Frames
High
Tensile Carbon Steel
Mountain bikes and all-purpose bikes are generally made of
steel because of the strength and durability. Steel is heavy,
and in this case is good because the weight will help keep
the rider and bike grounded when riding over rocky terrain.
Steel is in a way a form of suspension when compared to aluminum
alloy because steel absorbs some shock. A steel bike is more
comfortable to ride than an aluminum alloy bike. Steel has
slight bending capabilities; for instance a bent derailleur
from harsh riding can be bent back into shape.
Aluminum
Alloy
Do not confuse aluminum alloy for aluminum. Aluminum itself
is too soft to be used for building a bike, but aluminum
alloy works great. Aluminum alloy is aluminum combined with
another element such as magnesium, copper or silicon. Road
bikes are generally made of aluminum alloy because they
are meant to ride long distances. Aluminum alloy is strong,
lighter than steel and is quite stiff. This stiffness is
good and bad. For long rides a stiff bike requires less
energy because all the energy exerted on the pedal is transferred
directly to the wheel for increased power. The down side
to stiffness is the comfortability of the bike ride. Aluminum
alloy does not ‘give’ at all. Every crack, bump,
rock, pebble or slight difference in terrain is felt when
riding the bike. Steel has slight bending capabilities,
but aluminum alloy does not. Aluminum alloy will break,
but not bend. It is commonly used in the construction of
bikes because it is strong, light and less expensive than
steel. Aluminum alloy frames have a larger diameter because
the larger the diameter the greater the strength. A larger
diameter allows for a thinner wall and that in turn requires
less material for a lighter bike.
Tungsten
Inert Gas and Argon Welding
Welding for bikes is the process of joining frame tubes.
Efun’s bikes are welded using tungsten inert gas and
argon. In tungsten inert gas welding an electric arc is
established between a tungsten electrode and the part to
be welded. To start the arc an alternating current is used
to break down the oxide layer of the material. The current
is then transferred through the electrode to create an electrode
arc. The metal (in our case steel or aluminum alloy) to
be welded is melted by the intense heat of the arc and fuses
together either with or without a filler material. The arc
zone is filled with an inert gas to protect the tungsten
electrode and melted material from oxidation and to provide
a conducting path for the arc current. The shield gas used
here is argon, which is normally chosen according to the
material type to be welded.
|
