Laser Spoke measures cyclists' power output
Modern electronics have given us the means to measure nearly every part of our performance – speed, distance, vertical, heart rate, etc. But there are still other variables that go unmeasured by the average athlete. The Laser Spoke provides a simple aftermarket solution for tracking cycling power.
The Laser Spoke is a universal digital measuring device that fits the rear wheel of everything from BMX bikes to road racing bicycles. It measures power, passed from your legs onto the drivetrain and wheels of the bike, at the spokes of the rear wheel through a laser-based optical system. The designers chose to use the rear wheel, as they say it acts like a torsion spring, twisting in response to the applied torque. The Laser Spoke measures the amount of twist, to give you a power readout.
The system consists of a laser and position-sensitive detector mounted on the hub, and a right-angle prism attached to the rim. In operation, the laser fires its beam at the prism, which then casts it back upon the detector. The detector produces an electrical signal that is proportional to the position of the laser beam, the beam deflection and the applied torque.
The Laser Spoke currently stores data by way of an SD card, but the company plans to use a removable USB module with flash memory. It is also working on an ANT + interface for the device that would allow for wireless communications with ANT + monitors.
Laser Spoke says that its system is less expensive than existing power monitors. It claims the system is accurate and, because it uses optics instead of moving parts, is more durable in the long run. Plans call for a final module that weighs no more than 150 grams (5.3 oz).
Laser Spoke is currently looking for funding on Indie GoGo. The company has its first prototype built and is trying to raise money to further develop it into a production-ready model.
Source: Laser Spoke
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Or you could use the accelerometer on your droid/iphone and use basic kinematics equations in an app.
Reminds me of the American development of the space pen that wrote upside down in zero gravity - for a million bucks. Apparently the Russians just used a pencil....
It wasn't something the average club cyclist could afford as the system was a couple of thousand dollars 12 years ago. I assume this system will work on all wheels with different spoke tension and rim strength. One point on the rim (right hand prism) seems a less accurate means of measuring output in watts, compared to say having 2 or 4 prisms with a corresponding number of lasers. More would add to the cost, but I believe, this would increase accuracy at slower wheel rotational speed i.e. hill climbing.
Storage of info from the road or in a lab via an SD card is a given, but what I would like to see are a number of apps that are Windows 7.5, Android 4.0, iPhone compatible so that users only need mount one display on the bike.
If the 'Laser Spoke' comes in under $400 the unit will sell in the millions. Need colour choices also. Great concept.
Garmin is working on a solution to create PEDAL based powermeters. It is not just possible, but actually pretty easy and just a minor inconvenience to move pedals from one bike to another. The cleat setup for these pedals are of the road type (not mtb with Shimano, Time or Egg-beater cleats) but can be used on an mtb if you are riding terrain that would not require you to dismount too much (like when riding mostly non-technical trails or rail trails and fire-roads). With road cleats it's pretty hard to negotiate walking up rocks. A pedal-based power solution is really the most versatile. Hopefully Garmin can get it right since they've been delaying the release of the pedals for over a year now.