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Tapley Decelerometers, The Old Man Of Brake Testers

What Is It?

The Tapley Brake Test Meter 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. To damp out all vibration, the instrument is filled with a special fluid not sensitive to changes in temperature. No maintenance is necessary. The same meter can be used to test all types of vehicles, from heavy trucks and buses to vans and passenger cars. It needs no electrical connections and it’s so portable that you can take the Tapley Meter to the vehicle instead of the other way around.

How Does It Work?

To set the instrument for a brake test, start by loosening the two butterfly nuts at the sides of the swivel-mounting bracket. Tilt the head until the main needle (with arrow) is set at 3.5 if the unit is in meters or 13.4 if in feet with the face of the instrument JUST BACK FROM THE VERTICAL. This is important because it can be set with the face nearly horizontal, but it would then be near the end stop and would not move anticlockwise. When set in this manner the butterfly nuts can be tightened again, and the instrument is ready to start the test as pictured to the left.

With the main needle set, the recording needle (without arrow) should be turned clockwise by means of the chrome knob in the middle of the dial until it is against the left hand side of the main needle. The vehicle is then driven along a level road at about 20 miles per hour or 30 kph, and the brakes fully applied by means of the foot brake pedal only. When the vehicle has stopped the brake efficiency reading can be taken from the figure shown by the recording needle on the inner brake scale. Stopping distance readings are taken from the outer scale figures. A similar reading should now be taken from a lower speed using the handbrake only.

Tapley Testers have now been replaced with mordern electronic testers such as BrakeCheck from aide automotive ltd

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