To: Nascent Swanlings Design Group
From: Black Swan, First Assistant Chief Engineer
Subject: Bounce Me Baby (ME 3310 Project 2 Term A-92)
Date: Assigned 9/21/92 – Final report due on 10/5/92 @ 4 Pm

   While you have been working diligently on your Better-Baby-Transporter device, those babies have been busy growing! Their harried mothers are now clamoring for a device to keep the little darlings occupied and happy while they attend to their other chores. One popular device now on the market is the baby swing. These typically have wound-spring energy storage and suspend the child at the end of a pendulum that is oscillated by the spring energy.

    Our marketing group thinks that there may be a large, untapped market for a superior Baby Motion Device. Existing designs allow only very mundane and repetitive motions and require frequent recharging of their energy storage. After meeting with our board of directors (at the Boynton) to discuss how to approach this market, we have defined some constraints (task specifications) for the problem.

- The device should provide interesting but safe motions to the child for as long as the mother desires.

- The device must not injure the child in any way.

- The device(s) should accommodate children in the age range of 2 months to 2 years and could be user-modifiable to suit the growing child.

- The device must be a pin jointed linkage, either a fourbar or a geared fivebar (so we can use the recently purchased software programs Fourbar and Fivebar.)

    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 15 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 Dr. Spock Association has generously made available to you their computer programs, Fourbar, Fivebar and Sixbar. 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 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 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:

- child ergonomics (see material on reserve)

- existing similar devices

- Mother's preferences

2. There are two suggested linkage configurations to investigate, the fourbar 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 either program "Fourbar" or "Fivebar" 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 your coupler point. 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 anybody's computer program being correct until you have personally checked it by another method.