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[ChrisJC]

It's not a 2 stroke as I watched the valves being assembled.

But there was only one valve per cylinder?

Chris.

[Alan Drover]

Only one was shown being assembled. I'll have to watch it again and pause where necessary. The exhaust valve was mentioned on a text accompanying the film but I didn't have time to read it. When the engine was being assembled and it was turning over there were definitely 4 separate cycles. There is a crankshaft driven oil pump feeding oil through the stationary crankshaft as is the fuel.

[MartinC]

The early rotary engines were an attempt to produce higher power without overheating - a big problem at the time. Each cylinder was machined from a solid billet of steel and the cylinder walls were only 1/16" thick in order to reduce weight. The most famous rotary was the W.O. Bentley designed 150 HP BR2 which found its way into the legendary Sopwith Camel and Snipe - arguably the most lethal fighters of WW1. 150 HP was about the maximum an engine of this type could safely produce because the  torque reaction was massive and an inexperienced pilot could literally spin the aircraft around the engine / propellor often with fatal consequences. On the other hand in combat it gave an experienced pilot almost unbeatable manoeuvrability. The engines had no throttle as such and engine speed was controlled by a "kill button" on the joystick. Martin

[Herald1360]

Yes, stupidly I knew that - I now recall watching it too.
Then how does the fuel get in? You'd have thought the centrifugal force would complicate things a bit?
And lubrication - wouldn't any oil get flung up to the combustion chambers and rapidly soot them up? Simply running an ordinary engine upside down would do that even if it did have a dry sump.

The de Havilland Gipsy engine was an inline inverted type with the cylinders underneath the crankshaft. It handily got the propellor higher up without the cylinders obscuring the pilot's forward view.

[Alan Drover]

With a rotary radial engine the cylinders are vertical, horizontal, upside down and positions in between per revolution. A non rotary radial has vertical, horizontal, upside down and positions in between cylinders too but they're always in the same position.

[Craig T]

My dad worked briefly on the Blackburn Beverley aircraft that had 4 Bristol Centaurus engines on it.

It was an 18 cylinder radial engine with sleeve valves rather than having pushrods and rockers on the top of each cylinder. As the engine rotated and the piston went up and down, the cylinder sleeve rotated back and forwards to open up the inlet port, exhaust port and off course no ports for the compression stroke.
He said all the sleeves were driven by gears from the front of the engine and were quite something to set the timing up on!

You often see people hand turning propellers slowly before a radial engine start-up to clear any accumulated oil out the lower cylinders. Not sure how they did this on the Beverley as the engines were 20 odd feet up in the air!

Craig.

[Alan Drover]

I've had another look at the video and still can't make out how the fuel gets to the combustion chamber from the crankshaft. I thought of 2 stroke type transfer ports but it didn't appear that the piston rings were pegged to stop the open ends catching in the ports. The air input is controlled by the exhaust valve and looking at the camshaft assembly there appears to be a long period for the exhaust valve to remain open.

[MartinC]

As I remember it, some models had a sort of inlet valve in the piston crown secured with a light spring. As the piston descended on the inlet stroke the valve was forced open by pressure in the crankcase admitting fuel into the cylinder. This was a period when aero engine designers tried all sorts of ideas! As others have remarked fuel was admitted into the hollow crankshaft by the crudest of fuel systems and if the engine "spat back" the results would be fiery!! Incidentally rotary engines of this period were universally lubricated by castor oil and after even a short flying time pilots would be covered in the stuff. The purgative effect on the human "system" was legendary!  Martin

[Alan Drover]

I couldn't see any sign of a spring loaded valve in the piston in the assembly procedure.