CEE4014Lecture13

CEE4014Lecture13 - Estimating, Production & C t E i E...

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CEE 4014 Estimating, Production & Cost Engineering andling and Transporting Material Handling and Transporting Material OAD LOAD HAUL DUMP RETURN CEE 4014 Estimating, Production & Cost Engineering
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Construction Equipment qp achine Power Machine Power 2
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Engineering Fundamentals gg ycletimemadeupof: Cycle time made up of: Load time Maneuver time Travel time Dump time 3
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easure of Power Measure of Power • Required power • Available Power • Usable Power 4
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actors in Analyzing Equipment Operation Factors in Analyzing Equipment Operation olling Resistance 1. Rolling Resistance 2. Grade Resistance 3. Inertial Resistance 4. Horsepower 5. Altitude 6. Traction 5
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ower Available Power Available • Factors that determine available Factors that determine available power Horsepower Time rate of doing work (constant value) Speed achine speed is varied Machine speed is varied ravel fast and pulling ability will be low; travel Travel fast and pulling ability will be low; travel slow and the machine has the ability to exert a high pulling force. 6
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sable Power Usable Power • Usable power depends on project conditions, primarily haul-road surface condition and type, and altitude and temperature. 7
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POWER “Why does a machine only travel at 10 mph when its top speed is 30 mph?” This is a critical question because: Speed affects cycle time Cycle time drives production Production determines cost 8
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POWER REQUIRED A machine must overcome the forces of rolling and grade resistance to propel itself. These can be expressed as: /t lb/ton % effective grade Power required is the power necessary to overcome the total resistance to machine movement, which is the sum of rolling and grade resistance. 9
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Power Required 10
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ROLLING RESISTANCE olling resistance is a measure of the Rolling resistance is a measure of the force (lb/ton) that must be overcome to tate a wheel over the surface on which rotate a wheel over the surface on which it makes contact. Referred to as: Wheel resistance Track resistance 11
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Power Required • Friction: Rolling Resistance g Rolling Friction Vehicle Drag • Gravity: Grade Resistance or Assistance Positive Grade (resistance) Negative Grade (assistance) • Inertial Acceleration or Deceleration cceleration (mass x positive acceleration) Acceleration (mass x positive acceleration) Deceleration (mass x negative acceleration) 12
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Power Required ower required (expressed in lbs) = Power to Power required (expressed in lbs) Power to overcome the resistance to move = Sum (Friction+Gravity+Inertial Resistance) (y ) 13
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Rolling Resistance olling resistance is a measure of the force (lb/ton) Rolling resistance is a measure of the force (lb/ton) that must be overcome to rotate a wheel over the surface on which it makes contact.
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CEE4014Lecture13 - Estimating, Production & C t E i E...

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