Tuesday, July 13, 2010

Al'turn'ative Tuesday

The Moto2 race series has great potential due to its emphasis on chassis design (all teams use a spec Honda motor, but chassis design differentiates the competitors and will play a large role for the winner).

How long before an alternative to the telescopic fork finds its way onto a Moto2 team's bike?

RADD?, 6x Flex?, Wimmer? Bott?

"We want to develop a new chassis technology. We want to adapt a front fork system, that I built and patented for my Wimmer mountain bike, to motorcycle racing, and ultimately fit the MZ street bikes with the same system”  - Martin Wimmer of MZ from RoadRacerX

This link describes Martin Wimmer's design patent for an adaptive front suspension system.  In summary, this design allows for quick adjustments to suit track session feedback and, like many alternative designs, it can also reduce chassis weight.  The system has 2 designs in one that work together by, ironically, countering one another:

1. lower portion acts as a traditional telescopic fork. (rake & trail is reduced during compression)
2. upper portion acts through a swingarm (attached to a brace above the wheel & pivots on the frame).  During compression, the upward movement of the pivoting swingarm increases rake and trail)

His 1st prototype was used en route to a 3rd place finish in the 2002 German 250cc Championship.  Wimmer scored the podium himself, 8 years after he retired from GP racing.

tip: Motorcyclist magazine

From the patent document:

According to the invention, the fork joint, due to its two-part form, makes a subdivision of the necessary rotating 10 and swivelling movements. Thus, the fork joint on one hand allows for the use of less expensive bearings, and, on the other hand, depending on the particular embodiment, provides for the possibility of an additional change of trail, since it achieves a change of the fork off-set (that is, of the 15 pivot point of the steering axis in relation to the geometrically relevant distance of the fork-leg axis in the fork joint) over the swivel area.
As specially used for motorcycles and bicycles, the construction of the telescopic fork of the invention consists of 20 slidable connections, which are slidable into each other and which achieve compression and rebound of the front-wheel assembly during braking or acceleration as well as when passing over bumps. Due to the special form of the telescopic fork in at least three-parts, a different suitable relative 25 movement of the individual connection parts can be achieved over the entire range of spring, always depending on the setting of the individual spring and damping rates of the connecting parts with respect to each other. Thus, in the compression and braking processes, an additional modifi- 30 cation of the front-steering angle can be achieved over the course of the spring range, such as for example in connection with a variably suspended steering point, which modification differs from the known steering-angle modification as achieved by the compression of a conventional telescopic 35 fork.
What is characteristic of the system of the invention is the combination of at least two spring elements which are adjustable independently from each other, the individual ranges of spring of the elements being added to one overall 40 range of spring for the front wheel to be guided. This special arrangement therefore provides for variable frame geometries with regard to steering angle and trail. At least one of the spring elements needs to be attached in between at least one variably hinged steering point, which is supported by 45 means of a swingable arm by the vehicle frame. Due to this modification of at least one range of spring, the steering axis is defined in relation to the frame by means of the respective arrangement of the at least one swingable arm, thus defining the corresponding steering angle of the frame. At least one 50 second spring element is attached either directly to the lower fork joint alone, or within a telescopic fork which has at least a three-part form, the spring element is attached so that it guides the front wheel throughout its range of spring in relation to at least one swingable arm to which the variably 55 hinged steering point is attached. When this second spring element compresses, the steering angle of the entire vehicle changes in relation to the level of the roadway as such.
Thus, the driving behaviour of the vehicle can be changed by adjusting the individual spring elements, which will vary 60 the values of the critical parameters of steering angle and trail of the front-wheel suspension system. In other words, the selective arrangement of the individual spring elements can provide for respectively different geometrical modifications of the steering angle and trail which sum up over the 65 overall range of spring of the front-wheel suspension system.

1 comment:

Emmet said...

This is an excellent write up! Motorcycle manufacturers have long been tied to the conventional telescopic fork due to market interest and race homologations, but Moto2 may change the future of suspension and chassis design