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UNITED STATES OF AMERICA

TJD 76C Baby Mamba

Max Dreher

ln 1963, Max Dreher began work on the design of the youngest member of his turbin Family, the T.J.D.-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.

The whole job, from the begining to end, took about 3600 hours. Then the Baby Mamba had logged many starts had many hours on the stand and in flight tests.

Characteristics

Type

Single-shaft turbojet.

Air intake

At front. Air flow 0.50 kg (1.1 lb)/sec.

Compressor

Single-stage mixed-flow. 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

Compressor casing

Of 2024 aluminium alloy and 347 stainless steel.

Combustion chamber

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.

Nozzle guide vanes

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.

Jet pipe

Fixed type, 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).

Oil grade

MIL-L-7808E (Turbo 15).

Mounting

Two rigid connections on diffuser section and one flexible connection on turbine section.

Starting

Compressed air 1034 bars (150 lb/sq in), via three nozzles driving turbine wheel.

TJD 76C Technical data

ManufacturerDREHER Engineering Company
Initial testing1975
Certification
TypeSingle-shaft turbojet
Nb. built

Dimensions

Diameter151 mm5.94 in.
Length overall416 mm16.38 in.

Weight

Not equipped6.4 kg14.1 lbs
Equipped10.0 kg22 lbs

Performances

Max RPM96 000 t/mn96,000 rpm
Idle RPM t/mnrpm
Thrust at max RPM245 N55 lb
Thrust max continuous200 N45 lb
Thrust at idle RPMNlb
Pressure ratio2.8 / 1
Max Flow500 g/s1.1 lbs/sec
Max continue EGT675 deg.C1247 deg.F

Consumption

Consumption
Specific fuel consumption 0.6 kgs/kg/s 1.35 lbs/lb/s