But what does this think of, and how does an Accident Investigator/ Collision Reconstructionist go about establishing whether bracken failure has been one of the contributing factors to the crash ?
After the holocene awful crash at an overlap at Pinetown, we decided to approach well-known accident investigator Stan Bezuidenhout with questions to provide some clarity and insights on brake failure as a contributing divisor to fomite crashes .
We raised the following questions:
What are the most important differences between the braking system on trucks and the brakes on a normal passenger vehicle?
The most important difference between “ car ” and “ truck ” brakes include the following :
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- car brakes are basically in a permanent state of non-engagement. There are no brakes until you apply animal foot atmospheric pressure. This pressure is amplified by the brake booster ( brake organization components ) and converted into pressure applied via two cylinders to a couple of brake “ pads ” that clamp down on the brake harrow. basically, this means that there are no brakes until brakes are actively applied. The car brake system contains a fluent ( brake fluid ) that is used to transfer blackmail from the operator ‘s infantry to the brake callipers .
- Truck brakes basically dwell of TWO systems : Park ( or leap ) brakes and Service ( or Foot ) brakes. The hand truck brake system has a cylinder that contains a potent bounce and a vacuum chamber ( booster ). This is connected to a push-rod which is, in change by reversal, connected to an arm ( lax adjuster ) which twists a diaphysis with a cam ( S-Cam on it ). The S-Cam causes two brake SHOES to expand ( open up ) and touch with the inside of a brake drum. so, a hand truck brake system would be permanently ENGAGED if there was no external influence. A truck brake system works with a vacuum. If there is NO VACUUM, the springs would actuate the push-rod, which will lever the slack adjuster, turning the S-cam ( shaft ), engaging the brakes. When vacuum is applied, the push-rod ( end ) is “ sucked back ” and then the brakes are released. then – every time a driver tries to “ break ” the vacuum would be released and the brakes would be applied. You can “ basically, ” say that the truck brake system ( breeze brakes ) exploit in “ reverse ” to car brakes .
When we hear that the “brakes have failed” – What does this actually mean?
In the case of car brakes, this could mean a total of things, including :
- There is a “ leak ” in the brake pipes, causing brake fluid to escape ( leak out ) and this would mean that there is no long enough fluid to transfer pressure .
- Seals could damage, resulting in some of the imperativeness “ Escaping, ” reducing brake efficiency .
- The brake linings ( brake pads ) could become worn, requiring more and more bicycle propulsion to engage brakes .
- Brakes could overheat, resulting in poor brakes or even the brake fluent boiling or breaking down and reducing brake efficiency .
- In the case of air brakes, it gets a bit more complicated. The following things can lead to a “Failure:”
- If there is ANY defect ( leak ) on the vacuum system and the vacuum is lost, the spring brakes will “ actuate ” and stop the fomite .
- If there is any fluid escape ( bearing grease, etc ), the clash surfaces can be compromised ( made besides slippery ) and the vehicle could lose braking efficiency .
- If the Slack Adjuster is not set ( or adjusted ) by rights, the push rod might not be able to push the abate adjuster far enough to result in propulsion .
- If a booster is failing, operators sometimes remove the pipes, jacks off the brakes ( this can be done ) and seal the shriek so that the respite of the brake ( boosters ) can work ; but this can lead to total brake failure ascribable to overheating .
- If the S-Cam turns excessively far, it can “ flip over ” and it then stops having any effect on brakes, while “ everything looks ticket. ” This is very dangerous and renders the brakes ineffective .
As an expert witness in court – are there specific challenges from the prosecutor/defence lawyer you have come to experience with regards to testimony on brake failure?
One of the biggest issues with regards to brake failure is the actual tow and convalescence. When tow companies want to tow a vehicle that was involved in a collision and the brake system has been compromised, they need to “ jack off ” all the brakes .
This then forces the brake system, to compress the spring ( brake ) and release the wheel brakes .
If this is done the master condition of the brakes can not be checked efficaciously and therefore testimony becomes harder .
besides – if the truck ( horse ) is wholly destroyed, the efficiency of the vacuum pump and regulators can not be determined faithfully. This means that SOME components of the brake system might remain unexamined – limiting the accuracy of testimony .
Which brake components are the most likely to “fail”?
In cars, it would be the brake pads ( themselves ), the overlord cylinder ( chief cylinder near the foot-brake that applies initial press ) and the slave cylinder ( the cylinder at the wheels that actuate the caliper ) seals. But, as brake fluid gets older it besides starts to deteriorate, and this besides reduces braking efficiency .
In air brake systems the slump adjuster angles, vacuum ( press ) regulators and load sensors ( not set properly ), adenine well as wear brake linings, are the most coarse causes of bankruptcy .
When you are requested to investigate a crash with alleged brake failure – what do you specifically look for and what are the indicators that there has indeed been brake failure?
Drivers of cars must ALWAYS become alert and have their brakes seen to if:
- The brakes become “ spongy. ”
- The brakes work all right, but “ evanesce ” and become less effective at the meter ( normally after increased use ) .
- They find that there is a “ scrape ” sound when they brake .
- The vehicle pulls to either side while they are braking .
They have to “ pump ” the brakes to stop.
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Drivers of trucks and buses must become alert and report faults when:
- They have to wait besides farseeing for the spring brakes to release ( after starting up ) .
- The blackmail ( or vacuum – there is a gauge in most vehicles ) fluctuates at times .
- They can hear the brake system “ unloading ” intermittently while they are driving .
- They smell or see smoke from any wheels or brake system while driving or stopping .
- They are ineffective to stop effectively at any fourth dimension .
- Their dawdler brakes lock up when they are loaded or partially loaded when they stop .
- They hear any mechanical knock or banging sounds while driving or brake .
What would you suggest as the most important steps for the trucking company and passenger vehicle driver to do to avoid brake failure?
Drivers should have their fomite tested and checked REGULARLY .
Drivers should report BRAKE SYSTEM ISSUES IMMEDIATELY ( see those above ) and PUT IT IN WRITING .
If you experience any issues with brake, hear any curious sounds, see any fluids run out anywhere ( at wheels ) or if you can see brakes are hot ( steam, fastball, etc ), REPORT IT or HAVE IT SEEN TO immediately .
How significant is training on vehicle maintenance for the hauling company – van the accident detective play an crucial function in preventive measures as well ?
No person should be allowed to work on a vehicle brake ( or any other safety ) system who is not a qualify mechanic/technician .
What role can the accident investigator/truck brake expert play in crash prevention?
We conduct regular technical fleet audits for clients. This having been said, these are NOT ( mere ) roadworthiness checks .
We examine a vehicle completely and our evaluation is thus rigid that we even “ fail ” modern vehicles .
As crash reconstruction experts, we look not entirely at the functional elements but besides the theoretical/legal ones .
We look at any and all items that could, might, would or may ( one sidereal day ) contribute to a collision .
With our Technical Fleet Audits, we assign a fault gravity measure for each element we are able to predict as a possible cause or factor in COLLISIONS .
From this, we produce a graph, showing the components or aspects that need IMMEDIATE wish ( fomite must be removed from servicing ), pressing ( fault/element must be repaired angstrom soon as vehicle returns ), serious ( Fault must be repaired at following service ) or cosmopolitan ( it should be attended to at the following major service ) .
By being made aware of all the elements and seeing a chart ( with red indicators ) besides enables a fleet owner to IMMEDIATELY evaluate the timbre of his/her evanesce and to determine how urgently they need to act .
Our system is so effective that we have seen clients recall and immediately repair 84 vehicles in three days ( working nightlong ) .
By having us do an independent technical foul fleet audit and acting on our recommendations, our clients are able to show ( in the very unfortunate consequence of a collision ) that they are so serious about road safety, that they have appointed an independent expert to examine all their vehicles and that they took immediate steps to eliminate all possible risks .
Stanley S Bezuidenhout
Forensic Road Transport and Risk Expert
Crash Guys International
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Brakes/ Braking and Road Safety
Accident Investigation and Road Safety