PSAA Curriculum

1
PSAA Curriculum

• Unit
• Physical Science Systems

2
Problem Area

• Energy and Power Systems

3
Machine Performance Efficiencies

• Lesson

4
What factors have to be considered in order to
determine if a machine is performing efficiently
or not performing its tasks efficiently?

• What is the concept of efficiency?
• What is the concept of mechanical efficiency?
• What is the concept of performance efficiency?
• What is the concept of field capacity?
  Theoretical field capacity? Effective field
  capacity?

5
Why is machine efficiency so important in todays
agricultural industry?
6
Learning Objectives

• Define efficiency, performance efficiency,
  mechanical efficiency, and field efficiency.
• Identify theoretical field capacity and effective
  field capacity and the relationship between them.
• Identify how efficiencies are determined and how
  efficiencies are used to size and select
  machinery and equipment.

7
Terms

• Output
• Performance
• Performance efficiency
• Theoretical field capacity (TFC)

• Effective field capacity (EFC)
• Efficiency
• Field capacity
• Field efficiency
• Input
• Mechanical efficiency

8
What is the difference between efficiency,
mechanical efficiency, performance efficiency,
and field efficiency?

• Efficiency is the ratio of a machines output
  over its input.
• Efficiency is calculated by dividing the output
  by the input.
• Output and input have the same units, so it is
  common to express efficiency as a percentage.
• Performance of agricultural machines is measured
  by the rate an operation can be completed, and/or
  the quality of an operation.

9
Performance Efficiency

• Performance efficiency describes the quality of
  work done by a machine.
• An example of performance efficiency would be
  harvesting efficiency such as the amount of crop
  left in the field due to poor machine
  performance.

10
Combine Harvesting Efficiency
11
Mechanical Efficiency

• Mechanical efficiency evaluates energy conversion
  and energy converters.
• Mechanical efficiency answers the question, how
  well does the machine convert energy from one
  form to another?
• Examples include the conversion of chemical
  energy to heat energy to mechanical energy in an
  internal combustion engine and the conversion of
  electrical energy by an electric motor to
  mechanical energy.

12
Field Efficiency

• Field efficiency is the comparison of the time a
  machine actually spends doing what it was
  designed to do compared to the total time the
  machine was in operation.

13
Farm Implements are Capable of Working Many Acres
per Hour
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What is meant by theoretical field capacity and
effective field capacity?

• Theoretical field capacity (TFC) is the acres per
  hour a machine covers when operating at a given
  speed through its effective width.
• Effective field capacity (EFC) is the actual rate
  of acres per hour a machine can cover.

15
Theoretical Field Capacity

• Theoretical field capacity (TFC) is the acres per
  hour a machine covers when operating at a given
  speed through its effective width.
• Theoretical field capacity for a machine is
  calculated using the Unit Factor Method.

TFC (Acres) Hour
Speed (Miles) Hour
5,280 Feet 1 Mile
1 Acre 43,560 sq.ft.

x
Width (Feet)
x
x
16
Effective Field Capacity

• Effective field capacity (EFC) is the actual rate
  of acres per hour a machine can cover.
• Simply observe the machine in operation doing
  what it was designed to do for one hour or
  fraction of an hour.

17
Effective Field Capacity

• Determine the acreage that the machine actually
  covered.
• This represents the effective field capacity.
• The percentage field efficiency is calculated by
  dividing effective field capacity by the
  theoretical field capacity and multiplying by
  100.

18
What are machine efficiencies and how are they
used to size and select machinery and equipment?

• Efficiencies provide a measure of machine
  performance.
• Power sources rate the mechanical efficiency of
  the energy conversion process.
• Field machines are evaluated by their field
  capacity and field efficiency.
• Performance efficiency measures how well machines
  do their job.

19
Machine Efficiencies

• Efficiency is the ratio of the output over the
  input for a machine.

• Inputs are often difficult to measure.
• Therefore, output plus losses by the machine may
  be used as an estimate of input.

20
Machine Efficiencies

• It may be difficult to measure exactly how much
  corn enters a combine (input), but we can easily
  measure the actual corn harvested (output).
• We can also measure the corn lost in harvest by
  the machine (harvest loss), due to the dropped
  ears and downed stocks (preharvest loss).

21
Machine Efficiencies

• Recognizing that the difference between input and
  output is the loss, the expression is input
  output losses.
• Solving for input sets up the equation as input
  output losses.

22
Machine Efficiencies

• Efficiency is an important consideration in the
  evaluation of power losses, the selection of
  agricultural machinery and equipment, and machine
  operations.
• The equation allows us to determine efficiency
  even when inputs cannot be measured accurately.

23
Proper Sizing and Selection of Machinery and
Equipment
24
Machine Efficiencies

• Substituting the output losses for inputs means
  the equation will read as

output
efficiency

100
output losses
25
Machine Efficiencies

• The expression describes performance efficiency
  where outputs and losses can be measured and
  inputs cannot be measured directly.
• The rate at which a field machine does work is
  expressed as a unit area per unit time, and
  labeled as field capacity.

26
Field Capacity

• Field capacity is a function of speed, effective
  machine width, and unproductive time.
• Careful layout of fields and thoughtful patterns
  of machine operation can improve the effective
  field capacity and also the field efficiency.

27
Machine Efficiencies

• Non-productive time (losses) such as non-working
  turns and idle travel across field ends and the
  interior of the field should be minimized.
• Measurements or estimates of machine capacities
  are used to schedule field operations, power
  units, and labor, and to estimate machine
  operating costs.

28
Review/Summary

• What is the difference between efficiency,
  mechanical efficiency, performance efficiency,
  and field efficiency?
• What is meant by theoretical field capacity and
  effective field capacity?
• What are machine efficiencies and how are they
  used to size and select machinery and equipment?