Bicycle Frame

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The Rover "Diamond Frame" Safety was invented in 1885 by John Starley in England. It is called the "Diamond Frame" because of the triangular shapes that are outlined throughout the frame. Today, the "Diamond Frame" is commonly made from one of four materials; Steel, Aluminum, Titanium and Carbon Fiber. Each material has unique characteristics that differ from one to the other. Often, the type of frame material depends on what type of conditions the rider plans on using the bike. The sections below detail each material, and the conditions they are used for.

Steel

Steel frame.jpg

Steel bicycle frames can be built from many different types of steel alloys. The benefits of steel frames are their strength, ease of machinability and maintenance, and the relatively inexpensive price. Due to the steel tubing being less rigid than tubing in other materials, it gives the bicycle flex and in the end is a smoother ride. This can be compared to Aluminum tubing which is normally oversized, not allowing for much flex leading to a rougher ride.

Lugs, TIG & MIG welding, and fillet brazing are all efficient ways to join steel tubes to make a frame. Disadvantages of steel frames is not only that they can rust but also that they are typically heavier than other frame materials, especially when comparing it to aluminum, titanium, and carbon fiber. The cheaper steel frames found on common use bicycles are made of mild steel, the same that is sometimes used for cars and smaller trucks. In the higher quality bicycle frames that are used for competition and passionate bicyclist are composed normally of chromoly, which is an example of a high strength steel alloy. Typically the higher quality steel frame, the lighter the overall weight of the tubing and frame. A lighter steel frame allows for an easier ride whether you are traveling on a flat surface or especially on an uphill climb. An easy way to tell whether your steel frame is regular or high quality can be judged by a flick from your fingernail. If it is a bell-like ring, your bike has a high quality frame and if the tone is similiar to a thunk, then your bicycle has a regular steel frame.



Aluminum

Aluminumframe.jpg


While steel may be the most commonly used material in bicycle frames, aluminum has begun to "steal its thunder". One reason is that aluminum frames now cost much less than in years past. Another is that an aluminum frame weighs about 1/3 of a comparable steel frame. However, there is a trade off.

The lightweight properties of aluminum also comes with lower strength compared to steel. In general, aluminum frames are between 1/3 and 1/2 as strong as a steel frame. If a bike manufacturer simply changed materials without altering the design, the result would be catastrophic. Since aluminum is a soft material, it is able to bend much easier than steel. This can lead to cracking, and ultimately total failure of the frame. Though there is a solution to improve the strength of an aluminum frame...

To counter the low strength of aluminum, companies have begun to make the frames out of larger diameter tubes, as well as tubes that have thicker walls. This adds strength to the frame, but also keeps the frame lighter compared to a similar steel frame.

This final product provides the light-weight feel of a bike made from aluminum, with the strength that a steel framed can provide and a cost close to that of a steel framed bike.

Ultimately, it is up to the rider to determine which frame they prefer. Bikers world-wide agree that a steel framed bicycle has a softer ride than an aluminum frame bicycle. This may seem odd since aluminum is the lighter and softer material, but the larger tube sizes needed for an aluminum frame causes the bike to feel more stiff. On the contrary, a rider may prefer a lightweight aluminum frame regardless of the comfort.

(source: http://www.ransbikes.com/ITR41.htm)


Titanium

Leggera c disp.jpg

Nowadays some bicycle frames are made from titanium. Why titanium? because it is lighter. Titanium frame is about half the weight of steel frame. By increase the diameter of the frame, titanium frame have approximately same strength and stiffness as steel.

The most often types of titanium rod that are usually used to manufacture bicycle frame is 3Al/2.5V and 6Al/4V. The different between these two composite is due to the ratio of aluminum (Al) and Vanadium (V). 6Al/4V is much lighter, stronger and expensive.

There is one disadvantages of titanium frame, it is costly. Titanium frame approximately cost triple times compare to steel frame. To show how much titanium bicycle can cost you compared to steel bicycle, I use Google to find highest price of the titanium bicycle and steel bicycle. The titanium bicycle cost nearly $6000 while steel bicycle cost only $2000. And for your information, the titanium bicycle is just a normal bicycle(mountain bike) while the steel bicycle is racing bike.

The first mass production of titanium frame is in 1974 in United States.

"Teledyne markets the first titanium bike that was produced in any quantity (Speedwell of England had some Ti production frames as far back as the 1960s, welded by Lamborghini!) Litespeed brought titanium frames to a broader market in the 1980s."(from: http://www.jimlangley.net/ride/bicyclehistorywh.html)

There are several bicycle manufacturer that focuses in produce titanium bicycle such as Litespeed, Roark, LeMond and Merlin. All of these companies are hi-tech company and seriously involve in manufacture titanium bicycle. In addition, these companies offer custom bike for their customers.


Carbon Fiber

Carbonfiber.jpg

Recently, Carbon Fiber bicycle frames have become popular due to its many advantages. Carbon fiber is a combination of several thousand long, thin strands of material consisting of mostly carbon atoms. This process allows for the density of carbon fiber to be lower then any other of the frame materials discussed. Not only is it light, but it is corrosion-resistant unlike aluminum and it is still strong. Carbon fiber is an interesting frame material because it can be formed into any shape that is desired which really helps for those who wish to fine tune there bicycle for ultimate performance, including racing. With carbon fiber you can add specific strength to the frame where forces are higher and at the same time allow for comfort and flexibility, essentially a combination of other frame materials into one. One thing that might make the consumer rethink about getting a carbon fiber frame is that they are expensive. Also, unlike other materials, carbon fiber frames have been known to a high amount of damage in the case of a crash and also fatigue failures, an example of what we saw in the frame passed around in class.