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In-depth review: PowerPod power meter

24 Aug 2018

Page 1 of 2In-depth review: PowerPod power meter

Verdict:

An extremely innovative product that offers a cheap entry into power analysis, but has some niggling drawbacks and challenges in usability

Cyclist Rating: 
Price: 
£269.99

Buy the PowerPod Power Meter from Pro Bike Kit here

‘That’s not really a power meter, is it?’ I heard that again and again while reviewing the wind-measuring PowerPod power meter. My response, over time, became that the PowerPod has as much right to be considered a power meter as half the systems on the market. 

Since the advent of power meters at the crankset, we’ve interpreted power to be a measure of the force at the cranks using strain gauges.

But the deflection of the metal in one arms of a crankset, or from a single pedal, is an estimate of power too

The PowerPod, in strict terms of mechanics and physics, makes perfect sense. It’s all too easy to forget that the reason we generate power is for one functional result – speed. More power results in more speed.

Headwinds, climbs and cold weather mean that speed doesn't always accurately reflect the effort we put into the bike, hence why we want devices to measure power.

As all forces need to be in equilibrium when cycling, power can actually be derived in an equation described as the mathematical model of road cycling power.

We can work out the extra effort of climbing a hill from elevation data or even use basic gravitational potential and VAM (/speed) to calculate our power.

Wind is trickier, as aerodynamics is a complicated science, and it’s not easy to know how much wind we’re fighting in order to calculate the power needed to oppose it. Enter the PowerPod.

The PowerPod directly measures frontal wind force, along with elevation and atmospheric pressure. That leaves only rolling resistance and weight to be determined, the latter can of course easily be measure by the user.

The former requires an estimate.

Using a plastic channel with a Gore-Tex membrane at the end of it, the PowerPod measures the intensity of the wind, and so can algebraically calculate the necessary power from the rider to achieve a given speed at a given elevation with that level of wind.

Like any normal power meter, this is transferred to the head unit in ANT+ or bluetooth form. It does however have the added advantage of being usable without a head unit.

You can simply ride with the PowerPod and plug it into the Isaac software on a computer after a ride to analyse the power figures. That’s a considerable selling point.

The PowerPod is a complicated product, and has required extensive testing to fully explore its accuracy, usability as well as potential advantages and setbacks.

It's proved a very interesting and innovative product, though.

Setup

First off – using the PowerPod’s single button and the light, I needed to pair the PowerPod to my Garmin speed sensor.

It’s worth noting that you need to buy this alongside the PowerPod as otherwise it won’t pick up the necessary speed data.

The PowerPod designers recommend a front wheel-mounted wireless gyroscopic speed sensor, which is what I used. Cheaper alternatives should work too, but possibly with less consistency.

That’s an important consideration in the overall price tag too, adding £30 or so.

A steady green light informed me that this calibration worked. Following that I could take it on the road.

On my first run I hadn’t undertaken any calibration process in the software, only the PowerPod’s own basic calibrate to the wind speed.

You can ride the PowerPod straight out of the box and it will generate power figures, but you can’t expect too much of them.

Owing to the complex nature of the calculations the PowerPod needs to make, the precision of the variables which are set by calibration are totally vital.

On the first ride, the PowerPod counts up from 1 to 100 watts, in what I came to consider a fairly ingenious use of the available data field.

Rather than showing the perceived wattage it’s demonstrating the percentage of the calibration process.

The wattage displayed after this initial calibration were in the realms of accuracy, but quite a way off. My wattage was generally between 500 and 800 rather than 100 to 400 watts, but of course this is with no calibration.

The figures were vaguely useful and generally aligned to increases in power output, taking into account gradient changes and headwinds rather than simple speed.

For any sort of truly useful accuracy, it’s clear that the system requires a proper calibration and set-up, which is exactly what PowerPod’s designers recommend, so I installed the Isaac software and began the set-up process.

The software is not svelte, and doesn't feel fully finished. There is a need to connect the unit to a computer, which is a big drawback in my view, and once connected the software is cumbersome and frustrating to use at times.

It’s most like advanced training tools like Golden Cheetah, and crucially not a user-friendly no-brainer process, much as there has clearly been some admirable attempts to make it so.

An element of this comes down to the user, and certainly I think a more capable computerised mind would have done a better job than me.

For my part, I required four system restarts and two attempts at installation to connect the unit to my computer and begin the exchange of data.

Once connected and into the Isaac software, I was presented with the option for ‘Best Accuracy’ or ‘Better Accuracy’, pictured.

The latter asks for various information to formulate an estimate for the CdA (co-efficient of drag area, how much drag the rider and bike create) the unit needs to calculate the power needed to overcome wind force.

It was 'Best Accuracy' I was after, which would require a 10 minute calibration, split into two 5-minute segments in opposite direction to one another on the same stretch of road to estimate the rider's personal level of aerodynamic drag.

Calibration

On my first attempt the calibration started early, as I was still moving through traffic, which spoiled the process and left the power figures completely wrong.

This seemed like a frustrating potential flaw, as I needed to return to my computer to reset the PowerPod’s profile so I could repeat the calibration process.

This was ultimately down to my own error, and it’s very important not to misstep in this process.

‘When you start pedalling, you’ll notice that the PowerPod light starts flashing red/green,’ explains John Hamann, CEO of VeloComp and inventor of the PowerPod.

‘This means that PowerPod is “armed” for a best accuracy, out and back ride. You ride to your starting point for your out and back ride, then click the button to start the out and back ride.

'The light switches from flashing red/green to flashing yellow. Begin your ride and at the turnaround point, the light switches to solid red.

'Once you slow down and turn around, the light switches back to flashing yellow. At the end of the out and back ride the light goes out.’

The same process is at work as with the first ride, with the PowerPod wattage output counting up from zero to 100, but with a turn as it turns 50.

(Excuse the shaky photography demonstration, as I had to do the calibration on the road on account of the wind variant, it was not without its difficulties.)

Accuracy

Once the calibration was finished the unit initially displayed 0 watts, but then quickly began to generate reasonable figures.

A bonus is that when finding out the CdA as calculated by the PowerPod, I could go back to previous uncalibrated rides and manually put in my new CdA.

That would generate accurate figures, retrospectively for those rides.

Once calibrated, and working properly, I think PowerPod almost fully achieves what a power meter sets out to do. 

I found it to be up to the task for intervals, for pacing and to measure my improvements in threshold and top end power.

One of my early observations was that there was no need to use a 3-second average power reading, as I have done for literally every power meter I’ve ever used.

The raw power figure already seems to be smoothed over 3-seconds out of the box, and a little delayed as a consequence.

A Garmin's 3-second average, then, sometimes made for a 5-second delay in the accurate power figure. That's a little frustrating for spring training, as very short intense bursts in effort don’t show quickly enough to try to target the likes of 1,000 watt peaks.

How accurate were the figures themselves? Well the top and bottom range was exactly where I would expect it to be.

I maxed out around 40 watts of my measured best on my tried and tested Vector 2 pedals, while my perceived FTP power sat at around 320 watts, exactly what I’d expect for this time of year. I was pleasantly surprised.

While several people suggested I run two power meters in tandem to test the accuracy, I’ll save this for a further test of the PowerPod for time trial (which will include its CdA measurement capacity), as for the purposes of a first power meter I’ve always considered consistency and a generally accurate frame of power to be most important.

That said, the range of error that I would estimate from the PowerPod is the same as I would expect from a force-based power meter that isn't regularly manually zeroed, and probably less than the possible distortion from a single sided system.

Anyone who's time trialled and compared wattage will know how disparate power figures can be across various systems.

The PowerPod had minor niggles in accuracy - it tended to overestimate my power from a stationary start. It also sometimes seemed to struggle to factor mild ascents and descents into the power figure.

It underestimated the necessary power on some false flats and overestimated some mild descents. It would also occasionally take some time to run down to 0 watts when I stopped pedalling – as much as 5 seconds.

Then there’s more practical issues. If I stood up to sprint off the saddle, the power figures often went down. That’s because I’ve significantly increased my drag.

By contrast, ducking down into my aero tuck I’d have a strange inflation of my power figure despite not increasing my torque on the pedals.

The PowerPod only truly works if the position of the rider is totally consistent.

There were also some more startling errors in power consistency. The PowerPod was given to bouts of reading zero watts or several thousand.

Over time it tended to settle down to a reasonable figure eventually, but this could be 10 minutes into a ride, when I’d already be hoping for useful data.

Hamann explained that this was likely down to the the pod tipping ever so slightly from its position during calibration it could generate wildly high figures or nothing at all.

‘The PowerPod is extremely sensitive to its mounting angle; this is why our instructions ask the rider to gently rotate the PowerPod forward until it hits the stop on the mount,’ says Hamann.

‘If the angle is not the same when the PowerPod is reattached, or PowerPod rotates because it is not solidly locked into the mount, then the unit will recalibrate itself (automatically) for the first eight minutes of the ride.’

That seemed to be the case for me, and when I recalibrated it up against the stop and without moving it at all, these errors became much less frequent.

Playing the field

On the whole, the PowerPod offered the same level of informative background data that any other power meter has done.

Telling me when I was pushing hard into a headwind, pushing harder than normal on a steep climb and generally whether or not I was tapping out a respectable power on a long training ride.

It was both a training aid and indicator of form.

Would I choose it above a top-end dual sided system? As a training aid I definitely wouldn’t. Compared to the likes of an Infocrank or Garmin Vector 2 pedals the data just wasn’t as rich (in terms of live dynamics data and left-right balance), reliable, immediate or consistent as I would want.

But then those power meters are three times the price of the PowerPod.

At the same price point we would be looking at a older generation Stages unit, a 4iii single-sided crank arm based unit, or for a few hundred more a single-sided pedal power meter.

Here I think the PowerPod does hold its own against the competition. 

Pedals and crank arm power meters aren’t without their inconsistencies, and the PowerPod offers a great deal more information when delving deeper into the metrics created by the software.

We’ll explore that more in the second part of this review, looking at the CdA measurements and pedalling performance analysis.

I might still find myself advising a more conventional system over the PowerPod to certain users, as the plug-and-play nature of a ANT+ crank or pedal is a big bonus over the PowerPod.

Many users simply wouldn’t want to go through software installations and complex calibrations.

I would also prefer one of these systems for indoor use, although the Powerpod does offer a metric for indoor training based on wheel speed. 

The biggest barrier to my continued use of the unit was the difficulty of switching it between bikes and the tendency to lose accuracy if it shifted position (putting the bolt through the wrong side made this more awkward and again was entirely user error).

Admittedly switching a pedal or crank isn’t without hassle, but it doesn’t require delving back into the accompanying software.

Shifting between bikes can be tricky, and cable run was a minor issue

Parting thoughts

I was left with the feeling that the PowerPod is really a very clever piece of engineering, cleverer perhaps than even the SRM when it was released.

In a way that ingenuity is slightly squandered on mere mortals with a potential for misunderstanding. 

This is not an easy device to use. It lends itself to a technical mind, and indeed the data and info can be very fun to use and explore.

For many, though, it will be a labyrinth of flashing lights and decimal points, which lacks the plug and play appeal of so many systems on the market. 

But, the current crank and pedal systems also began with niggles and glitches. Where the PowerPod is headed, if it can iron out the problems, is a very good place.

Perhaps I’d hold out for the second or third generation for a more useable package, possibly compatible with a bluetooth app rather than needing a wired installation.

For now, it is certainly up to the task of measuring power output, but only if you have the patience and intelligence to use it.

Stay tuned for an in-depth look at the PowerPod’s more advanced CdA metrics, and more specific accuracy tests, in Part 2: PowerPod for time trial

Page 1 of 2In-depth review: PowerPod power meter

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