WolfeMacleod

I've read about this on this forum here.
I mentioned this over at the Mythbuster's show suggestions forum, and people are completely dismissing it, saying no way in hell is it possible.
One guy's saying a car battery does not have enough voltage to cause an arc by itself! Funny...what happens when you touch the free ends of a pair of jumper cables together? aaaaRrrRC. BBBZZT!
What do you guys think? Anyone with any direct experience wish to comment on this?

http://community.discovery.com/group...6/m/7441950808

Manning

You have to check with Bruce Carr over on the e-mail list. He is the one I quoted in the original thread on here. It is not BS, he works in the bearing industry supplying to the big auto makers. He knows first hand that this is FACT, not BS and that there have been several recalls as a result. I really wish he would post on here directly about it. fascinating read.

GlenL

This was covered on the email list and I was one who didn't believe it. Bruce clarified that the current path was from the engine to the body, and not from car to earth ground, and it made sense. With no ground strap from body to engine the current will go through the drivetrain and through the bearings.

Search the 924/944 email archives for more.

Manning

Oh yeah, one of the folks in that mythbuster thread posted a link to a bearing company claiming they list all failure modes. That person apparently missed the link in Bruce's post to Timken's own tech tips section. If they had actually looked at it they would have seen Timkens listed electrical errosion as a failure mode.

http://www.timken.com/industries/aut...ssue2-2005.pdf

Did any of those pinheads even bother to read any of the links provided?

Also the Einomies person was trying to debunk by virtue of the fact that electricity would not go to earth through the tires, but Bruce never claimed it would, though it was implied to a degree, and at one point in the original huge discussion clarified this point. I don't think I included that commentary though in the original thread.

pearldrum944

It would be really cool to see this on mythbusters...I'm not so sure it would be entertaining enough for the rest of the audience though.

Manning

Oh, and another thing, Metalmasher apparently didn't read the contents of the link he/she provide for if they had they would have seen photo A-10 on page 11 which shows "flaking originating from electric pitting" and then would have read section 5-13 regarding electric pitting on page 23. What a retard. Who said anything about static discharge anyway?

Manning

And, while I have not seen arcing from battery post to cable per se, I have seen arcing from spark plug wires to engine.

Heck, use Dan Wray's trick to check to see if your plug wires need replacing if you want to see a neat light show. Dark of night, engine running, water mist, lightning show. fun.

Granite 944

I wonder why they tell ya to ALWAYS disconnect your battery, and put the welding machine's ground wire CLOSE to where the target welding is being done. Electricity will always follow the path of least resistance........right?........no mater where or what that may be thru.

Keep THAT in mind, if your ever welding ANYTHING on your car? LOL a little different approach......eh.

GlenL

Not quite. Electricity will follow all available paths. The amount of current will be split between the paths in proportion to each paths resistance. More does go down the path of least resistance.

Granite 944

Yep, I stand corrected, that is a much better, and more accurate statement.

Manning

Hey Wolf,

Rickbrant seems to be missing the point that auto manufacturers have been listing electric related bearing failures for years. Two companies Bruce listed where Chrysler and FoMoCo, and he stated there where additional ongoing issues that he was not at liberty to discuss. Again, they don't seem to be reading the original material in that original thread.

They also all seem to be stuck on the battery as the only source of electric generation on an automobile, forgetting the charging system, and the fact that the iginition system produces massive bursts of energy. Again, as I stated above, bad wires in the ignition system WILL ARC.

Also, Bruce never stated the electricity was traveling to an earth ground through the wheel bearing. Rather, he was stating that the electricy was following a path through to the bearing and causing damage. It is really no different from the pitting you will find under a loose chassis ground. Same thing.

And I am not sure why they think it takes massive voltage to cause this errosion. When I was a kid I used to mess around with electic motors and batteries and such. One of the goofy things I would do was to take a 6V lantern battery and some bell wire and make little burn marks and pits on steel plate. That certainly did not involve massive current. And if they doubt the ability of a 12V car battery to cause metal errosion and pitting they need to look at the underside of my hood where the Optima battery shorted against it.

Manning

Here is a link to a description of a FoMoCo wheel bearing TSB

http://v8sho.com/SHO/Radio,%20Static...%2097-18-4.htm

Interesting, I guess static electricity was mentioned - BY FORD!

IceShark

As you note a 12V DC car or marine battery has plenty of current to arc weld. On a quick discharge type battery which most of us are running you can dump 650 to 700 amps. You can arc weld easy with that which is why you have your hood marks and why Perry951 had his car catch on fire. I won't go into the electrical engineering bits as it should be pretty obvious from common everyday experience, just because it is 12 volts doesn't mean it is not a force to be reckoned with.

WolfeMacleod

That's what killed my first 924. Battry contacted the underside of the hood.

Manning

I think those folk in that Discovery thread are thinking too big. They can't get their heads around the fact that (1) we are not talking about electrical errotion that will cause immediately visible results and (2) we aren't talking about something that takes a ton of energy. I kind of picture it being similar to electroplating more than like arc welding. I get the impression they only see it as being like arc welding.

In addition they don't seem to understand that the FoMoCo TSB demonstrates the potential for electrical related issues on the bearing in an automoble as much as an actual recognized failure.

While I was sitting around obsessing about this earlier, because that's what I do, I got to thinking about how weird electrical issues are with cars. Take the horns on our series of cars for instance. You would think the steering shaft and rack, etc. would be pretty well grounded to the vehicle through various contact points such as the tie rods to steering knuckles and shaft to support yolk, etc., but if you have ever removed that little brown wire between the cross member and rack you know your horn does not work without it. Amazing how that little wire has such an impact on something that doesn't seem to be very isolated.