Crank power meter – the beginning of a new era
With the invention of the crank power meter, the age of permanent power measurement in cycling began. This led to a completely new form of training control in cycling. Previously, only the pulse of the athlete and thus the stress on the body was measured. With a crank power meter it was now possible to measure the load exactly.
This is an enormous advantage, because the pulse is influenced by many other factors besides the load (e.g. outside temperature, fluid balance, fatigue, etc…) and is therefore only conditionally suitable for load control. However, the heart rate (pulse) is still very useful as additional information besides the power in watts.
In 1986 SRM developed the first powermeter. Today, SRM is still a big name in this field and is considered by many to be the standard for measurement precision in a system.
Crank power meters measure the force values with sensors in or on the crank. This can be done on one side or on both sides. A great advantage of these systems is that the force distribution during a rotation can be analysed in the compression as well as in the tension phase.
Another large producer of crank-based power meters is Quarq. Quarq was born out of necessity in 2006 when Jim Meyer was not satisfied with any of the power meters available at the time. Since he has always been a doer, he decided to simply invent a power meter himself.
In 2008, the first power meters were sent out. In 2011, Quarq grew its platform by becoming part of SRAM LLC. With they had more resources at their disposal. Today, Quarq still makes power meters, for example their latest model the DZero, which took 10 years to develop.
In the meantime, there was another manufacturer of crank-based measuring systems, Ergomo System.
The Ergomo system is located in the bottom bracket and transmits the data via cable to a display.
A pulsating signal was generated by creating light barriers on the left and right axes based on their rotational speed. This signal was then converted into power. In its day, the Ergomo system was very accurate and delivered data quickly and clearly to the display. However, the assembly was complex and only possible with the help of special tools. Furthermore, the reset process, which was unavoidable before each new trip, was very time-consuming. Ergomo systems are no longer produced.
At Stages, power meters are made from conventional crank arms from Shimano, Campagnolo, Cannondale, FSA and others. By gluing on a strain gauge and a printed circuit board, power measurement is made possible. The rest of the crank meter is then added. The data can easily be played back on a bike computer via ANT+ or Bluetooth.
Besides Stages, many manufacturers have adapted this technology and offer very similar crank power meters. With Wattteam there was even a manufacturer in this area who only offered the measuring unit of the powermeter as a retrofit kit for the existing crank.