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by Matt Wikstrom
August 11, 2016
Photography by Matt Wikstrom
TECH NEWS BROUGHT TO YOU BY BIKEEXCHANGE
Avanti’s track bikes have been travelling to the Olympics with New Zealand’s national team since 2004, when Sarah Ulmer won gold in the individual pursuit at the Athens Olympics. After the close of the 2012 Olympics, Avanti starting working on two new bikes for Rio, one for the pursuit team and another for the sprinters.
The official start date for the project was August 2013, when Avanti travelled to Invercargill velodrome with its Pista Evo II for a benchmarking study. The bike was equipped with a couple dozen strain gauges, and according to David Higgins, Avanti’s senior engineer leading the project, data from stress testing served as the foundation for the project.
From the outset, Avanti understood they needed to develop two distinct bikes to satisfy the needs of the Olympic track team, one for the sprinters, and another for the pursuit riders. The most important goal for the new sprint bike was to reduce the weight of the frameset without sacrificing any of its stiffness, while the pursuit bike demanded some innovation in order to improve the aerodynamics of the bike.
Avanti delivered both bikes to the team by the end of 2015. Both quickly gained the UCI’s blessing for competition, and in contrast to so many Olympic superbikes, both bikes will be part of Avanti’s catalogue for 2017. And while the company is keen to share the pursuit bike with the world, details on the sprint bike will remain secret until the new bike rolls out onto the velodrome in Rio.
While Cycling New Zealand is keeping Avanti’s new sprint bike under wraps, the pursuit bike is ready to be shared.
Data from the testing session on Invercargill velodrome demonstrated to Avanti’s engineers that there was room to improve the aerodynamics of the Pista Evo II along with the stiffness-to-weight ratio. As a result, the project aimed to save weight for every part of the bike.
“That’s the thing with a sprint bike,” explained David Higgins, “weight is so much more important because you’re always accelerating. If you’re not on 6.8kg, then you’re giving away time.”
The weight of the Pista Evo II was already quite competitive but Avanti’s engineers could see that they could save some more by adopting the production process developed for their carbon road bikes.
Referred to as “Internal Laminate Optimisation”, this process makes use of an internal mould as well as an external mould to create the frameset. Two moulds add to the production time, and therefore increase the cost of the frameset, but it is now lighter.
The front end of the new pursuit bike has less drag yet there is still plenty of stiffness for the first half lap of the race.
When combined with the weight savings made throughout the rest of the build, ballast must be added to the bikes going to Rio in order for them to be race-legal (i.e. to bring to total weight up to 6.8kg).
Details on the rest of the sprint bike’s features remain a closely guarded secret. David Higgins mentioned that the bike was stiffer and more aerodynamic but couldn’t explain how, other than to say that they couldn’t make use of the innovations developed for the pursuit bike.
Anybody that is familiar with track pursuit will understand how important aerodynamics is to the success of the rider and the bike. Indeed, this discipline has ushered in a variety of innovations since the ‘80s when so-called superbikes started appearing at the Olympics.
While the introduction of more rigorous regulations by the UCI has moderated the designs appearing at recent Olympiads, it doesn’t appear to have dampened enthusiasm for the challenge. David Higgins was all too willing to tackle to problem, and by using FEA (finite element analysis) and CFD (computational fluid dynamics) he was able to come up with a novel fork and handlebar design that improved the aerodynamics of the bike.
A look at the 3D-printed prototype that was created for wind tunnel testing at Auckland University. Photo courtesy of Avanti Bikes.
“Breaking up the head tube into three separate tubes gave us a large reduction in drag. We could also move the fork legs further away from the disk wheel to improve the airflow there. Because the disk is moving in the opposite direction with a boundary layer, there’s no way that air can move past it if the fork legs are too close.”
The new design resembles a motorbike fork with an extra wide crown. David found that the struts added a lot of stiffness to the bike that could be exploited to reduce aerodynamic drag. “Running the fork legs straight up to the handlebars meant we could thin other parts of the bike down, most notably the head tube, and still provide plenty of stiffness for the standing start.”
The new fork doesn’t have a steerer. Instead, a large bolt is used to secure the forks to the bike with small bearings to keep it in place. “We almost designed the front of the bike around the bearing,” said David, “it was the smallest angular contact bearing we could find with a chamfered edge.”
The new pursuit bike uses a very small bearing for the headset, small enough to fit within a standard-sized bearing.
There are four frame sizes, and each one uses the same fork and handlebar. Different-sized spacers are used to make up the difference as the handlebars are bolted to the forks. Rubber bumpers are positioned at the bottom of the head tube to stop the struts from striking the frame.
Elsewhere, the new pursuit frame boasts features that satisfy the demands of the riders and their mechanics. For example, a chain-tensioner is built into each of the dropouts to prevent the rear wheel from slipping under load. A similar tensioning bolt is also built into the seatpost that butts up against a floor in the seat tube. The design means there is no need to rely on a seatpost clamp to maintain the height of the saddle, yet the rider can make fine adjustments by winding the bolt in or out (though the seatpost must be removed from the frame first).
As each frame was finalised, Avanti’s design team made sure that it would accommodate each of New Zealand’s track cyclists (men and women). After a solid two years of development, the company couldn’t risk alienating any of the riders, but according to David Higgins, there was no need for any extraordinary considerations.
Each bike will be personalised for New Zealand’s track Olympians with custom-built handlebars. The track sprinters will be using an integrated carbon bar and stem while the pursuit riders will be using 3D-printed titanium extensions. In every instance, the final design will be millimetre-perfect to ensure the aerodynamic and biomechanical performance of the athlete.
This production version of the pursuit bike makes use of stock handlebar extension: each member of New Zealand’s pursuit teams get custom 3D-printed titanium extensions for a perfect fit.
As for the rest of the specifications, these have been left in the hands of Cycling New Zealand, and it is guarding its secrecy. Details on wheel and tyre choice, for example, will only be revealed once the bikes come out for racing, starting Friday August 12.
Avanti’s involvement with New Zealand’s Olympic team seems obvious, given that the brand hails from the same country. Established in 1985 by John Struthers, Avanti has been growing steadily ever since to become a recognised brand in the Australasian market.
Working on bikes for the national team has been a matter of pride rather than a commercial arrangement. The company is enjoying some benefits though, such as working with the nation’s elite cyclists to refine the design of its bikes. Such feedback was particularly important for the sprint bike as the geometry and carbon layup were refined for the final frameset.
While the new framesets, dubbed Pista Team and Pista Pursuit Team, are set to retail for 2017, Avanti is realistic about the returns it can expect from the project. Ultimately, creating new bikes for the Olympics has provided Avanti’s product development team with enormous motivation and focus, and the whole company is looking forward to watching their bikes in action in Rio.
This is the production version of Avanti’s Pista Pursuit Team frameset that is going to Rio, however there are no details on what kind of wheels and tyres the New Zealand team will be using.
There’s plenty of clearance around the disk wheels so that the air can flow through the forks and seat stays.
The pursuit frame makes use of a BSA-threaded bottom bracket… for now.
With a floor in the seat tube to secure saddle height, there’s only a need for a few grub screws to lock the seatpost into the frame.
There’s no word on what kind of cranks the New Zealand pursuit riders will be using at Rio.