What are dynamometers?
While a dynamometer (or dyno for short) is a common word in the motor/tractor industry, there are many who do not know its purpose and usefullness.
A dyno is, quite simply, a machine that measures force. In our industry, it simulates the load an engine/vehicle/tractor would take and through a torque measurement
device (commonly a load cell) would give a reading of the torque given out. This, together with speed, will give you the power output.
Dyno's come in many different types, ranging in maximum power/torque and different methods of applying this torque.
Since most engine dyno's in the country are over 20 years old, they employ the "Water brake" technique. Simply, by the engine pushing against trapped water inside the
machine, load is created and measured on a load cell. The load is increased by increasing the level of water inside the dyno to be pushed against.
Another common engine dyno employs an "Eddy Current brake" technique. By Creating a magnetic field inside the dyno, you create resistance against a conductive
shaft....resulting in load on the engine. By increasing the Amps to the dyno, you increase the field thus increasing the resistance and the load.
On the tractor side, two types of dynos are common in South Africa....namely the M&W P400/P2000, and the A&W NEB200/400/i-900 (More commonly known as
The M&W P400/P2000 uses hydraulic pumps turned by the tractor PTO to create load. As you turn a wheel it increases the pressure build-up inside the pump, increasing
pressure and thus increasing torque. This Torque is measured from an in-line pressure transducer.
The A&W NEB200/400/I-900 employs brake-drums to create load. Hydraulic pressure to the drums are increased by two control valves (one coarse, one fine). This
results in higher braking force, resulting in higher load. Torque is measured on a load cell.
There are many other types of dyno's on the market, for a more comprehensive understanding of the various types visit the link below.