How it Works: Comparing power and split values on the RP3 Monitor software

12 May 2023

How it Works: Comparing power and split values on the RP3 Monitor software

At RP3 the flywheel has been the constant between all our machines for decades. While rowing we continuously measure the angular velocity of the flywheel during both the drive and recovery phases. During the recovery, while the flywheel is slowing down, we can calculate the amount of drag the flywheel experiences originating from all external sources such as air resistance, but also from, for example, wear of the bearings. Combining this with known physical constants we can deduct how much effort is required to overcome this drag.

To calculate the speed at which the "boat" is traveling (i.e. the split time or interval: time/500m) we can directly deduct this from the speed at which the flywheel is spinning. There is little difference in speeding up a flywheel through air or a boat through water as they're both accelerating objects through fluids. Meaning we can use a linear correlation between the flywheel speed and the boat speed. Combining the speed of the flywheel with the drag coefficient as well as some constants describing the type of boat and weight of the rowers we can very precisely approach the speed of the boat. The baseline setting for RP3 is set with type of boat 4X and weight at 90kg.

This functionality appears within the RP3 app which is the dashboard or monitor during indoor rowing on the RP3.   

Power is a different story; the amount of power required to speed up the flywheel increases as the flywheel is spinning faster. Again, similar to a boat in the water, gaining the first few meters per second is relatively easy, but gaining a couple of meters per second while at the highest level is very hard. This is why we use a non-linear correlation between the flywheel speed and the power scales with a power of three compared to the angular velocity.

If you want to compare with other rowers such as Concept2?
Make sure to select "Split Power" instead of "Power" as a data field. This will show you the power based on the split time as per the Pace-to-Watts Calculator.