from Nature
Left: The Dolgorouki Engine.

According to Nature, this machine was exhibited at the Exposition Internationale d'Electricité, in both the Russian and the German sections; in the latter it was on the stand of the Siemens & Halske company, where it was running a direct-current dynamo. The example on display was destined for the Lichterfelde railway, (a suburban line of Berlin) and I would speculate that it was to be used for lighting generation on steam locomotives, like the Tower Spherical engine.

It had two pairs of semi-cylindrical rotors, synchronised by gearing which appears to have resided in the middle part of the casing. It was noted that it had no dead-centre points. There is a centrifugal governor in the steanm inlet pipe at top left. The lever on the front also controls motor speed; the technical French is a little hard to decode but it is now clear that it was a throttle, not a cut-off control. The cut-off was fixed.

The position of the steam exhaust is not clear, but it appears to have been the blanked-off flange just behind the inlet pipe.

Image & info from the French journal Nature 1882/1

So who was Dolgorouki? There was an aristocratic Russian family of that name; for example, a Princess Dolgorouki married Czar Alexander II. Whether that is relevant is unclear at present...

Pictures of real rotary engines that are still in existence are unfortunately very rare. I am therefore very glad to report that I have just discovered a Dolgorouki Engine in the Vienna Technological Museum.

Dolgorouki Engine photo
Left: Dolgorouki Engine at Vienna.

This engine-dynamo combination was put together by Siemens & Halske in 1883. The dynamo ouput was 20 Amps (at an unknown voltage) and was said to be capable of running two to three lamps. That doesn't sound like many- possibly they were powerful arc-lamps, and the engine-dynamo set was for lighting marshalling yards and so on, rather than providing lighting on trains.

There is a flywheel, and quite a substantial one. Obviously constant torque was not one of the Dolgorouki's best features. According to the description in front of the baseplate, the engine was supplied with steam at 58 to 72 psi and gave 5 to 6 horsepower at 900 to 1000 rpm. This is a much faster speed than a reciprocating engine would run at, and much better suited for direct coupling to a generator.

The engine casing is about 14 inches long. Possibly the control handle is on the other side- I couldn't get at that.

Author's photo July 2008

Dolgorouki Engine drawing
Left: Dolgorouki Engine at Vienna.

A drawing of the engine-dynamo combination.

Author's photo July 2008

Dolgorouki Engine drawing
Left: Dolgorouki Engine at Vienna.

A close-up (sadly of poor quality) of the engine cross-section, which gives some clue to the internal construction. It appears to be very similar to the Behrens engine of 1886, having two C-shaped rotors turning around fixed centres. The Behrens engine has the advantage that it avoids the usual rotary engine error of line-contacts between rotor and casing that make sealing virtually impossible, and it looks like the Dolgorouki also used one of the more promising engine geometries.

The control handle is at the left, on the inlet side of the engine. The exhaust duct is on the right, with a fitting for a drainage cock. (see photo below)

Author's photo July 2008

Dolgorouki Engine photo
Left: Dolgorouki Engine at Vienna.

A close-up of the left-hand end of the engine

Note the cups for lubricating oil. Clearly the Dolgorouki engine was not fitted with positive lubrication (unlike the Tower Spherical engine.) and so would have required constant attention to keep it lubricated. That rather argues against its use on a locomotive.

Author's photo July 2008

Dolgorouki Engine photo
Left: Dolgorouki Engine at Vienna.

A close-up of the side of the engine, showing what appears to be a drainage cock for releasing condensate from the exhaust duct on starting

Author's photo July 2008

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