ME 358 Semester Project

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Group 10
Jeri Sue Childers
Anthony Andrew Marciniak
Zachary David Zenz
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Nogys Dream Machine
(Click picture to play movie)
Return to Position
Return to Velocity
Return to Acceleration
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Table of contents

• Abstract
• Introduction
• Analysis
• Position
• Graphical
• Analytical
• Working Model
• Velocity
• Graphical
• Analytical
• Working Model
• Acceleration
• Graphical
• Analytical
• Working Model
• Results
• Position
• Velocity
• Acceleration

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Abstract

• This project entailed designing a fourbar
  mechanism that met detailed required guidelines.
  The main concept was to use fourbar linkages to
  create straight line motion, which had to be at
  least 9 inches long. Also, the maximum velocity
  output of the point moving on the straight line
  had to be 10 in/s. With that in mind, the goal
  was to create a mechanism that fit into the
  smallest rectangular box possible, with at least
  6 inches of clearance from the maximum
  displacement of all bars. The bars had no length
  restrictions, but they could only be 1 inch wide.
  The motor that runs the mechanism must be
  located between 3-5 ft (3650 inches) away from
  the straight line motion. In addition, the only
  design that was restricted was the Hoeken-type.
• To begin this project, research was obtained
  from the internet on various types of mechanisms
  that created straight line motion. After
  studying this information, two designs were
  chosen to be considered. These designs included
  a Watt type along with a Tchebicheff type. The
  two types were analyzed and preliminary
  calculations were made, and based on the project
  restrictions the Tchebicheff style was chosen.
  This combination of two fourbar mechanisms would
  be the more simplistic of the two while occupying
  the least amount of area.
• The results obtained from the 3 different types
  of analysis were very comparable. The analytical
  method was the most accurate, but the graphical
  didnt deviate much from the analytical values.

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Introduction

• The primary use of this mechanism was to convert
  a rotary input to straight line motion output. A
  motor was attached to the input link to run the
  fourbar device.

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Analysis

• After the design of the mechanism was completed
  on Working Model, the analysis begun. Since the
  straight line distance was initially 50 inches,
  based on the lengths of the bars, the first task
  was to start scaling the entire design down.
  This process was somewhat trial and error,
  although for the most part the mechanism was
  scaled down proportionally. The position of the
  grounds also had to be slightly altered to
  achieve only 9 inches of vertical motion. The
  mechanisms position, velocity, and acceleration
  was analyzed using three different methods
  graphical, analytical, and Working Model.
• For the graphical analysis, the design was drawn
  in the CADKEY program, to reduce human error in
  drawing it out by hand. This computer program
  supplied pertinent information, such as the
  values of angles.
• The analytical method was completed in the
  MathCAD computer program. The book formulas
  were entered, along with known values from the
  graphical analysis, to solve for the unknowns.
• Finally, the Working Model program was used to
  find the maximum velocity point, along with the
  extremes of x and y. This is also where the
  initial theta2 value that was used in the
  position analysis came from.

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Position

• Graphical

Maximum location of point P
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Position
Point P at max. velocity
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Position
Minimum location of point P
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Position

• Analytical

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Position
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Position
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Position
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Position
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Position
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Position

• Working Model

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Velocity

• Graphical

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Velocity

• Analytical

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Velocity
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Velocity

• Working Model

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Acceleration

• Graphical

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Acceleration

• Analytical

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Acceleration
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Acceleration

• Working Model

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Results

•  

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Results

•  

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Results
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Results

• Based on the previous slides containing the Excel
  charts, the methods of analysis were very
  comparable. The analytical method was the most
  accurate, but the graphical was very close to the
  analytical values found.
• This mechanism abides by all guidelines set forth
  in the project requirements. It is a Tchebicheff
  style mechanism that has approximately 10 inches
  of straight line motion. The design is a
  combination of two fourbar mechanisms, so it was
  easy to break them apart and perform the
  position, velocity, and acceleration analysis on
  each.

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Conclusion

• The purpose of this project was to build a
  mechanism based on certain requirements that were
  given. The design was researched, drawn, and
  then the analysis was performed. This group used
  three main forms of analysis learned in class
  which included graphical, analytical, and Working
  Model. The analytical method was the best method
  to use because it produced the least amount of
  error.
• For the most part, this project went pretty well.
  Decisions were made such as drawing the
  mechanism in CADKEY to reduce error. However, in
  order to improve this project, it would have
  saved time to double check equations and units.
• This mechanism fit into a 5.023 ft x 6.656 ft
  rectangular box, allowing 6 inches from each
  extreme point. So the total area of the box is
  33.433 square feet.

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Resources

• http//www.brockeng.com/mechanism/Tchebicheff.htm
• Norton, R.L., Design of Machinery, Third Edition,
  McGraw-Hill, New York, 2004.
• Microsoft Word
• Microsoft Excel
• Working Model 2D HW Edition 4.1
• MathCAD 2001 Professional
• CADKEY 99