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Re: A seemingly simple powerplant question

Posted by Christer on Wed Jan 16, 2002 08:20:31 PM

In reply top A seemingly simple powerplant question posted by Scott WRG Editor on Wed Jan 16, 2002 06:07:14 PM

Scott,
a long time ago I read in a book, I can?t remember which, that in the early 1930's a german delegation was invited to visit Rolls Royce. This was at the time when the PV12,
later renamed the Merlin, was still in it?s initial development phase. An inverted design had been considered and abandoned but they still had the wooden mock-up. This was put on display for the germans to see while the up-right design was tucked away out of sight.

The initial decision to invert the engine was taken in agreement with the Air Ministry to provide improved vision for the pilot, plus other sound technical reasons. When the mock-up was revealed to the airframe designers they were totally opposed to the idea since it, for them, involved too many design problems since their current projects were conceived with an up-right engine in mind. This was the reason for abandoning the inverted design.

I can?t remember which the "sound technical reasons" were but, I don?t think direct fuel injection was a prerequisite. Rolls Royce never used direct fuel injection. They always injected into the supercharger to take advantage of the charge cooling effect.
A prerequisite would be a dry sump oil system with scavenge pumps to return the oil from the rocker covers to a tank.
If memory serves me correctly the german guns, mounted in the nose with the breeches protruding into the cockpit, were manually cocked and that operation would be kind of awkward doing down at ones feet. If there was a stoppage the guns could be cleared by the pilot.

The bit about "showing the germans the inverted PV12" is probably a wartime propaganda variant of the answer to Your question which I?m sure was asked at that time too but, be that as it may, it would be my favourite answer.

Regards,
Christer

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