July 2006

TEACHING THE DESIGN HISTORY OF THE MOTORCYCLE

Leland Giovannelli

I teach a course in the History of Science and Technology to first-year engineering students. Elsewhere, I have addressed various conceptual difficulties involved in teaching this course, e.g., introducing an audience inclined towards numerical Right Answers to the rigorous analysis of open-ended questions (Giovanelli).  The greatest practicaldifficulty, though, is insufficient time: how does one construct a single semester’s syllabus from the many important and interesting episodes and developments in this vast field? Typically, I choose material that is historically worthwhile and yet also accessible to students. The internal combustion engine thus doubly merits its place on the syllabus, being inestimably important in having shaped modern American culture, and also essential to my students right now. Treatment of the automobile’s profound social effects can sometimes obscure, however, the mechanical development of the internal combustion engine. How, then, does one present this mechanical history, especially when the modern engineering student is rarely a gear-head?

To make matters even more challenging, today’s engineering students are not “gear-heads.” Modern cars do not require the regular mechanical attention that cars of an earlier generation required, so car maintenance is no longer a survival skill. Furthermore, today’s engineering curriculum attracts students with interests wholly separate from mechanical and automotive engineering: some students in computer and electrical engineering, for example, do not know how to check their motor oil. Practically speaking, this means that these students have no greater knowledge of cars than they have of windmills. How does one introduce the history of the internal combustion engine to this audience?

My answer to this question is fourfold:

  • first, introduce, through lectures and readings, the development of the four-stroke Otto cycle engine;
  • second, simplify the problem by concentrating on the motorcycle rather than the automobile;
  • third, show pictures of the history of design development in the motorcycle;
  • fourth, bring motorcycles to campus for a class exhibit.

Why choose the motorcycle?

I have chosen the motorcycle rather than the car for a variety of reasons.

  • At the outset of its history, the motorcycle was little more than a motorized bicycle. The students have almost all ridden a bicycle, and they have a good sense of the limitations and requirements of two-wheeled transport. Their physical intuitions about riding help them imagine some of the problems associated with motorizing a bicycle.
  • For most of the motorcycle’s history, the engine has been fairly simple and exposed. As a result, even the novice can come to recognize certain features of the motorcycle engine.  Furthermore, the engine itself becomes part of the aesthetic design of the whole vehicle. Ugliness cannot be hidden under the hood.
  • For these reasons, a side-elevation photograph of a motorcycle reveals a great deal about how the particular thing works. With one photograph of a motorcycle, one can show both its engine and its overall design.  
  • Typically, students have strong feelings about motorcycles and their riders: they either love them or hate them. They freely admit their prejudices about motorcycles, whereas they seem more reluctant to do so with respect to cars and trucks. The motorcycle then becomes, quite literally, the vehicle for discussion about the social implications of the transport that we choose.
  • Finally, because I am myself a rider, I can fairly easily arrange an on-campus motorcycle exhibit for my students. Many motorcyclists, even relative strangers, are happy to participate in a 90-minute “bike show” on campus. They enjoy the attention that they and their motorcycles attract. The students enjoy applying the knowledge that they have gained about the machinery, and they enjoy asking questions of the riders.

 

A bit of conventional history

In my syllabus, the historical development of the steam engine, the bicycle, and the internal combustion engine form a single sequence. For reasons of simplicity, I emphasize early developments in the steam engine: the steam cylinder of Denis Papin (late 17th century), and the steam engines of Newcomen and Watt (18th and early 19th centuries).1 Through this introduction, the students become familiar not only with pistons and cylinders but also with intake and exhaust moments in a power cycle. These relatively simple elements eventually find application in every aspect of industry and transportation. In order not to lose sight of this point, I purposely skip the details of Watt’s later improvements and leap ahead to applications of the steam engine: pumps at the mine, machinery at the factory, the steamship, and the locomotive. We briefly consider buses, cars, tricycles, and, bicycles—all of them powered by steam, not gasoline. Thus, when we finally arrive at the Otto cycle of the internal combustion engine, the students have already encountered the challenges in powering such vehicles with steam. They can, to some degree, anticipate the challenges that a gasoline-powered engine will offer to previously existing modes of transportation.

A pictorial survey of the design history of the motorcycle

The first two vehicles: a study in power contrast

Appropriately enough, then, the first item in my pictorial design history of the motorcycle is actually a steam-powered bicycle.2  This Michaux-Perreaux steam velocipede, built in 1868, could attain a top speed of 19 mph. The students find this vehicle fascinating because of their personal familiarity with bicycles; they know at once how uncomfortable and dangerous it would be to ride this thing. They readily note the following features:

  • relatively high wheels, made out of wood and rimmed in steel;
  • a steering column that seems relatively upright rather than angled (or raked) back;
  • a relatively narrow position for hands;
  • pedals on the front wheel (discussion suggests that this keeps the rider’s legs from being singed by steam);
  • a suspension (shock absorption) system apparently limited to the bent metal piece on which the seat rests;
  • a leather belt transmitting power to the rear wheel.

This vehicle leads into a discussion of rake: the angle at which the front forks are inclined from the vertical.3 The students recognize that the front forks of this vehicle are so close to perpendicular that steering would be very difficult. They know, in general, that a more inclined front fork—that is, greater rake—would give better handling. They can imagine, however, that this relationship must have a practical limit: too much rake would result in a vehicle just as unmanageable as this one seems to be. In other words, they have identified and articulated a design parameter.
          
The Michaux-Perreaux has its engine in what seems to the students an unusual place. They recognize, of course, that the engine has to go somewhere, but they do not take the engine’s location seriously as a design choice until I show the second image (Hough and Setright 15).  Now they can consider possibilities they had never before imagined; they can hypothesize the advantages and disadvantages of a few representative designs. No single location is absolutely perfect, they realize; designers must choose one based on their goals. This exercise reveals to the students not only a second case of a design paradigm, but also their own intellectual subservience to current motorcycle design. To put it in the popular idiom: they have been thinking well within the box.

Presenting the Curtiss V-8 (Krens and Drutt 106).  A V-8 engine of this size can power a full-size automobile. Here it is on a bicycle. One cannot deny one’s astonishment at the sight of this vehicle. The Curtiss V-8 was built in 1907, in the United States, and could attain a top speed of 136 mph. The huge eight-cylinder engine dominates the appearance of this vehicle and determines its construction. The engine’s size necessitates an extremely long wheelbase; the long wheelbase, along with the rear seating, necessitates extremely long handlebars. The handlebars are so long, in fact, that they need additional struts for strength. As in the Michaux-Perreaux, there is no suspension except for a sprung seat.
           
The Curtiss V-8 helps to illustrate the appearance of the cylinders of an internal combustion engine. Here, one can readily see the four finned cylindrical shapes that present themselves on either side of the bike. With a bit of prompting, the students can deduce the point of the finning of the cylinders: the finning helps dissipate the heat built up in the combustion chamber. Once the characteristic finning has been explained, even the novice can use it to locate the cylinders of various engines. Indeed, the number, location, and disposition of cylinders constitute important differences between the motorcycles in this pictorial overview.

The top speeds of the steam velocipede and the V-8 bicycle differ by over 100 mph. This difference emerges from their engine capacities, certainly, but is also suggested by their overall structural differences. The Michaux-Perreaux seems that it would fly to pieces at anything approaching that speed; furthermore, with its slightly recumbent rider position, it looks like a casual “jaunting” vehicle. The Curtiss, with its jockey seat, suggests a vehicle built for speed. On the other hand, bicycle instincts tell the students that neither vehicle corners well: the Michaux-Perreaux has the nearly upright steering column, and the Curtiss V-8 has such long handlebars that it seems incapable of negotiating turns with any accuracy or at any appreciable speed. Whereas the Michaux-Perreaux suggested a leisurely turn about the park, the Curtiss V-8 means business—and its business is speed.

The Megola and the BMW R-32: borrowing from airplane technology

The next motorcycle astonishes the few knowledgeable students more than the novices. Why? Because the 1922 Megola (Krens and Drutt 140-41) has its cylinders placed around the hub of the front wheel—where very few motorcycle enthusiasts would think to look for them. Precisely because of this unorthodoxy, the novices might recognize and count the cylinders more quickly than will other students. For all its strangeness, however, the circular arrangement of the Megola’s cylinders represents a perfectly logical adaptation of airplane technology to ground transportation.4 Historically, the adaptation is logical because the early fliers were often motorcyclists, and vice versa.

This link between air and ground transportation surprises some of the students, for whom the two realms are completely different. The Megola provides a link between these two realms of transportation, and offers the students a glimpse at an early kind of motorcycle enthusiast. Such a person might have enjoyed the fact that this vehicle, like its airborne cousins, and like both of the previous vehicles, had no clutch and no transmission. One had to get it moving right away, and keep it moving. It took considerable skill to start and ride a Megola; it constituted an athletic and a mental challenge, one that required physical strength and tremendous concentration. This motorcycle was not a casual means of transportation.5

The next motorcycle is an early BMW. Some students will know that the BMW factory made airplanes before it made motorcycles; in fact, the famous BMW logo represents a spinning propeller. BMW designers did not replicate a radial engine for this motorcycle, even though it was produced only a year later than the Megola. Instead, they replicated an engine characteristic rather than a configuration: by placing the cylinders on either side of the motorcycle frame, they approximated the maximal air-cooling characteristic of the airplane engine.6 The image shows their horizontally opposed twin engine: the R-32 (Krens and Drutt 148).

The students’ bicycle experience guides them in the discussion about the advantages of this engine design; they readily see that this motorcycle has an extremely low center of gravity, and they know that this lends great stability. With a bit of prompting, they recognize that the cylinders here receive plenty of airflow and that therefore they will stay cool. In fact, even when idling on a hot day of 100 degrees Fahrenheit, this engine does not over-heat. The students realize now, if not before, that the cylinders must get very hot indeed if they can be cooled by still air at 100 degrees! This fact gives rise to an essential conversation about the relative inefficiency of the internal combustion engine: it generates a tremendous amount of heat, and that heat dissipates into the atmosphere. (The inefficiency of the motorcycle engine is eclipsed only by the inefficiency of the automobile engine—unless one considers that the heat from the latter engine can be diverted into the interior of the automobile itself.)

A question of finances
These four motorcycles so far have been considered from engineering perspectives. The conversation that they inspire in class does not necessarily become extremely technical, but it nevertheless includes vital considerations: safety, speed, engine placement, cylinder number and disposition, center of gravity, engine cooling, and efficiency. By contrast, the next two motorcycles present an entirely different perspective: that of economy. Both motorcycles come from the post-World War II era. The first comes from the United States; the second comes from West Germany. Their stylistic differences express quite clearly a difference in wealth.

Consider the first one: a 1948 Indian (Krens and Drutt 216),7 made in the USA. For the moment, we do well to compare it to the BMW R-32. In the Indian, the students see a V-twin engine. It has an incredibly large displacement: 1209 cc. That makes it more than twice the size of the R-32. For all that, its top speed of 85 mph is only about 25% more than the R-32’s top speed of 62 mph. So what is that huge Indian engine doing? The answer is evident even from the photograph: this is an incredibly heavy motorcycle: 550 lbs. It seems to some students like a war horse, caparisoned in metal. The impression is confirmed when I indicate the width of the tires: students know that wider tires decrease efficiency. A great deal of the Indian’s power output must be directed at moving the motorcycle itself. It is a gas guzzler. Such a vehicle could find a popular market only in an economy with cheap, abundant fuel.

As inefficient as the Indian appears, however, it is not nearly as inefficient as the automobile. Now is the time to make this obvious point, if it has not already arisen. Many students have not considered that most of their gas money goes to moving their vehicles rather than themselves. The automobile provides other features that the motorcycle does not provide: greater comfort, greater physical safety, and greater cargo space. I find that very few of my students, however, have considered the trade-offs of their preferred means of transportation; they simply accept automotive transport as a standard that deserves no analysis. (I ask them now, if not earlier, if they are thinking inside the box again.)

The other post-war motorcycle makes a stark contrast to the American Indian: the Imme, made in West Germany in 1949 (Krens and Drutt 222, 224).  This date will not necessarily evoke any recognition from the students; they might need to be reminded of the Second World War. The Imme, weighing less than one hundred pounds, is a flyweight compared to the heavyweight Indian. Its engine is one-twelfth the size of the Indian engine, and yet it can travel at half the speed of the Indian. It requires so much less metal in its construction that the contrast between these two motorcycles echoes the difference in the post-war economies of their two nations.

This motorcycle, however, is not merely a low-budget motorcycle; it constitutes an outstanding example of engineering innovation. The frame is self-evidently light and simple, but closer inspection reveals its astonishing minimalism. The motorcycles we have seen so far have had two front forks, one on each side of the front wheel. The Imme has only one front fork. A three-quarter view of the Imme (Krens and Drutt 224) displays this single fork to good advantage. The other motorcycles have had two rear forks; the Imme, again, has only one.  The image makes this obvious. Look more closely at that single rear-fork support in the previous photo (Krens and Drutt 222): it doubles as the single exhaust pipe. (A second look at the three-quarter view will confirm that this motorcycle has only one exhaust pipe.) These innovations minimize the weight of this motorcycle without decreasing its safety. In addition, the single forks, front and rear, make wheel changes simple. That consideration is not trivial, as bicyclists know. The Imme has real style, too; lean and streamlined, with its distinctive single cylinder, it has as much personality as the Indian has.

You are what you ride
The next two motorcycles present two extremes of relatively modern design: the NSU Supermax and the Harley-Davidson Easy Rider Chopper.  Here, design seems driven not by economic necessity, but by artistic and psychological considerations.

What a study in opposites! To ride the single-cylinder Supermax (Krens and Drutt 266), one must sit fairly erect, in an upright riding style; the lines of the bike do not suggest to the modern eye speed or daring, but rather tidiness and control. The repeating curvilinear shapes do not shoot off into space, but always come back, closing in on themselves. Compared with the Chopper, the Supermax certainly does not suggest recklessness, danger, and rebellion; on the contrary, with its proper curves and matte finish, it seems instead the very portrait of restraint.

Now turn to the V-Twin Harley-Davidson (Krens and Drutt 294-296). The students do not know the film Easy Rider, but they can recognize an attitude when they see one. The easy-chair posture riding style of the Chopper suggests indifference rather than vigilance, and laxness rather than alertness. With their bicycle intuitions, the students know that the front wheel’s excessive rake sacrifices handling for style. With their own sense of object-identification, they know that image is everything here. The Chopper, encased in brilliant chrome, demands our attention. When the customary modifications increase engine noise to a roar, it is impossible to ignore this motorcycle. That, of course, is the point: the Chopper zooms by, its rider settled back—and we sit up and take notice.

Form follows function
The last pair of bikes affords yet another kind of contrast, permitting us to read their function from their form: another BMW, the so-called Flying Brick, paired with the Beta Techno.

This BMW, the K-100 (Krens and Drutt 358), has a very different look from the Easy Rider chopper “filled-in” rather than skeletal, beefy rather than rangy. It seems more hidden than any of the other motorcycles in this series except perhaps the Indian. Its four cylinders cannot be readily identified because they are not finned, and because they lie parallel to the ground, at right angles to the direction of the bike. This placement of the finless cylinders makes these new bike watchers ask, “How does this engine stay cool?” The answer, someone is bound to guess, is that this motorcycle has a water-cooled engine—just like a car. This fact, coupled with the overall appearance of the bike, hints that we have entered a new era. The upright posture suggests alertness without the rigidity of the NSU Supermax, while the long seat offers room for various riding postures. The K-100 is a cruiser: it is designed for long trips at high speeds.

Now compare it to the Beta Techno (Krens and Drutt 386). The mountain bikers in the crowd will soon piece together the distinctive characteristics of this bike: high clearance, stripped-down appearance, and knobby tires. Clearly this vehicle belongs off road. After a few more minutes, the students notice something very strange: this motorcycle has no seat! Clearly, whatever one does with this bike, one cannot do it for very long. The students guess that it must be used in some kind of off-road competition—and they are absolutely right.  The Beta Techno competes in observed trials, an advanced kind of obstacle course for motorcyclists. Form follows function quite clearly here.

Conclusion
In this brief paper, I hope to have shown the pedagogical benefit of a pictorial survey of the design history of the motorcycle. These ten examples differ so radically from each other that even the complete novice can, with some guidance, identify some of their most conspicuous characteristics. In order to help students articulate what they see, I use the images in paired overheads—this, of course, necessitates two overhead projectors. Sometimes I use the first ten minutes of class to assign particular motorcycles to groups of students, giving them photocopies to preview and discuss briefly in small groups. Then, when the overhead presentation begins, I call on individual students to initiate analysis of the particular motorcycles that they previewed in their group.

Admittedly, such a survey cannot be comprehensive in a classroom period of 50 or 75 minutes. Nevertheless, a great deal happens here. The conversation ranges over many of the complex issues in vehicle design. I have already indicated possible comments relating to structure, safety, speed, engine placement, cylinder number and disposition, center of gravity, engine cooling, efficiency, engineering economy, style, handling, clearance, and riding position. One could add to this list still more mechanical features, such as brakes, electrical system, and sophisticated suspension. The students learn not only about particular aspects of motorcycle design, but they also learn about operating within design constraints. Consideration of economic issues such as cost, market, and advertising, necessarily leads to discussions of sociology and psychology, and to their variations through time.

Does this pictorial survey substitute for a week’s worth of lectures of the internal combustion engine? I think that it does. In fact, I think that it goes one better. The combination of pictorial survey and motorcycle exhibit will stay with the students long after they have forgotten the date of the first automobile.


Notes

Many thanks to J. G. Everhart and to Kathleen Duke.

  1. This history can found in many texts. The 5-volume History of Technology by Singer, Holmyard, Hall, and Williams, continues to be valuable. A less complete but more contemporary work is Science and Technology in World History: An Introduction  by James E. McClellan III and Harold Dorn.
  2. Thomas Krens and Matthew Drutt, The Art of the Motorcycle (New York: The Solomon R. Guggenheim Foundation, 1998): 99.  Subsequent references are indicated in the text.  Links have been provided in the text to online versions as well. 
  3. I do not introduce trail, the partner of rake, because, as I will illustrate, it is less easily explained. Drop a perpendicular through the hub of the front wheel, and call its foot, or terminus on the ground, point P. Now consider the line made by the front fork, and extend that line until it hits the ground in a point Q. The distance PQ is the trail. The complex relationship between rake, trail, and steering can be studied in Chapter 2, Steering Geometry, of P. E. Irving’s Motorcycle Engineering. This classic was originally printed in Great Britain in or after 1959, and then reprinted in the U. S. by Floyd Clymer, Los Angeles, CA. My edition has no dates pertinent to publication or reprinting.
  4. For more information on the Megola, consult Alan Cathcart’s article “Megola Maniac.”  This article, in addition to relating the history of the marque, asserts that the Megola is not a radial but a rotary engine. In a radial engine, the cylinders remain in place; in a rotary engine, they rotate. This distinction comes from Jeff Craig, who rebuilt the Megola featured in the article.
  5. The Cathcart article describes the hair-raising experience of riding a re-built Megola.
  6. In fact, the American company of Harley-Davidson offered the first production-model horizontally opposed twin, and they did so over a decade earlier than the R-32. The boxer-type engine did not persist, however, and Harley-Davidson concentrated its energies in the in-line V-twin—i.e., a two-cylinder engine in which the cylinders form a V in the plane of the bike itself. By contrast, the Curtiss V-8 is a transverse engine. See Nicholson 23-31.
  7. Of course the Indian Chief was not new in 1948; it had first appeared in 1922. I use this vintage Indian for the sake of the economic contrast with the Imme.

 

Works Cited

Cathcart, Alan.  “Megola Maniac.”  Motorcycle Classics, Dec. 1997: 44-49.

Giovanelli, Leland.  “Conceptual Difficulties in Teaching History of Science and Technology to Engineering Students.” Annual Conference Proceedings, Michigan Academy of Science, Arts, and Letters, 34 (March 2003): 437-444.

Hough, Richard and L. J. K. Setright. A History of the World’s Motorcycles.  Revised edition.  New York and London: Harper & Row, 1973. 

Irving, P. E.  Motorcycle Engineering.  1959.  Los Angeles: Floyd Clymer, 1973. 

Krens, Thomas and Matthew Drutt, eds.  The Art of the Motorcycle.  New York: The Solomon R. Guggenheim Foundation, 1998.

McClellan III, James E. and Harold Dorn.  Science and Technology in World History: An Introduction.  Baltimore: Johns Hopkins, 1999.  

Nicholson, J. B.  Modern Motorcycle Mechanics.  Saskatoon, Canada: Nicholson Brothers Motorcycles Ltd., 1942.

Singer, Charles, E. J. Holmyard, M. R. Hall, and Trevor Williams.  History of Technology.  5 vols.  Oxford: Clarendon, 1958.