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Power equals torque times cadence. Or, if you want an icebreaker for your cocktail party, P = 2X [(F x 9.8 x L) x (R x .1047)]. You learn this pretty quickly upon arriving at the Stages headquarters on the outskirts of Boulder, Colorado. An unassuming building located in a corporate cul-de-sac that could be just about anywhere in the country (with the exception of the breathtaking mountain vistas to the west), the building houses a large portion of the Stages staff, including all of its manufacturing.
On entering the lobby, you’re greeted with a poster of Team Sky riding along the Champs-Élysées—Stages power meters have won the Tour de France four times (and counting). The manufacturing floor is buzzing with work. The two dozen or so employees are milling around at their various stations, building, gluing, heating, freezing, soldering, testing, cleaning and packaging each and every power-meter crank. Oh, and there’s also a laser.
So, what about that power equation? The cadence part is the relatively easy part. Anyone who has ever used some combination of a zip-tied magnet knows how it works. The torque, however, is a bit more complicated. Stages uses a set of proprietary gauges laid in a very precise manner along the crank arm. Borrowing some technology from the aerospace world, these gauges are used to detect even the slightest flex in the stiffest of crank arms. The way it works when you ride your bike is each pedal stroke causes a slight amount of flex on the crank. This force combined with the length of the arm is used to measure the amount of force applied to each pedal stroke. Voilà: torque.
And when it comes to cadence, Stages does not expect you to use magnets or zip ties. Each power meter uses an accelerometer that takes a number of readings during each revolution for much more consistent and accurate readings.
Looking around the building, the sense you get is just how involved each and every person on the floor is with their part of the process. Once the laser etches away the paint on the aluminum cranks (the carbon cranks come with the coating stripped off in the area where the strain gauges will be applied), the strain gauges are applied and clamped to the arm using highly sensitive adhesives and placed into ovens to cure. The strain gauges are then applied along with the rest of the power-meter housing. Along the way, multiple tests are accomplished to ensure compensation for changing temperatures and weather conditions (we’ve all been on those rides!) and to verify that the power-meter data is accurate.
In a nutshell, before that crank arm is attached to the bike you have at home, a number of people have put it through its paces and subjected it to loads, temperatures and conditions that you are unlikely to experience on your bike. Just in case.
And the work does not stop there. Stages maintains an active R&D lab, always working on improving current technologies and looking for future improvements. Having gotten its start in indoor bikes before starting its work with outdoor bikes, Stages also builds and tests the mass of indoor bikes here in Boulder. A byproduct of that is an indoor studio complete with a fleet of bikes that employees use for lunch rides when the Boulder weather mix gets a little too wintry.
Speaking of which, it is time to gear up for a lunch ride with the Stages crew. Stay tuned.