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copper pipe conductivity

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copper pipe conductivity

Unread postAuthor: rp181 » Thu Jun 19, 2008 7:09 pm

So, im making a capacitor bank, adn i was wondering if copper pipe has the same conductivity as electronic grade copper. I want to use copper pipe for bus bars, since there are high currents are encountered, skin effect makes high surface area needed, which pipe has, its also cheaper then regular sheet.
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Unread postAuthor: SpudFarm » Thu Jun 19, 2008 7:12 pm

i din't think there is much difference
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Unread postAuthor: rp181 » Thu Jun 19, 2008 7:16 pm

you would be suprised by the difference it makes, especially with more then 10KA. With 8 joules, it vaporizes alu wire, but not copper, and that as 8J, i plan on atleast 5KJ.
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Unread postAuthor: VH_man » Thu Jun 19, 2008 7:17 pm

i think you will do fine with plain old pipe copper.

honestly... electronics grade copper is really the same stuff. although i think the malleable stuff might be SLIGHTLY less resistant
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Unread postAuthor: rp181 » Thu Jun 19, 2008 7:20 pm

Guess ile just try it =)
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Unread postAuthor: pizlo » Thu Jun 19, 2008 7:26 pm

Care to share what the bank is for?
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Unread postAuthor: benstern » Thu Jun 19, 2008 7:27 pm

The difference I would guess is in the additives.
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Unread postAuthor: rp181 » Thu Jun 19, 2008 8:25 pm

Bank will be used for railgun, and 3 smaller banks for multi stage coilgun. Project thread: http://4hv.org/e107_plugins/forum/forum ... hp?47054.0
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Unread postAuthor: THUNDERLORD » Thu Jun 19, 2008 8:57 pm

It may seem like I'm being a jerk; But think about it... Building a 5kilojoule capacitor bank without a volt/ohm meter?

Guess/hope you just don't have the pipe around yet. :roll:

I had the same idea for using an old copper pipe to connect capacitors.
But my meters in a box somewhere. I'll try to dig it out later and check maybe.

Hope you post some pics after you finish it. (And be careful). 8)

BTW reminds me of an idea I had to cut the pipe in two halves lengthwise
And use a copper jacket with an iron-core, maybe with a neo-dymium magnet tip. (the current would pass through the jacket closing the circuit)

The pipe could be seperated into segments also to deactivate one coil and energize the next as the projectile moves.

This way each coil could be activated mechanically rather than electrically.
But there's other ways to do that also.
Friction would probably be an issue also for that design. :roll: 8)
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Unread postAuthor: starman » Thu Jun 19, 2008 9:02 pm

My only issue with copper pipe is that it really isn't designed to interconnect electrically...terminal lugs etc, won't be fitting right off the shelf. It is designed for plumbing uses obviously. Doesn't mean you can't rig some things up, tapping holes etc, but will be some extra effort.

Why not check the power panel section in the electrical dept of Lowes or Home Depot. There are lots of copper buss materials there you could use right out of the box.
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Last edited by starman on Thu Jun 19, 2008 11:05 pm, edited 1 time in total.
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Unread postAuthor: rp181 » Thu Jun 19, 2008 9:07 pm

Yes, i have a multimeter, but its accuracy is +/- 1 ohm (its a cheap meter). I have some copper pipe, but i get the same reading no matter the length of the copper AND i get the same thing for steel.

As for that triggering, i was thinking about using the moving projectile to induce current into a trigger coil to trigger the actual coil. I scrapped it because the intense EM fields from previouse coils would mess that up.

the 4hv thread isnt update, but i plan on using a quad comparator (LM339) and phototransistors with IR LED's. This should be simple and effective, though i will probably have to have it trigger a 555 delay timer.

It just crossoed my mind, but wouldnt a pipe have alot more inductance than a sheet? I dont have a LCR meeter to test, and railguns are supposed to minimize inductance/resistance.
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Unread postAuthor: Fnord » Thu Jun 19, 2008 9:10 pm

You have bus bars for your rails, right? You can probably get away with pipe to hook up your bank, but you'll need something better for rails. Why not just use the same thing for both?

Also, I had to do quite a bit of sanding/filing on my (still unused) bus bar rails, even though they were supposed to be perfectly straight, just a heads-up. (They still have a slight crack between them, but it's so thin it only lets blue-ish wavelength range light through).
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Unread postAuthor: THUNDERLORD » Thu Jun 19, 2008 9:19 pm

rp181 wrote:Yes, i have a multimeter, but its accuracy is +/- 1 ohm...

....the 4hv thread isnt update, but i plan on using a quad comparator (LM339) and phototransistors with IR LED's. This should be simple and effective, though i will probably have to have it trigger a 555 delay timer.


Ah that explains it. Sounds like you may know more about it than myself.

I like the IR and phototransister idea myself.
Except it could become blocked by debris or lubricant maybe.
Been wondering if a shot counter could be constructed for a bbmg using a design similar.

The pipe idea I was reminded of was for a coil-gun.
For some reason I'm more interested in a simple "disc-shooter" now.
Like the one that launches old hard-drive disks or smashes alum. cans. :wink: 8)
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Unread postAuthor: rp181 » Fri Jun 20, 2008 9:26 am

yes, im using 1/8in x 3/4in x 1ft rails, im getting that from mcmaster. Plus, if theres an defects, they send a free replacment =) Im not using that for rails because of two resons:
1)Cost. 3 ft. costs 17$, that gives me 1 set of rails, which i can use the back of.
2) having it 1/8in thick is a compleate waste, as i stated above, no more then 1/16th of the rails will be seeing electricity.

I can post schematic if you want, it uses 4 led/transistor, 2 for triggering, 2 for chronograph.
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Unread postAuthor: Ragnarok » Fri Jun 20, 2008 11:20 am

There shouldn't be any problems with it. The resistance shouldn't be noticeably different from electrical copper, and it's high cross sectional area should be a swaying factor.

Actually, copper pipe is very popular for high power electrics, because in addition to having a low resistance, you can run cooling water through the middle to stop it from overheating, allowing you to put even higher currents through it. :twisted:

With a sufficently hefty water pump, I could force thousands of amps down a piddlingly narrow piece of copper pipe, yet still keep it cool to the touch.
It's fairly common to do so on induction heaters.
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