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Retro Track and Air in Gloucesterhire are a specialist rebuilder of Merlins (and many other historic engines, cars and aircraft).
They provide engines for the RAF Battle of Britain Memorial flight, and this is the mobile Test-Bench. Fully instrumented,
it enables the engines to be run at all powers for the required duration to be cleared for airworthiness. The large steel
frame that holds the engine-bearers is mounted on bearings along the axis of the prop, to allow a few degrees of movement
relative to the outrigger, and has a strain-gauge attached....a clever method of torque (and therefore power) measurement.
My initial reaction to seeing this running was how different it is to my engine, the sound is painful, and the windspeed 200yards
behind it left me running like Linford Christie, completely unable to stop myself, and praying I did not fall flat on my face,
and camera, much to everyone`s amusement!
The Hamilton Standard airscrew is about 13ft dia. |
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Here`s Joseph again, giving some scale to the mighty SU updraught twin barrel carb. This goes part-way to explaining how this engine can easily consume three gallons of fuel in a minute. One choke has its main jet adjusted by boost pressure for enrichment, and the other is controlled by an altitude capsule. The mixture from both is combined as it enters the supercharger.
The engine has a pack of thin corrugated foils in each inlet manifold to act as a flame-trap, much like a Davy miner`s lamp, an explosion in the supercharger under boost pressure would be catastrophic. |
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This image, taken from video, shows the fuel still burning as it is ejected from the exhaust port. Running the engine without any stubs is quite revealing, you can watch the valve open and see the immense heat inside the cylinder, then the flame belching out. Packard produced a chart in their manuals describing the causes of differing colour flames, and how to correct them. This was, as far as I`m aware, not done in the RR manuals, maybe as it is open to differing interpretation, but nonetheless very useful. |
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People involved with aero-engines seem to be split in opinion about Tractor-Pulling, some feeling that valuable engines are
being run into the ground, where in most instances, they are carefully modified to cope with the increased power. These people
have to look after their investment just as a Spitfire-owner would. It is very unusual to see a Merlin in a tractor, but I
spotted this Merlin 500 in a German 5700kg machine "Super Kasper" in 1991. Nice pink colour scheme...not!
I think there is also a tractor in France with
two or three Merlins! |
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Which of these piston assemblies is for a Merlin engine? In fact it`s the middle one, proving that there is far bigger tackle
around! The smallest is a racing set for a Ford BDA, and the big boy is from a V12 Paxman-Ricardo diesel engine built in the
1950s to drive a rock-crusher. At a guess, I would say about 60 litres or so! It has the same "marine" type fork and blade
connecting rods as the Merlin. |
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