Davy Jones Inc., purveyors of the cast uranium, Jonathan Livingston Seagull Outboard Motor, is sinking fast (along with their boats and the local economy). We've been hired to re-float their company by designing a new outboard motor to replace their present clunker. J. Livingston Jones III, great grandson of Davy and current president of the company, has never been able to make up his mind. Thus he is uncertain as to whether he wants a two-cylinder or four-cylinder design. He also can't decide between the two- and four-stroke cycles. He has, however, expressed a fondness for Vee and opposed configurations.

    Thus, your assignment is to design a superior outboard motor, investigating both 2 and 4 cylinder vee and opposed configurations in both 2 and 4 stroke cycles. Your report will recommend your best design and provide good engineering justification for your choice.

    In order to maximize our impact on the company, we will design a variety of sizes of engine. Each of you will have a particular cylinder displacement as assigned in the attached chart. This number is the Stroke-Volume of one cylinder of each of the engines. Thus, the four-cylinder will have twice the total displacement of the two-cylinder.

    Our group is charged with the design of the mechanical aspects of the engine, and DJI has supplied us with the latest version of their "ENGINE" design computer program. We will not be involved in the design of the thermodynamics aspects. Messrs. Hot and Trot of the Thermo Design group have defined the gas force curve for the engine and have included it in program "ENGINE". This program will be available to you in the Aptlab and Micro Cad Lab (HL 204 and HL 215), and is on your ME 3311 distribution disks. Make sure you are using Version 5.2 or higher. (Please report any bugs to me right away.)

    DJI has also generously supplied us with some current engines and engine parts for study. These have been partly disassembled and will be available for your inspection and measurement in the Aptlab. This design task logically breaks down into several sub tasks which can be addressed sequentially. A chart of these sub-tasks and the due dates for their completion is provided in Table 1.

    The Goal Statement for this project is: "Design an improved, multi-cylinder, IC engine of specified displacement, optimizing its torque and dynamic characteristics".

    The Task Specifications are:

1. Engine to be designed in common individual cylinder sizes corresponding to the displacements specified on the attached list.

2. Your engine is to be designed in various configurations and compared.

3. Two will be Otto four-stroke cycle, and two Clerk, two stroke cycle, all with an idle speed of 800 rpm and red line at 7000 rpm.

4. Various configurations are required with different Vee angles including opposed. Compare these and discuss their differences.

5. The torque-time function should be as uniform as is economically feasible.

6. Shaking forces and moments should be minimized, as much as is economically feasible.

7. It will not have any reciprocating counterbalances such as are in one of the sample engines.

8. Engine dimensions, such as bore, stroke, conrod length, counterweight sizes and locations, and masses of all moving parts are to be determined by the individual designer consistent with the other task specs. A flywheel is to be designed and specified as well. Note that weight is a consideration - lighter is better.

9. Short progress reports will be required at each stage of the design as defined in Table 1. These must adhere to the progress report specification supplied with this document.

10. A final report will be required at end of term, which details the complete design and adheres to the Project Report specifications supplied. This final report can be considered to include only part of the "Design Process" as defined in that document (supplied) i.e. you will be beginning this project at step 5 of the Design Process, (ideation), since you have been supplied a Goal Statement and set of Task Specifications. Note that this problem is one of "Design by Successive Analysis", requiring much iteration between the Ideation and Analysis steps of the Design Process, but no Research beyond your textbook, and the several books and documents in reserve in the library. You may, if you wish, investigate existing outboard motor designs at the local marina.

11. The program "ENGINE" may be used to do the computations necessary for the analysis, but you must also show in your final report that you understand the mathematical basis for that analysis. The method is clearly derived in your text and in lectures, and this program "ENGINE" is based on that method.

    Note that this is an individual, not a group project, and the final design must be yours alone. However, it is acceptable and educational to work together in obtaining the necessary information to do the task, such as measuring the existing engines.

    To assist you in getting started, we will provide the means to measure the sample engines and their parts. You can then experimentally determine some starting values for input to program "ENGINE". Table 1 breaks the problem into (4) sub-tasks or stages.

Stage 1. will help you understand what needs to be done to design an engine by analyzing an existing example. You should exercise items 1-5 on the "ENGINE" menu until you understand how this engine works and what the equations in your text are telling you. Then apply this to your new design which will have the cylinder displacement as defined in the attached. Thoroughly investigate variation in the parameters described in Table 1 to see their effect on the engine's dynamics. Note you are still only using items 1-5 in "ENGINE"'s menu.

Stage 2. requires you to balance one cylinder of your design from Stage 2. Use items 1-6 in "ENGINE".

Stage 3. assembles the multi-cylinders of your engine for the first time. You may find a classic tradeoff here between conflicting demands on the torque-time function versus the inertia (shaking) force function. Also engine balance condition is a factor. Use 1-7 in "ENGINE". Compare the various configurations and choose one based on a compromise between smoothness, weight and cost. Note that for a Vee configuration you need to first design one bank as an inline engine and choose the design you recommend be produced - justify your choice.

Stage 4. Design the flywheel for the engines.

    The final result must be written up in a project report as defined in the Task Specifications. Have fun!

    P. S. Note that all progress reports and the final report must be word processed and spell checked on any such device! Word Perfect is in the ADP Lab in Fuller B16 and has a spell checker built in. It is simple to use and will save you time in all your courses. Please use it. You may of course use your own or any other word processor instead of Word Perfect.

Stage 1. Analyze the sample engines provided, using program "ENGINE". Using specifications for your particular configuration investigate the effects of bore/stroke ratio, and conrod/crank ratio on the dynamic performance of one cylinder only of your proposed design. Look at the equations! Understand the theory!

Progress report due (see syllabus)

Stage 2. Having chosen a bore/stroke ratio and conrod/crank ratio, investigate the effects of adding counterweights of various proportions to the crank to attempt to optimally balance one cylinder of your engine.

Progress report due (see syllabus)

Stage 3. Having balanced one cylinder, assemble the engine with the number of cylinders assigned to you, and investigate the effects of different crank throw configurations on the combination of inertial forces, and torque time diagram.

Progress report due (see syllabus)

Stage 4. Design the flywheel to smooth the engine, and the cam for valve motion.

    Final report due (see syllabus)

Bergstrom - 315 cc/cylinder

Drulard - 330 "

Levine - 345 "

McCullough - 360 "

McIntyre - 375 "

Pickar - 390 "

Poirier - 405 "

Torrey - 420 "

Vale - 435 "

White - 450 "

Wodziak - 465 "

Wurts - 480 "

Webster - 495 "

3311P2