The PowerTap C1 with chain on a bicycle

PowerTap C1

Client: Saris
  • Technology Development
  • System Architecture
  • Mechanical Engineering
  • Electrical Engineering
  • Software Engineering
  • Design for Manufacturing

A device that accurately measures and records a bicyclist’s power output with industry-leading accuracy. The PowerTap C1 enables cyclists to access performance data both during and after their training rides and leverage that information to improve their training.

Awards

Eurobike 2015 - Best New Product

Patents

7,975,561

As the patent for the original cycling power meter, the PowerTap H1, neared the end of its term, Saris wanted to extend its market share by releasing a new product that measured power with the same accuracy and lower cost but at a different spot on the bicycle.

Based on a history of successful collaborations and our deep understanding of the product and patent space from creating the original hub-based device years earlier, Saris asked us to develop a new power meter to offer its customers.

Widely compatible with common chainrings

Rugged, weatherproof construction protects from varying environmental conditions

Board relays readings to the bike computer and phone via Bluetooth and Ant+ radios

Strain gauge sensors and sophisticated algorithms accurately report power

The PowerTap C1 being tested on an internal machine

The technical challenge with these sorts of devices is to very accurately measure the productive torque transmitted from the cyclist to the road while being completely insensitive to all other loads that can occur, such as wheel forces from hill climbs or radial forces from rider weight and impacts.

Strain gauge-based sensor arrangement.
A patent diagram for the PowerTap C1 strain-gauge based sensor arrangement.

Leveraging research done during a previous engagement with Saris, we determined a crank-based solution would be the most cost-effective solution while providing the necessary accuracy using strain gauge-based sensors.

Through our understanding of the fundamental physics of how materials behave under shear stress, we determined the arrangement of the sensors, developed an associated algorithm, and strategized how to calibrate the system in production. The resulting PowerTap C1 accurately measures torque while being insensitive to other factors.

An animation showing the various PowerTap C1 prototypes

Various prototypes

The PowerTap C1 device was released in 2015 with great results; mirroring the successful release of the original H1, it received Best New Product at the annual Eurobike show and has continued to receive great reviews from cyclists since. By offering its customers another accurate way to gain insight into their training and racing, Saris maintained its long-held position at the top of the market.

The PowerTap C1 with chain on a bicycle