The Bristol Mercury is a nine-cylinder, air-cooled, single-row, piston radial engine. Designed by Roy Fedden of the Bristol Aeroplane Company, it was used to power both civil and military aircraft of the 1930s and 1940s.

Developed from the earlier Jupiter engine, later variants could produce 800 horsepower (600 kW) from its capacity of 1,500 cubic inches (25 L) by use of a geared supercharger.

There are other aviation finds that I located on this classic wreck, including:

Westland Lysander wings

Blenheim bomber engine exhaust rings and tail planes

Trolley accumulators

Pundit lights

The post Bristol Mercury Engines on the Thistlegorm appeared first on Beyond.

The pictures above, taken on the Thistleform and in the workshops of the Aircraft Restoration Company, show the distinctive shape of the leading edge of Westland Lysander – looking back towards the wing root. The wings on the Thistlegorm are stacked on top of each other, revealing the tubular structure of the Lysander wing.

There are other aviation finds that I located on this classic wreck, including:

Blenheim bomber engine exhaust rings and tail planes

Bristol mercury engine

Trolley accumulators

Pundit lights

The post Lysander on the Thistlegrom appeared first on Beyond.

A number of dive guides will tell you that you can see motorcycle sidecars on SS Thistlegorm. In fact, these odd-looking contraptions are trolley accumulators.

Trolley accumulators were produced in several forms, but they all had a bank of lead/acid batteries contained in a covered box, which had been wired ‘in series’ so that each lead/acid cell (nominally producing about 2 volts) produced 12 volts and sufficient power to turn over the standard aircraft engines of the day. The reason it is called an ‘accumulator’ is because some early batteries could not be recharged using an electrical current and needed to have their electrolyte renewed after discharge! In 1881, the standard sulphuric acid/lead plate battery (approximately one volume of concentrated to five volumes of distilled water) was revolutionized by the use of lead grids, into which lead oxide paste was pressed. If you connect the negative terminal of an electrical circuit to one plate, and the positive to the other, then electrons will be ‘forced’ into the -ve plate, making it contain a higher proportion of pure lead, and ‘stripped’ from the +ve plate, making it contain more lead oxide. Theoretically, therefore, in a fully charged battery, you should end up with a -ve plate of pure lead (Pb, and rather nice slate blue colour), and a +ve plate of pure lead oxide (PbO2, a rather sludgy brown); the liquid electrolyte flowing around them should be a much weaker mixture of sulphuric acid. As the ‘accumulator’ discharges, the exact opposite of the above process happens.

When not in use these trolley accumulators were connected to the mains electricity supply at the RAF station they were on, to build up charge (usually overnight); they would need periodic servicing, and topping up with distilled water, as they tended to lose that component of the electrolyte during the charge/discharge process. You may have observed that this ‘trolley acc’ has what appears to be an engine on top of it. This is because on remote sites, the small generator set/control panel mounted directly to the right of the engine’s cylindrical fuel tank, and capable of producing about 300 watts, would then be able to recharge the batteries fitted below it. This was also used if the ‘trolley acc’ had been used a lot during the day, or in cold weather. As a rough guide, for every 1 degree Centigrade drop in temperature, you lose about 3% in maximum available electrical charge. To access the batteries, you unbolted the engine/generator set, and two men lifted it off the battery compartment lid.

There are other aviation finds that I located on this classic wreck, including:

Westland Lysander wings

Blenheim bomber engine exhaust rings and tail planes

Bristol mercury engines

Pundit lights

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There are two of these of the SS Thistlegorm – often misidentified as armoured cars on a Rolls Royce chassis. Leaning against one of the Pundit Lights is a stack of Westland Lysander wings.

The pictures above include one that shows the Pundit light itself in its stowed position on the back of the trailer. When in use, this was mounted on the top of the trailer. Pundit lights were not always located on airfields. Sometimes they were located at a distance from the airfield – for example, ten miles due south. Pilots would locate the beacon and then fly ten miles north to find the airfield.

The components of the 3kW beacon were:

– Brockhouse forecarriage type trailer chassis
– Coventry-Climax 16.9hp engine – type ‘E’
– GEC 5KVA 230 volt single phase alternator
– GEC Exciter, 106volt, 3.22amp
– GEC 1/15hp 230 volt flasher motor
– Lucas type ‘C45’ 12 volt generator
– Lucas RF91-L6 voltage regulator

– Visco air filter
– 4 KVA single phase 1:1 transformer
– 8 off Tesla coils
– 8 off 400 watt neon tubes and resistances
– 8 off chokes and condensers
– Dimensions LWH 15ft6in x 7ft 6in x 12ft 3in.

Many thanks to Red Sea Water World and Ted Angus for the photographs of the pundit light which were so much better than mine.

Thanks also to the Aircraft Research Group for helping with the identification of the Pundit Light on the SS Thistlegorm.

There are other aviation finds that I located on this classic wreck, including:

Blenheim bomber engine exhaust rings and tail planes

Bristol mercury engine

Trolley accumulators

Lysander

The post Pundit light appeared first on Beyond.

Exhaust rings from the Blenheim’s Bristol Mercury engines are identifiable because of the second exhaust. Tail planes of Blenheim on SS Thistlegorm, taken by Steve Cain. For comparison, also shown is the tailplane of the Duxford Blenheim undergoing a rebuild, taken in July 2007.

Just visible is a Trolley Accumulator lying under the wings, with the plug just visible. Also shown is the tailplane of the Duxford Blenheim undergoing a rebuild, taken in July 2007.

There are other aviation finds that I located on this classic wreck, including:

Westland Lysander wings

Bristol mercury engines

Pundit lights

Trolley accumulator

The post Blenheim bomber, Thistlegorm appeared first on Beyond.