|
Motorcycle
Frames
Frames
Motorcycle frames are usually made from welded aluminium,
steel or alloy, carbon-fibre is used in some expensive or
custom frames. The purpose of a motorcycles frame is to act
as a base onto which all the various components can be bolted
to. The engine generally sits inside the frame, the rear swingarm
is attached by a pivot bolt (allowing the suspension to move)
and the front forks are attached to the front of the frame.
The frame can also help to protect the more sensitive parts
of a motorcycle in a crash.
Buell, one of the motorcycling world's greatest innovators,
uses the frame as a fuel tank on many of it's models like
the XB12S
Lightning.
The various types of frame commonly used include.
Single cradle frame. The single cradle is the simplest
type of motorcycle frame, and looks similar to the first ever
motorcycle frames. It is made from steel tubes that surround
the engine with a main tube above and other, smaller diameter
tubes beneath. If a single cradle becomes double at the exhaust,
as frequently occurs, it is referred to as a split single
cradle frame. Single cradle frames are usually found in off-road
motorcycles.
Double cradle frame. Double cradle frames are descended
from single cradle frames. They consist of two cradles that
support the engine one either side. Double cradle frames are
commonly used in custom motorcycles and simpler road bikes.
They offer a good compromise between rigidity, strength and
lightness, though they have now been technically surpassed
by perimeter frames.
 |
Backbone
frame. Far from the most desirable frame around, the backbone
frame comprises a single, wide main beam from which the engine
is suspended. The backbone frame allows for great flexibility
in design, since it is concealed inside the finished motorcycle.
The engine just seems to hang in mid air. It is simple and
cheap to make, and is used mainly on naked and off-road motorcycles.
 |
Perimeter
frame. Motorcycle racing research has shown that major
advantages are to be gained in terms of rigidity by joining
the steering head to the swingarm in as short a distance as
possible. Flexure and torsion are dramatically reduced. This
is the concept behind the perimeter frame. Two robust beams
descend in the most direct way possible from the steering
head to the swingarm, passing around the engine. The earliest
perimeter frames were made from steel, but the need to improve
rigidity to weight ratios led most manufacturers to adopt
aluminium instead. Aluminium is now by far the most common
road bike frame material and the aluminium perimeter frame
is the most popular frame for modern supersports motorcycles.
monocoque
frame. The monocoque frame is used nearly exclusively
on competition bikes and is very rarely found on road-going
bikes. Monocoque frames act as a single piece unit that functions
as seat mounting, tank and tail section. Though they offer
certain advantages in terms of rigidity, monocoque frames
are heavy and generally not worth the effort.
 |
Trellis
frame. The trellis frame rivals the aluminium perimeter
frame for rigidity and weight. A favorite of Italian and European
manufacturers it has proved a great success in racing and
competition. The Trellis frame uses the same principles as
the perimeter frame, and connects the steering head and swingarm
as directly as possible. The frame is made up of a large number
of short steel (or aluminium) tubes welded together to form
a trellis. The trellis frame is not only easy to manufacture
but extremely strong as well. The frame pictures is from the
Suzuki
SV650S.
Back
to all motorbikes |
Home page.
|
