InfoCrank® is the most accurate power meter available today. How do we know?
Read on to find out why.
Verve Cycling manufactures InfoCrank® to the high standard required of a precision instrument.
It’s precision engineered and exhaustively tested to ensure that it’s accurate, reliable and stable. By controlling the entire manufacturing processes, we set a standard of accuracy that’s not possible by adding a power meter to an existing crankset.
The crank is made by 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 minimal, 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 accurate assembly of mechanical and electronic components into a precision load cell capable of reliable and stable performance even in a hostile operating environment.
Load Cells and Strain Gauges
Why is InfoCrank® a precision instrument? Because each crank, right and left, is designed expressly around a strain-gauge load cell.
A load cell is a transducer that converts a force into an electrical current, and is used for measuring instruments such as lab and industrial scales.
A single InfoCrank arm is so very accurate because the strain gauge measures only tangential force, or torque—the force the rider puts in that drives the bicycle forwards. The load cell design means that side, radial, and twisting loads that are exerted on the crank (but do not move the bike forward) are not measured.
Every Load cell is calibrated at our laboratory. Independent certification tests on completed InfoCrank® sets have been conducted which showed <0.25% average error across all the normal riding zones. The greatest error in 100 tests was one outlier of 0.57%. No other power meter has achieved such high levels of accuracy with such consistent results.
British Cycling test each InfoCrank® they buy before putting it into work on the bikes (track and road) of the Great Britain Cycling Team, Tests on the Road InfoCranks® showed amazing results. Between zero and 464nm (equivalent to 3000w) the Road InfoCrank error was stable and well under 0.6% at every measurement.
The test result below shows the initial tests on the new Track InfoCrank®. This is the starting point from which we work to improve accuracy to the same level as the Road InfoCrank®.
A strain-based load cell’s accuracy is degraded by external temperature changes—a problem for cyclists who, as all-weather athletes, expect to be able to use their equipment in all conditions.
Temperature changes cause thermal expansion that can be confused with a load change and result in incorrect power readings, so power meters that use strain gauges must compensate for these errors.
InfoCrank overcomes these false readings by using the highest-quality strain gauges that are compensated for the thermal expansion of the aluminum crank. Additionally, the use of four strain gauges in each crankset in a full Wheatstone Bridge configuration inherently compensates for temperature, and makes the InfoCrank insensitive to temperature changes. The quality, match, and placement of the strain gauges with the alloy and the full Wheatstone Bridge configuration is the most accurate solution to temperature-corrupted readings.
256 samples per second
InfoCrank® has a sampling rate of 256/second, so with cadence of 60rpm, it’s sampling 256 times per rotation, 120rpm 128 times a rotation etc. This continuous monitoring of the power applied to the Crank ensures the rider has highly accurate data across the entire pedal stroke. Lesser sampling rates will miss key elements of each stroke.
|This graph shows how inaccurate a sample rate of 1 is.|
|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
Head units and beyond
InfoCrank® Power meters use ANT+ technology to sync with most Head Units. At Verve Cycling we like to monitor our live power output with the o_synce navi2coach
- Robust GPS bike computer with ANT+ technology
- Configurable data view with up to 4 bikes and six screens per bike. Everything you need to know at your fingertips.
- View Power Balance, Pedal Smoothness and Torque Efficiency as well as all the normal information.
- A simple interface to see your data and upload to your chosen analysis programme.
But collecting data isn’t the end. At Verve Cycling we can team up with you via our MYPOWER programme to help you get the most from your InfoCrank® data.
“Accurate data will always make the difference when combined with all the other work that we do with our athletes and Verve Cycling has proven to be committed to achieving best in class in this increasingly crucial area.”
Iain Dyer - Head Coach of the Great Britain Cycling Team