Braking Regulators
“Oh POOP” muttered Oakie. This is G-rated, so that's paraphrasing… but the bus was utterly silent, and the load of dignitaries seated him behind heard.
Oakie was spearheading the effort to get a new double deck model of coach accepted in the US, and that involved transporting a Demo to Albany, New York, and taking bus industry and regulatory VIPs on a ride that included the NYDOT brake test.
For the uninitiated, this involves sticking a G meter on the windshield, accelerating the coach to a specified speed… and dynamiting the brakes.
The bus came to a shuddering halt, silent because Oakie had stalled the engine, forgetting to disengage the clutch on a coach with a standard transmission.
Thence came “Oh POOP”.
There are two reasons for telling the story. First, any opportunity to embarrass Oakie should not be squandered, but also to point out that when NYDOT tests brakes they measure what matters. Do the damn things stop the coach quickly?
There are all sorts of other “thingys” that regulators measure to determine if brakes are in good repair, but doesn't it boil down to... does the bus stop quickly and reliably? Some of those “thingys” really do matter, but some are not very relevant.
Years ago an operator's brand new coach was stopped for a roadside inspection, and declared “out of service” because there was too much travel in the slack adjusters. After several hours of frantic phone calls and faxes from the brake vendor, the Trooper involved accepted that these slacks were designed to have a long stroke, and turned the bus (and it's passengers) loose.
There are two overlapping concerns here. If the inspection actually tested stopping distance, ala NYDOT, substantial inconvenience for both the operator and customers would have been avoided. Instead the Trooper was only trained in the use of an arbitrary measurement that, in this case, gave a false impression.
It may be more difficult and expensive to measure actual performance, but if a coach operator gave that excuse about safety related items… imagine the outcry.
You're probably aware that coach builders buy the braking systems they install. Years ago, during the switch to disk brakes, the manufacturer I worked for chose a particular model of brakes that had external slack adjusters. I asked an engineer why they picked that model, as opposed to a competitor's that did all that “adjusty stuff” internally, out of the gritty environment.
His response spoke volumes… “We wanted to give the Inspectors something to measure”. That's the tail wagging the dog…
AND… according to an article in a trucking publication, there's been a significant increase in the number of out of service violations related to automatic slack adjusters being either defective, or out of adjustment. This is on trucks where drum brakes are still common.
The writers point was that many drivers (and some shops) don't understand how automatic adjustment works. My guess is that, in our industry, where more complex disk brakes predominate, it's even more true.
The old way we did it… crank that sucker clockwise until tight and back off a couple of clicks… simply doesn't work. In fact, it can damage the adjustment mechanism.
Inspectors need to have a better understanding of brakes than just gauging slack travel or lining thickness. The measurement that REALLY matters is stopping distance. Drivers need to take note when a bus is stopping long or crooked, and get the brakes properly adjusted. The more they understand how modern braking systems work the better off we all are.
Back in the day, my buddy Dick was about to depart our Colorado property in a GM 4104. This involved descending a gentle cliff on a dirt road, replete with tight turns. Pulling in, before boarding a group of high school kids, he had noticed the brakes didn't feel quite right and sent for a mechanic to adjust them. When you're about to drive over a (gentle) cliff… brakes are a good thing.
THIS is the GENTLE Cliff
The mechanic rolled under the bus and cranked each slack adjuster tight, and then backed off the required 3 clicks.
Dick finished loading the bus, pulled the chock, and headed down... the cliff.
The first time he touched the brakes, and virtually nothing happened… he cleverly figured out something was wrong. We later heard that the rest of Dick's (and his passengers) descent reminded them of Disney's “Thunder Mountain” roller coaster.
It turned out that the mechanic had been a bit confused regarding clockwise vs. counterclockwise… and had cranked the brakes all the way off, before giving them a scant 3 clicks of “ON-ness”.
If he'd been a little better trained… or paid a bit more attention… well, things would have gone smoother. It wouldn't have hurt if Dick had tested the brakes before driving off.
Trust, but verify...
