Project 3320 Term C-95
Professor R. L. Norton

    Team Mirage Racing has asked us to design an improved Enduro motorcycle rear swing-arm assembly incorporating a shaft drive. An existing motorcycle chassis design is available for your inspection in the Vibrations Lab (HL035). A two-cylinder, 30 degrees Vee, 2-stroke engine with flywheel will be coupled to a spur gearset to reduce the engine speed and boost its torque appropriately. The ratio for this gearset is approximately 1:3.75. The 60 HP gasoline engine is redlined at 8800 rpm. The spur gearset’s output shaft drives the rear wheel through a bevel gearset. At least one universal joint will be needed in the driveline.

    Each group will have a different assigned engine-cylinder displacement and gear ratio according to the chart provided. A basic engine design will be provided as an input file to program Engine. Throughout the term you will design various parts of this assembly. There are many elements to this relatively simple machine. We will only have time to address a small fraction of the total collection of parts. Some of the elements that need our careful design attention are:

      • the suspension links, pivots and the shock-strut rod

      • the drive shafts and flywheel

      • the spur gearset and its keyed connections to the shafts

      • the shock spring

      • The U-Joint

      • the engine headbolts

    You will find that the designing of these parts is interdependent. Changes to one element may reflect through the system and require compensating changes in other parts. We will address the design of various parts as we develop and discuss the necessary theoretical aspects of the course topics.

    Some of the force and torque analysis can be done with the programs Dynafour and engine available in the WPI Computer Labs. The Aries system in combination with the adams Mechanical Analysis package also will model the system. Other analysis can best be done using a program such as TKSolver or MathCad, or with a spreadsheet. Note that it is required that a computer be used to solve this problem and TKSolver is recommended for the stress and design calculations. I will provide master TK files on disk to use as setups.

    We will attack this design project in seven (7) phases as defined below. Each phase will be allowed one week of effort beginning in week 1 of the course. This will be a group project. You will arrange your own groups of 3 or 4 students. I need a list of your group members and its name by Monday 1/16. Anyone not in a group by Monday 1/16 must let me know and I will put you in a group.

    Six weekly progress reports will be required in a format defined in the Progress Report Specifications handout supplied. A final Project Report will also be expected whose format will adhere to the separate Project Report Specifications handout supplied.

Phase

Topics

Due

1

 Define the problem in detail. Model the mechanism dynamically. Do calculations to determine the kinematics and kinetics of the linkage, approximate forces, torques, power levels, etc. Understand and bound the problem.

Week 2 Friday 1/19

2

 Based on the estimated forces from 1, determine the stresses in the coupler link and redesign it to be lighter than the current design. Determine the stresses in the pivot bolts and the shock strut and estimate their safety.

Week 3 Friday 1/27

3

 Redesign the links, pins, and strut for fatigue loading.

Week 4 Friday 2/3

4

 Design the engine output shaft, flywheel, keys and driveshaft.

Week 5 Friday 2/10

5

 Design a spur gear set of suitable ratio and size to transfer power from the engine to the driveshaft.

Week 6 Friday 2/17

6

 Design the shock absorber spring for fatigue loading

Week 7 Friday 2/24

7

 Design the headbolts for the engine against fatigue failure.

In Final Report 3/2

    Additional information will be provided as the project proceeds. The section meetings are intended as hands-on help sessions for project activity. Please come with questions prepared.