High Precision Motoring Dynamometer
As part of Currawong’s commitment to providing an end-to-end solution for the use of EFI on small engines, it manufactures a high precision AC motoring engine dynamometer. It is essential to use a motoring dynamometer when performing EFI calibration as it allows all load and RPM points of the engine to be reached, including over-run (descent) conditions and low speed heavy load (starting).
Motoring dynamometers can also be used to measure engine friction and the performance of absorbing devices such as pumps and alternators.
Performance development of small single cylinder engines on dynamometers is notoriously difficult due to the very high vibration and highly non-uniform torque characteristics of these engines. Currawong has gone to great effort to design an extremely stiff, zero-friction and tuned resonance mount for the absorber that delivers unprecedented smoothness and resolution to the torque reading.
This allows for the easy determination of optimum spark advance and fueling for each mapping point.
The absorber used is a Siemens AC asynchronous servo motor (induction motor) of machine tool spindle quality, rated to 12,000RPM. This high quality motor is very smooth and quiet and is controlled by an advanced closed loop vector drive with optional regeneration to deliver the power back to the mains and thus avoid the use of resistor banks. Being an electric motor, no water cooling is required as is the case with absorber type dynamometers.
Induction motors are very reliable with no wearing parts, thus giving years of service.
Torque Measurement System: Currawong has gone to great lengths to ensure that TigerDyne is a high precision instrument suited to the difficult task of measuring the performance of small engines. This has led to the use of high precision ball mounted air bearings for the trunnion bearings of TigerDyne. These bearings offer zero friction, high stiffness and no degradation over time, thus eliminating the problems associated with brinneling of ball bearings and the associated maintenance. Air bearings also avoid the potential false torque readings and mechanical complications of hydrodynamic bearings.
Tuned Resonance Mount: The high stiffness and zero friction of air bearings has allowed CE to implement a tuned resonance mount that attenuates impulsive loads above resonance without sacrificing torque sensitivity by the use of traditional dampers. When TigerDyne is operating at very low speeds the air bearings are automatically disabled thus avoiding the problem of exciting resonance. Of course, broad spectrum impulsive loads are also present during operation that can excite resonance, so TigerDyne incorporates an electrodynamic tuned mass damper to keep these in check.
Wiring Isolation: Currawong has also taken a lot of care to ensure that the wiring that runs between the outer and inner frames are enclosed in very low hysteresis conduit so that they do not affect the torque reading due to the movement of the inner frame, vibration or external cool fans. The built in cooling fan blows axially internally through the motor and exits radially, thus not having any effect on the torque reading.
Anti-Vibration Isolation Mount: Currawong has developed an isolation mount for use with high-vibration single cylinder engines. This mount removes the vibrations from the dynamometer bench and provides torsional compliance for the engine thus reducing the high forces seen in a rigid mount. The mount keeps the engine output shaft concentric and stable with the cardan shaft thereby giving a reliable connection to the engine.
- 10.5kW @ 7000RPM AC motoring absorber
- 17.5kW @ 5800RPM at 25% duty cycle
- Automatically controlled absorber cooling fan
- RPM control accuracy: +/-10RPM
- Bumpless transition from motoring to absorbing modes
- Torque accuracy: Static +/- 0.01Nm, Dynamic +/- 0.1Nm
- 12,000RPM cardan shaft for connection to the engine
- Guard for the cardan shaft
- Internal measurement of absorber temperature
- Full control via PC interface including real time display and graphing of torque and power
- Precision load cell and amplifier
- Optional isolation plate for mounting of high vibration engines
- Tuned electrodynamic mass damper system removes engine vibrations
- Compressed air filtration system
- Torque calibration arms
- Motoring operation – measures absorbed power (e.g. spinning a propeller)
- Absorbing operating – measures delivered power (e.g. power delivered by UAV engine)
- Thrust measurement (currently in development) – measures propeller thrust
Dynamometer Mass: 120kg
Data sheet: CE711.d01 – Dynamometer