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<h1 align=center>EG1004 Lab 4A: Mousetrap Car</h1>
= Objectives =
Using knowledge of gear ratios, torque, and basic physics concepts, design and build a vehicle that is powered by a standard mousetrap that will travel the farthest linear distance in a competition against other designs.


<h2>1 Objective</h2>
= Overview =


<p>Using your knowledge of gear ratios, torque, and other basic physics concepts,
Vehicles move by propulsion,  which is a form of energy conversion from a stored form into movement. The most common means of propulsion is to release the chemical energy in petroleum products to cause movement. The internal combustion engine in most automobiles works this way. Small radio-controlled cars use propulsion when the chemical energy stored in batteries is converted into electricity, and this electricity drives an electric motor that moves the car.
build a vehicle powered only by a standard sized mousetrap that will travel the
farthest linear distance. </p>


<h2>2 Overview</h2>
A recent development in automobiles is hybrid propulsion that combines an internal combustion engine and a battery to power a car. With a hybrid car, the battery is used  when not much power is needed, and the internal combustion engine is only used when more power is required for acceleration or to recharge the battery.


<p>A mousetrap car is a vehicle using a mousetrap as a propulsion source. In a
In many machines, including cars, gears assist by transferring mechanical energy from one gear to another. A gearing system, which uses multiple gears, has a measurable characteristic called a gear ratio. A gear ratio is calculated by counting the number of teeth on the input gear, or the initial gear in the system, and dividing that number by the number of teeth on the output gear, or the final gear in the system. When a system uses wheels or pulleys, the diameter of the gears is used.
traditional mousetrap car, a string is attached to the lever arm of the mousetrap
and the other end of the string is attached to the drive axle.</p>


<p align=center>[[Image:lab_Mousetrap_1.jpg]]</p>
Almost any energy source can be used for propulsion with enough ingenuity. For example, a wind-up toy car converts the energy from muscles by winding up the spring  and that energy is converted into motion when the car is released.


<p class=caption>Figure 1: Picture of a typical mousetrap car</p>
A mousetrap car (Figure 1) is a vehicle that uses a mousetrap as its propulsion source. In a mousetrap car, a string is attached to the lever arm of the mousetrap and the other end of the string is attached to the drive axle.


<p>The string is looped around a &quot;hook&quot; on the axle. As the string is wrapped
[[Image:lab_Mousetrap_1.jpg|frame|center|Figure 1: Picture of a typical mousetrap car.]]
around the axle, the mousetrap's lever arm will be pulled back. When the mousetrap is
activated, the lever arm will pull the string, which in turn will rotate the drive axle
and propel the vehicle forward. </p>


<p align=center>[[Image:lab_Mousetrap_2.jpg]]</p>
The string is looped around a hook on the axle. As the string is wrapped around the axle (Figure 2), the mousetrap's lever arm is pulled back. When the mousetrap is activated, the lever arm pulls the string, which rotates the drive axle and propels the vehicle forward.


<p class=caption>Figure 2: A possible mousetrap car design</p>
[[Image:lab_Mousetrap_2.jpg|frame|center|Figure 2: A possible mousetrap car design.]]


<h3>Principles involved in a Mousetrap Car</h3>
== Forces Involved in a Mousetrap Car ==


<p><b>Friction</b>:The force that resists the motion of two surfaces in contact.
'''Friction''': This is the force that resists the motion of two surfaces in contact. In a mousetrap car, power can be lost due to friction between the axles and chassis and between the wheels and the ground. Not all friction is bad; friction that prevents the wheels from slipping is called traction. In general, a design should reduce friction, but have enough traction so that the wheels do not slip.
In a mousetrap car, a lot of power is lost due to friction between the axles
and chassis and between the wheels and the ground. Not all friction is bad
though; friction that prevents the wheels from slipping is called traction. In
general, one may want to reduce the amount of friction, but have enough
traction so that the wheels do not slip. </p>


<p><b>Rotational Inertia</b>: The resistance an object has to changes in rotation.
'''Rotational Inertia''': This is the resistance an object has to changes in rotation. The mass of the object affects the rotational inertia, the greater the mass, the greater the rotational inertia.
Mass of the object affects the amount of rotational inertia, the greater the
mass, the greater the rotational inertia.</p>


<p align=center>[[Image:lab_Mousetrap_3.png]]</p>
[[Image:lab_Mousetrap_3.png|frame|center|Figure 3: Lesser rotational inertia.]]


<p class=caption>Figure 3: Small rotational inertia</p>
[[Image:lab_Mousetrap_4.png|frame|center|Figure 4: Greater rotational inertia.]]


<p align=center>[[Image:lab_Mousetrap_4.png]]</p>
Rotational inertia (Figures 3 & 4) is also dependent on the location of the mass from the axis of rotation (Figure 5). The farther the bulk of mass is radially from the axis of rotation, the greater the rotational inertia.


<p class=caption>Figure 4: Greater rotational inertia</p>
[[Image:lab_Mousetrap_5.png|frame|center|Figure 5: Comparison of rotational inertia.]]


<p>Rotational inertia is also dependent on the location of mass from the axis of
= Competition Rules =
rotation. The farther the bulk of mass is radially from the axis of rotation, the greater
* Only the Lego parts provided may be used
the rotational inertia.</p>
* The vehicle must be powered solely by the mousetrap provided
* The vehicle must have at least one wheel (no projectiles allowed)
* The mousetrap spring must not be physically altered
* The vehicle may not receive a push at the start
* The vehicle cannot be touched once it has left the starting position
* Displacement distance will be measured; not the total distance traveled
* If the car hits another object (e.g. the wall), distance will be measured at the point of impact


<p align=center>[[Image:lab_Mousetrap_5.png]]</p>
== Scoring ==
The design with the greatest displacement distance traveled wins.


<p class=caption>Figure 5: Comparison of Rotational Inertia</p>
= Design Considerations =
* Consider the power source; the position and length of the lever arm determine the torque produced
* Too much weight may prevent the mousetrap car from moving; weight will also affect the car's momentum
* Use CAUTION when handling mousetraps (mousetrap hammers snap at 70mph)


<h2>3 Your Assignment</h2>
= Materials =
* A Robolab kit
* A mousetrap
* Kevlar string
* Tape


<p>This lab has no lab report or presentation. All you need to do is build a mousetrap car
= Procedure =
and participate in
# Brainstorm possible designs for a mousetrap car.
the competition.</p>
# Sketch the design on paper and have it approved by a TA.
# Construct the design based on the sketch.
# The mousetrap may be attached to the car with tape (try not to use excessive amounts of tape; all tape should be removed from the Lego parts before leaving).
# Load the mousetrap by winding the string around the drive axle.
# Once the design is ready, position the vehicle behind the starting line and release it.
# Once the vehicle comes to a stop, the distance may be kept or quick modifications may be made and additional trials attempted. Each design is allowed up to three trials if time permits.
# Before leaving the room, the mousetrap car must be disassembled and all tape must be removed from the Lego parts.


<p>Extra credit will be given on your Reverse Engineering lab report for the completion of
= Assignment =
a functional mousetrap car. Additional extra credit will be awarded to the winner of the
competition as described in the Grading Policy. Make sure to get the sketch of the design
signed by the TA as well as a photo and attach it to your lab report in order to receive
extra credit. Your team may also want to include a picture and short description of your
vehicle in your presentation.</p>


<h2>4 Competition Rules</h2>
== Individual Lab Report ==
Follow the lab report guidelines in the page called [[Specifications for Writing Your Lab Reports]] in the ''Technical Communication'' section of this manual. The following discussion points should be addressed in the appropriate section of the lab report:
* Discuss the advantages and disadvantages of the design
* Discuss the characteristics of the design that won the competition
* Discuss the impact of engineering concepts on design and the results
* Include spreadsheet with every team's results. Describe the results and talk about other designs in the class and how you could improve your design


<ol>
Extra credit will be awarded to the winner of the competition as described in the [[EG1003 Grading Policy]]. Make sure to get the sketch of the design signed by the TA. Get at least one photo of the design and include it to the lab report.


<li>Only the Lego parts provided may be used.</li>
{{Lab notes}}
<li>The vehicle must be powered solely by the mousetrap provided.</li>
<li>The vehicle must have at least 1 wheel (no projectiles allowed)</li>
<li>The mousetrap spring must not be physically altered.</li>
<li>The vehicle may not receive a push at the start </li>
<li>The vehicle cannot be touched once it has left the starting position.</li>
<li>Displacement distance will be measured; not the total distance traveled.</li>
<li>If the car hits another object (e.g. the wall), distance will be measured at the point of impact.</li>
</ol>


<h3>Scoring</h3>
<!--
== PowerPoint Presentation (EGED I Only) ==


<p>The team with the greatest displacement distance traveled wins. </p>
Follow the presentation guidelines laid out in the page called [[EG1003 Lab Presentation Format]] in the ''Introduction to Technical Presentations'' section of this manual.
The following discussion points are to be addressed in the appropriate section of the presentation:
-->


<h2>5 Materials</h2>
{{Laboratory Experiments}}
 
<ul>
<li>Robolab kit</li>
<li>Mousetrap</li>
<li>Kevlar string</li>
 
<li>Tape</li>
</ul>
 
<h2>6 Procedure</h2>
 
<ol>
<li>Brainstorm about possible designs for a mousetrap car.</li>
<li>Sketch your design on paper</li>
<li>Construct your design based on your sketch </li>
<li>The mousetrap may be attached to the car by tape (try not to use excessive amounts of tape; all
tape should be removed from the Lego parts before leaving).</li>
<li>Load the mousetrap by winding the string around the drive axle.</li>
 
<li>Once your team is ready, position the vehicle behind the starting line and release it.</li>
<li>Once the vehicle comes to a stop, your team may decide to keep the current distance or make quick
modifications and try again. Each team is allowed up to 3 tries if time permits.</li>
<li>Before leaving the room, the mousetrap car must be disassembled and all tape must be removed from
the Lego parts.</li>
</ol>
 
<h3>Things to keep in mind when building a mousetrap car</h3>
 
<ul>
<li>The position of mousetrap and length of the lever arm are important in determining the amount of
torque wanted.</li>
 
<li>Weight is an important factor in building mousetrap cars. A mousetrap may not have enough force
to propel a heavy car. Weight will also affect the car's momentum.</li>
 
<li>Use CAUTION when handling mousetraps (mousetrap hammers snap at 70mph).</li>
</ul>
 
[[Main_Page | Return to table of Contents]]

Revision as of 17:34, 24 January 2019

Objectives

Using knowledge of gear ratios, torque, and basic physics concepts, design and build a vehicle that is powered by a standard mousetrap that will travel the farthest linear distance in a competition against other designs.

Overview

Vehicles move by propulsion, which is a form of energy conversion from a stored form into movement. The most common means of propulsion is to release the chemical energy in petroleum products to cause movement. The internal combustion engine in most automobiles works this way. Small radio-controlled cars use propulsion when the chemical energy stored in batteries is converted into electricity, and this electricity drives an electric motor that moves the car.

A recent development in automobiles is hybrid propulsion that combines an internal combustion engine and a battery to power a car. With a hybrid car, the battery is used when not much power is needed, and the internal combustion engine is only used when more power is required for acceleration or to recharge the battery.

In many machines, including cars, gears assist by transferring mechanical energy from one gear to another. A gearing system, which uses multiple gears, has a measurable characteristic called a gear ratio. A gear ratio is calculated by counting the number of teeth on the input gear, or the initial gear in the system, and dividing that number by the number of teeth on the output gear, or the final gear in the system. When a system uses wheels or pulleys, the diameter of the gears is used.

Almost any energy source can be used for propulsion with enough ingenuity. For example, a wind-up toy car converts the energy from muscles by winding up the spring and that energy is converted into motion when the car is released.

A mousetrap car (Figure 1) is a vehicle that uses a mousetrap as its propulsion source. In a mousetrap car, a string is attached to the lever arm of the mousetrap and the other end of the string is attached to the drive axle.

Figure 1: Picture of a typical mousetrap car.

The string is looped around a hook on the axle. As the string is wrapped around the axle (Figure 2), the mousetrap's lever arm is pulled back. When the mousetrap is activated, the lever arm pulls the string, which rotates the drive axle and propels the vehicle forward.

Figure 2: A possible mousetrap car design.

Forces Involved in a Mousetrap Car

Friction: This is the force that resists the motion of two surfaces in contact. In a mousetrap car, power can be lost due to friction between the axles and chassis and between the wheels and the ground. Not all friction is bad; friction that prevents the wheels from slipping is called traction. In general, a design should reduce friction, but have enough traction so that the wheels do not slip.

Rotational Inertia: This is the resistance an object has to changes in rotation. The mass of the object affects the rotational inertia, the greater the mass, the greater the rotational inertia.

Figure 3: Lesser rotational inertia.
Figure 4: Greater rotational inertia.

Rotational inertia (Figures 3 & 4) is also dependent on the location of the mass from the axis of rotation (Figure 5). The farther the bulk of mass is radially from the axis of rotation, the greater the rotational inertia.

Figure 5: Comparison of rotational inertia.

Competition Rules

  • Only the Lego parts provided may be used
  • The vehicle must be powered solely by the mousetrap provided
  • The vehicle must have at least one wheel (no projectiles allowed)
  • The mousetrap spring must not be physically altered
  • The vehicle may not receive a push at the start
  • The vehicle cannot be touched once it has left the starting position
  • Displacement distance will be measured; not the total distance traveled
  • If the car hits another object (e.g. the wall), distance will be measured at the point of impact

Scoring

The design with the greatest displacement distance traveled wins.

Design Considerations

  • Consider the power source; the position and length of the lever arm determine the torque produced
  • Too much weight may prevent the mousetrap car from moving; weight will also affect the car's momentum
  • Use CAUTION when handling mousetraps (mousetrap hammers snap at 70mph)

Materials

  • A Robolab kit
  • A mousetrap
  • Kevlar string
  • Tape

Procedure

  1. Brainstorm possible designs for a mousetrap car.
  2. Sketch the design on paper and have it approved by a TA.
  3. Construct the design based on the sketch.
  4. The mousetrap may be attached to the car with tape (try not to use excessive amounts of tape; all tape should be removed from the Lego parts before leaving).
  5. Load the mousetrap by winding the string around the drive axle.
  6. Once the design is ready, position the vehicle behind the starting line and release it.
  7. Once the vehicle comes to a stop, the distance may be kept or quick modifications may be made and additional trials attempted. Each design is allowed up to three trials if time permits.
  8. Before leaving the room, the mousetrap car must be disassembled and all tape must be removed from the Lego parts.

Assignment

Individual Lab Report

Follow the lab report guidelines in the page called Specifications for Writing Your Lab Reports in the Technical Communication section of this manual. The following discussion points should be addressed in the appropriate section of the lab report:

  • Discuss the advantages and disadvantages of the design
  • Discuss the characteristics of the design that won the competition
  • Discuss the impact of engineering concepts on design and the results
  • Include spreadsheet with every team's results. Describe the results and talk about other designs in the class and how you could improve your design

Extra credit will be awarded to the winner of the competition as described in the EG1003 Grading Policy. Make sure to get the sketch of the design signed by the TA. Get at least one photo of the design and include it to the lab report.

Remember: Lab notes must be taken. Experimental details are easily forgotten unless written down. EG1004 Lab Notes Paper can be downloaded and printed from the EG1004 Website. Use the lab notes to write the Procedure section of the lab report. At the end of each lab, a TA will scan the lab notes and upload them to the Lab Documents section of the EG1004 Website. One point of extra credit is awarded if the lab notes are attached at the end of the lab report. Keeping careful notes is an essential component of all scientific practice.