engine we used in our jet-powered go-kart is a modified Allied Signal
JFS-100/13A gas turbine starter. Through a number of modifications,
we converted the engine from a jet fuel starter to a pure turbojet
engine. Click here
to see specs for the JFS-100 gas turbine starter.
engine is originally designed as a starter motor for a military
jet engine, for example, the Pratt& Whitney TF-30 engine in
the Navy A7 Corsair. The JFS-100 is designed to mount directly to
the TF-30ís accessory gearbox. When the pilot hits the cockpit start
switch, the JFS-100 automatically spools up and lights off, immediately
accelerating to full power. The JFS-100ís free power turbine drives
a reduction gearbox which accelerates the main engine up to lightoff
speed. Once the TF-30 jet engine has accelerated to idle speed,
an overspeed sensor is tripped on the JFS-100, and the little jet
fuel starter automatically shuts down, only to run again the next
time the big jet engine needs to be started.
Pratt & Whitney TF-30 Turbofan
Engine, not for use on a go-kart.
Because of this
extremely narrow scope of usage, the JFS-100 has many operating
limitations as a turboshaft engine. First of all, there is no throttle.
The engine spools up to full power immediately. Secondly, because
it is only designed to run for short spurts at a time, it is very
prone to overheating if run for more than five minutes. Fuel consumption
is terrible, the nature of its electric starter engagement means
that it must idle at a high speed if equipped with a throttle, and
if the power turbine overspeeds even slightly, the engine is automatically
Because of these
limitations, we decided to modify the engine as a turbojet to power
our first turbine go-kart. Here is a list of the modifications we
made to transform it into a turbojet:
- Removed the
free power turbine, containment ring, and nozzle.
- Had a starter
control unit and tachometer made.
the oil system to run an external oil cooler, to prevent overheating.
the fuel system to install a throttle control.
a jet pipe in place of the power turbine.
- Bolted mounting
brackets to the engine.
a frame to mount the engine.
Here are some
stats for the resulting JFS-100 Turbojet:
- Thrust: 100
lbs. thrust @ 104% N1.
- Weight: 55
- Thrust to
weight ratio: 1.8:1
Fuel Consumption: 1.17 lb/lbt-hr.
- Fuel Consumption:
117 lbs/hr, 17 gallons/hr.
Speed: 75,000 rpm
The JFS-100 Turbojet is a single spool turbojet engine, with single
stage centrifugal compressor, annular through flow combustor with
five fuel nozzles, and single stage axial turbine. The exhaust nozzle
is a fixed area convergent nozzle with straightening vanes and no
Garrett/Allied Signal JFS-100 Jet Fuel Starter
- Type: Dual spool, free shaft turbine
- Inlet: Axial
- Compressor: Single stage centrifugal
- Burner: Annular with 5 fuel nozzles
- Turbine: Dual spool, single stage axial gas producer turbine,
single stage axial power turbine
- Exhaust: downward facing, single exit scroll diffuser
- Power Rating: 90 shaft horsepower at 3,000 rpm
- Peak Torque Output: 290 lb/ft at stall rpm
- Weight: 84 lbs.
- Power/weight: :1.07:1
- Air mass flow: 1.6 lbs/sec
- Compression Ratio: 3.5:1 at 73,000 rpm
- Maximum TIT: 1850 degrees F
- Specific Fuel Consumption: 1.3 lb/shp/hr