ROUVY Virtues - Advanced Pedal Metrics
Getting started with the ROUVY Virtues and Advanced Pedal Metrics
To use the Advanced Pedal Metrics you will need two things: the PowerTap P1 pedals (with firmware version .024 or later) and the latest version of ROUVY or PowerTap Mobile for iOS. Once the pedals are paired to your device, start an activity and you will see the Advanced Pedal Metrics. All of the data is recorded each time you start an activity and is available for playback and analysis at any time after your ride on the ROUVY community site in the activity detail.
Advanced Pedal Data - What is it?
Advanced pedal data sensors like the PowerTap P1 measure three physical quantities during the pedal crank revolution:
Tangential force, Ft – the part of the force that spins the pedal, tangential to the crank axis. Tangential force is positive when its direction is in direction of pedaling and negative when it is opposite to the direction of pedaling. A negative value indicates the rider is “dragging” their foot.
Radial force, Fr – the part of the force that points from the pedal to the crank’s center. A positive radial force points toward the crank’s center. This is an important component of the rider’s exertion because it represents wasted energy.
How the PowerTap P1 pedals collect data for the advanced pedal metrics
Before we dive into these answers, first a little background on what is being measured by the P1 pedals and how we can accurately extrapolate those measurements into the metrics that are displayed by the ROUVY and PowerTap Mobile apps.
If we look back to basic physics, we will remember that Power has both a force component and a speed component. Each of the PowerTap P1 pedals has four pairs of strain gauges that are measuring the force applied to the pedal body. This is done in both the vertical and horizontal planes. These forces, along with the rotational speed (angular velocity) are measured 40 times per pedal stroke on both the right and left sides.
A closer look at Advanced Pedal Metrics
Within Advanced Pedal Metrics we are displaying two different views. The first view represents the tangential and radial power.
Tangential power - represented by color. There are two colors displayed. Red, which represents positive force, and blue, which represents drag (fighting the opposing leg). The richness or depth of the colors represents the intensity.
Max tangential power pointer - represents the position of the maximum tangential force.
Shape - represents the radial power where the distance from the gray circle to the colored line is the magnitude of the radial force, either positive or negative. Since radial force is wasted energy, you want to keep this deviation as small as possible.
The number in the circle - Left or Right pedal balance
Because we are showing only the force component of the pedal stroke the data displayed is in Newtons, not Watts. The scale is 20 Newtons per pixel. So what exactly is a Newton? A Newton is a measure of force and is equal to 0.2248 pounds of force. The Vector Force metric gives a very detailed look at how you are applying energy to the bicycle. This plot can be used to improve how you are pedaling by 1) giving insight into where you are wasting energy by fighting the opposing leg (blue), 2) and 3) improving the direction of the force you are applying by reducing the amount of radial force as much as possible.
The second view shows the pedal angle through the stroke with the same color scheme as the vector plot.
The third view shows you the angle of the source and the amplitude of that source. That means what direction are you pushing and how hard. The red color represents positive force and blue represents drag.
Advanced pedal metrics in ROUVY apps
All ROUVY apps can display the advanced pedal metrics once the trainer/power meter enables these metrics. You can change the view by tapping or clicking on the plot. In iOS/Android, you can change the size and position of the APD window with push and swipe gestures.
If you haven't read Hunter Allen's piece on using pedal-based cycling power meters to improve pedaling, do yourself a favor and give it a read. In this piece, he explains how the right and left legs interact with each other during pedaling and gives a few examples of things you can try to help improve your pedaling. This helps you waste less energy which means you can go faster without increasing your energy output. At the end of the day, our Advanced Pedal Metrics are another tool cyclists can use to help make improvements, gain speed, and get the edge over their competitors.