DARLIND.COM ::: Over 30 Years Experience in Marketing Genuine Quality Crawler Tractor & Excavator Parts
Tracks help vehicles to distribute weight more evenly over a larger surface area than wheels can, keeping them from sinking in areas where wheeled vehicles of the same weight would sink.
A crude caterpillar track was designed in 1770 by Richard Edgeworth, and steam powered tractors using a form of caterpillar track were reported in use during the Crimean War. An effective caterpillar track was invented and implemented by Alvin Lombard, for the Lombard steam log hauler. He was granted a patent in 1901.
Perhaps the oldest concept of something like tracks is to be found in theories of pre-historic erection of large stone monuments, when megaliths may have been slid along atop rounded wooden cylinders. While most of the workers pushed or pulled the rock along the timber track, a task of a smaller group was to take each wooden log that the rock had already passed over and put it in front. This would have been a more efficient method to transport heavy rocks great distances than simply pulling it along the ground, though attempts by experimental archaeologists to reconstruct these methods have met with variable success.
Modern tracks are built from modular chainlinks which compose together a closed chain. These chainlinks are often broad and made of strong metal. Between every two pieces of the chain there is a joint enabling the chains to change the angle between them. This allows the track to be flexible and maintain its elliptical shape. Suspension design is a major area of research in modern track systems; early designs offered only a few inches of travel using springs, whereas modern hydropneumatic systems allow several feet of travel and include shock absorbers.
There are two main systems : one is called Christie suspension and uses oversized road wheels and the track simply lies on top of the wheels. The shape of the track as a whole is somewhat banana-like as the track droops onto the wheels after running over the driving wheel and idler. The other system, sometimes called a Vickers suspension arrangement, uses smaller return rollers to hold the track straight from the idler to the driving wheel, leading to a sideways D shape.
The advantages of tracks result in increased mobility through rough terrain. First, tracks are much more resistant to shrapnel (nails, broken glass etc) and sharp fluctuations in the ground (holes, small pits and ditches) than wheels, thus enabling the vehicle to drive over small obstacles that would stop a wheeled vehicle. Secondly, tracks distribute the weight of the vehicle over a larger area, thus decreasing its ground pressure. It is common to see tracked vehicles such as bulldozers or tanks transported long distances by a wheeled carrier such as a semi-trailer or train, though technological advances have made this practice less common than it once was.
This text has been summarised from the Wikipedia article "Caterpillar track"