How bumpy is my baby’s ride in my jogging stroller?

Stroller bumpiness, measured with an iPhone accelerometer

When our daughter was younger, I tried to quantify the "bumpiness" of her rides in strollers.  We had two strollers, an older Bugaboo Bee (can't find a link to the older version) and a Thule Chariot Cougar (single, not double).  We had the normal stroller attachment for the Chariot Cougar and the jogging attachment. 

Bugaboo bee
Thule Chariot Cougar with stroller wheels
Thule Chariot Cougar with jogging attachment

In addition to comparing the differences between strollers, I wanted to compare the "bumpiness" differences when walking and running.

Data collection was messy, as you'll see below, but hopefully the results are still interesting.

Measurements and Methods

I used an old iPhone 4S with an data logging app to measure its accelerometer output while the phone was placed in the bottom basket of the Bugaboo and in one of the front pockets of the Thule Chariot Cougar.

I used two different apps to record the data:

  • Axelerom: For measurements of the Bugaboo and the Thule Chariot Cougar with stroller wheels
  • xSensor: For measurements of the Thule Chariot Cougar with the jogging attachment

Both only recorded data when the phone screen was on, so I had to stop once and a while to make sure it was still recording.  The Axelerom readings were taken at 5Hz and the xSensor at about 19-20Hz.  The Axelerom readings were also somehow strangely rendered out of order in the data file.  I had to resort the data by timestamp.

Upon analyzing the data, I realized that 5Hz wasn't fast enough to do anything other than measure acceleration.  Even the xSensor measurements at 19Hz weren't that great.  This was a bit of a problem, because I couldn't reliably measure the "jerk", or the rate of change of the acceleration.  The jerk can have a large impact on the perceived quality of a ride.  A good analogy is the difference between slowing down in a car at an intersection and abruptly letting off on the brake when the car comes to a stop rather than gently easing off of the brake pedal.

Coincidentally, I learned during research that 5Hz is roughly the resonant frequency of important parts of the body, and possibly the least comfortable vibration frequency to experience.

The measurements were taken on the sidewalks and streets in Oakland, California, mostly along the same ones for each stroller.  I didn't take the exact same path or streets for each stroller though, so this is another potential source of variation.

The smoothest ride was with the Thule Chariot Cougar

Stroller bumpiness, measured with an iPhone accelerometer

The Thule Chariot Cougar looks like a SUV next to the Bugaboo Bee stroller.  It's got two 20" wheels with pneumatic tires and a suspension on the back.  The Bugaboo's wheels are suspended too, but are much, much smaller.

One can observe the difference in forces measured in the stroller on the graph: the pointier the curve, the smoother and less bumpy the ride.

The numbers

The Thule Chariot Cougar with the stroller wheels (in green in the chart above) provided the smoothest ride, with a minimum measured acceleration of 0.399 Gs and a maximum acceleration of 2.231 Gs.  The standard deviation was 0.108 Gs.

The Bugaboo Bee was the next smoothest, with a minimum measured acceleration of 0.087 Gs (nearly freefall, for a split-second at least!)  and a maximum measured acceleration of 2.452 Gs.  The standard deviation was 0.165 Gs.

As one may expect, the bumpiest ride was with the Thule Chariot Cougar with the jogging attachment, recorded while running.  I regret that I did not perform measurements while just walking with the jogging attachment installed to have that as a point of comparison.  The minimum measured acceleration was 0.089 Gs, the maximum measured acceleration was 2.382 Gs, and the standard deviation was 0.242 Gs.

What does this all mean?

It was really interesting to find that the maximum and minimum recorded accelerations for the Thule Chariot Cougar with jogging attachment, while jogging, was similar to that of the Bugaboo Bee.  And the Bugaboo Bee is a pretty smooth rolling stroller.  I found that to be pretty reassuring.  Though the ride while jogging was definitely bumpier, the maximum acceleration magnitude was smaller than that of the Bugaboo.

This was kind of just a fun exercise, but there are a couple of conclusions I came to:

  • The Thule Chariot Cougar is a very smooth-riding stroller.
  • Running with the Cougar's jogging attachment is sorta bumpy, but probably not way worse than the Bugaboo Bee.

 

 

 

north face endurance challenge – San Francisco (marin headlands, really) half marathon photos

I ran the North Face Endurance Challenge san francisco half marathon a few weeks ago, and brought my iPhone with me to take some photos.  The race was staged in the gorgeous Marin Headlands.

This was around mile 1 or less.  The sun was still low in the sky, it was still chilly, and I felt fresh.

 

Around mile 1.5?

 

 

Tennesee Valley trail

 

The turn up the coastal trail for the 2nd major climb

 

First glimpse of the Pacific Ocean

 

Pretty steep pitch.  Pretty even mix of runners and walkers up the hill.

 

 

A few people had stopped here to enjoy the view.  This wasn’t quite the summit.

 

It was somewhere up there..

 

Another view of the ocean

 

The descent down Fox trail was just as steep.  Definitely hard to run down in a controlled manner.  I didn’t.

 

The Marincello climb was the start of the 3rd and final major climb.

 I was predictably exhausted at the end of the race but I’m happy with how I paced myself.  I went out a little less conservatively than I had planned but I was probably being a little overconservative.  And the race-day excitement gives you a little boost of energy.

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ALC10 Orinda training ride

We joined an AIDS LifeCycle training ride at Orinda BART last Saturday.    Here’s everyone signing in with the beautiful hills in the background.  We did a 33 mile loop or so and then rode back home over the hills to make it a 45 mile or so day.

 

 

 

A crabapple or flowering cherry at inspiration point.

 

 

 

 

 

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Cotton and company shop to become crossroads

update 05.12.10: crossroads confirms that they’ll have a second rockridge location.  As of May 9th, the shelves were being stocked!

New tenants coming soon – we saw a banner for crossroads trading company while walking by the old cotton and company shop this morning.   I’m guessing that Crossroads is moving from their old location – two spots in Rockridge sounds like a little much.

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