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I had a very good day's flying on Saturday in the sunshine, going to Turweston & Old Warden. Between the two airfields I saw 3 Hawker Hurricanes in the hangars, how amazing is that?

Anyway, my question. One of the Hurricanes at Old Warden was in the workshop with its right hand engine cowling off. There I saw a shaft with 3 chain wheels on it. One chain went vertically downwards to what looked like a magneto. Another chain went forward & down to a shaft that passed under the engine and so out of sight. Another chain went up and back towards the engine. What was the purpose of all these chains?

Here is a period photo that shows the chain drive
Thanks Chris but I believe on a Merlin the magnetos and camshafts are driven by shafts and bevel gears at the back of the engine.

The chains I am referring to seem lightweight and at least the two forward sprockets are attached to the airframe not the engine. In the photo they are at the bottom of the cowling, forward of the head of the man leaning against the wing.
Thanks Korenwolf, I will be interested to see your info .

It seems that the shaft under the engine allows 2 handles to be inserted and turned by 2 people, one on either side of the aircraft. There is a copyrighted photo if you search on the interweb.

Then 2 of the chains take the drive to a sun and planet gear mechanism at the back of the engine that gears the drive down considerably so allowing the engine to be turned over. It still must be hard work though.

Then my supposition is that because the engine is turning over slowly the normal magnetos do not make enough of a spark . So the third chain drives a starting magneto at a higher speed. I presume this makes a shower of sparks that connects to the normal distributor.

And RobP the Mk1 Spitfire uses only 1 handle directly into the engine and the chain drives the starting magneto? A neat solution but it must really be hard work to turn the engine over.

Thanks all for the info.
Right, here we go; from the Spitfire I Air Publication,


And a bit of text, taken from the same book -

"The hand starting magneto is mounted on the starboard side of the fireproof bulkhead and is connected by chains and sprockets to the hand turning gear on the engine (see Fig.1) The socket for the starting handle is carried on a bracket on the engine mounting and the handle should be inserted in a hole on the cowling panel. The starting handle is stowed in clips on the frame behind the pilot's seat."

Not a huge amount of detail, but that's British manuals for you :)