Sweeper Creeper

The Sweeper Creeper

By: The Four Fathers Ryan - Research competition & PR Isaac – Construction, design sketches Michael – Testing - experimental design, set up data sheets & testing methodologies Ryan – Research problem & technical issues. Jon - Project management and report

ENGR1201, LSC-KW
Fall semester, 2019

Introduction (Jon Davis, Ryan Lewis)
Do you ever get tired of standing? Perhaps a long day at the office has you down, feet aching, legs burning. Now imagine a world where these problems are no more. With this revolutionary piece of technology. Standing is no longer an option as we, quite literally, sweep you off your feet, guaranteeing you won’t have the strength or willpower to stand after one hit from our technological marvel. Now introducing Sweeper, Creeper Sweeper Creeper is the latest breakthrough in all your anti-standing needs with its state of the art 2x4 frame and rocking the best bungee cords a broke college student can find. Sweeper Creeper is 100% guaranteed to knock you off your feet or to put you in so much agony you topple to the floor questioning all your life decisions. Wondering if the Sweeper Creeper can be used on friends? Wonder no more, because no one is safe when the Sweeper Creeper is out. Simply set up the Sweeper Creeper’s tripwire and blamo, they topple to the floor faster than you can say “ouch!”

Building materials and construction (Michael and Isaac)

Building Materials:

• 5 two by four boards
• Screws
• Nuts and bolts (to hold the bungee cord to the arm)
• Two foot long bolt (axle for the arm)
• Bent and sanded bolt.
• Wooden dowel
• Pipe insulation
• 8 bungee cords
• Loop screws
• string

Assembly and Construction Diagrams(Ryan and Isaac).

This was for the initial design. Its rather simple but this represents the core of the design. All the addition the were made during testing, and can be found. in the testing section.

Testing, Testing Methods, Modifications (Michael-pictures, testing, tables, modification and Ryan- physics equation strategy, technical help)

Methods of testing this machine were complicated and not entirely achievable with the equipment that was available. The initial task was measuring all the components of the machine. This involved measuring the length of the arm, the angle which it swept across, and how much mass it had. With measurements taken, the forces involved in knocking a person over needed to be determined. To start, the force output by the machine needed to be calculated. This force was to be calculated using a combination of different physics equations. We started with the equation for torque.

Torque=Force*radius

Torque/radius=Force

We did not have the torque involved in the swing so we needed another equation to find torque.

Torque=Angular acceleration*Moment of inertia

We had neither Angular acceleration or moment of inertia so we needed equations for each. The moment of inertia was found using the following equation.

Moment of Inertia=1/3*mass of arm*Length of arm squared

The angular acceleration was found with the following equation.

angular acceleration=angular velocity squared*radius

We then combined these equations into terms we could easily take from our data.

Force=angular velocity squared*mass of arm*length of arm squared*(1/3)

This equation gave us the striking force for the machine. This equation proved its worth up until it became impossible to determine the angular speed of the arm due to it completing the swing faster than .01 seconds; it was faster than we could measure its speed with our cameras. That is why our data is incomplete. Another force that was needed was the force necessary in order to knock someone down. This is given via this equation.

F=Nμ

Where μ is the friction coefficient for earth and rubber (~.9) N is the normal force and F is the force it takes to move the object. The normal force is the same as the force of weight. Therefore to knock the average person down we need the average weight which is 137 pounds. Converted in newtons this is 609 N. this number multiplied by the friction coefficient gives the force required which is 548 N. We likely reached this point but it is impossible to tell due to the speed of the swing. The spring constant of the entire mechanism was also calculated just for extra data. It was calculated by dividing the difference of the beginning and ending force the bungees exerted on the arm by the distance by which they were pulled. The forces the bungees exerted were found using a suitcase weight.

Testing this machine involved a hefty amount of physical challenges that required various modifications to the device. The first concern during testing was constructing a device that could carry out the task it was made for, as the initial build did not work without a great deal of manual handling. This involved adding wooden supports and a release mechanism. The release mechanism was constructed of wood which had a removable support drilled underneath it. This support was connected to a string that, when pulled, would cease supporting the wooden release mechanism which would, in turn, release the arm.

This release mechanism worked as long the number of bungee cords and force they exerted was small. As the forces increased however, the release ceased to work. The wooden release was to bulky to fit with the amount of bungee cords. Due to this weakness, the wooden release was replaced with a metal bolt that was bent and sanded down to create a release mechanism that was just as strong as the wooden one and a fraction of the bulk.

This was not a perfect solution, it simplified the tripwire system by connecting the release mechanism directly to the tripwire. Another notable modification was a support to the main axle that the arm was connected to. As the amount of bungees increased, the axle began to bend heavily. This bending adversely affected the swing of the arm. In order to solve this problem a small metal support was added.

wooden support

Observations, Results and Discussion (Jon Davis, Ryan Lewis)

Observations show that people enjoy being an audience to a good kicking, but understandably fear being the victim. The Sweeper Creeper has also shown ease of injury without correct padding, but these injuries are simply bruises, even the nastiest of which heal within days. Testing of various techniques has also shown that victims have a greater chance of having their legs swept if walking at a brisk pace when attacked. With safety measures, however, including padding on the contraption itself, placement at a safe location, and possible padding for the victim (as a precautionary measure), the contraption can be used to trip someone without permanent or hardly any effect at all. The force of the machine itself can also be adjusted manually, though we’ve calibrated it to trip while causing light and very temporary bruising.

Conclusions, suggestions for future work (Jon Davis)

The machine is a success in that it fulfills the highly entertaining purpose intended. It required intermediate understanding of basic machines in order to form a functioning and reliable release mechanism, as well as an understanding of forces in order to accurately quantify them and ensure safety for the victim. In the future, the release mechanism can be optimized to minimize friction and the force needed to actually trigger the trap. The design can be compacted and rebuilt with more efficient and durable materials, and refined to be easier and more portable for moving between multiple doorways.

Reference section (Ryan)

Formulas and Equations

Ling, Samuel J., et al. University Physics. OpenStax, Rice University, 2018.

Contest entry formatting (Michael)