THE SWINGARM

The final swingarm was the result of a development phase in which many different models and solution were analyzed.

The whole assembly model, designed in CATIA V5, includes the following parts:

- The main component is the swingarm, composed by the welded tubular steel truss and the two aluminium plates. Two fixtures for the wheel hub are fitted to the plates, in order to adjust the position of the wheel center and thus the chain tension by using an internal screw.

- Alloy wheel

- Shock-absorber

- Chain and sprockets (the chain was designed as a full single part because only its size concerned this project)

- Other minor components, such as screws and bolts

The main features of the swingarm tubular frame are:

Transversal elements. These parts connect the swing-arm to other components of the motorbike.

- Pivot (connection to the chassis)

- Shock-absorber attachment

- Pro-link attachment

Three longitudinal elements per side:

- Lower: the curved shape of this element allows to shorten the shock-absorber tube and so to reduce its deformation under stress. The design of this lower tube must consider also the size constraints of the lower side of the transmission chain and  the wheel

- Central: this element is located between the chain sides and "intercepts" the curved tube of the pro-link attachment

- Upper: it connects the pivot element to the aluminum plate and it is linked to the central beam via the upper lateral element. This part is important for increasing the flexural and torsional stiffness of the structure. Also in this case the position of the upper side of the chain has to be taken into account.

Two lateral stiffening elements per side: they link the central tube to the upper and lower ones, passing outwardly with respect to the transmission chain. These further rise the strenght of the structure.

The swingarm is symmetrical (excluding the pro-link attachment position, which is a geometrical constraint), because in this way the dynamic behaviour of the motorbike will be uniform and without significant differences in left and right turns.

The asimmetry due to the shifted attach of the pro-link is a design strategy to compensate the presence of the chain and the the sprockets.

The transmission chain passes near two lateral beams, but there is no contact because the free space is sufficient for a standard chain. Most of the chain will be shrouded in a chain-guide, tipically rectangular-shaped and made of plastic material, that protects from possible contacts with external objects.

The two tip plates link the swingarm frame to the wheel hub and are manufactured by aluminum casting. Due to the low stresses in those regions, they have large holes in order to reduce the weight. Each plate holds a rectangular fixture for the hub, commonly used on motorbikes, that can slide during its adjustment to control the position of the wheel. The triangular shape of the plates also follows the bending moment trend.

The right-hand side (seen from the back) aluminium plate may be easily modified to allow the installation the disc brake caliper components.

Lateral, front and top view of the swingarm assembly:

See the gallery page for other pictures and renderings of the complete swingarm