A number of different engines have been used to power aircraft.
A radial engine, which moves pistons radially outward from the drive shaft centerline, was frequently used in the early days of aviation (see episode photograph for an example).
The cycles for a four-stroke spark-ignition engine are air intake (“suck”), air compression (“squeeze”), fuel combustion (“bang”), and exhaust evacuation (“blow”).
A weed-wacker, or string trimmer, is a tool for cutting grass and plants, usually along sidewalks or garden borders.
The ability of gasoline to resist ignition under compression is measured by its octane rating.
Clay explains that the reciprocating engine has remained a staple in automobiles for many years because it is reliable and economic to manufacture.
In contrast to the reciprocation of a piston engine, a Wankel rotary engine uses a spinning Reuleaux-shaped triangle to produce the necessary compression of fuel and air.
The Mazda RX-7 sports car famously used a Wankel engine.
Gas turbine engines have three core sections, each of which function continuously (in contrast to the discrete cycles of a reciprocating piston engine). These sections are known as the compressor, combustor, and turbine.
Spinning blades at the front of a turbine engine, known as the compressor section, squeeze the intake air to make it more dense, thus providing more oxygen per unit volume.
In the center of a turbine engine, the combustor mixes fuel with the compressed air, before igniting the mixture to release energy from the fuel.
As the ignited fuel mixture rapidly expands in volume, the expanding gas rotates a set of blades known as the turbine section. These blades are connected to an axial shaft (turbine shaft) that, in turn, rotates the compressor section at the front of the engine.
A jet engine is a gas turbine engine that uses energy from the exhaust gas to produce physical movement. Thus, a minimal amount of energy is put into rotating the turbine shaft, as the remainder is used to produce propulsive thrust.
Jet engines use a nozzle to maximize the propulsive thrust that can be achieved from exiting combustion gases.
A turboshaft engine is designed to maximize the amount of work that can be performed by the turbine shaft. Thus, every effort is made to maximize the efficiency of the turbine stage in recovering energy from the combustion gases and transferring it to an output power shaft.
A supercharger is a mechanically-driven centrifugal air compressor driven by the crankshaft of a reciprocating-piston engine. Even at low speeds, it can effectively increase the density of air flowing into the engine cylinders.
Exhaust gases spin the turbine of a turbocharger. A compressor, connected to the same shaft as the turbine, squeezes the incoming air to force additional oxygen into the engine.
Jeff reminisces about his turbocharged four-cylinder 1984 Pontiac Sunbird.
Due to their high thermal efficiency, diesel engines are preferred over gasoline engines for generating torque at lower speeds.
Unlike a spark-ignition engine, a diesel engine does not add fuel until the piston is concluding its compressive stroke. The compression of the air/fuel mixture is sufficiently high to cause ignition, thus releasing energy from the fuel.
A rocket engine is similar to a jet engine, but carries with it the oxidizer (normally oxygen) that is mixed with the fuel to allow combustion.
Carmen mentions getting parts from Harbor Freight Tools, a US retailer with the motto, “Quality Tools at Ridiculously Low Prices.”
A conversation ensues about various types of torque wrenches.
Clay mentions the car he had during his college years, a green 1975 Dodge Coronet.
A water brake is a device that absorbs and measures shaft work.
Jeff gets quizzed on the formula for converting torque to horsepower. Clay notes that $latex \text{HP} = (\tau\cdot\text{RPM}) / 5252$ when torque $latex \tau$ is measured in pound-feet. Jeff struggles to recall that 1 HP = 33,000 ft-lbs per minute.
Biochemical engineer Kai Zhuang walks us through the evolving relationships between technology and humanity, especially as it relates to engineering education, in this episode of The Engineering Commons podcast.
Jeff and Adam discuss the high salaries being offered to software engineers in Silicon Valley.
Adam notes that the U.S. Federal Highway Administration (FHWA) placed a value of $2.6 million on the economic loss suffered by society due to a traffic fatality in 1994. The current estimates (2013) are considerably higher, in the range of $9.1 million.
Our guest for this episode is Kai Zhuang, a biochemical and operations engineer who has an interest in engineering education.
Kai’s application to the University of Toronto’s National Scholarship Program was a little more avant garde than most, consisting of creative art pieces.
Biomedical engineering is a fairly new engineering discipline that is only now beginning to work out its own sub-fields and areas of emphasis.
Kai was frustrated with the rigid curriculum structure he encountered as an undergraduate engineering student.
The ongoing shift of engineering instructors from expert to coach has been examined by Dave Goldberg, founder of Big Beacon.
When looking for innovative approaches to engineering education, Kai was advised by filmmaker Ryan Varga to investigate York University in Toronto, and Olin College in Boston, Massachusetts.
A recent quote from software developer Dave Winer concerns the inevitability of serious problems resulting from our increasing dependence on a “fragile and insecure” internet system.
Kai is disappointed that systems thinking is almost completely missing from the engineering curriculum.
Our guest notes that most fears are “past pain extrapolated incorrectly into the future.”
We talk with mechanical engineer, product designer, educator, and executive consultant Craig Sampson about the importance of storytelling in this episode of The Engineering Commons podcast.
Carmen likes the universality of engineering stories, in that all engineers eventually encounter similar difficulties in dealing with customers, managers, and organizations.
In a prior episode of this podcast, guest Bob Schmidt talked about the importance of stories in conveying information about problem-solving methods and approaches.
Jeff and Craig were classmates at Stanford University in the early 80s, while both were taking the Smart Product Design (ME 218 A/B/C) sequence of classes.
Craig was good at math and science in high school, so he gave engineering a try at the University of Colorado.
Jeff and Craig joke about programming in FORTH during their Stanford days.
Larry Leifer led the Smart Product Design program during the time that Craig and Jeff were students.
Craig has fond memories of watching a robot arm that performed ballet-like movements to the music of Trois Gymnopédies, composed by Erik Satie.
Also on the Stanford campus at the same time as Craig and Jeff was David Kelley, the founder of Hovey-Kelley Design, which later became David Kelley Design (DKD) and eventually merged with two other firms to form IDEO in 1991.
Craig started the IDEO office in Chicago, which now employs more than 60 designers.
Our guest references a book by Tom Kelley (brother of David Kelley), The Art of Innovation: Lessons in Creativity from IDEO, America’s Leading Design Firm.
Storytelling is the process of making your engineering work relevant in the lives of others, according to our guest, by presenting a believable vision of a better future.
Our ability to integrate visual and auditory information is pushed beyond its limit by the McGurk Effect (YouTube video).
Pareidolia describes human perception of a random stimulus as being significant; this is a form of apophenia.
Synesthesia is the phenomenon that occurs when stimuli normally associated with a single sense activate a secondary sense, such as sensing that numbers have colors, or words have tastes.
Craig notes that our confidence in a product is completely intertwined with our confidence in ourselves.
It is increasingly the case that designers are creating tools, rather than products, for their customers.
SketchChair allows people to sketch out the profile of a chair, which is then delivered as a set of cross-sectional cutouts that can be assembled.
Skeumorphism is the use of a stimulus that is referential to other products or experiences.
Aeronautical engineer Clay Coons explains the most common types of engines, and why each type is optimal in certain applications.
