The system, unveiled last week, uses your smartphone to calculate the best gear to be in for the current pedalling speed – then wirelessly shifts up or down.
It also uses the phone’s accelerometer to know when to change down in an emergency stop – so you can pull away afterwards with ease, and will eventually be able to use the phone’s GPS capability to get the bike into the correct gear for an upcoming incline.
Mechanical automatic gear boxes for bikes already exist – but they wear out quickly as they’re based on moving flywheels. The new wireless method activates an electric gearshift that has no such issues – and thanks to its use of a smartphone can also analyse performance for serious cyclists.
Developed by Mark Wilson and colleagues at Cambridge Consultants Limited (CCL), the wireless bike is based on electric gear shifts made by firms like Shimano Inc of Japan. These are normally connected via cable to a lithium battery and gear switches on the handlebars.
“We’ve cut the cables between the switches and the gears and replaced them with a smart, low energy version of Bluetooth designed for very long battery life,” says CCL’s Tim Fowler.
In manual mode, Bluetooth on the gear switch communicates with an iPhone in the rider’s pocket. An app on that phone then relays the rider’s commands to a Shimano electric gear shift system modified to receive Bluetooth signals.
In automatic mode, a magnetic sensor on the main crank tells the app your pedalling speed – known as cadence – while a wheel sensor tells it your road speed. It then computes the correct gear and beams it to the Shimano mechanism. “It’s not difficult. The link between cadence and speed is the gears,” says Wilson.
For the last two months, CCL has been trying the system on a fixed rolling road. “Our tester tells us he never feels like he is in the wrong gear,” says Wilson.
As might be expected, it needs some rider-specific tuning. “In set up mode you pedal for a while and then set the maximum and minimum cadence levels either side of where you feel comfortable,” Wilson says.
CCL’s next step is to integrate the iPhone’s location sensing into the app – so it can switch gears ahead of downhill or uphill sections.
Given the cost, Wilson anticipates use by riders who spend a lot on their equipment and want to improve their performance by having their optimum pedalling rate set automatically.
Perfect for triathletes?
Some will worry about the system’s dependence on Bluetooth, says Joel Natale, head buyer at Evans Cycles of London, which runs 50 UK bike shops.
“Shimano could have made their system wireless but decided not to. Imagine 200 riders in a peloton are using it. How can you make sure the signals don’t interact or that somebody else can’t get control… to stop you changing gear?” he asks.
Natale thinks CCL will face an uphill struggle getting most riders to abandon manual gear changing. “However, there is one group for whom this may make total sense, and that’s triathlon riders – who like to ride at constant cadence and power”, he says.
Next, CCL wants to develop a bike version of a car’s anti-lock braking system (ABS), with the iPhone controlling the bike brakes to prevent a skid. “A front wheel lock is generally catastrophic. This may help,” says Wilson.
Syndicated content: Paul Marks, New Scientist