Tuesday, March 17, 2009

The engine on the 'plane goes around...

In the early days of aviation, one form of aero engine was the rotary. This was one where the engine was bolted to the propeller and the whole engine rotated around the crankshaft. Here's an example with the prop and mounting removed so you can see into it:

I filmed this at the RAF Museum's Great War Grahame White Factory building at Hendon, North London.

An excellent technical description and animation of how they work is shown here on Matt Keveney's fascinating engine site. Because it runs on a total loss oil system (can't get it back to the tank in a revolving engine) and the oil has to go through the same pipes as the petrol, and not mix, an organic rather than mineral oil is used - castor oil. The burnt remnants of the oil was thrown out of the engine a good deal of which covered the pilot, with the otherwise well known effect of castor oil. Thanks to Sahlah for a reference from The Rise and Fall of Castor Oil which touches on the origin of the oil, and use in World War One:
Since castor oil was needed for lubricating airplane engines, 100,000 acres of land in the southern United States had to be planted in castor beans. Castor Oil used by the radial engine was supplanted by Voltol, an oil derived from coal. The Germans tried to use Voltol since the Allies had am embargo to stop shipments of castor oil.
What does a Rotary engine look, sound and smell like in action? There are a few in action if you know where to look. at la Ferte Alais in France, and The Shuttleworth Collection in England. This bit of film (see 'Shuttleworth 2008 trailer') can be downloaded and gives a great feel for pioneer aviation. The first aeroplane featured is the Bristol Boxkite, and has a modern engine.

RAAF Museum Archive.

(To digress a moment; here's a picture of Richard Williams, the 'father' of the Royal Australian Air Force, with a rotary engine on a Boxkite when he was learning to fly in 1914. The Boxkite is a 'pusher' so the engine is behind the wing, pilot and fuel tank, and even behind the propeller! I'm lending a hand to a team, Project2014, building a replica of this aircraft, for the centenary.)

The second aircraft in the film (the monoplane) is the oldest airworthy British aircraft in the world, the 1912 Blackburn, and is flown here by chief pilot of the Collection (and qualified test pilot) Andy Sephton, who makes it look easy. Yes, they do call "Contact!"

Andy Sephton aloft in the Blackburn 1912, last year. James

You'll note Andy 'blipping' the engine - the bits where it goes quiet. The pilot carefully juggles the fuel/air mixture by hand, so the engine doesn't stop accidentally - but power variation is done by deliberately stopping the engine and re-starting it before it gets fouled or cold - rather like having a stuck-on accellerator, no gears and driving the car by using the ignition key...

Meanwhile, in New Zealand, the Vintage Aviator team have built a brand new replica German rotary, the Oberursel and have video of it on the test stand here. (Well worth a look.) The wooden propeller is a sculptural work of art, I feel. Note the castor oil dripping from the engine at the end of the film.

The details and how they did it are here. Amazing. (The Vintage Aviator team are funded by Peter Jackson, the film-maker, so hobbits are useful after all.)

From when 'planes were wood, wire and linen, and engines took skill; when men were men - and regular!

Sorry we can't bring you the smell of a rotary powered aircraft, but the internet has it's limitations. It's one of my favourite smells anyway.


1 comment:

Anonymous said...

Lovely post! I would agree that wooden propeller is a work of art, but then so is that engine. I loved the sound of it running. Did you also notice the vintage truck in the background?

Such interesting machines, no wonder they fascinate you.