[geeks] Whee! Lightning strikes, AGAIN!

[wa2egp at att.net]

>  From what I have read, they are very sure.

Depends on where you read and who "they" are....unfortunately.

> Tests with and without the systems on both existing and purpose built  
> structures show they work.  The Space Shuttle was damaged many times  
> until they started using a lightning rod.

Citation?

> >> Regarding sharp points.  New research indicates that round or blunt
> >> points produce better intercept performance, and in the US all new
> >> lightning rods are round or blunt.
> >
> > Gee, Maybe the sharp points dissipate the charge.
> 
> So do the blunt points, but that isn't why they protect against  
> lighting.

Not as well.  You need to create enough field strength to cause the air to ionize.  A point will create a larger field at the point than a blunt tip for a certain amount of charge.

> None of them can discharge enough to work as you suggested.  What it  
> does do is ionize the local are and create a field above that helps  
> intercept strikes to bring them to a controlled ground.

Discharge enough could be the problem.  Maybe that's why the devices I see have sharp points but also have a decent sized conductor to ground in case they don't dissipate the charge (enough).

> You were saying that they bled off all the charge so the strikes would  
> not happen, and no one has been able to do that.  There is no way to  
> prevent strikes, at least not with any knowledge or technology we  
> currently have.

In one posting I suggested they work like an auto theft deterrent device that makes stealing another car easier rather than making you car theft proof.

> Tall objects that create dissipation over wide areas do lower the  
> amount of power in a storm, but even millions of trees have never been  
> able to fully dissipate one.

I wasn't talking about the power of a storm.  I was talking about a single object.
 
> > I read where he did not connect the wire on his first one to ground  
> > but had it
> > dangling in his chimney (I guess so he could do other experiments)  
> > and touched
> > it when a storm was nearing.
> > I guess after he picked himself up, he decided to connect it to  
> > ground. :-]
> 
> Who knows, I'm not sure we have the precise details.

I know the kite thing is accurate (possibly that story too).  I was trying to solder coax to a 75 mtr dipole that I was constructing (ends of the dipole already in the trees) before a thunder storm hit the area.  Couldn't understand why my hands were shaking and tingling whenever I held the antenna.  When I realized what was happening, I hauled up the antenna (minus coax) and went inside. :-]

> Google for NASA with related topics.  They tried to make them work and  
> were never able to.

I will.  Hope it's better than their space shuttle design. :-]

> You can also easily find research projects for several purpose built  
> lightning shelters, and dissipation systems have never worked.

Well, not viewing the articles yet, I could hazard a guess that there might have been a flaw in the design.

> Lightning rods work quite well, as do faraday cages, dielectric  
> structures, steel exteriors (*), surge suppression systems, and good  
> grounding systems.
> 
> * -> at least one shelter's outside is 1/4" steel, which of course is  
> rather impractical for widespread use, but one of the projects is  
> struck almost continuously as part of research, so it needs the  
> protection.

> Or you maybe can't see the grounding.

There were some posts where there was no mention of grounding or implied there was no grounding. 

> An ungrounded rod (or anything that creates a field and ionizes the  
> air) is dangerous.

A conductor would allow charge to flow easily while a nonconductor wouldn't so a nonconductor could allow a charge to build up in spots.  Not a good thing.
 
> >>> If the frame takes the lightning strike, then why use lightning
> >>> rods at all?
> >>
> >> To intercept the strike and bring it to a controlled ground.

Through the metal frame of the building?  That can make a good ground if it actually connects to earth which happens in many skyscrapers.

> A metal frame and roof has nothing to do with it.  Metal, wood, stone,  
> plastic... you still need a good grounding system or the strike will  
> take a path you don't want it to.

Many skyscrapers use the metal I-beam frame of the building as part of the ground system to transfer charge to ground.

> >> I'm sure if you ask someone who knows, you'll find they are grounded,
> >> they are lightning rods.
> >
> > Find someone who knows.  Hmmmmm.  IIRC they are grounded and pointed  
> > tips.
> 
> Then why did you say they were dissipators?
> 
> If they are grounded with pointed tips, they are old lightning rods.    
> New ones are round or blunted.

IIRC one post stated that dissipators were blunt.

> A dissipator has already been tested there: it was the people on the  
> platform.  Worked really good huh?

You're a sick man. :-]

> If the place had been properly grounded with a preferential strike  
> point, they'd be alive most likely.

My point was to see if a sharp point rod would have reduced strikes.  Or blunt ones for that matter.  The beginning of this whole thread was a statement (not my me) that lightning rods attracted lightning.  I disagreed.  I gave my reason (right or wrong) why I disagreed.  So far, I don't remember anyone offering "proof" they increase strikes, just that they don't reduce strikes.  I think we all went in different directions.


Bob