Bike with front swing arm uses sensors from Variohm

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Alto Performance Racing has developed a highly innovative bike for the 2008 Thunderbike UK motorcycle championship that uses a front swing arm suspension system with hub-centre steering - and numerous sensors supplied by Variohm.

Bike with front swing arm uses sensors from VariohmWhen the 2008 Thunderbike UK motorcycle championship commences on 8-9 March at Brands Hatch, racing enthusiasts the world over will witness a new beginning for Alto Performance Racing and for the sport. With its novel Vyrus 994cc bike featuring a front swing arm suspension system with hub-centre steering, the Alto team will be pioneering a design conceived decades ago that modern materials, production technologies and electronics systems have now made a potentially race-winning reality. Working closely with the Alto team, Variohm-EuroSensor is supplying position, pressure and temperature sensors to measure and continuously improve the impressive machines’ performance.

Unlike conventional motorbikes with front forks that suffer from inherent handling problems caused by deflection and stiction, plus a tendency to ‘dive’ under braking, the aluminium swing arm separates the steering and damping systems to offer much improved handling as the trail and the steering angle remain constant in all conditions.

As with all levels of competitive autosports, monitoring dynamic data and interpreting results is fundamental to performance improvement. At the test track and on race days, Alto uses Variohm's sensors under extremely arduous conditions to acquire fast and precise feedback for race-critical parameters that include front/rear suspension position, front/rear brake pressure and throttle position, along with tyre and ambient air temperatures, barometric pressure and engine speed.

These real-time readings combine to pin-point information delivered from the bikes’ CANbus network by telemetry to data loggers that determine exactly how a machine and rider have responded to the intricacies of the track and provide the race team with essential statistics for continuous design and set-up improvement - and race-winning performance.

Reliable position sensing

The ruggedised autosport version of the ELP series slimline linear position transducers are used for the suspension ride-height feedback during braking, cornering, track bumps and undulations. The compact sensors' conductive plastic track is sealed to IP67 and fast replacement is assured with optional ‘pop’ mountings. High linearity and excellent positional repeatability combine with a very wide temperature range and mechanical life in excess of 25million operations to provide a highly reliable position feedback transducer.

Throttle position is measured with a Vertex 13E series, 14-bit resolution angle sensor. This highly durable and compact 13mm diameter sensor is sealed to IP69 and the non-contact Hall effect and magnet design yields an almost limitless life. Within the Vyrus application the programmable 0–360degree electrical angle is calibrated in situ to provide highly accurate and repeatable power feedback. The throttle reading can even provide the race team with precise details of when control is momentarily lost due to unexpected track bumps affecting the riders grip.

EPT series 1200 pressure sensors provide dynamic and high-speed brake pressure information from a very rugged yet compact high-strength stainless steel packaged design. Measuring up to 400bar, the welded, hermetically sealed, thin-film measuring cell and high-level output circuit technology ensure this sensor is suitable for the demanding shock and vibration levels experienced within the application. The sensors help confirm when and how the bike is losing traction and detect the minute compression changes in front and rear suspension.

Front swing arm suspension

The bike's unusual front swing arm suspension system with hub-centre steering design can be attributed to two mechanical engineering students in the 1980s as a graduation project with additional development carried out by the Italian Bimota Company and later by Vyrus of Rimini. The history should also include thanks to the British engineer Jack DiFazio for the hub-centre steering system he developed in the 1970s and even to the 1920s Neracar motorcycle that attempted to improve the limitations imposed by front forks for combined steering and suspension.

It is true to say that these previous designs suffered from production quality and weight problems but, as materials and manufacturing technology moves on, there is strong optimism that hub-centred steering could make a big difference to the motorcycle racing industry and even prove a safer and more durable design for road bikes.

Northampton-based Alto Performance Racing, led by brothers Ben and Aarron Shaughnessy, with rider Phil Read, raced in the same competition last season with a traditionally front-forked Laverda 750cc and finished in third place with fifty per cent podium positions. For this year’s Thunderbike series, which is based upon strict power-to-weight ratio rulings, the team and rider will remain the same - so the new chassis and steering design has a definitive benchmark to compete against.

Ben Shaughnessy, the Alto Team Technical Director who has always had a passion for hub-centre steering and took six months off from his ‘day job’ running the team to develop the design, says: “This is a genuine attempt to race and demonstrate this technology to its natural winning conclusion - and to show that motorcycle forks and frames are truly ‘old fashioned’ and in need of newer technology. Thanks to our mostly British-based sponsors like Variohm, who have provided the worlds leading engineering and technology solutions, we have the best possible chance to succeed.”

Full details of the bike and the technology can be found at

Full details on Variohm’s range of sensors can be found at

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