Static Electricity Shock

I agree with lynlynch. Static can build to surprising levels.

Some changes were made to the sawdust collection system in the woodshop, and there were complaints of some pretty hefty static shocks. The revised system had overlooked grounding... added ground straps liberally, end of problem (not my design).

Glass beading can give you some healthy jolts, too. Even through the gloves.

"Glass beading" ?

Ya got me there. As in bead blast media?

Same thing.

Yes, solid glass microspheres blasted by high 120PSI speed air.

Interesting trivia bit: The reflective glass spheres widely used today on highway signs and to produce low density materials such as syntactic foam came into being by being rejects of the solid glass bead manufacturing process.

Some enterprising person saw them as a product, not waste. 3M, I think.

Two North Americans, separated by a common language?

I've seen and heard enough. I am outta here.

This is interesting. I have experienced a similar sensation, usually after doing something repetitive. I have touched things and it feels exactly like current traveling up my arm, like grabbing an electric fence, or getting bit by 120. Never could find any source of current in whatever I was touching. I wonder if you could enlist a volunteer and have them touch the casing, after "you've" done the polishing and see if they get shocked also. This has bugged me for a while. My theory is that some nerve is getting pinched and causing this sensation. I'm a little hesitant to think that static electricity would behave this way. I used to do electrostatic painting, my helper and I would aim the gun at the other person occasionally, while they weren't looking. No paint coming through, but it would build a hell of a static charge in the unwary person. There always was a shock and the accompanying snap and spark would get bigger and bigger depending on the charge. Funny as hell!, unless you were on the receiving end. I've had my wife touch things that I thought I was getting shocked from and she's never felt a thing. I've attributed this to a pinched nerve of some kind, because I've experienced it touching things I know don't have a charge on them. You've got an exact experiment that you can replicate. I'd like to hear what happens.

Could this happen with the motor casing grounded? It doesn't seem like it. I've been doing some more thinking about this happening to me. It does seem to happen more often after doing something like running an orbital sander. And it sure does feel just like being shocked.

How was the ally workpiece held? Was it in a (grounded?) clamp or vice, or were you holding it?

Seems to me that the only way you could get a belt by touching the grounded motor case is if you were charged. This could happen if you were in contact with the (ungrounded) workpiece while rubbing hell out of it with a polishing wheel.

That's it - totally a manual operation - the aluminum was touching only myself and the wheel.

... then PWSlack's suggestion of grounding the workpiece should sort you out.

How about a grounded wrist strap to bleed off the static.

I had similar sensations in my arm for a while caused me to take a boring desk job as I was working in electronics at the time and never knew is somthing was accidentaly live or if it was just my nerves eventualy tracked it down to a nerve thing in my shoulder.

Could the aluminium/aluminum piece be connected to earth/ground, maybe using a wire with two crocodile/alligator clips on it, one attached to the aluminium/aluminum and the other to the motor casing, perhaps?

Some people do not get the same intensity shocks because they are, shall I say, a bit more damp, thus dissipating the charge through their more moist surface. The plastic bushing provides a type of static insulator, allowing the accumulation of prodigious voltage. The amount of current produced at the wheel/aluminum interface, although small, has at some point of the current's fluctuation a resonant equal current within the motor field, which, momentarily combines with the static current to produce a comparative macro current along with the timing of the exit charge. You get a ZAP! The result being, a strangely aggravated deep tissue shock. Luckily the dwell time is so short that the spike does not interrupt the nervous system and heart/brain synapse. You are alive. Replace the plastic bushing with a metal bushing and see what happens.

Duh, anyone who has sand blasted or buffed is simply making a low grade wimshurst machine or van de graf generator, albeit with a rotary charge transfer pump from the disc or sand to the workpiece to you.

All sand blasters and polishers used industrially have a metal workpiece clamp to prevent this

Duh??? - you obviously DID NOT read my post. See a portion of my post below you missed.

So, is there a difference in the static electricity developed with cotton and aluminum where the cotton is moving at 9500 feet per minute (6000 RPM at 6" circumference) versus the usual jolt you get sliding your Kahkis across your car seat and touching the door? Is there a possible larger current capacity with the set I have described?

I know its static and how it was generated. What I didn't know was if the static electricity can generate enough current that my muscles contracted. That generally takes a pretty good flow of current. At 120VAC, I usually only feel a good tingle. Go to 200VAC and then I start to contract. (yeah - I've been shocked a few times) I've played with Van De Grafs as a teenager and do not ever remember a shock that contracted my arm muscles. The closest shock I remember to this was as when I was quite young and was playing with 120VAC on the inputs of a step up transformer I salvaged from a old dump and was very well grounded. Got against the outputs (where were my parents???) and got one heck of a jolt.

Duh??? - you obviously DID NOT read my post. See a portion of my post below you missed.

So, is there a difference in the static electricity developed with cotton and aluminum where the cotton is moving at 9500 feet per minute (6000 RPM at 6" circumference) versus the usual jolt you get sliding your Kahkis across your car seat and touching the door? Is there a possible larger current capacity with the set I have described?

http://en.wikipedia.org/wiki/Wimshurst_machine

http://en.wikipedia.org/wiki/Van_de_Graaff_generator

Look at these. The buffing wheel, the Van de Graaf and the Wimshurst all have similarities. They move charge and accumulate it. When you buff, it accumulates on you.

Van de Graaf machines can create very high voltages, lots more than buffers or Wimshurst.

Don't forget that Aluminum always has an oxide coating, which is a good insulator, so you are rubbing two different insulators together, just like a standard Van de Graaff machine or the traditional cloth and rod. The small gap across the plastic between the wheel hub and the shaft guarantees that sparks jump before the voltage builds up to more than a few thousand volts. The initiation of the spark has a very short rise time, which is equivalent to a very high frequency, so the case and its grounding system have enough inductance to allow part of the charge to enter your body even if the grounding system is intact, and the spark has short enough duration to avoid blowing the GFI.

Been there, done that. Bet you were wearing nice insulating shoes. You are transferring charge from the earth to yourself. You can fix this elegantly by getting one of the nifty grounding kits that techs use when installing static sensitive components, little carbon fibre strap around your wrist attached to ground via a flexible wire. Or do it the way I do, a chunk of plumbers chain screwed to your buffer case and a couple of inches tucked into your belt to contact your body,, it's out of the way loops down, not likely to get caught in the machine.

Wear a strap and ground yourself. See if it stops.

YES. THE CHARGE BUILDS IN YOU; NOT THE MACHINE. IF YOU STILL DO NOT BELIEVE, TRY POLISHING FOR A WHILE AND THEN TOUCH ANOTHER MACHINE OR ONE OF YOUR ENEMIES WHEN THEY WALK BY. I TELL MY OPERATORS TO TOUCH THE POLISHED WORKPIECE TO THE MACHINE BEFORE TOUCHING ANYTHING THAT WOULD GROUND THEM. MOST OPERATORS DO NOT LIKE BEING RESTRICTED BY A GROUND STRAP. THE ANKLE STRAPS THAT ARE CONNECTED TO SHOE PLATE ARE THE MOST LIKED BY OPERATORS.

You are describing the same electric shock one gets when grounding a spark plug wire with your hand. If you don't get hit clear to the shoulder the coil is weak.

That sounds almost as fun as sucking up whole kernel corn with a vacuum with a plastic hose. Even though there is a wire hose support (supposed to act as a ground) you get a hefty jolt every second or so. Makes for a fun afternoon to be "priveleged" with the "opportunity" to run one of those systems for an few hours.

Like testing a spark plug/coil, except you can't let go until the job is done!

Grounding yourself is the answer.

Or you could try storing up the charge all day long and then kiss your wife on the lips as you walk in the door at night!!!! Now, THAT would be electricity! You might want to contact a good lawyer before conducting the experiment, though...

If you want a similar but even stronger shock grab a hovering helicopter. It won't matter a hill of beans if you're wearing insulated shoes.

Hooker

Because the buffer is running, the potential for higher current and longer duration of shock makes a big difference on how the shock feels. It's current that acts on the muscles and nerves. Most static shocks have very little current potential. If you suck up a lot of toner from a copier with a vacuum cleaner, you'll probably find a similar feeling if you complete the circuit. The helicopter comment reminds me that high voltage does break down almost any insulator. You might as well deal with lightning. Ground everything!

Try grounding the work piece. that should help a lot. I think the current is felt this way due to the fact that you are still generating current by the wheel when this happens.

Wal

It is true that it is you that is charged. When you touch ground you drain all the charge accumulated in you to ground. Kiss in that state and you and your partner will also know. Retrench fast before you get a tight rap. Jokes aside. People who work with steam lines in a steam network have experienced the same thing. Shake hands after working in a steam network with another person and see the fun. Or touch a steel railing with a neon tester (screw driver) and it will glow without giving you a shock. If At All You Get A Shock Be Happy You Are Alive.