The true beginnings of the wheel date back possibly as far as the Paleolithic era (15,000 to 750,000 years ago). This wheel was nothing more than a log, laid alongside others, which was placed beneath a load to be moved. The main problem with this method of transportation was that many rollers were required, and care was required to insure that the rollers stayed true to their course.
One theory as to how this obstacle was overcome suggests a platform, or sledge, was built with cross-bars fitted to the underside, thereby preventing the rollers from slipping out from under the load. Two rollers would be utilized, with two cross-bars for each roller, one fore and the other aft of the roller.
Another theory involves simply putting pins down through the corners of the sledge, utilizing two pins on the end of each roller, to hold the rollers in place. The latter theory provides a logical transition to the grooved roller, by the simple fact that friction caused by the underside of the sledge on the rollers would wear grooves in the rollers over time. In response to this, the roller may have been made thinner in the middle, and larger ends. At this point in the evolution of the wheel, we begin to see distinct, solid wheels connected by an axle-tree replacing the primitive roller.
As with the simple roller, there was a significant flaw in the design of the axle-tree and solid wheel configuration. When a cart with wheels of this design is towed, cornering is an awkward, sometimes dangerous maneuver. In a sharp turn, the inside wheels are dragged around the turn, with the potential of overturning the sledge. One solution to this issue was found in the fixed axle, with wheels that rotated freely around the axle. Arranged as such, the wheels were free to rotate independently when cornering, allowing the inside wheel to turn more slowly while the outside wheel sped up. This leap forward in technology necessitated alteration of the wheel itself as well. Solid wheels were developed, with a hole bored through the center for the axle.
Two types of solid wheels are presented in this exhibit. The first is a solid cross section of a tree. The main shortcoming of this wheel is the fact that its design, by nature, is flawed. In a cross section of a tree, the strength of the grain of the wood is not utilized, as with a plank cut lengthwise from a tree. This causes the wheel to split easily, as seen in the display wheel (shown in the image at the top of this page). In order to strengthen the solid wheel, the strength of the tree's grain was utilized by building wheels from planks. Such wheels were typically made from three pieces. These three pieces were pinned or banded together, with the axle hole bored through the center piece.
The next evolutionary step for the wheel was the advent of the spoke. The spoke was developed in an attempt to lighten the wheel. The first attempts at wheel lightening resulted in solid wheels with gaps between the planks, leaving rough spokes. From this design stemmed the idea of the spoked wheel, consisting of a hub-with an axle hole, felloes (a felloe is one section of the rim of a wheel) and the spokes themselves. Note that the felloes of the Persian cart wheel are not carved to shape with the wheel, rather one side is left straight to save time and labor. This wheel was crude, but it was lighter and stronger than the solid wheel, and it used less material.
As the need to move faster, and with greater ease drove man further from his home, for hunting and conquering purposes, wheels became lighter. Another reason wheels became lighter, was scarcity of materials. In order to make wheels lighter, and use less material, spokes became narrower, as did the rims of the wheel. The felloes were slimmed down by carving both sides to shape, eliminating a considerable amount of wood from the wheel, as seen in the Egyptian chariot wheel. This wheel, while lighter and faster, bore the disadvantage of requiring a skilled wheelwright to build it. The Greeks are credited with introducing the cross-bar, or H-type, wheel as an efficient, easily built wheel. The well to do used the spoked wheel, and the common, less wealthy population used the cheaper cross-bar wheel.
When wheel making became an endeavor requiring a skilled artisan, measures were required to protect the wheel from damage. Protective sheathing was utilized for this purpose. These covers on wheels, known today as tires, began as such simple substances as leather, iron, wood, and later, rubber. The leather tire on the solid constructed wheel is held on with nails, and offers a minimal amount of protection to the wheel. The tire serves as a buffer from damage to the wheel. Should the vehicle encounter a jagged rock, or other impediment, the tire, which can be replaced with relative ease, will be damaged instead of the wheel, prolonging the life of the wheel.
Iron tires were introduced later, and proved to create a more durable protective surface for the wheel. The first iron tires were pieced together iron strips laid end to end and nailed or riveted to the wheel. The fact that such tires were piecemeal would suggest a lack of structural integrity, and a fairly regular schedule of maintenance. The iron shod wheel featured in our display, however, is clearly built with a single, continuous band of iron. Early attempts at placing a band of iron around a wheel were ill-fitting, being larger than the wheel, and requiring rivets to hold the tire in place. Our wagon wheel, with a well fitting, continuous iron tire, is the result of taking an iron hoop slightly smaller than the wheel and heating the iron until it expands enough to girdle the wheel. As the tire cools, it shrinks, creating a powerful grip on the wheel. The strength of this grip was almost all that was needed to hold the wheel together, allowing for elimination of materials, and thus weight, from the wheel.
G.F. Bauer registered the 1802 patent on the first wire tension spoke, but it was not until 1869 that W.F. Reynolds and J.A. Nays incorporated them in their Phantom Veloce. This wire spoke consisted of a length of wire threaded through the rim of the wheel and secured at both ends to the hub. Over the next few years, this wire spoke evolved into the round tension spoke we see on bicycles today. The first major use of such spokes is credited to James Starley, inventor of the Ariel and other bicycles. The main advantage of the tension spoke is that it allows slight flexing of the spokes while retaining the structural shape of the wheel. The functional difference between tension spokes and wooden spokes is that the weight of the rider and the frame is suspended from the top part of the rim by tension spokes, where the wooden spokes provides support from the ground up. The tire placed around the first tension-spoked wheels was typically hard rubber, as displayed on our highwheel and safety bicycles.
The Museum's 1879 Harvard Bicycle
The bicycle also claims responsibility for the pneumatic tire, which was first patented as a concept in 1845 by R.W. Thompson, of England, although he never produced a single one. In 1888, John Dunlop, a Scottish veterinarian, improved upon and patented the pneumatic tire, earning true credit for it (Dunlop is also credited with coining the term "pneumatic"). Dunlop reportedly developed the air filled, pneumatic tire to ease the headaches his young son suffered when riding his tricycle, which rode on hard rubber tires. Dunlop's tires quickly became the most sought after tire for bicycles, providing the smooth, high speed ride that replaced hard rubber as the tire of choice for serious cyclists. Within a few years, virtually all new bicycles sold were equipped with pneumatic tires.
The pneumatic car tire, featured here in solid white, with a Ford hub, was far different from today's 50,000-mile tires. Constructed from white, carbonless rubber, the tire had a maximum life expectancy of around 2000 miles. And a hard 2000 miles those were. On average, an automobile tire lasted around 30 or 40 miles before it needed repair. Punctures, the tire coming off the wheel, and the tube being pinched accounted for the majority of blow-outs, which required that the tire be removed from the wheel, and a spare placed on the wheel. In order to complete a car trip of any length, a number of tires, which were strapped to running boards, roofs, etc, were required. At the end of 2000 miles, there was usually not much of the tire left, and its remains were discarded.
Asserting prevalence in the 1920's, the disc wheel is the next evolutionary step in wheel technology, despite the fact that the steel disc wheel is reminiscent of the solid wheel. While the disc wheel has its shortcomings, it offers many advantages over spoked wheels, the foremost being cost efficiency. While building a spoked wheel was a difficult process, one requiring a skilled wheelwright, a disc wheel was relatively simple to build. The rim could be rolled out of a straight strip of metal, and the disc itself could be stamped from sheet metal in one easy motion. The two components were welded or riveted together, and the resulting wheel was one that was relatively light, stiff, resistant to damage, easily produced in mass quantities, and most important, cheaply produced.
Further advances in metallurgy and plastics have allowed the relatively solid disc wheel to be whittled away to produce extremely lightweight, strong spoked wheels. Just in the manner that the spoked wheel first evolved with advancing wheel technology, the three modern wheels on display - motorcycle, bicycle, and automobile - were created through advanced technology providing metals and plastics that are both very lightweight, and extraordinarily strong. As materials become lighter and stronger, less material is needed to make a wheel, creating a much lighter wheel than ever before, allowing for more speed and ease of use. This progression, from a solid disc to a spoked wheel, is a contemporary version of the same progression from many years ago, with modern components allowing the advance. It is a fitting end to this display that the emerging technology is simply a cyclic progression, coming around, much like a wheel, full circle, leaving us to only wonder, what will come next.