Project 1.1.6 Compound Machine Design
– VEX
Introduction
Mechanical systems often require a combination of
mechanisms to complete a given task. Any time two
or more machines are combined, the result is a
compound machine. If many mechanisms are
combined, the machine may even be referred to as
a complex machine. Compound machines can
range in complexity from a crane or automobile to a
simple manual can opener. A bicycle is an example
of a compound machine. The pedals, brakes,
handle bars, and sprocket systems are just some of
the mechanisms on most bicycles. In this activity
you will work in teams to design and build a
compound machine to accomplish an instructorspecified task.
Equipment
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
VEX POE kit, including gears (sprockets), chains, belts, axles, and support
pieces
Rope for pulley systems (masonry line works well)
Design Constraints



The applied effort force may only be provided by a single human input.
The final design must include a minimum of three mechanisms including any of
the simple machines: a gear system; a pulley and belt system; and/or a sprocket
and chain system.
The compound machine must have a mechanical advantage greater than 1.
Procedure
1. Determine the instructor-assigned task in detail, including all required operations
and time constraints.
2. Investigate available equipment components and possible configurations.
3. Brainstorm ideas for accomplishing the assigned task, and record at least three
ideas in your engineering notebook.
4. Using isometric grid paper or 3D modeling software, sketch and annotate a
preliminary design solution including the individual mechanism’s mechanical
advantage and the drive ratios.
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POE Project 1.1.6 Compound Machine Design VEX – Page 1
5. Build, test, and modify your compound machine design.
6. Using isometric grid paper or 3D modeling software, sketch and annotate your final
design solution including the individual mechanism’s mechanical advantage and
the drive ratios.
7. Use the tables below to document and illustrate the mechanical advantage and
drive ratios of the individual mechanisms utilized within your final compound
machine solution. Show work and units throughout.
Mechanism 1 Type
Illustration: Include proper documentation such as force, distance, direction, and key
mechanism features.
Formula
Mechanical Advantage / Ratio Calculations
Substitute / Solve
Final Answer
27in/13 in
2.08
De/Dr
Mechanism 2 Type
Illustration: Include proper documentation such as force, distance, direction, and key
mechanism features.
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POE Project 1.1.6 Compound Machine Design VEX – Page 2
Mechanical Advantage / Ratio Calculations
Substitute / Solve
Formula
3
Final Answer
3
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POE Project 1.1.6 Compound Machine Design VEX – Page 3
# of strands
Mechanism 3 Type
Illustration: Include proper documentation such as force, distance, direction, and key
mechanism features.
Formula
Mechanical Advantage / Ratio Calculations
Substitute / Solve
Final Answer
(4.25/0.75)(1.5/4.25)(2.75/1.5)
3.66
Dout/Din
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POE Project 1.1.6 Compound Machine Design VEX – Page 4
8. Calculate total/overall system mechanical advantage.
Formula
Substitute / Solve
2.07*3*3.667
Final Answer
22.77
Multiply IMAs
together
Conclusion
1. For which mechanism was it the easiest to determine the mechanical advantage or
drive ratio? Why was it the easiest?
-
The pulley system was easiest to calculate because there was no math involved,
just counting strands
2. For which mechanism was it the most difficult to determine the mechanical
advantage or drive ratio? Why was it the most difficult?
-The chain & sprocket/ wheel and axel system was the hardest to calculate because it
had a lot of variables involved, as well as it being a compound system.
3. At what value would you estimate the input and output forces of your compound
machine? How did you arrive at your estimated values?
-The output would be the weight of the book which is 10.68N so the input force should
be about .47N because if you use the equation IMA=AMA and plug the numbers in
order to find Fe, Then you would get 0.47 N.
4. What modifications could you make to your compound machine to make it more
mechanically efficient?
-
I think we could make it more stable so less energy is lost in unnecessary motion
created by the input force and we could also make the inclined plane cause less
friction to the book by making it smoother.
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POE Project 1.1.6 Compound Machine Design VEX – Page 5