WEIGHT
| AERO DYNAMICS | WHEEL
STRENGTH | RIDE
CHARACHTERISTICS | TIRES
WEIGHT:
There are three types of bicycle weight:
1. Static Weight: This weight
is not affected by movement. This is a 1 to 1 ratio,
if an item weighs 3 lbs it is 3 lbs. This is the least
affective place to save weight. Some examples include
hubs, bottom bracket, or cog sets.
2. Lateral Moment of Inertia Weight:
This weight is shifted left to right repeatedly (accelerated
and decelerated weight.) This is a 1 to 2 ratio, if
an item weighs 1 lb it is roughly 2 lbs. If you were
to draw a horizontal line across the center of the bicycle
everything above that line applies to lateral moment
of inertia weight. Some examples include brakes, headset,
seat post, or saddle.
3. Rotational Moment of Inertia Weight:
This weight resides on the outside of a rotational item.
This speeds up and slows down (accelerated and decelerated
weight.) This is a 1 to 3 ratio, if an item weighs 1
lb it is roughly 3 lbs. This is the most affective place
to save weight. Some examples include rims, tires, tubes
spokes, pedals or shoes.
Weight
Explained: The goal with saving weight
is to limit the effect that gravity has on our sport.
It is important to understand that not all weight is
the same. Static Weight is
anything that does not move. Although, the items that
we apply this term too do move there movement is considerably
less than other items. This type of weight has the lowest
impact on forward movement. Moment of Inertia
Weight will require an example. Throw
a ball, then take that same ball and connect it to the
end of a stick. When throwing just the ball there is
less initial start up energy, than the ball at the end
of the stick. This is because the balls moment of inertia
has shifted from the hand to the end of the stick.
Lateral and Rotational Moment of Inertia
are both important weights to save, however rotational
weight is the most important. The most prominent place
to save rotational weight is the wheels. This is due
to the constant rotational nature of a wheel. The constant
need to accelerate and decelerate a wheel means that
what ever weight is saved at the rim, spokes, and nipples
is exponentially more important than anywhere else on
the bike.
AERO
DYNAMICS: There are five factors
that make up aero dynamics:
1. Coefficient of Drag: Changing
height, width, or length will increase or decrease the
Coefficient of Drag by changing the surface area.
2. Boundary Layer: This is
the air that comes in contact with the surface of the
item.
3. Laminar Air Flow: This
is when the air remains adhered to the surface. This
maintains the profile of the item.
4. Tripping Boundary Layer:
This is when the air lifts off the surface due to surface
texture, vibration, or an imperfection in the surface
such as a ripple.
5. Turbulent Air Flow: This
is when faster air has lifted off a moving item and
collides with the slower air surrounding the moving
item. This increases the effective width of an item
therefore increasing the Coefficient of Drag experientially.
Aero
Dynamics Explained: The goal with Aero
Dynamics is to have the smallest Coefficient of Drag
while maintaining a shape that promotes Laminar Air
Flow. Although, with the perfect shape there are still
several factors that can disrupt Aero Dynamics, such
as vibration, imperfections in the surface, or sudden
changes in direction. All these can Trip the Boundary
Layer causing the Coefficient of Drag to increase by
developing a Turbulent Air Flow. Out of all the items
that you can replace on a bicycle wheels have the greatest
impact on Aero Dynamics. This is due to there rotating
nature which is always developing the greatest possibility
for Turbulent Air Flow.
WHEEL
STRENGTH: There are four factors
that affect wheel strength.
1. Rim Shape: The shape of
a rim determines how much surface area there is to help
distribute load.
2. Technique: The choices
a wheel builder makes can make the difference between
a good wheel and a great wheel.
3. Spoke Tension: This is
the amount of linier tension put on the spoke.
4. Nipple Spoke Thread Interface:
This is when the number of interfacing male and female
threads is determined.
Wheel Strength Explained:
Wheels strength is broken down into two categories,
equipment and technique. The strength
of equipment has a lot to do with the quality
of the materials that are used, such as carbon fiber,
stainless steel, aluminum or titanium. Also the shape
and the quantity of the materials are just as important.
For example, a shallow rim has less surface area and
requires more spokes where as a deeper rim has more
surface area and therefore requires fewer spokes. Technique
comes down to choices. How many spokes to use, what
kind of nipple material to use, how high the spoke tension
should be, and determining proper spoke length to assure
adequate nipple spoke thread interface. Spoke tension
and nipple spoke thread interface are the two more important
techniques I will talk about. Spoke tension
is very important. Once weight is applied to a wheel
only the upper spokes are supporting all the weight.
The lower spokes on the other hand have less tension
now and are more likely to loosen up. There is less
chance of spokes loosening or a wheel going out of alignment
if the spoke tension is kept high. If nipple
spoke thread interface is not correct
the nipple will be forced to bear all the forces put
on it and will fail prematurely. Please see fig. 3,
4, and 5 below to better understand
nipple spoke thread interface. A wheels strength comes
from all its parts as well as the techniques used to
build the wheel.
RIDE
CHARACHTERISTICS: Comming Soon!
TIRES:
Comming Soon!
TOP OF PAGE
Sincerely,
The Staff at Pro Wheel Builder
|
