June 15, 2014
June 15, 2014
June 18, 2014
24.663.1 - 24.663.14
Helicopters as a Theme in Teaching Machine DesignA machine design course is required in most undergraduate mechanical engineering curricula.This course generally covers an introduction to mechanical engineering design, a review ofmaterials engineering, a review of mechanics of materials (shear force and bending momentdiagrams, stress and strain analysis, deflection and stiffness analysis of beams, columns, etc.),models for failure due to static loading and variable fatigue, and then presents (in somewhatarbitrary order) the design of specific mechanical elements: shafts, fasteners, springs, bearings,gears, flexible elements such as belts, chain, and wire rope, clutches, brakes, couplings, etc.For some topics in machine design it is not possible to develop analytical models from firstprinciples, as is done in fluid mechanics or thermodynamics. Rather, there are guidelines and"rules of thumb" and "equations" that include "factors" that must be taken on blind faith andsomehow used to get an approximate answer. The approach can be unsatisfying, arbitrary, andnot meaningful unless it is tied to real-world problems.To help motivate student learning, foster interest in the topics, and make the material more alive,we are testing the idea of studying helicopters and their components throughout the course as atheme to teach students about the different mechanical elements. Helicopters are an ideal systemto exemplify the concepts taught in the course because all aspects of machine design areencapsulated in the design of a helicopter and the price of failure of the components or design ishigh (human fatality). In the standard helicopter configuration, two turbine jet engines are usedto drive a main rotor and a tail rotor and the pilot controls are mechanically linked to both rotorsto allow for handling of the aircraft.For each topic in the course the connection to helicopters is presented and helicopter designchallenges are posed. For example, the shafts and gearboxes used to transfer energy from thehigh-speed turbine engines to the low speed rotors can be used to teach students about shaftbending, gear design, and fatigue failure. When asked to design a gearbox to achieve the speedreduction between the turbine jet engine and the main rotor, students discover why planetarygears are used. Other topics such as clutches, brakes, couplings, fasteners, springs, and vibrationeffects are all prominent features of helicopter design. They serve as excellent motivatingexamples to show students the real-life applications of machine design concepts.In closing, students generally view the machine design course as very challenging and, due to themany specific machine elements covered, have difficulty seeing how the separate components fitwithin the needs for a real system. To address this concern, enhance learning, and bring moreexcitement to the topics, we explored the value of using a theme physical system, namelyhelicopters and their components, to bring the material to life when teaching machine design.
Turner, D., & Nagurka, M. (2014, June), Helicopters as a Theme in a Machine Design Course Paper presented at 2014 ASEE Annual Conference & Exposition, Indianapolis, Indiana. https://peer.asee.org/20554
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