There are at least three different types of brake tester used to calculate the braking efforts and efficiencies of a motor vehicle: * Roller brake testers, consisting of a chassis with a driven roller system * Plate brake testers, consisting of two parallel measuring plates * Decelerometers, usually handheld

Roller brake testers

A roller brake tester is a method of allowing the dynamic assessment of the

braking system A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...

of a

motor vehicle A motor vehicle, also known as a motorized vehicle, automotive vehicle, automobile, or road vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on railway track, rails (such as trains or trams), does not fly (such ...

, whilst the vehicle itself is in a static condition. This type of brake tester is normally used in UK garages when used as part of an inspection lane for the

MOT test Mot or MOT may refer to: * Montserrat, UNDP country code Media * Ministry of Truth, the propaganda ministry in George Orwell 1949 novel ''Nineteen Eighty-Four'' * ''mot'' (magazine), former German car magazine * Mot (Star Trek), a minor charac ...

. Roller brake testers consist of a mechanical floor unit which contains

electrical motor An electric motor is a machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate Laplace force i ...

s, two independent sets of three measuring rollers, brake force

transducer A transducer is a device that Energy transformation, converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, M ...

s and additional safety

sensor A sensor is often defined as a device that receives and responds to a signal or stimulus. The stimulus is the quantity, property, or condition that is sensed and converted into electrical signal. In the broadest definition, a sensor is a devi ...

s.
The driving rollers operate at a low (known) speed using a

gearbox A transmission (also called a gearbox) is a mechanical device invented by Louis Renault (who founded Renault) which uses a gear set—two or more gears working together—to change the speed, direction of rotation, or torque multiplication/r ...

and motor arrangement and during a test measurements of the maximum braking force are taken by applying the vehicle brakes which induces a reaction force on the electric motor itself. An electric transducer with

strain gauge A strain gauge (also spelled strain gage) is a device used to measure Deformation (mechanics)#Strain, strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an Electrical in ...

s then measures the individual induced forces which are acting during the deceleration phase in order to calculate the individual braking forces for each wheel. In order to minimize any inaccuracy and variation in the measurement, the roller diameter is sufficiently large to reduce the effects of the mechanical relaxation, or flexing, of the tire itself. A special coating on the rollers is designed to be very wear resistant and provide good

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

values, both in wet and dry conditions. A third smaller roller, on each side between the driving rollers, has two functions: The first is to detect if a vehicle is present in the roller bed (a built in safety device to prevent the motor from starting up unless a vehicle is in the brake tester), the second function is to detect when and if tyre slippage occurs in order to make the measurement before a maximum, predefined value of time passes. During the test, the computer measures the brake force values and the system will calculate the imbalance between the left and right brake forces of an axle, as well as the brake efficiency of the service brake and the parking brake provided that a vehicle weight is either inputted manually or by using an integrated weighing system.

Plate brake testers

A plate brake tester is a method of measuring a vehicles braking system in a dynamic test. The unit consists of two moving parallel plates mounted on force transducers. A measurement of the braking force is made when a vehicle passes over the plates and then applies its brakes. The braking action causes the individual plates to ‘slip’ forwards allowing a calculation of braking force to be made. Brake imbalance between the left and right hand side can also be measured by the differences in voltage measured on each of the force transducers under the chassis. Due to the nature of it dynamic operation, plate brake testers are far less common than roller brake testers in UK garages although they are also an extremely accurate method of measurement. The extremely accurate plate brake method of measuring a vehicle's braking performance in countries such as Australia and New Zealand is increasingly becoming a far more popular alternative to basic decelerometers due to not only accuracy, measurement speed, and the ease of use, but predominately the greatly improved safety offered by removing the need for vehicle inspectors to brake test vehicles on public roads amongst other road users .

Decelerometers

A decelerometer is a hand held device for measuring dynamic braking forces during a vehicle road test. A vehicle decelerometer operates as if it were, and it could also be known as, an

accelerometer An accelerometer is a device that measures the proper acceleration of an object. Proper acceleration is the acceleration (the rate of change (mathematics), rate of change of velocity) of the object relative to an observer who is in free fall (tha ...

as it calculates braking efficiency by using those forces captured during a vehicle's deceleration. A decelerometer is a basic method by which braking effort can be accessed quickly and easily but it is generally used as an indicator to acceptable brake performance. Low efficiency readings should lead to further investigation on either a plate brake tester or a roller brake tester. Motorcycle-3-1

References

{{reflist Automotive tools