used to make your trike determine how and how frequently to inspect.
Ignoring this WARNING can lead to frame, fork or other component
failure, which can result in serious injury or death.
A. Understanding metals
Steel is the traditional material for building Trike frames. It has good characteristics, but
in high performance Trikes, steel has been largely replaced by Chrome Moly The main
factor driving this change is interest by riding and cycling enthusiasts in lighter Trikes.
Properties of Metals
Please understand that there is no simple statement that can be made that characterizes
the use of different metals for Trikes. What is true is how the metal chosen is applied is
much more important than the material alone. One must look at the way the trike is
designed, tested, manufactured, supported along with the characteristics of the metal
rather than seeking a simplistic answer.
Metals vary widely in their resistance to corrosion. Steel must be protected or rust will
attack it. Aluminum and Titanium quickly develop an oxide film that protects the metal
from further corrosion. Both are therefore quite resistant to corrosion. Aluminum is not
perfectly corrosion resistant, and particular care must be used where it contacts other
metals and galvanic corrosion can occur.
Metals are comparatively ductile. Ductile means bending, buckling and stretching
before breaking. Generally speaking, of the common Trike frame building materials
steel is the most ductile, titanium less ductile, followed by aluminum.
Metals vary in density. Density is weight per unit of material. Steel weighs 7.8 grams/cm3
(grams per cubic centimeter), titanium 4.5 grams/cm3, aluminum 2.75 grams/cm3.
Contrast these numbers with carbon fiber composite at 1.45 grams/ cm3.
Metals are subject to fatigue. With enough cycles of use, at high enough loads, metals will
eventually develop cracks that lead to failure. It is very important that you read The basics
of metal fatigue below.
Let’s say you hit a curb, ditch, rock, car, another cyclist or other object. At any speed
above a fast walk, your body will continue to move forward, momentum carrying you
over the front of the trike. You cannot and will not stay on the trike, and what happens
to the frame, fork and other components is irrelevant to what happens to your body.
What should you expect from your metal frame? It depends on many complex factors,
which is why we tell you that crashworthiness cannot be a design criteria. With that
important note, we can tell you that if the impact is hard enough the fork or frame may
be bent or buckled. On a steel trike, the steel fork may be severely bent and the frame
undamaged. Aluminum is less ductile than steel, but you can expect the fork and frame to
be bent or buckled. Hit harder and the top tube may be broken in tension and the down
tube buckled. Hit harder and the top tube may be broken, the down tube buckled and
broken, leaving the head tube and fork separated from the main triangle.
When a metal trike crashes, you will usually see some evidence of this ductility in bent,
buckled or folded metal.
Summary of Contents for Commuter 2.3
Page 30: ...Connect Mainframe ...
Page 31: ...Handle Bar Connection ...
