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Lifting devices

This section addresses aspects of the following syllabus outcomes:

Outcomes

H1.2 differentiates between properties of materials and justifies the selection of materials, components and processes in engineering

H2.1 determines suitable properties, uses and applications of materials in engineering

H3.1 demonstrates proficiency in the use of mathematical, scientific and graphical methods to analyse and solve problems of engineering practice

H3.2 uses appropriate written, oral and presentation skills in the preparation of detailed engineering reports

H4.1 investigates the extent of technological change in engineering

H4.2 applies knowledge of history and technological change to engineering based problems

H4.3 appreciates social, environmental and cultural implications of technological change in engineering and applies them to the analysis of specific problems

H5.1 works individually and in teams to solve specific engineering problems and in the preparation of engineering reports

H6.2 demonstrates skills in analysis, synthesis and experimentation related to engineering

Source: Board of Studies (1999) Stage 6 engineering studies preliminary and HSC courses. Sydney: Board of Studies

Activities

Activity 1: Levers

Activity 2: Design and build a lifting device.

Activity 3: People and Lifting Devices: An investigation

Activity 4: An engineering report on hydraulic and electric powered lifting devices

Activity 5: Investigate the development of car jacks

Definition

Lifting device: mechanism or structure used to raise loads

Examples of lifting devices

• Crane
• jack
• lever
• lift
• hydraulic ram
• block and tackle
• wedge
• forklift
• escalator.

Lifting device

1. Levers - crowbar, tinsnips, human elbow
   • First order of levers
   • Second order of levers
   • Third order of levers
     
     
2. Inclined plane
   
   Screw thread
   • screw pump
   • jacks
   Wedge
   • Egyptian pyramids
     
     
3. Pulleys
   • single
   • block and tackle
     
     
4. Gears
   • Archimedian screw
     
     
5. Wheel and axle
   • Smeaton's water wheel
     
     
6. Hydraulics

Activity1: Levers

Aim:

To investigate the relationship between the length of a lever and the position of the fulcrum point when a force is applied in attempting to move a load.

Procedure:

• Take a number of pieces of suitable material (e.g. wood, galvanised pipe) to make four different lengths of levers.
• Make a suitable fulcrum on which the levers may be pivoted.
• Attempt to lift an appropriate mass with each of the levers ensuring that the distance between the load and the fulcrum point is kept constant. You should use a spring balance to record the force applied. Record your observations and measurements.
• Repeat Step 3, but this time vary the distance between the fulcrum point and the force applied. Repeat this for each length of lever.
• Attempt to lift the same load, but this time move the load so that it is between the force and the fulcrum point. Use the four different lengths of levers.
  1. Make freehand sketches to illustrate the position of the fulcrum and the load applied in the different applications.
  2. Develop a free body diagram for each application.
  3. Write up a report in table form to indicate the results obtained from the experiments.
  4. Discuss the concept of force equilibrium and the relationship with the positioning of the fulcrum, the lever arm and the load arm.

Consider your findings in the light of this range of lever applications

Activity2: Design and build a lifting device.

Design and, if possible, construct a prototype lifting device that will raise a mass of 2 kg from a horizontal position to a height of 300 mm and maintain this position safely once the effort has been removed.

Investigate how you could build this device in a commercial environment.

1. Outline the selection of materials required to make the components.
2. Justify the materials used in relation to the manufacturing and service properties of the materials.
3. Calculate the stresses developed in the materials.
4. Include freehand sketches showing the development of your design.
5. Develop a dimensioned orthogonal drawing to AS1100 standard.

Leonardo da Vinci developed some interesting ideas that may be useful to you.

Activity 3: People and Lifting Devices: An investigation

Examine the effect of new devices for lifting people on the height of buildings over the ages. Consider the historical development of steps, escalators and elevators, and the various methods of powering elevators.

You may consider the application of these devices to the disabled and the resulting engineering implications.

Activity 4: An engineering report on hydraulic and electric powered lifting devices

1. Discuss the advantages and disadvantages of hydraulic or electric power, highlighting the social and environmental implications of this source of power as a means of lifting loads.
   
   
2. Select one lifting mechanism and then develop a report that traces the development of hydraulic or electric power as a method for raising loads.

Activity 5: Investigate the development of car jacks

You are required to compare the range of techniques that are used to raise an automobile. You will limit your research to:

1. hydraulic powered jacks
2. mechanically operated jacks

Discuss:

• the basic operating principle of jacks
• the changes in power sources used to operate jacks
• the social and environmental implications of the changes in power sources used
• the effects of changes in materials technology on jack design
• the manufacture of one type of jack. Evaluate the reasons why these manufacturing processes are used.

Develop labelled freehand sketches outlining the operating mechanism of the jack selected.

When you have completed activities 1 to 5 you should try the problems that you will find at the following internet address:

http://www.mos.org/sln/Leonardo/GadgetAnatomy.html

References

• Burstall, A.U. (1970) A history of mechanical engineering. Faber.
• Derry, T K, Williams, T.I. (1960) A short history of technology. Oxford Paperbacks.
• Higgins, R A. (1974) Engineering metallurgy part 2. The English Universities Press Ltd.
• Schlenker, B R, McKern, D (1994) Introduction to engineering mechanics. Jacaranda Press.

Internet Sites

• ® http://www.bradleylift.com/product.html
• ® Otis Elevator Company Pty Ltd
• ® http://www.mos.org/sln/Leonardo/InventorsToolbox.html
• ® http://www.mos.org/sln/Leonardo/InventorsWorkshop.html
• ® http://www.waythingswork.com/contents.htm
• ® http://interoz.com/egypt/construction/construc.htm
• ® http://www.wedgeit.com/howitworks.htm