I bought a Velocomp PowerPod BLE power meter for my bike and promised Brian of The Forks Bicycle Shop that I would let him know how it worked out.
Traditional power meters measure Direct Force (DFMs). They have strain gauges built into either the pedals, cranks or wheel hub. They measure exactly what force you are applying through the drive chain and display it on the head unit in Watts. They can cost as much as a $1000.
Velocomp’s PowerPod relies on Newton’s Third Law. If it knows what forces are opposing you, then it knows what force you are applying. The opposing forces are due to: Wind resistance, gravity (up a hill), rolling resistance and acceleration.
It mounts under the handlebars, with no other physical connection to the bike. It measures wind speed, through a port in the front, and inclination and acceleration. It also needs to know your road speed.
So, to set it up you pair it with an ANT+ or BLE speed sensor and to your “head unit” (Garmin, ELEMNT Bolt, etc). Then you do a short out and back calibration ride. This is mainly for it to figure out the inclination adjustment – because you mounted it only approximately horizontally. During the calibration ride, instead of actual Watts, it displays 1-50 for the “out” portion and 51-100 for the “back” portion of the ride. After that it displays actual power.
That would be enough for rough power measurements. There are factory defaults for rider’s weight, bike weight, riding position, tire size etc. But you can fine tune all of these using free downloadable software (Mac and Windows). Connect the unit via the USB cable and you set your actual weight, that of the bike, whether you ride mostly with the hands on the brake hoods or drops, and lots more. You can save this configuration data into the PowerPod for up to five different bikes, so you can easily move the unit from bike to bike.
The same software displays a lot of other data for each ride you have logged. For example, it plots road speed and apparent wind speed together (the white and blue respectively) You can see where I rode into the wind (blue is greater) and after I turned around I had a following wind. The altitude profile shows when you were coasting and braking.
I’ve been using a smart trainer with Zwift and FulGaz all winter, so I now have a feeling for what power I’m generating. I’ve also done regular FTP (Functional Threshold Power) tests as part of a 12 week climbing program. After doing the fine tuning described above, I think the PowerPod is quite close to a DFM.
I was amazed how quickly the Wattage goes to zero when I stop pedaling. It “knows” that for the combined weight, slope and head wind I don’t need to apply any other force to achieve the speed I’m coasting at.
My version cost $299 US. (Online from the manufacturer. Local bike shops don’t carry it.) There is a slightly cheaper one that has only ANT+ connectivity. Mine has BLE too. Some Garmin speed sensors are not compatible. I’m using Wahoo’s magnet-less sensor around the wheel hub.
For about $50 you can buy a software license to unlock pedal stroke analysis. For that you need a cadence sensor on the crank (not on your shoe).
There is also the AreoPod that helps a rider perfect their aerodynamics. But this requires a DFM.