Firetruck chains

[Grim/Don]

Why do I see chains dragging the road under the trucks? I'm guessing it's to dissipate static electricity, but that's only a guess...

Thanks!

 

[DaveH]

I think you're right, I also see them under propane delivery trucks.

 

[dniice87]

ambulances have them too, i was actually wondering the same thing yesterday

 

[Mike G]

Provides a ground in case of accidental contact with live power lines.

 

[Bronco]

ambulances have them too, i was actually wondering the same thing yesterday

Wow, y'all must have some tall ass ambulances in Westchester County.

 

[Esav Benyamin]

No, we just have some low-hanging power lines.

 

[faramir]

ambulances have them too, i was actually wondering the same thing yesterday

Many cars have a length of steel cable running down from below to the ground over here; it doesn't cost much and it dissipates static. Cars that don't have one of these "zap" people sometimes which is mildly annoying Just get yourself a ~25 cm (10") chunk of steel cord and screw it onto something metallic (exhaust pipe holder ?) and make sure it touches the ground. Shoudl you come across an obstacle the cable will simply bend instead of rattling the way I imagine a free-hanging chain would.

 

[uncle Alan]

Why do I see chains dragging the road under the trucks? I'm guessing it's to dissipate static electricity, but that's only a guess...

Thanks!

Jerry had a dialogue about this . One of his friends,maybe Marcel Ledbetter , had one dragging off his ratty old pickup .Jerry asked why & Marcel said it was for prosperity . How ? "Well, didn't it work for Standard Oil ? "

Uncle Alan

 

[JTC]

We went on a tour of the local ambulance service with the boy scouts. They had several chains hanging by the rear tires of the ambulances. They told me it was some sort of deal where it could run the chains under the drive wheels in case of snow or ice. In other words they could basically put chains on their tires on the go. the chains apparantly spin under the tires giving them something to drive over.

John

 

[Doug C]

And here I thought what was forging Damascus with Firetruck Chains doing in Gadgets & Gear! :foot:

 

[Gollnick]

In the event of an accidental contact with a power line, a ground connection is the last thing you want.

Dissipation of static electricity, on the other hand, could be very important.

Automatic tire chains, while they may hang down some, shouldn't drag all the time.

 

[Ken C.]

Most of the new engines have automatic tire chains that will drop down and spin under the tires when engaged. The problem that is inherent in these systems is that they rely on existing hydraulics in the brake system rather than being totally independent. After a few years on the road and due to lack of regular use and maintenance the systems wear which causes the chains to hang lower than normal. I the 5 years that we have had them on our engine we used them 3 times.

Here is a pic of our ambulance wi the chains disengaged. As you can see the left rear set of chains hangs lower than the right. The last time they were used on this particular rig was...well...NEVER! Rough road surfaces allow these things to bang around alot.

 

[mete]

Gollnick has it right .If you are in a sitiuation where power lines have dropped onto your vehicle DO NOT STEP OUT OF YOUR VEHICLE !!! I can remember two examples both fairly recent . A TV van extended it's antenna to make a broadcast and the antenna touched an overhead high power line. The driver was OK until she stepped out of the van and shorted out the power through her. She survived with serious, permanent injuries !!! A couple was in a car in a large puddle of water and a power line had dropped into the puddle. When they stepped out of the car they completed the circuit and died !!!

 

[brewthunda]

Yeah, they're automatic tire chains. Click this link and scroll down for the video of automatic chains in action. Pretty cool stuff:

http://www.onspot.com/

 

[Grim/Don]

Automatic tire chains... Whoodathunk it!

Brewthunda, thanks for the link. Since KV mentioned them earlier in the thread, I was wondering how they worked.

Faramir... Thanks for the idea about a cable running to the road for static electricity. I'll be hitting Home Depot this weekend for some wire. I HATE getting shocked getting out of my vehicle.

Found this link in a Google search:http://www.autotrader.com/research/...ticle_id=2762&refpage=safetyinfo&restype=used sSeems that spray fabric softener on the seats may help.

And the answer to my origianl question in this link (with solutions): http://www.cartalk.com/content/columns/Archive/1997/June/07.html

Thanks all for the interesting and informative thread. I was a bit leery of posting, thinking everyone one but me knew! :foot:

 

[Mike G]

I forgot about those automatic tire chains. :foot:

And, yes, some of our newer rigs have cables hanging down for static dissipation, and not electrical grounding. :foot:

We don't have the auto chains on any of our rigs because they usually won't work properly. If it snows enough to need chains, the rigs are chained up the old fastioned way, and left chained up until after the snow melts.

 

[Gollnick]

Some may wonder what the difference between static dissipation and electrical grounding is. The answer is about a megaohm. For static dissipation, they insert an electrical resistor, often about a megaohm, in series with the wire. Generally speaking, electrocution fatalities start at about 20mA. With a megaohm resistor in series, you'd have to tangle with 20KV to get 20mA.

In the old days, tire manufacturers added a pinch of carbon to the rubber of tires to bring their electrical resistance down to about 4 megaohms. With four tires on the car all in parallel, that'd be about 1 megaohm for static dissipation. But, carbon in the tires increases friction and reduces milage. So, facing EPA milage requirements, car manufacturers had the tire manufacturers leave the carbon out. The result is that a car may pick up a harmless static electric charge and you may get a harmless but unpleasant static shock as you get into our out of the car. Harmless, that is, unless your in an explosive environment. Ambulances which carry oxygen and alcohol, fire trucks which may be responding to a hazmat situation, etc. could be in an explosive environment. Furthermore, firemen often carry tools that have small gas engines. A chainsaw is a good example. A spark in the vicinity of the chainsaw's gas tank could cause an explosion. So, static dissipation grounding would be a good precaution for a fire truck.