Ground spike under a tire.... (Unsafe grounding practices)

[chrisf]

This is not quite true. The ground spike is still dangerous when dealing with large currents (such as from a short circuit, wire or lightning strike).

While I'll be the first to admit, I make plenty of mistakes, for this, it's 100% true. In case you're wondering, this is "what I do".

Please understand, I don't mean this as a insult, but this is again what I referred to earlier as a little knowledge being a dangerous thing. I'm trying very hard to fight against a few commonly held misconceptions about electricity I've seen repeatedly in the signals world, this is one of them. Several of these misconceptions, such as the ground spike under the tire, are extremely dangerous, and I'm trying very hard to end them before someone is injured.

Any time in a person in a position of any authority unintentionally passes on any of these misconceptions, its very hard to remove them at a later time. (I'm still wary of eating water melon seeds for fear a water melon may grow in my belly).

Contrary to popular belief, current does not "travel through the path of least resistance". Current travels through all paths to the point of lower potential (voltage) at all times. The less resistance, the more current that travels through that path.

In low voltage systems, under a thousand volts, current through insulation is negligible, so we typically ignore it.

In higher voltage systems, with more parallel insulator surface, say, underwater transmission cables, current through insulation is large enough to note, for power loss and safety. The majority of the current travels through the conductor core, however, a small minority of current travels through the insulation to ground.

With regards to a grounded vehicle, if the truck is at a higher potential than the earth, then current will flow to the earth. This is why we pound a ground spike, to give a low resistance path for the majority of current to flow.

If you happen to touch the truck, and earth at the same time, if the truck is grounded properly, some current will flow through you, some will flow through the grounding electrode (spike). Under normal conditions, nearly all will flow through the spike. Some will flow through you, a tiny tiny tiny amount will flow through the vehicles tires, and some will flow through the air.

If the truck is not grounded properly, and you touch it, more current will flow through you, the amount depending on your connection to earth. If you're standing on dry pavement, not much will flow through you. If you're kneeling in wet dirty, more will flow through you.

Under fault conditions, such as a lightning strike, there will be a great deal more current. Further, the voltage present in a lightning strike will break down resistance in insulators. If the vehicle is properly grounded the majority of that current will flow through the spike, some current will flow through the tires, and some will flow through the air. If you happen to be touching any part of the vehicle, or even standing close to the vehicle, some of that current will flow through you to ground.

Proper actions on lightning should also have the operator remove their headset, and wait for the storm to end. A set up should also not be attempted during a lightning storm.

For maximum safety, installation of the ground spike should be the first thing done on set up, or at least prior to operation of any electrical equipment or installation of antennas. If I remember correctly, the first two things done in a "normal" set up of  a3 man LSVW rad det are installation of the ground spike and placement of the drip pan, prior to anything else.

(If you want further reading, http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html as an added bonus if you read the article, you'll get to dispel the myth about rubber tires insulating you during a lightning strike)

 

[Edward Campbell]

Alright, I have no idea where this ridiculous practice came from, but I have been fighting hard against it.

Take this to your units. Take this to CFSCE. Take this the hell out of the heads of sig ops.

PUTTING A GROUND SPIKE UNDER A TIRE DOES NOTHING! NOTHING WHAT SO EVER! IT PROVIDES NO SAFE OR USEFUL GROUND! STOP DOING IT!

I don't know where the practice originated from, but for some reason, but it's quite common. Connecting a grounding cable to the grounding lug on a vehicle, laying the grounding spike behind a tire, and backing the vehicle a few inches backward to put weight on the spike... somone at some point decided that if the ground was too hard to pound in a spike (Read: The det commander is too lazy/incompetant to move their truck give feet backwards to the edge of the pavement).

Now courtesy of the pyramid scheme that is army education, this unsafe electrical practice propogates...

Placing a ground spike on the ground under a tire accomplishes nothing, it provides functionally NO electrical conductivity between the vehicle and the ground, and thus no ground protection.

Why do you want ground protection you ask?

#1. Grounding for your electrical system, provides protection in the event a live wire comes in contact with an enclosure or somthing else electrical. Basically, keeps you from getting shocked.

#2. Lighting protection. Helps to disapate lightning to ground.

#3. Secondary grounding protection when using AC, should the bonding wire to the generator or utility supply fail.

#4. It forms half your freakin' antenna! Using half wave antenntas, no ground, and half your antenna is missing!

So please, stop this practice and start fighting against it, it's going to get people hurt.

This is a very interesting and very useful thread. Thanks, a Sig Op for starting it.

Much of the discussion over four pages has focused on items 1 and 2. During the last 1/2 of my career I had a great deal to do with radios: big, fixed radios and radars; little handhelds, shipborne rigs and pretty much everything that radiated. I want to add some emphasis to Item 4: your radio (or radar or whatever sort of emitter) is, broadly, only as effective as the antenna and, as a Sig Op said, proper grounding is a major factor getting the signal "through." Grounding can often be a big problem: ask any sailor or airborne system designed or anyone who has served in a desert.

That fact that getting a proper ground can be hard does not mean that it cannot be done; it can be done - in nearly 20 years I never saw/heard of a problem our experts could not solve (given enough money) - and, indeed, it must be done if you professional Signals people are going to do your jobs. If you do find it too hard, ask: ask the Foreman of Signals, ask a smart officer (some are, you know ... really, I'm not kidding), if they cannot help ask them to ask the geeks and nerds in Ottawa.

 

[RADOPSIGOPACCISOP]

While I'll be the first to admit, I make plenty of mistakes, for this, it's 100% true. In case you're wondering, this is "what I do".

Please understand, I don't mean this as a insult, but this is again what I referred to earlier as a little knowledge being a dangerous thing. I'm trying very hard to fight against a few commonly held misconceptions about electricity I've seen repeatedly in the signals world, this is one of them. Several of these misconceptions, such as the ground spike under the tire, are extremely dangerous, and I'm trying very hard to end them before someone is injured.

Any time in a person in a position of any authority unintentionally passes on any of these misconceptions, its very hard to remove them at a later time. (I'm still wary of eating water melon seeds for fear a water melon may grow in my belly).

Contrary to popular belief, current does not "travel through the path of least resistance". Current travels through all paths to the point of lower potential (voltage) at all times. The less resistance, the more current that travels through that path.

In low voltage systems, under a thousand volts, current through insulation is negligible, so we typically ignore it.

In higher voltage systems, with more parallel insulator surface, say, underwater transmission cables, current through insulation is large enough to note, for power loss and safety. The majority of the current travels through the conductor core, however, a small minority of current travels through the insulation to ground.

With regards to a grounded vehicle, if the truck is at a higher potential than the earth, then current will flow to the earth. This is why we pound a ground spike, to give a low resistance path for the majority of current to flow.

If you happen to touch the truck, and earth at the same time, if the truck is grounded properly, some current will flow through you, some will flow through the grounding electrode (spike). Under normal conditions, nearly all will flow through the spike. Some will flow through you, a tiny tiny tiny amount will flow through the vehicles tires, and some will flow through the air.

If the truck is not grounded properly, and you touch it, more current will flow through you, the amount depending on your connection to earth. If you're standing on dry pavement, not much will flow through you. If you're kneeling in wet dirty, more will flow through you.

Under fault conditions, such as a lightning strike, there will be a great deal more current. Further, the voltage present in a lightning strike will break down resistance in insulators. If the vehicle is properly grounded the majority of that current will flow through the spike, some current will flow through the tires, and some will flow through the air. If you happen to be touching any part of the vehicle, or even standing close to the vehicle, some of that current will flow through you to ground.

Proper actions on lightning should also have the operator remove their headset, and wait for the storm to end. A set up should also not be attempted during a lightning storm.

For maximum safety, installation of the ground spike should be the first thing done on set up, or at least prior to operation of any electrical equipment or installation of antennas. If I remember correctly, the first two things done in a "normal" set up of  a3 man LSVW rad det are installation of the ground spike and placement of the drip pan, prior to anything else.

(If you want further reading, http://www.lightningsafety.com/nlsi_pls/vehicle_strike.html as an added bonus if you read the article, you'll get to dispel the myth about rubber tires insulating you during a lightning strike)

Chris,
I understand what you are saying, which is what I am saying as well, except I didn't want to get into the nuts and bolts of it as well.  All things said, touching the groundspike is dangerous, because current will travel through any path. Perhaps I was simplifying things by saying "least resistance" when I should have said "low resistance". Current will travel through any path of sufficently low resistance for the particular voltage of the circuit. Being essentially a bag of water, our happy Sig Op is a path of low resistance. So he will feel the effects of his share of the current based on the diffential of the resistances of him and the primary path.

 

[chrisf]

No, we're not saying the same thing.

Provided SOPs for vehicle set-up and operation are followed, touching the ground spike is no more dangerous than any other part of the vehicle, which in turn is safe under normal conditions when used with proper grounding.

Fault conditions, like lightning, are an entirely different bag of tricks, as discussed above. Lightning will quite happily arc through the air if it feels like it, no touching anything required. This is why we have a whole set of safety SOPs for lightning.

 

[SevenSixTwo]

Had an argument recently about ground spike needing to be grounded. Needless to say they just setup the generator on dry pavement and put the ground spike underneath the tire.

 

[chrisf]

The worst part about this is you can't even rely on Darwinism. It's likely not the twat who put the ground spike under the tire who's going to get shocked.

Further notes on unsafe grounding practices, because I've seen this one done a few times as well, tossing a ground spike into a snow bank, or pounding it into snow will not provide an effective ground either. Snow is an extremely poor conductor of electricity. Spike still needs to be pounded into the earth.