The recent media attention surrounding heavy vehicle accidents across
Australia is forcing industry regulators to set their considerable sights on
company driven maintenance programs.
According to the NTARC (National Truck Accident Research Centre), 25% of
all accidents are caused by speed, 12.1% through fire losses and mechanical
failure, with fatigue coming in third at 11.9%. Each of these top three causes are
shining a light on contributory brake issues.
With the 2013 major accident report released by the NTARC stating that
brake problems can result in tyre fires and explosions, recommendations are
being made that brake and tyre maintenance become a priority.
Coupled with the recent woes of one of Australia’s largest transport
companies being issued with multiple defect notices for brake, wheel and
suspension faults (taking 26 of their 80 strong fleet off the road), the major
impact on company earnings and reputations cannot be ignored. Neither can the
cause.
WHY TEST BRAKES?
Safety
Put simply, we test brakes to ensure vehicles are safe to use. For
drivers, for the general public and for the client’s product that is being
transported.
Legislation
While each state has their own regulations in place, it is becoming more
of a national focus from a regulatory point of view to frequently test brakes.
Liability
Regular brake testing allows the operator to keep an auditable record of
testing. In the event a vehicle is involved in an accident, the risk of legal
action can be reduced if accurate testing information is readily available.
Economy
Regular testing can minimise vehicle downtime in the workshop, reduce
brake lining and component wear and can assist in decreasing tyre wear, saving
businesses time and money.
OH&S Fatigue Management
As part of the National Heavy Vehicle Accreditation Scheme (NHVAS)
minimising driver fatigue is a critical component. By regularly testing you can
provide a smoother ride for operators, resulting in a positive effect on
fatigue management.
THE EQUIPMENT
As with any product, there are multiple types of brake testers available.
The three main contenders are Decelerometers, Plate Testers and Roller Testers.
The most common and cost effective piece of test equipment is the
Decelerometer. Usually found strapped to the passenger seat of the vehicle
being tested, it measures and records the inertial force of the vehicle as it
decelerates from a pre-determined speed to a stop. Service brake speed is
generally around 30klm/hr with the park or emergency brake speed being
15klm/hr.
There are plenty of different types available on the market, however they
all basically work off the same “G Force” principal. The transducer of pendulum
is read to determine if the vehicle can develop enough brake force to
theoretically stop the vehicle safely within a set range of distance.
Being relatively inexpensive and fairly compact, the Decelerometer allows
ease of use in most environments.
You have the option of printed paper tape to provide the results and
maintenance is cheap and easy, with annual calibration ensuring the accuracy
and legality of your testing. They also spend their time in the vehicle cabin
so mud and dirt is not an issue.
What they don’t do is provide information pertaining to individual wheel
performance. This type of testing will also not show hidden faults like drag
and cracked or warped brake drums or disks, as it doesn’t weight the vehicle.
Motion is also a factor, with the vehicle required to be moving for testing to
be conducted, so there is potential safety issues due to the possibility of the
operator getting distracted.
The second type of testing is called Plate Testing. While similar to a
Decelerometer in that it measures the inertial deceleration force of a vehicle
being driven at a pre-determined speed, the Plate Tester is installed in a
static position on the ground and the vehicle is driven on to it. The brakes
are then applied while the wheels being tested are on the skid plates, allowing
the reading of sideways movement of the vehicle wheel under braking as well.
You can power a plate tester using an extra low voltage source (12vdc)
which means minimal exposure to low or high voltage AC power. Plate testers have
fewer moving parts, principally the plate itself. One up on the Decelerometer,
these testers provide a more in-depth test allowing weighing of vehicle axle
(static).
However, like the Decelerometers, Plate Testers require the vehicle to be
in motion to allow for the test to be conducted, making for a greater level of
distraction as the operator must concentrate on keeping the vehicle at the
correct speed, lining up on the plates and then applying the brakes at the exact
moment they hit the plates. This is especially important for long vehicle
testing such as road trains or B-Doubles, usually this would require other
helpers to work with the operator, which can result in reduced consistency in
some test situations.
Rounding up the brake testing posse is Roller Brake Testing. Using this
style of testing vehicles are driven onto a set of rollers which are covered in
a plastic medium infused with friction material. When tested the wheels are
turned by the constant speed of the roller keeping the vehicle static during
the test.
Roller Brake Testing measures deceleration by means of torque force
produced by the decelerations of the wheel against the rollers. This method
produces the most consistent results across all axles. You can test one wheel
at a time, review efficiency of service, and test parking and emergency brakes.
Roller Brake Testers can be configured for air pressure testing, ovality
(warped or cracked discs/drums), Bind (rolling resistance) and in some makes
you can accurately test time lag which can help reduce the likelihood of
“jack-knifing”. One of the more impressive services that this style of testing
provides is the ability to match prime movers to trailers, maximising vehicle
balance and efficiency.
Greater safety is achieved with this style of testing with the single
operator system allowing control on some systems direct from the vehicle cab
via remote control. There are also a number of options to enhance the system
including speedo checking, play detectors, emission testers, headlight aimers
and noise meters. These accessories give this unit the added advantage of being
able, in some cases, to form the basis of a complete vehicle test lane.
While the Roller Brake Tester sounds like the darling of the three it
does have some dirty laundry to air. Due to the powerful drive systems, they
generally require 3 phase power to operate and can be very unforgiving to
humans if safety precautions are not strictly adhered to. The weight of the
mobile units can be inhibitive (weighing in a 1.2t for the brake tester). While
installation can also present some challenges, with the in-ground units
requiring some civil work to get the job done.
THE BOTTOM LINE
When it comes to operation, Roller Brake Testers will measure the torque reaction generated by the vehicle
brakes against a roller turned by a motor, while the Plate Brake Testers have
strain gauges attached to a plate supported on bearings, and measure the forces
required to hold the plate, when a vehicle is braked on top of it. Decelerometers
are placed in the vehicle and have a pendulum (more recently, airbag type
accelerators) that moves when a vehicle is braked, the amount of ‘swing’ on the
pendulum is measured to indicate deceleration during braking.
When it comes
to safety Roller Brake Testing is a comparatively safe method of testing, the
vehicle does not move during the brake test, the rollers ‘act as the road’ and
turn under the wheel. With both the Plate Brake Tester and the Decelerometer,
testing requires the vehicle to be driven and braked on the plates, usually
within the confined space of a vehicle workshop or roadside. This could be a
hazard to other road or workshop users.
Roller Brake Testers
use the same braking surfaces to test all of the wheels, on all of the
vehicles; ensuring accurate comparative tests. Plate Brake Testers use the same
braking surfaces for all of the wheels, on all of the vehicles, while the Decelerometer
tests on road so the braking surface can vary from very good to very bad pending
conditions.
While Roller Brake
Testers test all vehicles at a consistent test speed, both the Decelerometer
and Plate Brake Testers tend to test at variable test speeds; depending on how
the vehicle is driven.
Roller Brake Testers
can test the entire range of every brake fitted to the vehicle, from zero to
full braking, or wheel lock, consistently and repeatedly, without the influence
of momentum or weight transfer. The Plate Brake Testers and Decelerometers
cannot test the entire range of a vehicles brake successfully.
Decelerometers
cannot test individual axles, Plate Brake Testers can compare the balance of
brakes across individual axles, while Roller Brake Testers are able to
consistently and repeatedly compare the balance of the brakes across individual
axles.
Roller Brake
Testers use external power for the brakes to work against, typically electric
motors, therefore the time taken for the test can be controlled by the operator.
On average brake tests applications last approximately 20-40 seconds. Plate
brake testers and Decelerometers use the vehicles inertia to provide the power
to conduct the brake test, results have to be achieved in the time it takes for
the vehicle to stop, brake testing results are typically taken in a couple of
seconds.
Roller Brake
Testers are able to achieve consistent and repeatable results for brake tests
for individual wheels to full brake effort or wheel lock up, while Plate brake
testers and Decelerometers normally do not brake to full capacity, as this
would be too dangerous. The brakes are tested to try to exceed a pre-defined
deceleration and if this figure is exceeded then the brakes are deemed to be
‘good enough’.
The Roller
Brake testers are compact but require sufficient room each side of the brake
tester for the vehicle. Plate Brake Testers are the most space greedy, with a
large area required for the plates and a suitable amount of room required for
acceleration and deceleration including a safe overrun area. The Decelerometer
is the most space friendly, with no installation required for the vehicle
mounted unit.
To give
meaningful loading results with the all three of the testers, the vehicle needs
to be loaded to more than 60% of its carrying capacity, or in the case of the
Rolling Brake Tester, a simulated load applied.
THE FACTS
Driver fatigue, mechanical failure and speed dominate as the main causes
of heavy vehicle accidents, costing lives and billions of dollars across
Australia every year. Safety and maintenance is being brought into focus
through critical media attention which will send a ripple out across the entire
industry.
It is safe to say that with the introduction of the National Heavy
Vehicle Regulator in February, a greater focus on a national standard for
vehicle maintenance and inspection cannot be far behind. Will you be ready?
