MI_rider

I was at the LBS earlier today to test ride a couple of bikes. (Trek 2300 verus the 5200) I will save that for another thread. While I was there a guy comes in and asks one of the employees if he can ask him a strange question.

The guy tells the employee that he has a Trek 4300. He bought it at the lbs about a month before. He says that when he and his family ride under the main power lines that he gets shocked on his bike but that nobody else (wife or kids) gets shocked. He says that he has to make sure he is only touching the rubber grips and the seat. He has to take his feet of the pedals and put his legs way out to the side so he doesn't touch any metal on the bike. He said that one time he didn't spread his legs wide enough and that he got shocked on his inner thigh becuase he was touching the saddle rails.

After waiting long enough to ask with a straight face we asked a couple of questions. Did his wife try his bike? He tried to get her to but she refused. Did he ride through on her bike? No but he was going to try that tonight.

He said that his old bike didn't do this and that this only happens when going under a certain spot of the main power lines that supply his area.

Nobody there had ever heard of anything like this, so my question is has anyone out there ever heard of anything like this before? I tend to believe the guy because I don't think anyone could make up a story that good and then tell it with a straight face and demonstrate how he had to ride through the area to not get shocked. Any ideas on what could cause it?

Steve

Spire

The account has little basis in reality for several reasons. The first one is that the voltage and energy needed to brdige from powerlines to the ground is immense and likely not the be carried in the lines. In the event that there is enough and for some reason a shock will come out, it makes much more sense that the bolt will spark from wire to tower to get to the ground (always takes path of least resistance). Also, there is no direct ground connection on the bike, the wheels are made of rubber. This is why you are not really at risk in a car.

I personally, knowing a lot about electricty (through engineering studies) find this account to be extremely unlikely and suspect that there must be another explanation, futher tests need to be done to prove anything conclusivly. Either way, it surely isn't the bike manufacturer's fault.

khuon

Well, although unlikely that air between the powerlines and the rider/bike has undergone dialectric breakdown, the rider could be experiencing the effects of induction.

MI_rider

I know the basics about electricity and magnetism also.
What makes this a funny story is trying to figure out what could be happening. Also nobody was trying to claim it was the fault of the manufacturer. I just thought it was a funny story that everyone would enjoy. I do believe this guy but just can't imagine what is causing the problem.

khoun, I also think it has to be induction but I am not sure why it would affect just him and not the other riders. What is so different about his bike. I will have to get out my college physics book and try and figure this out.

Scooby Snax

Only explanation could be induction, which is highly unlikely, as t he distance form the overhead transmission lines are specified to keep things like this from happening.


Scoob

khuon

I'm grasping at straws here... Metal content of his bike might be different than previous bikes or other rider's bikes? Conductivity of his skin due to sweat content/water content of his body may cause him to draw the charge off the bike whereas others wouldn't?

Bobatin

Conductivity of carbon tires? He would have to be passing through in the middle of two towers.

Take a flourescent light bulb under those power lines at night and it will glow like a light saber.

Prosody

Actually, I have had the same thing happen to me, though not as dramatically. On most of my rides I pedal under high-tension transmission lines, and I have noticed that, when I tap my fingers against the brake levers on my hybrid--havn't noticed this on the road bike yet--I get mild shocks. I have heard that high-tension transmission lines can create an electromagnetic field.

The Rob

Could it be simply static electricity? Perhaps this fellow was creating friction somehow, say between his clothing and the saddle. If subsequently he moved his body in a certain way that caused his skin to come into contact with the frame (steering through an obstacle or bracing for a bump, etc.), could he not sustain a shock? This possibility assumes that he must move in much the same manner every time he passes that spot.

Straws? I gots a handful. :confused:

-Rob

The Rob

Heck, maybe it's an alloy thingie. Steel vs. aluminum? (Like that argument needs yet another facet!)

-Rob

Prosody

I do know it isn't static electricity because it happens only under the power lines. Steel vs. aluminum? Hmmm... The hybrid frame is aluminum. I'm not sure what metal the brake levers are.

DnvrFox

Research: Power lines enhance static electricity, creating "positive static electricity"

‘Positive Static Electricity’

https://www.justlogiclifescience.com.au/powerlines.html

Also

Don't VanDeGraaff generators cause static electricity by the electromagnetic field they cause?

Seems to me this is a viable explanation, also dependent upon the tires and material of the bike, and the dryness of the person.

greywolf

This could be true , if you walk through a power transmission switching yard on a high humidity day ,you can feel the electricity in the air ,your hair starts to stand on end & if your wearing wool ,it starts to stand on end too, may be this guy is more sensative to electricity

joeprim

Wow

Yes induction and yes more sensitive person sweat or more dry ???

Yes to EM field

But some how to get a shock there has to be a potential (voltage) difference. This makes me think that the tires must conduct

Van de graph humm
The bike being insulated from the ground, but a good conductor gets a charge the rider doesn't so there is a difference but where is the flow???

Neat post thanks

Joe

Prosody

Of course, in the college physics lab we used a rubber mat and the business end of a VanDeGraaff generator to play wizard--build up a charge and with the index finger zap a passerby from a distance of about three feet.

DnvrFox

Drive under high power lines while your car radio is turned to a weak AM station to get some kind of an idea of the extensive EM field being generated.

DnvrFox

Same place the flow is with a lightning strike. Non-existent until the charge releases because of the potential difference.

Rev.Chuck

This is not, by a longshot, my speciality, but wouldn't induction require ferrous metal?
Is itnotalso possible that the guy is a little off? I have a customer that believes that loosening the adjusting screws on her rear der. makes the bike faster even tho I have shown her exactly what they do.

uciflylow

Personal experence talking here! We use to shoot .22 rimfire rifles off the side of a bridge in the country here that had a high power electric towers running over head. One day I noticed that my rifle was shocking me when I touched the trigger guard just before shooting. I could actually hold the gun by the plastic stock, inch my finger twards any metal part of the gun and a small arch would appear with a tingling shock, so the fella isn't tellin a big one!
After this experence I would not want to live close to one of those, it would be like living with your microwave door open all the time! I also have a friend who works for TVA as a lineman doing helocopter line checks and in the air repairs and I can tell you that there are instruments that can detect when a insulator is going bad just by the field around it. Why do you think those lines have to be so far from anything metal? He says that if you get closer than 5 ft of one of the lines, you will become the path of least resistance to the ground and ZAP! You just became a poodle in the microwave!

N_C

First of all yes this can and does happen. More ofthen then people may think.

Why? Well I really don't know. It could be because of static electricity in the area or the power lines are faulty for some reason or another. Maybe its because certain people conduct electricity better then others.

What ever the reason the shocking experience can be and is surprising to say the least and can be painful at worst.

It has happened to me, once.

It was a long time ago during the 2nd day of a Iowa MS150 ride. I do not remember what county highway I was on but it did happen.

At first I thought I was imaginning it. But 2 other cyclists next to me had the same experience.

It was while we rode under some high powered electrical lines. We just got a brief static shock.

The thing is we felt it all the way through our bodies. It was actually kind o weird.

When we got to the end of the ride we reported it to a county sheriff. Hopefully the problem was dealt with before someone got seriously hurt by it.

jim-bob

It doesn't? I thought my plan was foolproof!

MI_rider

For induction you just need any material that will conduct electricity. Copper is what is commonly used and it is not ferrous

I guess that is why I started the thread was to see if anyone else had ever heard of anything similiar. I believed the guy but since I didn't know him I wasn't sure. I guess that it happens more than I realized.

My best guess for what is happening is that he really has two complete loops on the bike. The bike frame and the cables that on his bike run across the top of the bike. They are probably seperated by some kind of insulater (plastic spacers). Since the cables are steel and the frame is aluminum when it passes through the magnetic field generated by the lines it will create two differnt flows in the two different metals. Thus the potential difference and the shock when he completes the circuit between the two. Of course we would have to hook the bike up to volt meters to verify this but it is my best guess.

Thanks for all of the responses.

Steve

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uciflylow

My guess is that he is absorbing the electrons, and when he makes contact with the metal of the frame it results in a shock, as the electrons flow to ground.

I have heard of cases where people have been convicted of theft by running an insulated wire paralell with the hv lines and capturing this "bleed off" electricity.

RainmanP

This is what I was thinking, that in the highly charged region under the power line it wouldn't take much for a static charge to arc the 2-3 cm from the rim to the ground

Bobatin

So if this guy grounded himself to the frame while passing under the power lines he would not get shocked?