Building a Tractor – Operations

• In a tractor Dozer the driving power from the diesel engine is transmitted to the main clutch through the flywheel.
• Power from the main clutch shaft is transmitted through the universal joint to the main shaft of the transmission.
• Power obtained through a gear selected according to the load is transmitted from the transmission to the bevel pinion at the rear end of the transmission case.
• This power is directed into the right and left directions by the bevel pinion and the bevel gear.
• Steering clutches which are provided at both the ends of the bevel gear shaft intercept and control the direction of power from the bevel gear shaft to the final drive.

• The direction of the dozer is changed by operating the steering control valve provided at the steering case top to cut off power of the steering clutch on the side interested for travelling.
• The turning radius is determined by the steering brake mounted on the periphery of the steering clutch brake drum.
• The power is transmitted to the sprocket by means of pinions and gears. The revolution of the sprocket drives the track to cause the tractor dozer to travel.

Under carriage construction

• During operations – high impact loads
• Wear condition load – metal to metal riding over, working mud, hard rock and hard gravel.
• Wear resistant materials
• Track frame: support frame – steel structure shaped to present a box like construction in cross-section
• Designed to withstand the shock loads, bending, deformation and breakage.
• Up and down movement is avoid tilting and pitching of the front end of the machine during crawling on the rough ground.
• Vibration absorbed by rubber pad to improve the machine life and operator comfort.
• Equalizer Bar : This is a welded box like beam of steel plates which distributes the weight of front portion of the machine equally to the two track frames. Its center point is pivoted to the cross bar of the chassis.
• Sprocket: Sprocket revolves in a loop of endless track chain to transmit driving power to the track to roll.
• Front idler: This supports the front end part of the track chain to allow the track to roll straight over rough ground.
  • The idler slides as well as can move upward and downward at the front end of the frame by the guide plates attached to the underside of the bearing and connected to the recoil spring assembly through yock to maintain track tension tight enough to keep sufficient engagement of the sprocket wheel with track.
• Track Rollers: These are arranged under each track frame and bolted on to it. They evenly distribute the weight of the machine on the track and ride on the tread surface of track link.
• Carrier Rollers: These are installed on to the upper side of the track frame over a support. It guides and support the upper half of the track loop to proper rolling condition and avoids dangling due to its weight.
• Track Chain Assembly: Track chain assembly is formed by joining links, pins, bushings and mounting track shoes on the links with the help of bolts and nuts.
• Track link assembly: The links support the weight of the machine and are subjected to frequent impact load due to riding over rocks.
  • These are made by forging of alloy steel (manganese steel) and surface hardened to provide wear and shock resistance property.
  • Links act as rail along direction of machines travel.
  • A pair of links fix shoes, pins and bushings, seals and spacers.
  • Pins and bushes both are press fitted in their respective holes provided in the links.
  • Sections of the track are joined by passing the pin of one section through the bush of the next section.
  • Outer surface of a bushing wears out as it comes in contact with sprocket teeth where as inner surface wears out as it is rotation ally supported by the pins involved.
  • The bushing act as the medium of transmission of driving power from the sprocket wheel to the track.
• Track shoe: A track shoe is composed of a plate which support a part of the machine weight and grousers which permits the shoe to grip the ground and penetrate soil to its full depth for a good traction and protection against side slippage under most conditions.
  • Track shoes are subjected to impact load, large stress and abration due to sliding contact with ground. These are cast or forged of special alloy steel and heat treated.
  • The shoes are bolted to the links.
  • Narrow shoes with heavy, rugged grousers and plate sections are recommended for rock jobs. Wider track showes are suitable for soft underfooting to acquire maximum floatation and maximum drawbar pull
• Track roller guards: These protects track rollers from being damaged by rocks and debris, these also prevents track from slipping.

Long life under carriage

• Avoid unnecessary high speed operation
• Avoid sharp and pivot turn
• Avoid reverse direction traveling
• Avoid loading only on one side for long periods of time
• Avoid track shoe slip under undue load
• Aviod riding over big boulders
• Avoid leaving a machine stopped on slant
• Avoid turning machine only in one direction

Under carriage maintenance

• Regular checking and maintenance is most necessary to get best performance.
• Replacement of undercarriage part high
• Bad operation too causes premature wear and failures, spinning causes fast wear and reduced life
• Ripping
• Dirt is still enemy of tracks and roller
• Right quality nut and bolts
• Proper track tension