Professional Engineering Exam Review Machinery Management

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Professional Engineering Exam ReviewMachinery
Management

• Gary Roberson

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Topics for Discussion

• Implement performance
• Draft and power estimation
• Fuel consumption
• Machine capacity

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Documents to Review

• ASAE S296.5 General Terminology for Traction of
  Agricultural Traction and Transport Devices and
  Vehicles
• terminology to assist in the standardized
  reporting of information on traction and
  transport devices and vehicles.

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Documents to Review

• ASAE S495.1 Uniform Terminology for Agricultural
  Machinery Management
• Uniform use of machinery management terms.
• Definitions used in system analysis, economic
  analysis, and mechanical concepts.

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Documents to Review

• ASAE S496.3 Agricultural Machinery Management
• Management decisions related to machine power
  requirements, capacities, cost, selection and
  replacement

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Documents to Review

• ASAE D497.5 Agricultural Machinery Management
  Data
• Data for use with decision tools from ASAE S496.3

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Books of Interest

• Machinery Management, W. Bowers, Deere and Co.
• Farm Power and Machinery Management, D. Hunt,
  Iowa State University Press.
• Engineering Principles of Agricultural Machines,
  A. Srivastava, et al , ASABE
• Engineering Models for Agricultural Production,
  D. Hunt, AVI Publishing Co.
• Agricultural Systems Management, R. Peart and W.
  Shoup, Marcel Dekker

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Implement Power Requirement

• Drawbar power
• Power developed by the drive wheels or tracks and
  transmitted through the hitch or drawbar to move
  the implement.
• Power is the result of draft (force) and speed

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Implement Draft

• D is implement draft, lbf
• Rsc is soil and crop resistance, lbf
• MR is total implement motion resistance, lbf

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Implement Draft

• Where
• Ddraft, lbf
• Fsoil texture parameter
• itexture indicator 1fine, 2medium, 3coarse
• A, B, And C machine parameters
• Sspeed, mph
• Wwidth, ft or tools
• Ttillage depth, in. (1 for tools that are not
  depth specific)

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Implement Draft Example

• A 12 foot chisel plow with straight points and
  shanks spaced 1 foot apart is used at a depth of
  6 inches in medium textured soil at a speed of 5
  mph.

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Table 1, D497.5
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Implement Draft Example

• Chisel plow with straight points
• Table 1 in D497.5
• A 52, B 4.9, and C 0
• Medium soil texture
• Table 1 in D497.5
• F2 .85
• S 5 mph
• W 12 ft or 12 tools
• T 6 in

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Implement Draft Example

• DFiAB(S)C(S)2WT

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Implement Draft Example

• DFiAB(S)C(S)2WT
• D0.85x524.9(5)12x6

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Implement Draft Example

• DFiAB(S)C(S)2WT
• D0.85x524.9(5)12x6
• D ?

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Implement Draft Example

• DFiAB(S)C(S)2WT
• D0.85x524.9(5)12x6
• D 4682 lbf

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Implement Draft Exercise

• A 4 shank subsoiler with straight points is used
  at a depth of 16 inches in coarse textured soil
  at a speed of 4 mph.
• Whats the Draft?

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Drawbar Power

• Pdb Drawbar Power, HP
• D Draft, lbf
• S Speed, mph

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Drawbar Power Example
An Implement with a draft of 8,500 lbf is
operated at a net or true ground speed of 5.0 MPH
with 10 percent wheel slippage. What is the
implement drawbar power?
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Drawbar Power
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Drawbar Power
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PTO Power

• PTO power is required from some implements and is
  delivered through the tractor PTO via a driveline
  to the implement.
• The rotary power requirement is a function of the
  size and feed rate of the implement.

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PTO Power

• Ppto PTO power
• W implement working width, ft
• F material feed rate. t/hr

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PTO Power Example

• A large round baler has a capacity of 10 tons per
  hour. The baler has a variable bale chamber

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Table 2, D497.5
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Implement PTO Example

• Variable Chamber Round Baler
• Table 2 in D497.5
• A 5.4, B 0, and C 1.3
• 10 t/hr capacity

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Implement PTO Example
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Implement PTO Example
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Implement PTO Example
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PTO Power Exercise

• A rectangular baler has a capacity of 3 tons per
  hour. Bale dimensions (cross section) are 16 x
  18.
• Whats the PTO power requirement?

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PTO Power Exercise

• A rectangular baler has a capacity of 3 tons per
  hour. Bale dimensions (cross section) are 16 x
  18.
• Whats the PTO power requirement?

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Hydraulic Power

• Fluid power requirement from the tractor for the
  implement
• Hydraulic motors and cylinders used to drive
  implement functions

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Hydraulic Power

• Phyd fluid power, HP
• P fluid pressure
• F fluid flow, gpm

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Hydraulic Power Example

• A harvester uses hydraulic power to drive a
  conveyor. The requirements were measured at 10.5
  gpm at a pressure of 2200 PSI.

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Hydraulic Power
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Hydraulic Power
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Hydraulic Power
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Electrical Power

• Some implements require electrical power supplied
  by the tractor for certain functions.
• Typically electrical power for control functions
  is small and can be neglected.
• Electrical power for pumps and motors should be
  accounted for.

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Electrical Power

• Pel Electrical Power, HP
• I electrical Current, A
• E Electrical potential (voltage), V

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Electrical Power Example

• A sprayer uses electrical power to drive a pump.
  The requirements were measured at 20 amps at 12
  volts.

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Electrical Power
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Electrical Power
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Electrical Power
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Implement Power

• Combined total of drawbar, PTO, Hydraulic and
  Electrical power
• Drawbar power adjusted by tractive and mechanical
  efficiencies
• 80 rule
• Implement power should not exceed 80 of rated
  tractor power

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Tractive Efficiency

• Ratio of drawbar power to axle power
• Takes into account the added resistance the
  tractor will encounter in moving through the
  soil.
• Firmer soil, higher TE
• Softer soil, lower TE

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Mechanical Efficiency

• Accounts for power losses in the tractor drive
  train.
• Accounts for friction loss, slippage in a clutch,
  torque converters, etc.
• Usually constant for a given tractor
• 0.96 for tractors with mechanical transmissions

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Power Efficiency Chart
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Implement Power

• Pt total power, HP
• Pdb drawbar power, HP
• Em mechanical efficiency
• Et tractive efficiency
• Ppto PTO power, HP
• Phyd Hydraulic power, HP
• Pel electrical power, HP

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Implement Power Problem

• Determine the recommended tractor size for an
  implement that requires 48 drawbar horsepower, 12
  PTO horsepower and 2.5 hydraulic horsepower. The
  tractor should be 2 wheel drive and you will
  operate on a tilled soil surface.

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Drawbar Power Conditions

• Determine the tractive efficiency anticipated.
• From Figure 1, D497.5
• 2WD on tilled soil surface, TE 0.67
• Assume a mechanical efficiency of 0.96

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Implement Power
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Implement Power
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Implement Power
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Tractor Size

• Determine the implement power requirement
• Apply the 80 rule
• Example
• Implement power 79.4 HP
• Tractor power 79.4/.8 99.3 HP

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Tractor Size Exercise

• An implement uses 25 PTO horsepower, 3.6
  horsepower through the hydraulic system and 1.9
  horsepower in the electrical system. What is the
  minimum recommended tractor size?

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Tractor Fuel Consumption

• Fuel consumption can be estimated for tractors
  used in various operations.
• Specific fuel consumption is quoted in units of
  gal/hp-hr
• Average fuel Consumption (Diesel)
• Qs 0.52X 0.77 - 0.04(738X 173)1/2
• where X ratio of equivalent PTO power to rated
  tractor power

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Tractor Fuel Consumption Example

• A 95 PTO horsepower tractor is used with a 55
  horsepower load. How much fuel will be consumed
  in one day (10 hours)?
• X 55/95 0.58
• Qs 0.52x0.58 0.77 -
• 0.04((738 x 0.58) 173)1/2
• Qs 0.092 gal/hp-hr

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Tractor Fuel Consumption Example

• Estimated Fuel Consumption
• Qi Qs x Pt
• Qi 0.092 x 55
• Qi 5.06 gal/hr
• Total Fuel Consumption
• 5.06 gal/hr x 10 hrs 50.6 gal

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Equipment Economics

• Required Capacity
• Size of machine necessary to get the job done in
  the time available.
• Acres/Hour
• Effective Capacity
• Available capacity of equipment in operation
• Acres/Hour

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Machine Capacity

• Required capacity will tell you how large the
  machine should be
• Effective capacity will tell you what a given
  piece of equipment can deliver
• Effective capacity should equal or exceed
  required capacity for most applications

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Machine Capacity

• Ci required capacity, ac/hr
• B days available
• G working hours per day
• PWD probability of a day suitable for field
  work in the given time frame

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Machine Capacity Example

• What size machine is needed to cover 1000 acres
  in a three week (5 days per week) window in
  August. You can work up to 10 hours per day.
• From Table 5. D497.5
• PWD 0.51

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Machine Capacity
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Machine Capacity
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Machine Capacity

• Ca available capacity, ac/hr
• S speed, mph
• W width, ft
• Ef Field Efficiency

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Field Efficiency

• Ratio of effective field capacity to theoretical
  field capacity
• Effective field capacity is the actual rate at
  which an operation is performed
• Theoretical field capacity is the rate which
  could be achieved if a machine operated 100 of
  the time available at the required speed and used
  100 of its theoretical width

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Theoretical vs. Effective Width

• Theoretical width
• Measured width of the working portion of a
  machine
• For row crops, it is row spacing times number of
  rows
• Effective width
• Actual machine working width, may be more or less
  than the theoretical width

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Machine Capacity Example

• What is the capacity of disc harrow that operates
  at 6 mph with a working width of 18 ft?
• From Table 3. D497.5
• Typical field efficiency is 80 (0.80)

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Machine Capacity Example
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Machine Capacity Example
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General Problem Solving Guides

• Study the problem
• Determine the critical information
• Decide on a solution method or equation
• State all assumptions, cite data sources
• Solve the problem
• Indicate solution clearly

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Machine Capacity Exercise
You are given an implement that covers 8 rows on
a 36 inch row spacing. This implement is
effective at 6 miles per hour with a field
efficiency of 80. You have a 2 week window
working 5 days a week, 10 hours per day.
Probability of a working day is 60. Is this
implement large enough to get the job done?
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Contact Information
Gary Roberson Associate Professor and Extension
Specialist Biological and Agricultural
Engineering North Carolina State
University E-mail gary_roberson_at_ncsu.edu Phone
919-515-6715
Good Luck!