A look at aerotesting with ERO Sports and the Alphamantis System

Upon the conclusion of my Las Vegas trip last month, I took a 40 minute flight over to Long Beach, California (greater LA area) to visit the folks at ERO Sports.  I’ve long followed the Alphamantis work around aerodynamics, and have seen early closed-door prototypes over the past few years.  So I was looking forward to checking it all out in a production capacity.

The testing would occur at the VELO Sports Center track, which is an indoor velodrome normally used by track cyclists.  The velodrome was originally outdoor during the 1984 Olympics, and lasted until 2003, when it was demolished and re-built as an indoor structure.

We had blocked off about 5 hours of time at the track for just our use.  Interestingly, afterwards some of the local kids cycling teams were out training on it:

The goal of the Alphamantis system is to be able to determine aerodynamic drag in a dynamic environment.  In other words, while you’re riding your bike and going somewhere – rather than just being put on a trainer in a wind tunnel.  This post focuses on how they’re doing that indoors in the track.  Down the road they’ll be moving that to outdoors as well (including all the complexities that comes with measuring wind and wind direction in real-time).

While the system is built and designed by a company called Alphamantis (based in Montreal, Canada) – the operators of that platform is a company called ERO Sports, which is based in Carson, California.  The technology behind Alphamantis was largely locked down to the Canadian cycling teams until the completion of the 2012 Olympics in London.  Since the Olympics, that’s been expanded and and is now being used by national teams, the world’s top pro cycling teams, and individual pro athletes in sports like triathlon.

I should point out this isn’t a ‘Review’ of their services.  I didn’t experience that, the focus as you’ll see wasn’t actually on me as an athlete.  Instead, I was trying to understand how it technically works – and then some fun scenarios and tests around it.  Because of my travel schedule, I was unable to join the rest of the media folks that were there a few weeks prior during a day of presentations/testing – so during a trip I had nearby, I arranged time with them to get an inside look at how things work.  But a review of their services/offerings this is not.

Pre-testing:

Prior to getting on the track you’ll need to come prepared with whatever you’d use in training and racing.  This is probably a logical time to point out that you should really train on the same equipment that you race with.  I know this sounds obvious, but I often hear folks that train on entirely different bikes than they race with.  Of course, I don’t think anyone expects you to train with an aero-helmet though.

In my case, I brought with me my bike (triathlon), as well as my trisuit and aero-helmet.  And of course all the normal stuff like cycling shoes, bike computers, etc… Ultimately, you want this to be exactly like what you’d show up on race day with.  So if you’re taking a Bento Box on race day – then yes, take that too.  As you’ll see, all those things really do matter.

At any rate, you’re going to show up to the Velo Sports Center, which houses the aforementioned velodrome in Carson, California – just a few miles away from the Long Beach airport (which is a few more miles away from LAX).  The Velo Sports Center sits within the Home Depot Center grounds.

Here’s the outside of the building:

Once you arrive, you’ll check-in at the front desk to sign some waivers.  Roughly they translate to “if you crash, it’s your problem”.  Ok, noted.

From there you’ll head over to get fit on your bike.  While most serious athletes coming into a facility like this would probably have been fit before, the ERO team does want to briefly take a look at things.  In my case, they did it purely to demonstrate the technology – though we did end up re-rising my saddle and aerobars up to where they should have been the last time I was fit (ironically, it ended up almost spot-on where it was configured a long while ago before things slowly slid out of compliance).

The fit process includes adding a bunch of stickers to you, which the sensor system (that bar on the tripod below) reads and understands.

These sensors are then reflected on a TV screen showing a wireframe model of your position on the bike.  At the same time, that system is recording the exact distances/angles.

This can then be combined with the Retül fit bike, which enables them to slowly tweak your position on a bike that doesn’t require you to get off the bike to feel the difference.  So he’s able to simply adjust the bike in real-time and I can feel the differences between positions.

In my case, since I was mostly focused on understanding the track portion for this post, we only spent a few minutes here in this area.  Additionally, in my case we did the change in seat height after my runs on the track (just for those Slowtwitch folks who might want to say my seat is too low…which it was.)

Testing on the Track:

This is probably as good a time as any to point out that I’ve never been on a velodrome track before.  I was relatively confident that I’d not only crash, but would manage to do so just walking across the track.

Everything is setup inside the track down near the starting line area.  In this case, their setup includes computers to monitor the sensors in realtime, timing systems to monitor exactly when you complete each lap, and an Alphamantis Bridge that transmits and repeats your ANT+ sensor data in realtime from your bike to the computers  via WiFi– no matter where you are in the velodrome.

At a high level, the system is designed to produce an aerodynamic drag value based on the known (very precise) distance around the track in conjunction with your bike transmitting data from an ANT+ speed sensor and ANT+ power meter.  By understanding how much power is required to go a given speed on a specific surface without any wind, they’re able to determine the drag.  Obviously, more drag is bad.  Less drag is good.  This drag value is measured in CdA, which is the  aerodynamic drag area.  Less is better.

In order to start things off, they’ll precisely measure out your wheel circumference, which is used by the ANT+ sensor and corresponding computers to measure speed.  It’s critical this is absolutely perfect – hence why they measure it out with a tape measure.

Note that if you don’t have an ANT+ speed/cadence sensor on your bike, they have spares.  It was interesting to see how frequent they are parsing the data.  For example, during travel my speed sensor had gotten bumped out of alignment.  As a result, when we did the first warm-up set, you can see how many false-positives it was getting (Green), and even the speed-only sensor (another ANT+ sensor on my bike) was having some troubles.  Yet, the PowerTap speed was very constant (no dependency on having the magnet aligned right).  Even more interesting is that my Garmin head unit thought the world was perfectly fine as far as readings go.  Only the more detailed real-time reporting surfaced it as seen below.

Next is then pairing your ANT+ power meter to their system.  Their system can pickup multiple power meters at once (which was actually interesting in my case since I had a few), though they focus on just using a single power meter normally.  Note that like the ANT+ speed sensor, they can loan units here as well.  I’ll talk more about the power meter aspect a bit later.

With those things all setup and paired, it’s time to get out and ride.  In my case since I’d never ridden on the track before, they gave a few hints.  This essentially boiled down to ‘don’t go slow on curves’, and ‘don’t stop’.  If both of those rules were respected, I’d in theory not crash.

Thankfully a bunch of smart guys and theories worked out.  I started off just riding around the very bottom, not even so much on the curves, and then over the course of a few laps I got more and more comfortable until I was up a bit on the wall.  For the purposes of all of the testing here, they want you as close as possible to the thin dark blue line near the bottom.

Fear not, you don’t have any reason to go up high.

Now, they actually want you to track that line as close as possible.  But even if you don’t, it’s alright, they’re able to see that variation since they know your exact speed throughout each loop – and then further reconcile that with data each time you trip the sensor at the completion of each loop around the track.  In fact, if you look at my lap by lap summary information, you  can see the slight variations in the distance I went as I’d wander a few inches here and there on the line.

They noted that anywhere within about a foot or so is more than sufficient for accuracy.

Now that I got comfortable going round and round, it was time to calibrate my power meter.  We tested against all three power meters I had on my bike, but for most tests we used the PowerTap, since (as I explain later), it’s the closest power value to the equations being used.

The calibration of the power meter is done every single test set, always after about 2 full laps (to clarify, technically this is just a zero offset, not a full-stop calibration).  As I enter that third loop they’ll give me the signal to calibrate.  In my case I just simply coast along the backstretch and they’ll confirm they received the calibration notification via the ANT+ repeater.

The actual test data then is gathered after the completion of that loop.

The reason for the constant calibrations is because the power data is so critical to getting accurate numbers.  And drift can occur for any number of reasons – though primarily environmental (temperature shifts).

Now onto the actual testing.

Each test set involves about 10 loops.  The reason for this is to attempt to determine the actual patterns.  As you’ll see, tiny changes to your position or bike can make a substantial and visible difference.  Thus if you just did a single loop, you might have numerous false positives.

First we started off with a baseline – this would be used to compare any future changes to equipment or position.  Because it can actually be fairly hard to hear in there, for each loop they’ll tell you how many loops left via hand signals.

Then, after the baseline we moved into testing different setups and configurations.  For example, some of them were person-specific that involved no equipment shifts.  In this case, it was just shrugging my shoulders (relaxing them).  In many triathletes, this will result in an immediate and notable gain in aerodynamic efficiency.

In my case…not so much.  While there was some almost perceptible gains, one could see over the course of that 10-loop test set that I slowly unconsciously shifted back to normal – mostly because it didn’t feel natural.  However, if you look at the below chart, you’ll see one of their regular athletes that was able to very clearly show this.

Look at the bottom right chart, and then notice about 60% of the way across it the red line dips down.  That dip is the slight change in shoulder position.

And in fact, that’s a really interesting point here.  As they noted numerous times, just because you can put someone in a given position – doesn’t mean that person can ride that position for 5+ hours (as in an iron-distance race).  A 40K time-trialist has very different needs than someone who’s going to run after it.  Or run a marathon after it.  Or eat during the race.  All impact position and whether or not an athlete can hold that position.

Some of it, of course, is adaptation on the part of the athlete, and some of it is finding other ways to gain those efficiencies.

From there the afternoon progressed as a series of tests – I did some 25 miles of loops around the Velodrome.  That may not sound like a lot in the scheme of an outside ride, but that’s actually a lot of loops (over 100).

Perhaps the most interesting revelation here is just how person-specific aerodynamics are – far more than I would have thought.  Going into this, I would have thought that Helmet A vs Helmet B is a simple case of ‘Helmet A is more aerodynamic than Helmet B”.  When in reality, it’s far more based on the positioning of that helmet on a given person.  Thus as they’ve seen (and showed me) – on one person Helmet A is faster, while on another, Helmet B is faster.  And that applies to many more things than just helmets – from full bikes to tiny details such as hand placement.

As we looked at positions, they brought out a few riders that have significant experience riding on the track – and that can more easily demonstrate some of the changes and impacts to aerodynamic position.  Everything from shifting one’s position on the aerobars, to just how one grips the bars themselves.  Or shrugging shoulders.  Or changes in aero helmets or regular helmets.

Post-Testing Results:

While basic ‘better or worse’ information is given in real-time while at the track, there’s additional information that’s handed over a few days later.  This information includes the lap-by-lap detailed numbers of each test set that was done.  It also includes summary information.  I’ll walk through examples of the files, and then explain my thoughts.

The whole PDF file includes many different pages of information.  But it starts off with a summary page.  Again do keep in mind that in my case, we weren’t aiming for making me faster – the goal was simply to allow me to understand the technology and test a few other random things.  As a baseline number, .2935 is actually pretty high.  They suspect that cleaning up the cabling (brake/gearing) towards the front end of my bike would go a long way towards reducing that number.

Once we get beyond the summary information, we get much of the same in a more graphical layout:

Then comes the more detailed information for each wattage level that’s calculated.  The tests are listed along the bottom.

I then get information about each test run within the set, all part of the booklet.  The test runs can then be tied to a specific scenario (i.e. with aero bottle, without, etc…).

Ultimately though, you’re going to likely make most of the time saving changes immediately on the track, rather than looking too much at the reports later on.  Further, for most riders, the reports would help them to quantify the time savings made that day as they progressed through different iterations.  The weekend I was there it was scheduled that a top triathlete was going to ride the next day.  Unfortunately things got rescheduled, as it would have been interesting to see that progression over the course of the day from a numbers standpoint.

Now, the challenge here is that this information isn’t terribly ‘portable’.  Meaning, it really is all about you.  And even more specifically, you on that specific bike.  I attempted to explain this during my review of the Profile Design Aero HC.

While on the surface it may seem that you could take this information and compare your aerodynamic your significant other (if he/she raced), in reality that’s actually somewhat difficult.  Variables such as the power meter used can impact the final numbers.  In fact, we tested this a bit using the three different power meters on my bike.  Each resulted in different numbers – due to the fact that all three measured power in different locations.  Further, that testing is based on the accuracy of that particular unit on your bike.  This is one of the reasons why they re-calibrate each test set, to mitigate against drift.  So even comparing a test from this week to one four months from now might be difficult with just a given power meter, let alone two different power units on two different bikes.

To mitigate this they are looking at potentially just providing power meters that they own for the testing – rather than using each persons own power meter.  Of course, that introduces significant logistical complexities.

They have found some patterns (both in general, as well as even in my session), Andy from Alphamantis noted that:

“Between the PowerTap and Quarq, the PowerTap is closer to physics, whereas the Quarq is closer to physiology. This is due to being closer to the the wheel due to loss of drive train/etc, and thus closer to what we’re measuring.”

Now, don’t mis-read this statement.  This isn’t saying the PowerTap is more accurate (actually, it’s almost saying the opposite). What they are explaining is that because they are ultimately measuring your data based on the track surface, the PowerTap is physically closer to the track from an output standpoint.  Versus the Quarq power output stream needs to take into account drive train loss – which could be variable (but the Quarq is closer to your actual human output).  And while it’s a very tiny variable, for this scenario, that variable can make a difference.  Below is a visualization of that data as it hits the system.  As you can see, the differences there can and would have an impact on the results.  As long as you stick to one of them though, you’d have a consistent baseline from which to work from for that specific day.

(Note: This is showing a given set, thus the drop you see below the 50s marker is the calibration occurring)

All that said, for same-day testing, all of that is mostly nullified through the calibrations.  Hence the reason so many top pro cycling teams and individual pro cyclists/triathletes are using it in blocked off time periods.  They aren’t as much trying to compare it to data from months ago, but rather making tweaks that can be immediately applied.

Random Tidbits:

Going into the testing, I had cobbled together some thoughts on fun things to test while there.  What I found though is that the day becomes a little bit of a case of ‘Riddle me this’.  Meaning, you can stand around as a bunch of data geeks and ponder: “Riddle me this: Is it faster to have the GoPro on the bars, or mounted just above the wheel?” or “Riddle me this: Is it faster to use this water bottle, or that water bottle?”.  Ultimately, each one of these exercises takes a fair bit of time to get the baseline established (10 laps), then the test for each (10 laps per test).  But that’s sorta what makes it so fun.

I could have sat there for days pondering ‘Riddle me this’ type questions with this group of folks.  The inner-data geek I suppose.

Of course, the challenge with that is then taking one of those tests and validating it on other riders.  That’s where all of a sudden a test suite that you could have knocked out in 20-30 minutes becomes something that could take hours with a small army of testers.

In any case, using the limited people I had handy, we did play around with a few scenarios for fun.  For example, a GoPro.  What impact does a GoPro have on aerodynamics?  We did a test with one of the riders there where we placed a GoPro on a road bike.

First up, was the baseline.  The way the average works is the set high (red) and low (green) CdA values are thrown out (excludes lap #1 as always), and then everything else is averaged:

Then, the GoPro up above the bars:

And then finally, the GoPro below the bars:

Results:

Baseline: .3279
Above Bars: .3305
Below Bars: .3262

It comes out virtually a wash.  In fact, technically it was slightly faster below the bars than baseline – which likely can be explained by the road bike position being slightly more dynamic than the time trial position.  In any case, you can see there’s very little impact to CdA here from the GoPro.  This sorta surprised us both.

Looking at the triathlon bike, we did some tests there as well.  I placed it below the aerobars.  In fact, the impact was less than the impact of the aerobottle system.

Ultimately I think it would be an absolute blast to sit there and test all sorts of interesting things.  And then potentially to go to a wind tunnel and test the same things.  Understand how the different testing methodologies (and results) differ, and what that means to consumers.

Summary

As a data geek, I found the time at the track fascinating.  As a triathlete, I found it eye-opening to see what an impact aerodynamics may have.  But even more importantly, to understand that just because something saves time doesn’t mean it’s viable – especially for long-course athletes going 5+ hours on a bike in time-trial position.  Though at $800 for a session (including fit), it’s a pricey option for age group athletes.  Thus I suspect you’d likely only see front of the pack AG’ers in there – of course along with professional athletes.

I think that the indoor track testing is an incredible tool to start to understand how to literally get free speed – even with no equipment changes, and do so in an environment where you’re actually riding.  The next step will be extending that outdoors to controlled locations (such as Formula 1 style tracks which can be ridden without interference), to take into account aspects such as wind at various angles.

Is this better than a wind tunnel?  It’s not a simple yes or no question.  It’s probably better when a rider is involved, because it can be fit to actually riding.  Whereas when a simple piece of equipment is tested – then using a wind tunnel makes more sense.  But of course, as you’ve probably come to realize – one starts to seriously question the usefulness of generic wind tunnel test data using the marketing of much of the equipment we buy, especially given how obviously individual the results may be from person to person.

As always, if you have any questions – feel free to drop them below.  Thanks for reading!

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