History of the Motorcycle Part Two

The Otto Cycle

In this second article of the series I'd like to delve into the development of the internal combustion engine on which motor vehicles of any kind, and motorcycles in particular are so dependant. Rather than bore you with the technical details of the inner workings of 4-stroke, 2-stroke and rotary designs, which many of us may already be familiar with, I would like to concentrate on the history of the internal combustion engine's early development and some of the folks that helped create it and thus start the whole transportation revolution of the 20th century. While some of the first motors used a 2-stroke design, the 4-stroke engine received the majority of the effort to design a compact internal combustion engine, even though the 2-stroke is a much simpler engine incorporating nearly one third fewer parts. There just didn't seem to be much interest in two stroke engines and most early motorcycles utilized the more "popular" four strokes.
In researching IC or "Internal Combustion" engines I found that even today the four stroke engine is often referred to as the Otto Cycle, named after Nicholas Otto, the man whom many give credit to for the first successful design. While engines have become much more sophisticated over the years and their power, performance, endurance and efficiency have been greatly improved giving us a much wider range of transportation choices, the basic operating principle remains unchanged.
Yet no matter what type of engine used in motorcycles, two-stroke four-stroke, or rotary, they all fall under the broader category known as "Heat Engines". A heat engine is one that derives it's motive power through the transfer of or creation of heat. All heat engines share this common factor, fuel in one form or another is burned to produce heat, which in turn causes the expansion of a gaseous or vaporized fuel/air mixture that pushes on a piston, or rotor (in a rotary engine), which in turn transmits it's power through some kind of drive mechanism to one or more wheels and thus propels the motorcycle along the ground. For those curious about heat engines and would like to learn more about various other designs, here is an excellent site with animations of the numerous design possibilities.
In researching the history of the IC engine, I found that just like the bicycle, the history of this invention dates much farther back in time that I had at first thought. As far back as 1680 a Dutch physicist named Christian Huygens first experimented with such an engine. Then in 1860 Mr. Lenior developed the first self-sustaining internal combustion engine, which used coal gas its power source. This engine used a "double-acting" piston that had two combustion chambers, one at each end of the piston. It incorporated sliding valves along the length of the piston chamber to regulate the opening and closing of the ports that allowed for the intake and exhaust of the coal gas/air mixture. A system much like the typical steam engine. It also used a battery and coil ignition system to provide the spark to ignite the gas. However due to it's large size, its dependence on coal gas and other factors, it was not practical for use in a vehicle, and was designed for stationary use, such as to drive machinery in a factory. Also since it used coal gas, it was designed to be connected to a furnace that heated the coal to produce the gas on which it ran. Note here that when I refer to "gas" I am referring to a fuel in a gaseous state, not "gasoline" or other liquid form. The importance of this is that at the time of the first IC engines, petroleum had not yet been "cracked" or broken down into it's constituent parts, and liquid fuel such as we now use was not yet available. Until Abraham Shreiner, a Jewish chemist working in southern Poland successfully refined petroleum, the internal combustion engine was dependent on a gaseous from of fuel. Such a configuration was not easily adaptable to motive use.
In 1862 a French scientist patented, but did not build, a four-stroke engine. Again this was designed to use gaseous fuel, as apposed to a liquefied fuel. Sixteen years later, in 1876 Mr. Nicholas Otto, a traveling salesman, developed an internal combustion engine based on the work of Mr. Lenoir. His first machines were in fact two-stroke designs, though he never made any headway on these for a number of reasons. His later designs, due mostly to the efforts of Mr. Daimler (who designed the wooden motorcycle seen in the last article) and others in Mr. Otto's employ, are credited as being the first fully function engines capable of sustained and controlled operation for use in a non-stationary application. Or so the majority of historical records would seem to indicate. However, upon doing further research I found at least one reference that seems to dispute this. According this version of history, not only was it Mr. Daimler, while working for Otto, then later on his own, who was mainly responsible for the development and design of the Otto Cycle engine, but it also states that Mr. Otto was not really a designer or inventor himself, he simply saw the possibilities of such devices and provided the funds for others work.
Furthermore, in this version of the history of internal combustion engine design, it gives credit to one Siegfried Marcus as actually having developed the first fully operational IC engine incorporating not only the use of a liquid fuel, but also a "spray" carburetor, as apposed to a evaporation carburetor and battery and coil ignition system, as opposed to a "flame" ignition system, used by several other inventors of the time. These three factors allowed for a design that was compact enough for mobile use and also allowed for a means of controlling the speed of the engine, while most other designs of the time worked well only for running the engine at a single RPM. Useful for stationary machinery, but not practical for transportation. I have included the link here for those who wish to pursue this further, it is quite lengthy and very detailed and appears to be quite authentic.
So then, who to believe? I conjecture that there is most likely some truth to both accounts, that many developments were done in parallel, with a generous intermixture within each from others work, and feel I would have been remiss in my own retelling to not have included such compelling documentation as is presented in the work linked above.

Flame Ignition and other Matters

I mentioned "flame" ignition a moment ago so lets take at look at this while you're still wondering about this. You are still wondering about this, right?
In the early days of the development of the IC engine electricity was still in it's infancy. In order to use an electrical spark to ignite the fuel mixture through the use of a spark plug, the current has to be strong enough and timing be reliable enough to properly do the job of providing ignition. It also had to occur at the right point in time to be effective, to soon before compression or to late afterwards and the exploding gases would have little, or even a detrimental, effect on the operation of the engine. Thus some form of timing device was required. The next requirement for electric ignition using a spark plug is a coil to produce a high tension discharge to the fuel in the combustion chamber, preferably without delivering the same electric charge to the operator! Remember from the last article, the development of rubber was not till very late in the 19th century and thus still a few years away. So they had the problem of isolating the current running though the wire from the coil to the plug to prevent shocking the operator. And without proper ceramics technology to isolate the spark plug from the motor housing, you have the same problem. Furthermore batteries of the time were not terribly powerful, so that too was something of problem. Thus a high tension discharge to a sparking device in the engine would be transmitted through the engine and any adjoining metal parts, without proper insulation of both wiring and spark plug. So, while the timing issue was easily solved by mechanical means, the high tension ignition system had to await the advent of rubber and ceramic insulation near the turn of the century. While several attempts were made with electric spark, a more reliable form of ignition in the early days of IC engines was to have a sliding valve that would trap a small amount of the fuel mixture, expose it to an open flame, then continue on to the combustion chamber where the small amount of burning fuel inside the sliding valve would ignite the remaining mixture. This may have worked well on the stationary engines of the time but was hardly practical on a motorcycle or other moving vehicle. So, until the development of a workable high tension ignition system using points, coil and spark plug, a number of engines used a low tension coil ignition system wherein the points themselves were internal to the combustion chamber. Thus you only needed a fairly low current, derived from either a battery or magneto, and very little insulation, with the spark from the opening of the points themselves providing the means to ignite the fuel.
As discussed earlier, while the earliest engines used coal gas as fuel, this was not practical for mobile use since you needed a rather large container to store it in, or would have to take along a separate device, known as a gas generator, a rather bulky device in it's own right, to create the fuel to power the vehicle. These gas generators themselves needed an additional fuel source to heat the coal to produce the goal gas, making for additional weight and size, again hardly practical for mobile use! Nor was there any means of delivering it in a manor that allowed for controlled regulation.
Once liquid petroleum was cracked, or broken down to such fuels as benzene (one of the first fuels used) and gasoline, there was the problem of vaporizing the liquid fuel, as it would not burn in it's liquefied state. The first carburetors where known as "evaporation" carburetors. These employed a method of vaporizing the fuel by drawing air across the surface of the liquid. Again this may have been adequate for stationary engines but once you put the vehicle in motion, the fuel would slosh around and controlling the mixture was nearly impossible. There was really no means to meter it, you just "took it as it came" so to speak. While this was first used until the invention of the spray carburetor, engine design was limited to very low power, single speed applications and thus not practical for vehicular use. Since regulating the speed of the engine was dependant on controlling the fuel rate, something better was needed. Imagine riding a motorbike with only one speed? The advent of a "spray" carburetor, such is used to today, which vaporizes the liquid fuel, allowed for controlled variations in amount of fuel and fuel/air mixture ratios and thus changes in RPM of the engine.
As these problems were resolved and higher RPM's were achieved other problems came into play. Most notably the need to advance the spark as the RPM's went up. This was necessitated by the fact that fuel burns at a constant rate, if it is ignited too late the piston is already passed the point of maximum compression and the further down the piston is at the time of maximum burn, the less effective the power stroke. Therefore a way had to be devised wherein the point of ignition could be advanced to start the burning process earlier in the compression stroke the faster the piston traveled. On most early machines this was done through the use of a manual advance, you will see many early machines with one or more additional leavers compared today's machines. One of these was a manual advance that was adjusted "on the fly" by the operator.
As you can see, there were a number of factors that had to be overcome before the IC engine became practical for use in other than stationary applications.
By the year 1900, these obstacles had been mostly overcome. And while some systems still employed aspects of the recently outdated technology of the previous century, the Wright Brothers for instance, used an engine that employed internal-spark ignition and evaporation carburetors on their early flying machines, the development of the engine that powers the motorcycle was well on it's way. Thus, by the turn of the 20th century the basic layout and operation of the motorcycle was much as we see it today, with the emphasis on Basic!
And now, for a sampling of coming attractions I leave you with these examples of a few of the early 1900's entrees into the world of motorcycling.

A sampling of early machines

Within a few years of the turn of the 20th century, there were quite a number of motorbikes being offered to the public. While multi-speed transmissions and electric headlights were some years away, the choices being offered for sale continued to rise each year. These early machines were, for the most part, very low power, low compression engines. From what I have been able gather starting was merely a matter of peddling the machine, flipping a switch to close the electric circuits for the spark and you were on your way. While I have seen some references to a centrifugal clutch while researching early motorcycle engine designs I am still not clear if this was in common practice on the earliest machines. From studying the pictures, it would appear that most were direct drive, when the machine came to rest, the engine would die. The peddles were also required to provide additional thrust when encountering hills, as these machine had such limited power. You will probably also notice that most had a stand that propped the rear wheel off the ground, this, I assume, allowed for starting the machine while stationary, then raising the stand to embark upon the days adventure. And what an adventure riding those early machines must have been!
Here, for instance we have a wonderful entry from 1901 built by NSU
These had a motor rated at 1.5 horses clipped to the down tube of one NSU's early bicycles. Engine displacement was under 500 cc and was built by Zedel, a Swiss company that manufactured motors based on the DeBion-Burton design. The initials NSU stood for Neckarsulm Strickmaschinen Union (Neckarsulm Knitting-machine Union), quite a mouthful, not surprising that they soon adopted the use of just the initials NSU.
Another offering in 1901 included the first Indian motorcycle.
This was a small displacement machine of 260cc, featuring a single speed chain drive. Only three were produced that year by George Hendee and Carl Oscar Hedstrom, two of which were offered for sale, the third being the prototype itself.


In the year 1903 this FN (Fabrique Nationale) incorporating a 188 cc, 2 hp engine using a Bosch Magneto and featuring a carbide headlamp was introduced. Produced in Belgium, this company produced machines from 1901 to 1905.
1903 was, of course, the first year that Harley Davidson introduced it's line of motorcycles. Like NSU there were three built during first year.
This had a single cylinder motor with 3-1/8 bore and 3-1/2 stroke, used a belt drive and was designed as a racing machine. 21 Year old William S. Harley and 20 year old Arthur Davidson built these first machines in 10 x 15 wooden shed, to be later joined by Arthur's brother, Walter.


Jumping ahead to 1905 we find this 4 cylinder entry, again for Belgium, the 1905 FN Four. Boasting a whopping 5 hp, it's 360cc four cylinder engine and shaft drive represented a first in several aspects.

Thus we conclude this second article in the series.
In the next article I plan on reviewing more machines of the first years after the turn of the 20th century and discuss other aspects of early motorcycle design. Till then, enjoy, and keep the rubber side down.