ME 3311 Project 1
Term B-89

Assigned 10/31/89 ----------- Due 11/14/89 (15 days!)

    A common method used to sink construction piles in sandy or muddy soil is to vibrate them at their natural frequency by attaching a shaker mechanism to the top of the pile. The induced vibrations travel down through the steel pile and displace the soil at its bottom. The pile literally "falls into" the ground. The ideal situation is to have a device which will give large vibrations along the long (vertical) axis of the pile, and little or no vibration transverse to the pile. An added benefit might be to have an asymmetric up/down amplitude of the dynamic forces.

    The concept to be investigated in this project is the design of a fourbar linkage whose ground link will be clamped to the pile in any orientation you specify. When the input crank is driven at a constant rotational velocity specified by you, a shaking force will be felt by the pile.

    Your mission (should you decide to accept it) is to design a Fourbar Grashof mechanism which will drive the shaker according to the above constraints, and to arrange the shapes and sizes and materials of the links such that the shaking forces applied to the pile to be driven are maximized in the axial direction, and the motor speed variations due to torque fluctuations are minimized. The pivot pins must be sized against failure, and the dimensions and materials of the links specified.

    Your report should include titled plots and tables from program 'DYNAFOUR'. This program will calculate all the forces and torques on a Fourbar linkage for multiple positions. You must supply it the link dimensions, masses and moments of inertia for your design's elements, and also the crank input angular velocity. Note that DYNAFOUR imposes a constant angular velocity on that crank, which assumes that the motor used has sufficient torque available at all speeds. A real motor has a torque that varies with speed (see Fig 2-18 in Design of Machinery.). So you have to determine what the speed variation will be with the type of motor supplied for the input torque variation predicted by the program. You also have to specify what horsepower will be required of this motor, and the required diameter of the pivot pins based on the dynamic pin forces in your linkage and the material strength.

    Note that you may find it more convenient to begin the design process by using program FOURBAR to develop the kinematic accelerations of your linkage design. The two programs are the same for kinematic calculations. But DYNAFOUR requires much more input data in the form of masses and moments of inertia of your links. Fourbar does not. I STRONGLY URGE you to use TK Solver to calculate your link properties. The time spent to learn this equation solver software will be paid back in spades when you are changing those link dimensions for the tenth time! Punching those calculator buttons gets old fast. TK Solver is on all APTLAB machines and can be purchased at Academic Computing for $19.00.

    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 go through at least ten iterations before arriving at an acceptable one. DYNAFOUR makes this an easy process.

    You are also required to document your solution in a professional engineering report which adheres to the "Project Report Specifications" document on your disks. This report will document the process by which you iterated to your final design as well as the design. 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 concepts and the relevant course material.

IT IS CRUCIAL THAT YOU START THIS PROJECT RIGHT AWAY! Do not kid yourself that you can knock this off over the weekend before it is due! You cannot! This type of problem requires incubation periods. Work on it until stumped, then put it aside and do other course work. Then come back to this problem after your subconcious has had a chance to work on it. You'll be surprised how effective this 'time-sharing' of your tasks can be. Read The Design Process in chapter 1 of Design of Machinery. It really does work. You should plan to have all the analytical work done three days before the deadline, and use that time to write it up. It will take about three times longer to write up the report than you think it will!

    The report must be word processed and spell checked! PCWRITE (with built-in spell checker) is available in (5) campus locations, (Aptlab, MicroCad lab, 205 Olin PClab, Washburn Management PClab, and CCC in library basement). If you have your own PC and word processor, that's fine too. Letter quality output is not required but does make a better looking and easier to read report.

    Now please re-read this document to ensure you understand what is being requested. If you are the least bit confused, ASK QUESTIONS IN CLASS OR SECTION MEETING. Above all, Have Fun!

Final Report due on Tuesday November 14,1989 at 4:00 Pm in HL203

R. L. Norton, 10/26/89