The present disclosure relates to vehicles and vehicle components. These vehicles can include, but are not limited to, bicycles, electric bicycles, motorized bicycles, motorcycles and the like.
For simplicity, portions of this disclosure will discuss bicycles, but this is only done for the convenience of the reader. The vehicle components, suspension systems, and the like, can apply to a wide range of human powered and motorized vehicles.
Bicycles and related vehicles often include front and/or rear suspension in an attempt to cushion, or suspend, the rider from uneven terrain with the aim of increasing control, safety, and comfort. Since the 1990s, attempts have been made to perfect bicycle suspension systems, especially with mountain bicycles because they are often ridden uneven terrain. Early suspension designs suffered from several problems. For example, in some early designs, known as a single-pivot rear suspension, a swing arm fixed at one end to the rear wheel pivots from either the seat tube or downtube near the bottom bracket. The swing arm can be suspended from the top of the seat tube near the seat by a spring dampener or other shock absorber. One of the problems with this type of suspension is the tendency of the pedals to move or bob up and down as the swing arm pivots the rear wheel on uneven terrain. Pedal bob is caused by the tension and compression on the chain as the rear wheel pushes up and then swings back. Another is the tendency for rear wheel to effectively lose contact with the riding surface because the upward force on the contract surface of the rear wheel during pedaling tends to rotate the swing arm and lift the wheel away from the ground.
One early attempt to solve these problems, that is still in use today, is known as a Horst link suspension. This suspension attempts to isolate the pedal forces and braking force from the suspension. The Horst link suspension uses what is called a four-bar linkage. A four-bar linkage includes four members called “bars” or “links” connected together by pivoting joints or a by a combination of pivoting and sliding joints. The Horst link suspension uses four pivoting joints. The four bars or links in the Horst link suspension can include the chain stay, the seat stay, a portion of the seat tube, and a lever arm. One end of the chain stay is pivotally connected to the seat tube above the bottom bracket. The other end of the chain stay is connected to the end of the seat stay near rear dropout (i.e. the portion of the seat stay the holds the rear axle). The lever arm pivots at one end against the upper end of the seat stay and at the other end against an upper portion of the seat tube. A shock absorber suspends the mid-point of the lever arm to an upper portion of the frame.
Another example of a suspension that attempts to advance the art is known as the DW link suspension. The DW link suspension attempts to eliminate the tendency of the rear suspension to compress as the bike is accelerated during pedaling. Some of the energy associated with pedaling gets lost because of this compression. The compression of the rear suspension under power is known as squat. The resistance to rear suspension compression is called anti-squat. The DW-link uses a four-bar linkage that is designed to reduce the loss of energy during pedaling from suspension compression by providing more resistance to rear suspension compression (i.e. more anti-squat) at the beginning of the suspension travel than later in the suspension travel. The DW link suspension joins a rigid rear triangular portion of the bike frame to the seat tube by two short links. One of the links is pivotally connected to the bottom of the rear triangle and the bottom of the seat tube. The other link is pivotally connected between the top of the rear triangle and an upper portion of the seat tube. A spring dampener is used to dampen the rear triangle to the front frame. During hard acceleration, the upward force on the bottom of the rear wheel rotates the upper link and pushes the upper member of the rear triangle into the dampener causing it to compress. When the dampener compresses, some of the energy that would normally go into accelerating the bicycle is lost to friction. In order to prevent this, the dampener can include a restriction valve or some other mechanical or electrical locking mechanism to prevent the dampener from moving. While this prevents energy from being lost during acceleration to frictional forces of the dampener, it restricts movement of the frame. During acceleration, since the suspension is restricted or “locked out,” the bicycle acts like a non-suspension bicycle, i.e. as if it has a rigid frame.