Читать реферат по английскому: "Mountain Bikes Essay Research Paper Mountain Bikes" Страница 1

(Назад) (Cкачать работу)

Mountain Bikes Essay, Research Paper

Mountain Bikes

It has been a decade in the making, but the mountain bike has become a passion for many people.

Along with this passion it has also become the most environmental way to get from point A to B. It has

gone through a very intense evolution process over the past decade.

It all started with some guys from California who took their bikes out for a ride on their day off,

they modified their bikes and turned a hobby of theirs into a worldwide phenomenon. The mountain bike’s

rapid increase in popularity was influenced by social and economic situations, and by technological

improvements that had the needs of bike riders in mind. The introduction of the mountain bike at a bike

convention in Long Beach, California, early in the 1980’s coincided with the need for a bike that combined

technical superiority, ease of care, and multipurpose use.

Technological advances came extremely fast after it’s introduction into the world. The advances

have made riding mountain bikes easier, which makes it possible for the rider to explore new terrain. I hope

that this report will be able to provide some information on the subject of mountain bikes and the advances

in technology that the bike has gone through, and what might be in the future of the mountain bike.

The road bike has taken more than a hundred years to evolve into the frame that it is being used on

todays bicycle. Because of the increasingly popularity of the mountain bike the demand for advances to be

made have come very rapidly.

The evolution of the mountain bike has been a stormy one over the past decade. Within one

decade the design has changed radically; this is due to three reasons. First , because geometry and design

were copied from the first “Stone-Age bikes”; second, because off-road riding created different problems ;

and third, because innovative frame design mirrored the “spirit of the times”: young, new, dynamic, and

strong. The off-road bike required extra stability.

Frame

It is important to know the basic frame geometry and how to measure it. The combination of tube

length and angle determines not only the maneuverability of the bike, but also determines the seating

position and the transfer of power. Variances of 1. of the headset angle, or a 1′ (2cm) difference in the

distance between the rear-wheel axle and the center of the bottom bracket, can have very serious

consequences.

Frame Geometry

The basic elements of frame geometry are: A- Height of the seat tube; B- Length of the top tube;

C- Seat-tube angle; D- Headset-tube angle; E- Trail, F- Distance between the rear-wheel axle and the bottom

bracket; G- Distance between the front-wheel axle and the bottom bracket; H- Wheelbase; I- Height of the

bottom bracket; J- Stem angle; K- Length of the headset tube.

A. Height of the Seat Tube

This is determined by the length of the biker’s inseam. This measurement is only of little

importance, because of the different frame designs and the different methods of construction used by

different manufacturers.

B. Length of the Top Tube

This length should correspond to the rider’s trunk (length from the seat to the shoulders). With

mountain bikes this measurement should be increased by a few inches. This increases the distance between

the two axles, which increases the riding comfort and makes for a straight and stable ride. Some times the

top tube is slightly slanted, this is because some bike frames are designed so high off the ground, the slanted

top tube makes for an easier dismount.

C. Seat-Tube Angle

This angle basically determines how the bike will handle. Today the standard for a seat-tube is to

be set at a 72. to 73. angle. At 69. to 71., it is a more comfortable ride, but a sharper angle increases the

bike’s agility and ability to climb.

D. Headset-Tube Angle

Along with the fork and trail, the headset-tube angle determines the steering characteristics of the

bike. A steep angle together with a curved fork reacts more sensitively when steering; a flatter angle reacts

less sensitively. In the past the angle was set at 68., but today the standard angle of the headset-tube is 71..

E. Trail

The trail is the distance between two points marked from the center of the headset to the floor and

by the extension of a line from the center of the front axle to the floor. This distance depends on the

curvature of the fork and the angle of the headset tube. A longer trail makes for easy steering; a short trail

causes the bike to react quickly to every movement of the handlebars.

F. Distance Between the Rear-Wheel Axle and the Bottom Bracket

The longer this distance is, the more comfortable the ride. A shorter distance creates a “lively

action” and a good climbing ability. The average span from the bottom bracket to the rear wheel for a

mountain bike is 17″ (43 cm).

G. Distance Between the Front-Wheel Axle and the Bottom Bracket

This distance determines the amount of toe clearance. Toe clearance means that the front tire and

the tips of the rider’s shoes never come into contact as the rider pedals and turns at the same time. To do

this, measure the distance between the center of the axle at the front-wheel hub and the center of the axle of

the bottom bracket.

H. Wheelbase

This is the distance between the centers of both the front-wheel and rear-wheel axles. A long

wheelbase

Похожие работы