InfoCrank is technically dense, yet incredibly simple to use
What allows us to assert so plainly that InfoCrank is the most accurate power meter available today? Read on to find out why.
The design and manufacture of your InfoCrank is the culmination of years of behind the scenes research and testing. We control the whole process to ensure our accuracy claims are, well, accurate. We then submit our InfoCranks to external verification.
Designed for true and precise power measurement
1 : Tangential load (power generating) – This force generates power as the crank rotates. A power meter should accurately measure this force, or its equivalent torque about the bottom bracket bearings.
2 : Axial load – Produces tension or compression in the crank arm. It is highest when the rider’s weight acts downward on the pedal when the pedal is at its lowest point.
3 : Side load – This load can be present when the rider leans the bike during hard acceleration.
4 : Pedal axis torque – It is not possible to apply this load to the crank through the pedal unless the pedal bearings are faulty.
5 : Crank axis torque – This load is always present since the pedal ce ntreline is necessarily offset from the crank.
6 : Side torque – This torque bends the crank towards or away from the frame. This load is highest when the rider’s weight acts downward on the pedal when the pedal is at its lowest point.
Control in Manufacturing
Verve manufactures InfoCrank to the high standard required of a precision instrument.
By controlling all manufacturing processes, we set a standard of accuracy that’s not possible by adding a power meter to an existing crankset. The crank is a top-quality, conventional 2D cold forging.
The pockets are machined to a precision of 5-100ths of a millimetre (0.05 mm).
The strain gauges are bonded into symmetrical pockets in the inner and outer faces of the crank. Variations between left and right cranks in a pair, or from pair to pair, are vanishingly small, amounting in no case to greater than a 1-watt difference as manufactured—eliminated in any case by factory calibration.
Our focus in manufacturing the InfoCrank is on the accurate assembly of mechanical and electronic components into a precision load cell capable of reliable and stable performance even in a hostile operating environment.
Accuracy in Processing
An accurate power meter is only one half of the equation, the ability to transmit and process the data is equally important. Again InfoCrank leads the way.
|1 sample per crank revolution doesn’t pick up the huge variation in power applied during the pedal stroke|
This graph shows a sample rate of 32 per crank revolution. Sampling 12, 32 or 64 times per stroke increases accuracy but complex algorithms are needed to “calculate” the power output.
Only InfoCrank power meters sample the torque 256 times per pedal stroke.
This results in every pedal stroke giving an accurate reading without the need for complex algorithms. With independent measurements taken on both left and right crank, a detailed understanding of the pedal stroke is available to the rider.
It is not possible to achieve 0.5% accuracy in a power meter with fewer than 50 samples per rotation. InfoCrank’s 256 samples per second rate far exceed this requirement even at high cadence.
InfoCrank measures torque at 256 samples per second, so at 60 rpm, it samples 256 times per rotation, at 120 rpm, 128 times, and so on. With a low sampling rate, important torque information is not recorded, especially during the torque peak of the rider’s power stroke.
This has been put to the test: torque data of a track rider’s session was collected at 480 samples/sec, using local storage on the bike. After download, it was plotted using a discrete Fourier transform.
The data was then plotted again using the simplified algorithm implemented within InfoCrank’s firmware—the waveform is identical to the Fourier plot.
A sampling rate greater than 256/sec does not increase precision, requires more compute power (so more battery power), and requires more bandwidth than is currently available to transmit reliably to the head unit with no data