high qualtiy lightning rod - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: April 06, 2024, 09:18:45 am
content: They don't build them like they used to. Manufacturers are always making conductors thinner nowadays.https://www.accuweather.com/en/weather-news/a-bolt-of-lightning-strikes-the-statue-of-libertys-torch/1638224

author: tooki
author_rank: Super Contributor
timestamp: April 06, 2024, 10:33:49 am
content: Quote from: coppercone2 on April 06, 2024, 09:18:45 amAnd what’s the evidence for this? Or is this just another of your fever-dream “the olden days were always better” conspiracy theories pulled out of thin air?The physics of lightning haven’t changed, and the thickness of the lightning protection conductors is prescribed by code. That’s NFPA 780 for you in USA. Tables 4.1.1.1.1 and 4.1.1.1.2 on page 780-11 (PDF page 14) of the standard, attached below, give the required conductor cross-sections for both copper and aluminum conductors.

author: Gyro
author_rank: Super Contributor
timestamp: April 06, 2024, 10:51:26 am
content: According to my between the wars 'Wonders of World Engineering' book. The copper shell (approx 3/32" thick) was insulated from the iron frame by Shellac coating and Asbestos strips so that no part was in direct contact, to prevent electrolytic corrosion. Obviously it wouldn't eradicate direct corrosion of the Iron from salt, but it helped it survive for well over 100 years before replacement.Edit: I would assume that most of the lightning discharge current probably passes to ground via the copper shell, it would be difficult to sufficiently insulate a lightning conductor at the top.

author: ebastler
author_rank: Super Contributor
timestamp: April 06, 2024, 03:42:37 pm
content: Quote from: tooki on April 06, 2024, 10:33:49 amI took coppercone's post as a humorous one. The whole Statue of Liberty acting as a lightning rod, with undoubtedly larger cross-section than what you would typically find today (or yesterday, for that matter...)

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2024, 09:01:15 am
content: Quote from: ebastler on April 06, 2024, 03:42:37 pmExactly. I seriously doubt a structure made of iron and copper needs a lightning conductor.

author: jonpaul
author_rank: Super Contributor
timestamp: April 07, 2024, 11:00:57 am
content: In USA nowadays, the wiring, earthing, bonding and rods are well specified in the regulatory, NEC, NFPA, etc.I am sure other locales EU, AU, UK have smilar.I have not encountered anything but thick copper rods, clamps, wiring.Earthing is usueally a number of 0.375" = 8mm 10' long copper rods spaced out in moist earth.Resistance to the earth is specified and measured.Bon ChanceJon

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2024, 11:14:20 am
content: Quote from: Zero999 on April 07, 2024, 09:01:15 amWell, it does need one to bridge the base, since the copper is not in the soil.I also wonder whether the infernal iron structure is grounded separately, since it is insulated from the copper to prevent galvanic corrosion.

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2024, 11:21:34 am
content: Quote from: tooki on April 07, 2024, 11:14:20 amI would have thought there would be some sort of electrical connection to limit the voltage between the two, yet also limit corrosion. Sacrificial anodes connected to earth, or a spark gap, which limits the voltage below 1kV, so it doesn't damage the insulation, when lighting strikes.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2024, 11:30:14 am
content: Quote from: Zero999 on April 07, 2024, 11:21:34 amCould be, I don’t know the details. (Haven’t looked into it. I just know I found mention of them being insulated to prevent corrosion.)

author: shapirus
author_rank: Super Contributor
timestamp: April 07, 2024, 11:41:07 am
content: Quote from: tooki on April 07, 2024, 11:14:20 amI too have always had a feeling that there was a slight hint of something infernal about it...

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2024, 11:55:42 am
content: Quote from: tooki on April 07, 2024, 11:30:14 amAnother thing is there will be a considerable capacitance between the two conductors, so it's possible it will just charge up to a relatively low voltage when struck, then gradually decay, due to the parallel resistance created by the water.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2024, 12:23:52 pm
content: Quote from: shapirus on April 07, 2024, 11:41:07 amHahahaha that autocorrect typo is too good to fix, so I’ll leave it!