Last week, I began riding my new commute bike, a GT Transeo, to work. My new bike allows me to get off the streets with their heavy traffic, and onto the local canal system, which is almost unused. My route to work is along the canal bank on the irrigation canal that runs E-W, between Elliot and Guadalupe, in Mesa, Arizona. I ride almost 4 miles on the canal before I cut South to Elliot for the final mile or so on the road. The canal portion is traffic-free, quiet, and quite pleasant except for one annoying phenomenon. As I ride to and from work I get occasional, fairly sharp electrical shocks, normally to one of my legs at the inside of the thigh, just below my shorts (sometimes the left leg, sometimes the right, sometimes one then soon after, the other). These shocks are sharp enough that the first few times it happened, I thought a bee had stung me, or that I had jabbed a bare bike cable end into my thigh. This happens at least once or twice on each ride, and has had me groping for some kind of explanation. No bees, no bare cable ends, no debris being kicked up by my tires and hitting me in the legs, no residual marks to indicate injury. A couple of times, I’ve reached down right after this has happened and felt an electrical shock to my finger or hand.
This has happened frequently enough that I am certain it’s not my imagination. After a week of this, I finally figured out what was going on. It’s a practical demonstration of the physical laws that govern many of the machines we take for granted around us.
My route on the canal banks runs parallel to, and about 50 feet directly under, the high-voltage transmission lines that share the right-of-way with the canal and distribute power throughout much of the East Valley in Phoenix. These lines produce a sizable electro-magnetic field (EMF), which is one of the reasons they’re in this right-of-way to begin with. It is well known that a conductor moving through an electric field will generate an induced electric current. This is one of the operating principles behind power transformers, motors, and generators.
My bike frame, as it moves through the EMF generated by the power lines, has an induced electric current (stored in the “loop” that the frame makes). The frame is isolated from earth ground by the tires. It is also isolated from me by the rubber-covered pedals, my running shoe soles, the rubber handlebar grips, and the insulated seat. As I move down the canal, a potential difference gradually builds up between me and the frame. The magnitude of the potential diffeence is a function of speed through the field, the strength of the EMF of the lines, and a secondary function of the humidity (high humidity allows charge to leak away more easily). As the potential builds, eventually some body part (usually the inside of one of my legs) gets close enough to some pointy part of the frame, like a nut or something on the down-tube (static field energy dissipates over long, smooth surfaces, and can concentrate at sharp points) , and ZAP! A shock jumps and equalizes the bike frame and me.
So, in order to prevent this phenomenon, I need to make sure that my body and my bike frame keep at the same potential while riding through the EMF. If I do so, no shocks should occur. I can do that by making sure some part of my body has direct contact with the frame always, or at least frequently enough to keep the potential difference less than the “jump” energy. To test this, this morning on the way in I rode with my thumb off the rubber handlebar grip and resting on the handlebar itself. Nary a shock, for the first time in 5 days.
It also turns out that if I simply ride on the side of the canal opposite the power lines, that added distance is enough to reduce the potential difference build-up to the point where the invisible bees that have been plaguing my otherwise enjoyable commute have gone in search of other victims.
Popularity: 24% [?]
Bike Commuter Essentials at PricePoint.com
15 responses so far ↓
1 Moe // Apr 9, 2008 at 9:46 am
Dude, that’s crazy!!! I guess you have a good ‘reason’ to upgrade to a Carbon Fiber bike!
2 Apertome // Apr 9, 2008 at 9:51 am
That’s disturbing. Even though you seem to have found a solution, somehow the idea of riding in a big EMF for an extended time would bother me. Maybe that’s why nobody uses those canals …
So with your new method, when you get off the bike and touch something else do you get a shock?
3 RL Policar // Apr 9, 2008 at 9:52 am
Or he can get a wooden bike…
4 Quinn // Apr 9, 2008 at 9:52 am
No wonder the canal is hardly used! Although IM one of those people that would see the power lines and figure “Discharge, Duh” and then if I didn’t know how to fix it, I would take time to figure it out.
5 cafn8 // Apr 9, 2008 at 10:01 am
Huh. So finally the the real reason for all those gripless fixies.
6 Ghost Rider // Apr 9, 2008 at 11:10 am
What a weird phenonmenon!
You should try cycling with a 48″ fluorescent tube sometime to see if it lights up — I’ve seen someone walk into a power-generating station and the bulb just lit up due to all the “loose” electricity in the air!
7 Ben C // Apr 9, 2008 at 11:37 am
Just wire yourself to the bike just like computer repair guys. At least you didn’t get shock in your crotch. That may do some damage! OUCH!!
8 Tim // Apr 9, 2008 at 12:49 pm
Amazing! Staying in contact with your bike is one solution, and grounding the bike frame is another, maybe better, solution. You could drag a grounding strip of some sort to bleed the static charge from the frame. Try an old piece of brake cable clamped in the rear quick-release skewer at one end and dragging on the ground at the other end. Many heavy vehicles have this kind of arrangement to avoid a charge buildup. Some of them, like fuel tankers, even drag a big chain to absolutely minimize the risk of electrostatic discharge.
-Tim (aspiring Ph.D.)
9 RocBike.com | The RocBike Review » Links of the Day: 9 April 2008 // Apr 9, 2008 at 12:59 pm
[...] Guest Article: An Electrifying Commute, by Jim Tolar (Bike Commuters) [...]
10 Fort Orange Cycling » Links of the Day: 9 April 2008 // Apr 9, 2008 at 1:00 pm
[...] Guest Article: An Electrifying Commute, by Jim Tolar (Bike Commuters) [...]
11 miker // Apr 9, 2008 at 2:07 pm
I used to experience that along Virginia’s W&OD trail in Falls Church. The trail is also along a power right-of-way & only in the Falls Church section was the power high enough or the lines close enough to cause that effect.
I used to play with watching the sparks fly between my fingers hovering close to the brake levers (with my hands on the rubber grips).
Interesting science experiment, but yes, what does that high voltage do to your body systems in general?
12 Bill // Apr 9, 2008 at 4:54 pm
Ben C has the right idea. If you get an anti-static wrist strap used for computer repair, that should keep the potential energy balanced quite nicely.
Just watch that first step off of the bike.
13 Rick // Apr 9, 2008 at 5:36 pm
I remember riding under those types of power lines. There was a constant crackling. I always assumed that there was some sort of charge in the air.
14 Dartanyon // Apr 11, 2008 at 10:47 am
Have you given any thought to grounding the frame? Just drop a piece of conductive wire off the bottom bracket to the ground, just barley long enough to make sure that it makes contact most of the time?
15 Jot // Apr 28, 2008 at 8:41 pm
The solution to this is obvious. You have a metal bike, and you need something that can connect you to that. Cut a hole in the front of your bike shorts, and voila, you’re set!
Probably solves the problem of the extra charge you generate between you and your chamois.
I’m just saying…
-Jot
Leave a Comment