Equipment and Power Basics

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Equipment and Power Basics

• CE 477, SSI 2009

RICarr
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Tractor, Scraper
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Bulldozer
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Loader
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Mobile Cranes
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Forces to Overcome

• Rolling Resistance
• Grade, weight of vehicle
• Push
• Traction check

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Rolling Resistance
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Rolling Resistance Example

• 2-wheel tractor, gross wt 160,000 lb
• Rubber tires, low pressure, poorly maintained
  earth RR factor 85 lb/ton
• 160,000 lb/2,000 lb/ton 80 tons
• 80 tons 85 lb/ton 6800 lb RR.

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Grade

• 2-wheel tractor, gross wt 160,000 lb
• 4 percent grade
• 160,000 lb 0.04 6,395 lb grade resistance
• 6,395 GR 6,800 RR 13,195 lb total resistance

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Traction
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Traction

• 160,000 lb gross wt
• 13,194 lb RRgrade
• 50 of wt on drive axle
• 80,000 lb on drive axle
• Required Coefficient of Traction 0.16 OK

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Definitions

• Flywheel Horsepower (brake horsepower) Power
  output at engines flywheel
• Standard temperature, atmospheric pressure, rpm.
• Usable Horsepower Output horsepower available
  after losses fwhpe (e80-90)
• Usable hp should be corrected for pressure
  (elevation) and temperature
• Dont run at 100 of usable!
• Rimpull Useable force between tire and ground.
• Drawbar pull force available at drawbar.

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Power versus Force

• Work Force times Distance
• Power Work/Time
• PowerForce times Velocity

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Power Example

• 280 hp tractor (fwhp)
• 85 efficiency
• 80 duty
• 190 usable hp
• 104,720 ft-lb/s
• 13,195 lb RR Grade
• V P/F 7.9 f/s
• V 5.4 mph

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Accel
Haul
Decel
Load
Dump
Turn
Turn
Return
Accel
Decel