Dreher TJD-76C Baby Mamba
ln 1963, Max Dreher began work on the design of the youngest member of his turbine family, the TJD-76 Baby Mamba. It was designed to power a sailplane and had a static thrust of 55 lbs. He tried to keep it as simple and light as possible. No gear reduction was used and it had a free-spinning rotor. He selected a single-stage mixed flow compressor, an annular combustion chamber and a single stage axia-flow turbine for the basic layout.
A single-shaft turbojet, the air intake at the front, with an air flow of 0.50 kg (1.1 lb)/sec. The compressor is a single-stage mixed-flow, with single 17-4 PH stainless steel impeller with sixteen vanes. Splined to shaft and supported in two ball bearings. Mixed-flow two-stage diffuser of 347 stainless steel. Pressure ratio : 2.8 : 1
The compressor casing is of 2024 aluminium alloy and 347 stainless steel.
The combustion chamber is an annular type with Hastelloy X outer casing and flame tube. Vaporising system with fuel/air pre-mix. One spark plug in flame tube.Fuel system: Manual with pressurised fuel supply, or electrically-driven fuel pump. Fuel pressure 5.52 bars(80 lb/sq in). Automatic system for drone applications. Fuel grade: Kerosene or petrol.
The nozzle guide vanes are single axial stage, with sixteen investment-cast vanes in Stellite 31.Turbine: Single-stage axial-flow, with nineteen integrally-cast blades, of Inconel 713 LC. Gas temperature 770°C before turbine, 675°C after turbine, at continuous cruising power.
A fixed type jet pipe, with jet pipe and cone of Hastelloy X. LUBRICATION: Air/oil mist system with total loss, using bleed air equivalent to 2.5 per cent of total mass flow.Capacity 1 litre (2 US pints) of MIL-L-7808E (Turbo 15).
Mounting is by two rigid connections on diffuser section and one flexible connection on turbine section. Starting is by compressed air 1034 bars (150 lb/sq in), via three nozzles driving turbine wheel.
The whole job, from the begining to end, took about 3600 hours.
After initial running on the test stand, Max Dreher installed the engine on his Prue 215A sailplane. To do this he designed a jet pack consisting of the engine, the pressurized fuel system and the lubrication unit. the total weight of this first pack was 25 pounds. An auxiliary oil tank is mounted separately and employs an electrical driven gear pump.
A third unit, the jet control pack (engine controls, instruments, switches) is located in the cockpit.
Prue 215A - Mamba Jet
Length overall: 416 mm (16.38 in)
Diameter: 151 mm (5.94 in)
Dry weight: 6.4 kg (14.1 lb)
Complete weight with fuel tank: 10.0 kg (22 lb)
Specific fuel consumption: 42.5 mg/Ns (1.5 lb/hr/lb st) At max rating
Oil consumption: 25 cc/min At max rating
Max rating: 0.245 kN (55 lb st)
Continuous rating: 0.20 kN (45 lb st)