Racing Bicycle Design and ConstructionSteve Maus
Most people have heard of Lance Armstrong, but how many remember the first American to win the Tour D'France, Greg LeMond who won three times. In this talk we will look a bit at the background, design considerations, materials, and current state-of-the-art associated with racing bicycles.
Bicycle racing is a major sport in Europe. Tours of Italy, France and Spain often shut down sections of those countries for 2 - 3 weeks and involve 1500 - 2100 miles of riding for the athletes. Lance Armstrong has won the Tour D'France seven times. Stelvio Pass in Italy involves a climb through 48 switchbacks. Speeds on the mountain downhills often reach 60 mph and place very high demand on the bicycle. Gavia Pass is often snow covered for the race and is only a gravel and mud road near the summit. Andy Hampsten won the Tour of Italy stage race over this pass in a driving snowstorm in 1988. On flat ground many racers run about 40 mph. During the final sprint, (at the finish of a race), riders prefer a very stiff frame to maximize control in heavy bicycle traffic with much pushing, shoving, and even contact with spectators who are right at roads edge.
A major design consideration for a racing bicycle is to have a frame which fits the rider. Most of this is controlled by selection of tube length for the various tubes which comprise the frame. Most competitive cyclists will pedal about 6 million strokes per year. Correct frame sizing will greatly reduce the fatigue associated with this task. Tube length is optimized for lower leg length, upper leg length, and torso.
Materials have developed a lot over the years, with a major emphasis on weight reduction, although shock absorption, and rigidity have proven to also be of major importance. Bicycles made from 1900 to 1940 were made from seamed steel tubing (a flat steel plate bent into a tubular shape and seam welded). Fork crowns were also assemblies of formed steel and were brass brazed to the tubes. In those days the frame and fork of a bike weighed about 10 lbs, and a complete bicycle weighed 27 lbs.
In the 1950, butted steel tubes (extruded tubing with variable wall thickness) were introduced to replace the seamed tubing. These tubes has extra thickness near braze attachment points, but thinner walls between such points. The amount of assembled pieces was reduced with the use a pressed steel lugs, and the fork crown assembly was replaced by a single forged steel crown. The result of these changes reduced frame/fork weight to about 6 lbs. and the complete bicycle to about 25 lbs. Lugged construction with mitered weld joints presented the challenge that the miters must be nearly perfect. If not, fatigue cracking would rapidly progress from the weak point of the joint. .
During the 60's and 70's Reynolds 531 steel and Columbus 4130 heat treated alloy steels were introduced which allowed for even greater weight reductions. Frame/forks now weighed about 5 lbs and full bicycles about 22 lbs.
In the 80's both titanium and aluminum frame construction was introduced. Titanium proved to be very hard to cut and work with. Early aluminum frames had to use large tube diameters for strength which also increased rigidity. These proved to be real "bone shakers" for the riders. Steel frames continued to develop with tube walls becoming as thin as .012" - .028" with an increase in tube diameter from 1.125" to 1.25". Investment casting produced more accurate lugs and fork crowns. The result of these efforts got frame/fork weights down to 4.5 lbs and bicycles to 20 lbs.
The 1990's saw the introduction of carbon composite materials. These proved to be very light, but also "dead" (too much vibration dampening which made it difficult to respond to conditions and dangerous to ride at high speeds. Bonded (glued) Aluminum lugs were introduced. A company called "Trek" introduced an OCLV (Optimal compaction low void) process to make some substructures as molded carbon composite assemblies. These made for very strong carbon molded pieces, but because molds are expensive, only "standards" could be produced. Angles of molded pieces were fixed allowing limited tube length selection. The process would be cost prohibitive to "customize". The result of this technology was a 3.5 lb frame/fork, and 18 lb complete bicycle. In steel frames, the 90's saw the start of the use of TIG welding and air hardening tubing for frames achieving a 4.5 lb frame/fork weight. Difficulties with larger tubes of aluminum frames and forks which were "too stiff" remained, and butted titanium tubing was developed, but results were forks that were too flexible and hard to control.
In the 2000s the harshness of the aluminum frame ride was solved by replacing the rear tubes with carbon composite. This combination creates a responsive yet comfortable ride and reduced frame/fork weight to about 3.5 lbs. Most of these come from Taiwan and China. In titanium frames the United States leads with the advent of hydroformed tubes. Such frame/forks also weigh about 3.5 lbs. The carbon frames by the "Trek" OCLV process has been improved. The use of modified tube sections (non circular) and "wrapped joining" has achieved frame/fork weights as low as 3 lbs, and total bicycles as low as 15 lbs. Steel, however, remains popular for "custom" frames with most components now being "carbon".
One has to wonder what a Greg LeMond might have been able to do with one of today's bicycles.