Solent (Plessey Dynamics) gas turbine starter

As fitted to a Rolls Royce Spey Jet engine - Photographs and Details.

This beautifully engineered little motor is fitted into the UK version of the Phantom F4 fighter aircraft. Its sole job in life was to provide shaft power to start the main engines. (70 shaft horsepower rating.)

My one has been modified for thrust and possible flight by removing the rear casting that houses the free power turbine / gearbox and shaft. This leaves a compact little pure jet engine once the other 'unnecessary' clutter has been removed. (It comes with an acceleration control unit, a fuel pump, an oil pump, and an electric starter as stock)

The alloy front cover was machined to remove the parts of the casting not needed, and this is a relatively simple operation. Some rectangular alloy plates had to be made up to fit the tail pipe (rolled from stainless steel sheet) and the same long bolts actually hold the combustion chamber and other internals in position. These can be seen in the photos. This was originally held together by the casting that housed the power turbine/gearbox.

The two spark ignitors (sticky out silver things!) will be removed to save weight and keep size down and a flat alloy plate made to cover the holes (and the holes in the combustor) as these will not now be used. Ignition is achieved by the same method as my little 'Shreckling' i.e. Matches, lighter, blowtorch, hand held cooker sparker or whatever is about. This seems to work fine.

This motor uses eight duplex injectors, (duplex means two!) and these have a small starter jet, to allow starting on kerosene so propane is not needed. The large ones are used after safe idle is reached. (We think..) Fast enough rotation is easily achieved using a cheap leaf blower bought for this purpose. Actually RPM is not to important, but the required airflow is, so a hair dryer or blower starts jet engines more easily than a direct drive system.

Known details (Thank you Ian!)

Case pressure 47psi max

Max RPM 62,000

Weight 15.5lb

Estimated thrust approx. 110 LB (when tailpipe is completed we will measure this properly and update the page)

Ex gas temp - not measured but very cool! and nothing glows. No visible flame at all!

Oil system - modified from the original 'single shot' system to allow continuous operation. Labyrinth seals at both ends of shaft and a hollow cross drilled shaft vented to atmosphere through the front nut. Bearings preloaded forwards with about 50lb pressure.

Reverse flow combustor.

Turbine wheel approx. 120mm diameter, 37 blades.

Compressor centrifugal single stage, inlet 79mm, outside diameter 162mm. Straight blades open front with only the very front part that sees the air 'shaped'.

General case diameter 195mm (Ignoring projections and tapings)

Overall length 310mm

Pictures Detail of the transistorized pump controller

After rebuild.

Rear end showing the alloy plates that hold everything together.

Front end showing the size in comparison to the Shreckling - Which now looks like a kind of cartoon character....

Turbine Wheel, looking into rear end of the home made jet pipe exhaust. this is made from 0.5mm stainless steel sheet rolled and spot welded. It is convergent towards the rear end by 2.5 degrees. A central fairing or cone still has to be made (similar to the Shreckling seen in pic 1) to complete the rear end, so that the hot gasses can get out smoothly, and to prevent them from circulating over the central part of the turbine disk. This will keep the shaft and bearings cooler.

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