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At the end of 2002, the following exchange among bicycle specialists took place in regard to Rhonda Roland Shearer’s article “Why is Marcel Duchamp’s Bicycle Wheel Shaking on its Stool” (1999), posted on Art Science Research Laboratory’s website (the publishing company of Tout-Fait). On December 28, 2002, John S. Allen writes:
In
response to a discussion of the Duchamp bicycle sculpture on the massbike
listserv, I have a couple of quibbles about statements on bicycle
history on your page http://www.artscienceresearchlab.org/nav/whyshakef.htm
The term "boneshaker" applies to bicycles built from approximately 1863 to 1878, with a relatively small front wheel constructed like a wooden wagon wheel--the bicycle shown in Illustration 6 on the page is of this type. Most bicycles made from approximately 1878 to 1890 had tensioned steel spokes, a larger front wheel and a smaller rear wheel. These bicycles had straight forks and were called "ordinaries", highwheelers" or, with derogatory intent "penny farthings"--not "boneshakers." The rough ride of the boneshakers was due largely to the solid steel or rubber tires. Highwheelers also had solid rubber tires, but the ride was smoother--the large front wheel, nearly directly under the rider, bridged road surface irregularities better. The rear wheel was small, but it was far behind the rider, and the frame member between the rear wheel and the saddle was rather long and flexible. The real breakthrough in ride quality came with the introduction of Dunlop's pneumatic tires in the 1890s--along with chain drive, this invention made for a comfortable ride with the bicycle frame design still in use today. Straight forks were used on highwheelers as well as boneshakers. A curved fork does somewhat smooth the ride, because it is springier than a straight fork--however, its effect in smoothing the ride is much less than the effect of the pneumatic tires or the highwheeler's large front wheel. The boneshaker in your illustration has a vertical steering axis, a straight fork and therefore zero trail. It was discovered at some time in the early development of the bicycle that a bicycle was self-steering (like a supermarket shopping cart caster) if it has trail--that is, if the tire contact patch is behind the projection of the steering axis to the road surface. Only a bicycle with trail can be ridden no-hands. This was the case with typical highwheelers; the slight tilt of the fork's attachment to the frame created the trail. With the rear-wheel chain-driven safety bicycle, the steering axis had to be tilted even further so the front wheel would clear the rider's feet. Although the fork of such a bicycle is curved ("raked") *forward* at the bottom, the tire contact patch is still *behind* the steering axis. A straight fork would bring the wheel closer to the rider's feet and place the tire contact patch too far behind the steering axis, resulting a heavy feel to the steering, and excessive response to shifts in rider position. What is the provenance of the fork in the Duchamp construction? It might be from a unicycle -- unicycles still use straight forks to this day. Or it might be from an old highwheeler, and cut down to fit the smaller wheel used in Duchamp's construction. Or, more likely in my opinion, the fork could be from an early safety bicycle, for example, the "bantam" bicycle shown on page 20 of the book *Bicycle Science*, 1983 edition (MIT Press), by Whitt and Wilson and also on page 158 of the wonderful 1896 book *Bicycles and Tricycles*, by Archibald Sharp (reprint edition from MIT Press, 1979). Many early safeties had a straight fork. There are other examples of such bicycles on pages 154, 280 and 288 of Sharp's book. And in connection with this, the following statement is not accurate:
I
am not a real expert on old bicycles. A member of the Wheelmen, who
collect and restore old bicycles, might have a more definite opinion
of the provenance of the fork. I am sending this message to the massbike
list and Prof. Wilson, who, I'm sure, will be interested in having
a look at your page. John
S. Allen
The
factor in the comfort of the fork, its springiness or compliance,
the degree to which it will bend in response to a bump in the road,
is the horizontal displacement of the fork tips from the straight
line passing through the head tube. A curved fork and a straight
fork with the same position of fork tips will have about the same
compliance. By "straight", I think John means in line
with the head tube. There are road forks which have straight
blades which are angled forward so that they have trail. Douglas
Kline
On the same day, December 30th, 2002, John S. Allen replies to Douglas Kline’s response:
I
don't think it's that simple, and particularly not with a fork made
of taper-gauge tubing (such as Reynolds --wall thickness kept constant
by making it thinner at the lower end before the tubing is rolled
do make the blades taper). As Dick miller surmises, the curved part
of the fork, which nearly reaches the horizontal, will give it somewhat
more compliance than one which achieves the same trail with straight
blades. Even a fork with straight blades will have a horizontal component
of flex, because the head tube is at an angle and the blades are angled
slightly more. But with a curved fork, there is more of a vertical
component to the flexing --and it is the vertical displacement, not
the horizontal displacement, which cushions against bumps in the road.
Yes, that was the case with the early safety bicycles shown in Sharp's book, to which I gave page references.
True,
and they would have even more trail if they were not angled forward. John
S. Allen
Figs.
1~3
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