Gas Turbines Builders Association

Diameter:	110mm
Length:	265mm
Thrust:	4-24 Newtons (5.3 lbs
Max revs:	75,000 rpm
Temp:	630 deg C
Weight:	0.87 KG

This was the first published design that the amateur could follow and produce a working jet engine. This is the engine that the Golden West engine was designed from. The design uses easily available components and employs building techniques that the average model engineer might have in his workshop. The design is deliberately kept conservative and the choice of materials makes the finished design more tolerant of workmanship standards than the Kamps or later designs. However all turbines rev at high levels and care needs to be taken when making and running them.

The original design set out in the book has a conical shaped inner combustion chamber shape. The fuel is vaporized in a coil and emerges in a series of 5 holes at the front face of the chamber. The shaft is fabricated in 3 pieces, the middle section is in aluminium.

                 

The outer can is a camping gas cylinder. This is a cheap. free! way to make a light casing. The front diffuser assembly can be made of a mixture of wood and aluminium glued with araldite epoxy glue. Most are made of all aluminium. The front housing is made from aluminium and can be turned or spun to the required shape. The combustion chamber and the rear NGV's and shroud are made from stainless steel (UK 316 or 310).

The compressor is made of plywood and when reinforced with carbon fibre, can withstand revs up to 75,000 rpm.

           

Kurt came up with a simple way to make the turbine wheel. He uses stainless steel (UK 316 or 310) sheet in disc shape that has blades formed by slitting and twisting the blades are profiled by hand mini grinder. This has proved an adequate way to construct the wheel if revs are kept to the levels he suggests. If the temperature is high or revs are exceeded the material can elongate and cause the wheel to stop in the shroud in a noisy but unspectacular way. A better material is Inconel 718 but is not easily obtainable. It cannot be twisted without high heat and is better ground from the solid form.

This is usually the first engine that aspiring builders make. It has been refined over the last 2-3 years and the principle changes have been to:-

1. The combustion chamber has been revised twice. The second version has hooked tubes on the front face and parallel sided inner and outer tubes. Fuel is injected into the tubes by small hypodermic needles. This chamber produces cooler running and is used by Mark Drake in his Hobbyjets 631 engine. The third version has a chamber similar to the Kamps combuster but with straight sticks fed from the rear of the engine. This chamber has produced the most consistent results.
2. The compressor can be machined from solid aluminum in an open form with no cover. Care has to be taken with the specification of the aluminium.
3. The shaft can be machined in the solid from stainless steel rather than made in pieces.
4. The central tube can be made without the leg supports if a better securing flange is attached to the tube.
5. Part 17 can be omitted when using the revised combustion chamber.

Detailed drawings of parts referred to above and the member's experiences are set out in the newsletters. Rather than attempt any modification you are urged to join the group and obtain the back copies.

A number of these FD3 64 engines have been built and have been flown successfully. Many have however only been bench tested and been subject of many tweaks to try and keep the temperature down. The design is now dated but is still a good way to learn about building and the operation of gas jet turbines.