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Author Topic: Copper tape  (Read 629 times)

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Online Lazy-Ferret

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Re: Copper tape
« Reply #15 on: September 29, 2017, 01:22:52 pm »
If it is the product of 12v x 7a = 84w and your thinking that is an awful lot of watts that is worrying , nope
That's exactly how one large, well known DCC supplier used to rate their cable :)

Saying it can carry X Amps is totally meaningless unless you also know the resulting voltage drop.

Andrew

It's not TOTALLY meaningless in the context the reply was made though.

This is a model train forum, and the OP was talking about using it in relation to model trains.

In my post, I not only said I had made a few assumptions based on using it for model trains, but also put a link to the web site, that will give you all the extra information like volt drop etc, should they wish to pursue the mater further.

For the sort of normal train currents, the fact that most run on a very wide voltage range, and very rarely on their full "rated" voltage, then take the relatively short distance runs the copper is liable to be used for on a train layout, most of these extra factors can be ignored.
"Only a man that drives a second-hand car knows how hard it is to drive a bargain!"
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Offline MalcolmAL

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Re: Copper tape
« Reply #16 on: September 29, 2017, 01:33:40 pm »
 :thumbsup: Yep :)
and the OP (me ) made the op because he had never used nor even seen  sticky copper tape, so whilst being fully qualified in electrical, electronics, and telecommunications engineering ( a loooong time ago)  was uncertain if it was just ever-so-thin decorative copper coloured-ish tape or, as it turned out upon receipt, proper reasonably substantial foil :)
We are now entirely happy, all is well.

But still may do a test to destruction (out of scientific curiosity you understand, nothing to do with childhood fireworks making, honest ! )

Offline themadhippy

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Re: Copper tape
« Reply #17 on: September 29, 2017, 01:34:16 pm »
Quote
they perhaps assume that the  resistance of the tape

Quote
by the load impedance
surely that should be tape impedance,an as were using Z instead of  R dont that cos theta thingy come out to play.

Resitivaty of copper at 20c  is 1.6810−8 ,poull that about and you'll end up  with the number of car batteries  needed to melt the stufft
« Last Edit: September 29, 2017, 01:36:39 pm by themadhippy »

Offline MalcolmAL

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Re: Copper tape
« Reply #18 on: September 29, 2017, 01:44:42 pm »
Quote
by the load impedance
surely that should be tape impedance,an as were using Z instead of  R dont that cos theta thingy come out to play.
I thought that might amuse someone :)
The load impedance determines the current flowing and thus the fuse action, assuming the fusible link is resistive (reasonable since it is not coiled) The wattage (of the load)  is determined by that part of the amps that is in phase with the volts ( the theta θ thingie !) which all depends upon the impedance cos θ thingy of the load.
and my coffee is now cold  :laughabovepost:

Edit : ohh look I think I have a proper θ symbol in there, clever browser, can you all see it ?
« Last Edit: September 29, 2017, 02:34:25 pm by MalcolmAL »

Online dannyboy

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Re: Copper tape
« Reply #19 on: September 29, 2017, 07:05:28 pm »
Well, I've just read the entire thread ..................... err .................
can copper tape be used for model railways?  ??? ;)

(My tongue is firmly in cheek  :))
« Last Edit: September 29, 2017, 07:06:29 pm by dannyboy »
David.
I used to be indecisive - now I'm not - I don't think.

Online austinbob

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Re: Copper tape
« Reply #20 on: September 29, 2017, 07:42:16 pm »
Well, I've just read the entire thread ..................... err .................
can copper tape be used for model railways?  ??? ;)

(My tongue is firmly in cheek  :))
I think the answer is yes. Locos don't take much current so not a problem on dc. Probably ok for point motors over a distance of 2 or 3 meters.
If you've got loads of locos on dcc then might be a problem.
But what is copper tape... How wide, how thick?
The ultimate test is... If the tape gets hot then beware. If it doesn't then pour yourself a pint of IPA (beer) and enjoy the trains....
 :beers:
Size matters - especially if you don't have a lot of space - and N gauge is the answer!

Bob Austin

Offline MalcolmAL

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Re: Copper tape
« Reply #21 on: September 29, 2017, 08:20:04 pm »
Well, I've just read the entire thread .....................
(My tongue is firmly in cheek  :))
:laughabovepost:
Brave man GungaDin.
Hope we didnt cause you too many ripples this time ?  ;D

Offline NinOz

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Re: Copper tape
« Reply #22 on: November 27, 2017, 12:28:11 am »
To be called pompous and arrogant - hell of a come down.
I tried so hard to be snobbish and haughty.

Offline MalcolmAL

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Re: Copper tape
« Reply #23 on: November 27, 2017, 02:53:30 am »

Online dannyboy

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Re: Copper tape
« Reply #24 on: November 27, 2017, 02:57:25 am »
Fuse guide:
https://i.imgur.com/TtFotWu.jpg

Somebody somewhere will have probably used some of these at some time.  :)
David.
I used to be indecisive - now I'm not - I don't think.

Offline Zogbert Splod

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Re: Copper tape
« Reply #25 on: November 27, 2017, 05:23:17 am »
Chocolate foil wrappers in the car fusebox...  Ummmmm, a long time back.  :-[ :-[ :-[
"When in trouble, when in doubt, run (trains) in circles..." etc.
There, doesn't that feel better? 
Lovely!

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Offline David Asquith

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Re: Copper tape
« Reply #26 on: November 27, 2017, 08:51:11 am »
Having read the whole thread and not understanding very much at all of it.  A simple reply from a simple person:

I have used it for about seven years with  no problems.  My layout consists of a 9 foot board, a 4 foot board and an 8 foot board in a n shape.  I have 2 lengths of tape running parallel to each other down the centre of each board.  I have recently run 2 trains on each of the up and down concurrently lines using a NCE powercab and the systems coped without problem.  My peco points were powered via a CDU using electrical wire not the copper tape.  I have now moved to Kato points so removed the CDU.

Hope this helps.

Dave

Offline daversmth

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Re: Copper tape
« Reply #27 on: November 27, 2017, 09:35:19 am »
In my view there are two separate issues to consider.

1. The voltage drop along the length of the tape.
2. Risk of fire or tape melting.

So for voltage drop, ohms law says

V=IR

or in English

Voltage drop = current x resistance

The current will be whatever is drawn for your application.
Lets assume 100mA , ie 0.1A for this example.

Resistance = resistivity x  length/area

Resisitivity = 1.7 x 10-8

Area is the width x the thickness of the tape.
Lets assume 5mm wide and .01 mm thick.
Of course you will need to change these values based on your particular tape, I just guessed for an example.

So the resistance of 1m of  the tape will be

1.7x10-8  1 /(5x10-3  x 1x10-5) = 0.34 ohms

Note all dimension units are in metres for the calculation

If you have 100mA in the tape, this would give a voltage drop for 1m of tape of

V = 0.1 x 0.34
= 0.034 volts

Whether that concerns you would depend on your application but I am guessing not.
It means if you stick 12v in one end you would get 11.966v out of the other end.

The value I calculated will scale for your actual data.
So:
2m long tape would be double the value
0.5m long tape would be half the value
2.5mm wide tape would be double the value
10mm wide tape would be half the vaule
0.005mm thick tape would be double the value
0.02mm thick tape would be half the value

2. Fire risk or tape melting

I would hope that the tape would come with a rating, and there are of course many external factors that would effect the safety, for example is the tape buried somewhere or in free space. Free space being better to allow heat dissipation. If they dont give a safe rating, then that may be the reason, as it is dependant on the environment where used.

But to get an idea,

Power dissipated in the tape can be calculated as
Voltage drop  x current

P = V x I

To make things more convenient, we know
V = IR

So power can be expressed as

P = I X I X R

In our example the power dissipated in 1m of tape would be

P = 0.1 x 0.1 x 0.34
= 0.0034 watts

Which is a tiny amount of power to dissipate as heat and should cause no problem.
To put it in context this is " a 3millionth" of the power of a 1kW electric heater.

Of course the figure would need to be scaled for the I and R for your own application.

I would also add that this is for continuous dc current. For a short pulse such as current for a point motor, the current carrying capacity of the tape would be much higher because the heat has time to dissipate between pulses.

I would be grateful if someone could check my calculations as they have been done in a bit of a rush.

Bottom line conclusion is copper tape should be ok for n scale applications as long as you dont go too silly with the amount of current you ask if to carry.



« Last Edit: November 27, 2017, 12:32:56 pm by daversmth »

 

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