The Bowmonk Dynometer MKIII is a scientific instrument, indisputable in its accuracy as it is based on one of the basic laws of applied physics. It consists of a finely balanced pendulum free to respond to any changes in speed or angle, working through a quadrant gear train to rotate a needle round a dial. The dial is black with silver white graduations and having a linear length of 5 1/2 inches (114mm). To damp out all vibration, the instrument is filled with a special fluid not sensitive to changes in temperature. No maintenance is necessary.

The dial is calibrated in percentage "G", the accepted standard throughout the world for measuring acceleration and deceleration. There are no connections to the vehicle other than mounting either with two self-tapping screws on to a heavy stand (as pictured above) or the suction cup operated by the small side lever. In the latter case smear the suction cup with glycerine, or Vaseline to increase adhesion.

Test the vehicle on reasonably level road. The meter is set to zero by releasing the thumbnut, tilt the bowl in its pivots until the main needle points to zero and re tighten the thumbnut. The meter is now ready for use, it is not necessary to watch the instrument continuously as it is fitted with a recording needle. Depending on the test to be performed the recording needle is positioned to left or right of the main needle by turning the centre chrome knob, and will accurately record the maximum reading.

For almost 100 years Tapley instrumentation has been the market leader engaged in the manufacture of portable brake testing equipment. The Tapley meter is the most recognised international standard decelerometer and as such trusted by many leading government authorities around the world to set local brake testing standards. Results of Tapley meter tests are accepted as evidence of braking efficiency in Courts of Law throughout the world.