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CNC is only limited by our imagination.

Tweakie.CNC

In the 1940’s a number of companies within the UK were, with Government backing, developing Sir Frank Whittles jet engine design and the Rover car company were there amongst the leaders.

Rover’s 1s60 was a success which went into production, with a number of variations, to power many different types of stationary engines including my airborne auxiliary power unit described here.

One variant was trialled as a prop-jet power source in a Chipmunk light aircraft and another in Rover’s jet car ‘JET 1’ which was first shown to the press at the Silverstone race track in 1950.

 

For me this is just a little project, it is not intended to be a restoration but rather bit of a ‘tidy-up’ to make a rather scruffy generating set look more presentable and be fully functional - the full restoration job I leave for someone else in years to come.

This is the heart of an Auxiliary Power Unit (a.a.p.p. Mk.1031) built by Rover around 1967 and fitted in a B2 Vulcan Bomber. Its main purpose was to provide the aircraft's electrical needs whilst on the ground and prior to starting the main engines but it could also be used in flight, in an emergency, as the back-up electrical source. From the various mod record labels it is evident that this unit was in service until November 1978 but after that, who knows. The Vulcan, delta winged aircraft, was perhaps the forerunner for the current "Fly by Wire" system as it's duplicated sets of control surfaces were all electrically operated.

The gas turbine engine itself is rated at 60 horsepower and has a speed governor fitted to the fuel pump to set the compressor shaft to run at 30,000 RPM - then, through a reduction gearbox, it drives the Rotax 30 KVa alternator at 8,000 RPM which outputs 208 Vac, 3 Phase, 400 Hz. and although its airborne days are perhaps over, it will run again - much to the delight of my neighbours within a 3 mile radius.

One of the first problems I encountered when working with this unit is the spanner sizes – they are a mixture of Whitworth and A/F but to compound the issue there was a 1940’s wartime directive to reduce the head dimension of the Whitworth range (as a steel saving measure) and this seems to have carried over with some of the Whitworth sizes. Thanks to Terry, a very good friend, (who has boxes of spanners which I can just about lift) I have managed to make up a complete set which now seems to cover just about everything.

 

These photos have all been taken at various stages of the clean-up process and hopefully will be in the order that the work was completed.

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(1) There are two of these Rotax actuators used on the apu with one to operate the fuel on / off valve and one for the oil cooler radiator air shutter. Both had age related faults, one with a sticking limit switch and the other a seized-on shaft brake.

(2) Whilst repairing the actuators I compiled this schematic of the internal connections which may come in useful one day (click image for enlargement).

(3) These are just a couple of the components that will no longer be used. On the left is a Graviner fire extinguisher system nozzle P213.B28 (1956) and on the right a Thermal Control Co. fire detector 5CZ/6188 TP7700 (1965). The detector contains two thermocouples, wired in series (one shielded and one exposed) and produces an output of 7.5mV upon a 185 degF temperature differential.
Both, along with another nozzle and three more detectors were fitted to the casing, above the Vulcan's apu.

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(4) Not something I was looking forward to doing but it had to be done. The four K.L.G./ Smiths exhaust thermocouple leads were each insulated with a woven asbestos sleeve which had to be carefully and safely removed and replaced with a woven fibreglass sleeve. Although fibreglass is still not good stuff to be around it is a lot safer than asbestos.

(5) The new fibreglass sleeving. It will not stand as high a temperature as asbestos but I believe it will do the job just perfectly.

(6) This is the asbestos sleeve removed from just one thermocouple. Now to find out the rules and regulations for properly disposing of all this.

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(7) Just about every nut, bolt and fitting is secured with locking wire - a pretty safe way of making sure things don’t just drop off when subjected to extreme vibration and temperature changes etc.

(8) If you have ever wondered just how the locking wire is twisted - they use special pliers, such as these. The wire is threaded through a small hole in the part to be locked then both wire ends (at a distance determined by the next part to be locked) are clamped in the pliers, which have a jaw locking mechanism, then by pulling on the silver knob at the end, the pliers rotate and twist the wire. Simple.

(9) Another of the components which will no longer be used. This is the drive shaft for the oil cooler blower assembly, wonderful piece of engineering and certainly built to last. The Rover drawing numbers, marked on the alloy parts are R426722 B2 and R426723 B2.

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