More than 90% of all motorcycles currently produced today use a telescopic fork front end. While this design is well accepted and understood, it does present a number of problems in the areas of steering, braking, suspension and overall stability. Telescopic forks are basically 30 inch (75cm) long unbalanced levers that magnify any front wheel shock load three fold and transfer this energy into the headstock of the motorcycle which is forward of and high above the centre of gravity of the bike.
Braking forces put through these stanchions cause the suspension to compress under load creating ‘stiction’ – unbalanced sliding friction. This compression also changes the steering geometry, reduces the rake and trail and makes the motorcycle more nervous. Under acceleration the forks extend, rake and trail are increased and the motorcycle’s ability to steer becomes more sluggish.
Under heavy braking, unbalanced stanchion compression also moves the suspension out of its optimal operating range and reduces its ability to deal with any wheel bump or other road irregularities. In the case of extreme deceleration such as an emergency stop, telescopic forks collapse or “bottom out”, rendering the suspension completely incapable of dealing with any further road or camber combination anomalies. This lack of further suspension travel has historically and continuously ended in catastrophic results for both the motorcycle and rider usually in the form of the dreaded tank slapper or the release of any front end grip of the tyre resulting in a lowside or combination highside.
These issues are well known and understood by designers and engineers and over time, what we have come to perceive to be ‘adequate’ measures, have been developed to minimise the effects of each issue. These measures have included creating larger and heavier forks, more complex suspension damping systems, heavier and stronger chassis and head stock components and the introduction of steering dampers, all of which create a higher centre of gravity and have added to the overall weight of the motorcycle while never fully overcoming the original problems.
So, the fundamental issues remain and conventional motorcycle handling is still dictated in this day and age by the inherently flawed handling characteristics and limitations of telescopic and steered stanchion suspension systems.
The premise of a compliant motorcycle requires the following attributes – stability in a straight line and under all braking loads, including during cornering – and especially in rapid changes of direction – it must also have consistency on exit from a corner in forward acceleration. In a telescopic fork or stanchion front end system all of these qualities are difficult, if not impossible to achieve at the same time because one or more characteristic must be sacrificed in order to achieve another.
The telescopic and stanchion steered suspension motorcycles that we ride today have obvious base flaws because of their inability to conform to the basic fundamental needs of consistent stability which can never be totally overcome no matter how good tyre development becomes. We continue to ride around on this flawed system, not because we have to, but because as riders we have historically been told that there is no better alternative to pursue. In this day and age, this observation does not ring true.
Hub – Centre Steer Design
Over the past century many other suspension and steering systems have been proposed and developed but Hub-Centre Steering (HCS) appears to offer the best alternative to telescopic, girder fork and stanchion steered front end systems.
Compared to conventional steering and suspension designs, a HCS system is a fundamentally more stable front end platform as It offers several advantages over conventional front end suspension systems in that it allows the steering, braking and suspension functions to be separated and dealt with independently – while keeping front wheel geometry stable.
Typically, a HCS is a type of front end suspension and steering mechanism characterised by some form of swing-arm that extends from the bottom of the engine or frame to the centre of the front wheel.
With a HCS system the braking and bump forces can be redirected horizontally along the suspension arms away from the normal vertical suspension forces in a quick and direct path to the centre of gravity of the machine instead of having to travel up through the head stock and then back down to the COG of the motorcycle.
Past HCS designs have overcome several flaws of previous alternate and telescopic systems, yet each of them have introduced their own set of distinctive problems and challenges.
The relative complexities of previous HCS systems have created their own issues. The higher the number of joints and linkages in a system can create the potential for free play which can lead to slack, vague, or even inconsistent steering movement across its range.
While reducing steering king pin loads by placing them in the centre of the steering hub, previous HCS systems have not been able to eliminate all front end king pin oscillation harmonics that are detrimental to the stability of the front end. Many previous designs have also been criticised for having poor corner lean clearance issues, limited lock to lock steering and a very heavy feel in cornering. Some have even been likened to having the feel of power steering common in an automobile.
Motoinno TS3 steering and suspension system
The patent pending configuration of the MCI TS3 technology addresses and overcomes all the problems associated with steered stanchion, telescopic, girder forks, alternate steering systems and previous HCS steering systems while creating an advanced, highly tune-able and more compliant front end.
Unique to the TS3 system, the suspension arms form a highly adjustable offset parallelogram which, together with its highly stable triangulated steering mechanism and virtual king pin that stabilises the front wheel – from the ground contact patch (‘the tyre braking point’) to the top of the wheel (an added secure and stable point along the steering axis) – ensures that the TS3 system maintains constant and stable steering geometry over the full range of its suspension travel and tuning capabilities. This in turn leads to consistency in the motorcycle’s handling characteristics under bump, braking, cornering and acceleration to create a safer and more compliant motorcycle without any corner lean, limited lock to lock steering issues or destructive front end oscillation harmonic forces.
The motoinno TS3 ‘shockwave’ has been designed, built and empirically tested to be the next generation in the development of a safer, more stable, fully adjustable and totally compliant motorcycle.