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Posted: Oct 13, 2015

Brake Fade and Antilock Brake Options

In "Introduction to Braking Energy" (August 2015), I discussed how a vehicle is brought to a stop by converting its kinetic energy into heat.

The primary tools used to turn this energy into heat and bring the vehicle to a stop are the brakes. Ideally, when you purchase a fire truck, the engineers who built it will properly specify the correct amount of braking force needed based on the size and weight of the truck. As long as the truck stays within the weight parameters set by the engineers and you maintain a safe speed while driving, the brakes that were put on the truck will provide enough braking force to bring the truck to a safe stop. However, problems tend to arise after the rig is delivered and we decide to add more tools or hose than the vehicle was designed to carry. By exceeding the maximum gross vehicle weight rating (GVWR) or by driving the vehicle too fast, fire departments are inviting disaster.

What Is It?

Fire apparatus operators must be aware of "brake fade." To understand brake fade, we must first have a basic understanding of how air brakes work. The following is a brief summary; it is not meant to be an in-depth discussion on air brake operations. See "Air Brakes and the Driver Operator" by Terry Eckert (Fire Engineering, March 1998) for an article on air brakes.

  1. To apply the brakes, you press your foot down on the "foot valve," aka the "brake pedal."
  2. Air travels from an air tank reservoir through the air lines into a brake chamber. Air presses against a rubber diaphragm in the chamber, which in turn pushes a plate and pushrod. The pushrod is pushed out, which pushes a slack adjuster, which turns a camshaft, which twists the S-Cam, which forces the brake linings to make contact with the drum.1
  3. The amount of force these brake chambers can create depends on the size of the chamber and the air pressure being applied. The size of this brake chamber depends on the size and weight of your truck as well as which axle it is located on. They can come in sizes that range from nine to 12, 16, 20, 30, and 36 square inches and work along the same principles as a lifting air bag. Applying 100 pounds of air pressure to a size 20 brake chamber results in 2,000 pounds of force on the pushrod.
  4. The distance the pushrod has to travel to properly apply the brakes is known as the "stroke." Properly adjusted brakes have enough stroke so that when the brakes are applied, the brake shoes are spread apart and come in full contact with the brake drum. The friction of the brake shoes rubbing against the brake drum creates the heat that "uses up" the vehicle's kinetic energy and brings it to a stop.

The problem arises when there is too much energy to convert into heat so the vehicle can come to a stop. The amount of energy created by a moving fire apparatus depends on how much it weighs and how fast it is going. If you are going too fast or the rig weighs too much, there may be more energy than the brakes are designed to "bleed off." This can result in brake fade.

In a brake fade situation, the excess heat created by the brake shoes rubbing against the brake drum causes the metal brake drum to expand. Each time the brake drum expands, the pushrod has to travel farther so the brake shoes can contact the drum. Eventually, the brake drum may expand to a point greater than the pushrod can travel. In other words, the drum gets too big and the brake shoes aren't able to come in contact with it properly. This results in a loss of braking efficiency and quite possibly the complete loss of braking ability

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Posted: Oct 13, 2015

Why Not Just Stop?

Chris Mc Loone   Chris Mc Loone

It’s still happening. We are still wrecking fire apparatus. And in recent months, we have been wrecking them with other emergency vehicles.

I watch the videos-we all do. A simple Internet search will reveal all sorts of videos of apparatus responding. I’ve posted some of them myself on FireApparatus.com. Some of them are interesting, and some of them have lessons to teach. I see some of them though and wonder, what in the world is the driver thinking? When I first got qualified on our apparatus, I made rookie driver mistakes. We all do-no one’s perfect. But, some of these accidents-they’re not rookie mistakes. When has it ever been OK to run a red light with fire apparatus in the modern era?

One recent accident occurred in Florida. I’ve seen the video of it. And, video was made available shortly after the crash from four different angles. One of the angles pretty clearly shows one emergency vehicle not slowing down or stopping for a red light at the intersection. But, let’s not focus on that. There is no doubt the striking vehicle should have stopped. It’s a red light. But, let’s talk about the struck vehicle. The struck fire apparatus didn’t stop either. From the video, it looked to me like the apparatus operator didn’t even slow down. He had the green; he went. Most of us have seen the result.

A couple of lessons I recall from my days as a young apparatus operator come to mind. First was my deputy chief at the time saying, “Let me tell you something about driving an emergency vehicle. When you come to a traffic light, you stop.” The second is the chief engineer who trained me. He always told me when driving to make sure other drivers know what I am going to do. He said drivers who drive with a degree of uncertainty are just as dangerous as or more dangerous than drivers who do so with wreckless abandon.

The first bit of advice came after a mistake. To this day I maintain that I had control of the vehicle. However, the white hat sitting to my right didn’t share my confidence, and the passengers in the vehicle are the ones who count. If the officer isn’t feeling real confident, imagine how the crew in the back of the truck must feel about the ride. Having moved to the right side of the truck and having stepped on the imaginary brake pedal on that side, I have a good idea of how my deputy was feeling at that moment. He did the right thing. At the incident before we left, he took me aside, and he hasn’t had to take me aside since. I was young.

Making sure other drivers know what you are going to do-this is the responsibility of the driver and the officer. If you give the driver clear instructions about how you want to go, how you want him to respond, and any other expectations, the driver will be a lot better off, won’t be as jumpy, and will drive confidently.

Recently, we had a torrential downpour for about 15 minutes at around midnight or so. When it rains like that, and we experience floods, and the water rescues start, we go nonstop for probably a couple of hours, responding all over our township. Because of the time of day, we didn’t have any water rescues. We did have flooding though, and I was up front in our first-out piece for a fire call with a driver who had just been qualified on it the week before. He did well. We knew where we were headed, and I knew where the flooding was. He’s new though, and still young. He was itching to get going. We got to some water, and I made sure he knew in no uncertain terms that he was to slow down big time as w

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Posted: Oct 13, 2015

Scene Lighting, Part 2: the Confusing World of LEDs

“Scene Lighting Viewed from the Crew Cab, Part 1” (May 2015) illustrated the history of apparatus scene lighting leading up to today’s acceptance of 12-volt light emitting diode (LED) lights.

Part 2 was intended to provide manufacturers’ and apparatus vendors’ perspectives of LED lighting, the products they make and use, and what they recommend for scene lights-all in simple terms. It’s not going to happen. Understanding LED technology must be the first step in evaluating product and vendor presentations. This part will attempt to explain LED lighting in terms firefighters can understand. Apparatus dealers and OEMs can have their say later.

Technospeak (highly technical terminology) and advertising’s glitz and glitter can cloud judgment and play on emotions. It’s challenging to write purchasing specifications for scene lighting because of the ambiguities in regulatory standards, confusing advertising, and what I perceive to be a general misunderstanding of LEDs. Apparatus vendors not well versed in lighting products and terminology can find themselves in an uncomfortable position. It isn’t fair to them and the purchasers. Why spend so much time on scene lights? A halogen scene light can cost around $200. A similar sized (physical) LED scene light is about twice as much. Or, you can spend $2,000 for the brightest LED offered.

LED Lighting

The first accredited LED in an infrared (invisible) spectrum was developed in 1927 by Oleg Losev. In 1962, Nick Holonyak received a U.S. patent for an LED with a visible red light. Originally used as indicator lights in electronics, LEDs have been accepted by the fire service as an industry standard. Halogen lighting is following two-stage pumps into obscurity the same way incandescent lighting followed piston pumps into irrelevance.

I predict a transformation in the advertising and demeanor of scene light suppliers for several reasons. The first reason is that when LEDs were initially introduced to the fire service, light manufacturers compared them to halogen and incandescent lights. Now that LED technology is the norm, manufacturers will have to compare their own product to their competitors’ to retain or gain market share. The second reason is the educated consumer. Apparatus vendors shouldn’t assume purchasers will carte blanche accept their lighting sales pitches. Via social media and the Web, firefighters have unlimited access to product information from multiple sources. Vendors accustomed to purchasers dutifully accepting their every word as gospel may be in for a rude awakening.

The third, and most important, reason is the entrance of new players. Early suppliers of LEDs to the fire service were manufacturers of warning lights and sirens and other fire-related products. LED technology isn’t exclusive to the fire service. The electronics, aviation, and mining industries have embraced the concept for more than 50 years. They have been supplied by specialty manufacturers whose sole product lines are optics and lighting. Those suppliers are entering the fire service market. They speak a different language; they’re aggressive; they attend trade shows; and they’re willing to educate the end user-the firefighter. Jockeying for market share may become interesting at the least and ugly at the most. My objective is to help purchasers understand the product and make sound purchasing decisions by deciphering some of the LED technospeak. I have no preference for any type of lighting or manufacturer.

1 The inner workings of a typical LED scene light. The round yellow piec
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Posted: Oct 13, 2015

King County deputies, firefighters practice active shooter drill

A number of law enforcement agencies will conduct active shooter drill at Tahoma Junior High Tuesday morning as part of a yearly exercise. The goal is to test how students, staff, police and firefighters react to an intruder and to test the school's lockdown procedures. To make the drill feel as realistic as possible, a deputy will pose as an intruder and a group of student and adults will act as if they've been wounded and need medical attention.
- PUB DATE: 10/13/2015 7:42:40 AM - SOURCE: Northwest Cable News
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Posted: Oct 13, 2015

King County deputies, firefighters practice active shooter drill

A number of law enforcement agencies will conduct active shooter drill at Tahoma Junior High Tuesday morning as part of a yearly exercise. The goal is to test how students, staff, police and firefighters react to an intruder and to test the school's lockdown procedures. To make the drill feel as realistic as possible, a deputy will pose as an intruder and a group of student and adults will act as if they've been wounded and need medical attention.
- PUB DATE: 10/13/2015 7:42:40 AM - SOURCE: Northwest Cable News
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