To: Nascent Swanlings Design Group
From: W. D. U. Swanee, First Assistant Chief Engineer
Subject: JAWS IV (ME 3310 Project 2 Term A-94)
Date: Assigned 9/16/94 – Final report due on 9/30/94 @ 4:30 PM

    I just returned from a power lunch with the CEO of the Mall of America in Minneapolis, Minnesota. She has hired us to design a new attraction for her Mega-Mall which now has several amusement rides in it. These rides are fairly conventional ones such as a roller coaster, Ferris wheel, spin cage etc. She has a concept for an exciting new ride that will rival those at Six Flags and Disney World.

    The concept is as follows: The riders (two at a time) are strapped into a high-tech seat-cage that looks like a ski-slope chair lift. The first stage of the ride is a relatively calm and leisurely passage over and along the surface of a river which flows through a canyon. The seat is picked up and carried on a linkage at some point in the river passage of the ride. Suddenly, the river drops over a waterfall and the riders are plunged straight downward over the falls (still in the grips of the linkage).

    As they approach the rock-infested bottom of the falls, a giant white shark (named Charlie) looms up from the water with jaws agape. The riders are carried into Charlie’s yawning dentures but are suddenly reversed and pulled back out of his mouth just before it snaps shut. The linkage then carries the riders back up to a release point where the linkage lets go of the cage which then coasts to a stop back at the start point. You are encouraged to add any exciting features that you want to the return trip from the jaws to the release point.

    After meeting with our board of directors (over pizza at the mall) to discuss how to approach this problem, we have defined some general constraints (task specifications) for the problem. You are expected to develop many more appropriate specifications.

- The mall is four stories tall but floor space is limited and expensive.

- The device must not injure the occupants in any way nor expose any parts of the body to unacceptable accelerations or velocities.

- The device should accommodate adults and large children of reasonable size.

- The device must be a pin-jointed or slider-crank linkage, either a fourbar, sixbar, or a geared fivebar (so we can use the software programs Fourbar, Fivebar, Sixbar, and Slider recently obtained at the mall.)

    You must follow the Design Process to fully define and constrain the problem. You must do Background Research into the problem and any existing solutions. You must create a general Goal Statement. You must generate a list of at least 16 additional Task Specifications. As with any design problem, there is an infinity of solutions possible. You are expected to come up with one solution which will work. To do so you will have to try out many alternate designs and iterate to your 'best' solution. You should expect to typically go through at least ten iterations before arriving at an acceptable one.

    There will be a need for extensive kinematic analysis in this project in addition to the synthesis activities. You are expected to do a complete velocity and acceleration analysis of your design to determine its feasibility and its effects on the occupant. In order to make it possible for you to accomplish this task in the short time available, the mall rats have made their computer programs, Fourbar, Fivebar, Slider, and Sixbar available to you . You may use these programs to analyze your potential design solutions. However, to ensure that you understand your results and to discourage a BFI approach, we require that you include a complete derivation of all equations necessary to the analysis of your design. These must be a general (non-numeric) derivation and you must use your derived equations to numerically check the computer program solutions for a minimum of two positions of your device. (You can’t trust a mall rat!)

    You are also required to document your solution in a professional engineering report which adheres to the Project Report Specifications document previously received. The background data should be written up in the Background Research section. The report will document the process by which you iterated to your final design as well as the design itself. Do not just describe the final result. Rather show me how you arrived at it, including the failures encountered along the way. This will demonstrate to me that you understand the engineering concepts and the relevant course material. Note that unreferenced and undiscussed computer or other illustrations will be considered to be report "filler" and will be ignored. Do not put anything in the report unless you discuss its meaning. A working cardboard model of at least one plane (one side) of your design is required.

Some suggestions to get you started:

1. Do research before trying to solve the problem! Don't 'shoot from the hip'. Avoid BFI (Brute Force and Ignorance). Engineer it. Some suggested background research areas are:

- human factors and ergonomics (see material on reserve)

- existing similar devices

2. There are several suggested linkage configurations to investigate, the fourbar, sixbar, slider-crank, and the geared fivebar. Consult the Hrones and Nelson 4-Bar atlas and the Zhang et al Geared           5-Bar atlas on reserve in Gordon Library, and select some linkages whose coupler curves look like they will do what you want. Note the link ratios and other parameters of these linkages.

3. Input these data to the appropriate program in the Aptlab to investigate the velocities and accelerations of the points on the coupler corresponding to various points on the occupant's body.

4. Redesign the linkage as necessary to improve the desired output parameters. Cardboard models make designing much easier.

5. Pay particular attention to the polar velocity and acceleration diagrams for the coupler point’s corresponding to locations on the user’s body These will, along with the printed data, show you           the velocity and acceleration at any point of interest along its path.

6. Iterate steps 1-5 as necessary to obtain a reasonable solution.

7. Check the computations of the computer program for velocity and acceleration of one point using any manual methods, graphics or analytical. Note that in engineering practice, you should           never rely on the output of anyone’s computer program being correct until you have personally checked it by another method.