The Early Days

The 20th Century

Retarders

Development of the D-Brake LCDB

 



History of Braking

 

Foreword

The D-Brake liquid-cooled driveline brake (LCDB) is a supplemental brake, designed as a solution for the inevitable thermal problems associated with braking. The D-Brake LCDB is a driveline brake which utilizes the vehicles cooling system. The integrated pump moves coolant from the brake to the engine’s cooling system, providing a virtually unlimited thermal mass to dissipate the brake energy. By taking the load off the service brakes we keep them cool; and cooler brakes means decreased stopping distance, decreased maintenance, decreased pedal effort, extended brake life, and increased safety. The hand controlled unit has 5 different power settings that let you adjust the strength of the D-Brake to your individual needs, including the revolutionary new "Braking Cruise Control" feature, D-Brake Cruise™. This feature allows you to set a max speed while descending slopes, maintaining a constant speed as the The Wooden Block and Lever grade varies. In order to fully appreciate what the D-Brake represents and the problems it has overcome, we have provided a brief history of braking.

The Early Days

It is important to understand the problems associated with braking in the past, and the advances that have been made in order to overcome these problems. One of the first types of brakes was a very crude system used even before the Roman Empire. This involved a brake lever that pressed a simple wooden block against the wheel in order to slow a cart down by friction. 2000 years went by with no improvement to this technology! In the Old West, the lever and block method was still prevalent on stage coaches. Early locomotives also used the block against the wheel. This system is still in use today, but mostly in combination with disc brakes and other systems.  Improvements in materials (wood blocks to cast iron brake shoes) were not adequate to prevent runaways, which were common in the Old West - an early example that there was a need for better brakes.

 

 

The 20th Century

The 20th century brought many advances to the types of braking. As the automotive and trucking industries developed, brake systems improved. Early automobiles had band brakes which were then followed by drum brakes; both were applied mechanically through linkage. Hydraulic systems were a major improvement in the 1920's - 1940's, allowing more consistent force distribution. Since the 1960’s, disc brakes have become common on cars and trucks, resulting in shorter stopping distances due to improved fade resistance. However, much like the drum brakes, the design flaw of the disc brake is its limited thermal mass. Every time you apply the brakes, the mass increases in temperature. This can be demonstrated by modern race cars, whose brakes glow red-hot during races. When brakes get hot, the stresses increase and performance fades. This is a very dangerous problem, especially when you are dealing with heavily loaded vehicles. In most cases it is impossible to design enough braking into the wheels to absorb all of the thermal energy that may be required.

Retarders

The inability of air-cooled friction brakes to absorb energy for prolonged durations created a market for products called “Retarders”. There are several types of retarders, which are auxiliary devices that provide a braking or “retarding” force. These products are available for many types of vehicles, aiding in the downhill braking while improving safety and brake life. Safety is improved due to the energy absorbing capability of these non-frictional devices. The life of the original brakes is improved due to the reduced usage on long downgrades and subsequently lowers operating temperatures. Some common types of retarders are engine brakes, exhaust brakes, electromagnetic, and hydrodynamic retarders. The following describes the basic types of retarders:

Engine brakes are mostly for large tractor-trailers. They absorb energy by converting a diesel engine into an air compressor by hydraulically opening the exhaust valves at the end of the compression stroke. This produces a “popping” noise, which has caused these brakes to be outlawed in some areas.

Exhaust brakes are mostly used on diesel engines with standard transmissions. They are less effective with an automatic, and not practical on gas engines. They are located after the exhaust manifold and create a back pressure on the engine exhaust by closing a butterfly or gate valve. These products are not very effective at low speeds, but for the cost they provide reasonable performance in long downhill braking when matched with the correct powertrain.

Electromagnetic Retarders are a driveline braking system. They create a retarding force by shearing magnet flux lines. These products can be used in heavy-duty applications in conjunction with other types of retarders, or alone in school and transit buses. The negatives are the weight, installation time and the large draw on the electrical system. They do produce a lot of braking and for some markets they are a good choice.

Hydrodynamic Retarders are another driveline auxiliary braking system. These products produce retardation by shearing fluid, usually oil. The kinetic energy produced by the shearing is converted into heat which is dissipated indirectly to the engine cooling system. Some of the negatives of this type of product are the high parasitic losses when it is not in use. The unit always has some oil in it for lubrication purposes, which produces an unwanted drag that lowers fuel economy. These products are popular for markets such as transit busses and heavy-duty trucks.

 

Development of the D-Brake LCDB Overview

The D-Brake was developed as an improvement over previously existing braking systems. We addressed the issues of the past and forged into the future to provide the following:
• Good braking at both low and high speeds
• Light weight
• No electrical draw
• No dangerous electromagnetic fields
• Very low parasitic losses
• Anti-skid protection
• Braking cruise control
• Simple installation

Click Here for the full story behind the development of our Liquid-Cooled Disc Brake.

Click Here to check out our Professional Tow Brake

Click Here for our Liquid Cooled Driveline Brake

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“Fitting new Brake Shoes.” Online Art. Frederick’s Renault 4 Workshop. 12 Dec. 2008 <http://www.renault4.co.uk/tech-brake-drums.htm>
“Red Hot Braking News” Online Art. CD-adapco. 10 Dec. 2008 <http://www.cd-adapco.com/press_room/dynamics/24/renault.html>

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