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Graphite Treatment to Rails.


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16 hours ago, Graham Radish said:

 

 

for low voltage applications graphite on the rails will put resistance between the rail and the wheel, which in turn you will be using more power (current) to do the same job as youre adding an extra layer of material of lower conductance

 

 

I hope one day peco will come up with better track thats a nice shiny silver colour instead of light brown, maybe some sort of copper formulation that is silver in colour.

Increasing the resistance between the rail and wheel, will use more power (current) to do the same job?

I think something is wrong with your interpretation of Ohms Law. Increasing the resistance will reduce the amount of current that flows.

 

As I said much earlier, in theory graphite shouldn't work for track/wheel adhesion reasons as it is slippery, but it does. Graphite is also a conductor, but not the best one (which I suspect, is the point you were trying to make), gold I believe is far superior, but good reasons for not using chunks of it for brushes!

 

Nickel Silver (NS) is not a bad conductor for rail, better than brass or steel, the usual alternatives, as the oxide conducts. As you point out, it's weakness for model railways is the colour. Perhaps it is possible to come up with a modified material that looks like polished steel but isn't. I'm no scientist to know if such a product would look better, but work no worse than NS?

 

Would the market tolerate a product that cost say 25% more than Nickel Silver? Somehow I don't think so.

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I was going to have a lovely old "someone is wrong on the internet" rants before I read this comment more carefully:

 

27 minutes ago, kevinlms said:

Nickel Silver (NS) is not a bad conductor for rail, better than brass or steel, the usual alternatives, as the oxide conducts.

 

This spirit of this statement is very much a truth - because of the properties of the oxide, it makes NS a good compromise material for rails.

 

Just as a point-of-fact in addition; NS itself is a relatively poor conduction material, hence the generally accepted advice that a set of copper bus wires under the baseboard helping the angry pixies get to where they need to be much more easily is "a good idea".

 

It's alway about cost for products like this.  I think from a solving an engineering problem point of view, you could use a zinc-chromate (look up chromate conversion coating) on steel to get a nice bright conductive material with fair corrosion resistance...  but the cost and ongoing maintenance of the processes (steel needs to be zinc plated first) probably don't really stand up to using NS as the base material.  We could suggest that an aluminium-extruded rail of a decent hard grade of aluminium might get us the colour, corrosion resistance, and conductivity we desire if correctly post-processed, but I dread to think the cost, and we have to suspect that even a robust grade of aluminium will be a touch too soft to combat accidental damage from a clumsy cack-handed fool like me.

 

As far as on-topic discussion goes, I'm on the 'graphite is good' bandwagon.  (I think some of my comments on the topic have been quoted in this thread.)

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59 minutes ago, FoxUnpopuli said:

 

 

Just as a point-of-fact in addition; NS itself is a relatively poor conduction material, hence the generally accepted advice that a set of copper bus wires under the baseboard helping the angry pixies get to where they need to be much more easily is "a good idea".

 

 

I was always under the impression, that the purpose of having a set of copper bus wires underneath, was to reduce the losses at rail joiners and the like, because that is where corrosion, dirt, dust, paint and oxides get in (all definitely non conducting), thus causing poor conduction. Not because of the nickel silver rail itself.

 

In 4mm scale the rail section isn't exactly small, indeed for the larger scales, the rails are usually bigger in cross sectional area, which is perfect, because generally speaking, larger models require more current. I say generally, because it depends SIGNIFICANTLY on the actual motor design, quality and the drive train.

 

I've yet to notice any model train get progressively slower as it progresses along a single pair of rails. On a long run over several lengths of rail, even in an oval, without any alternative path most certainly. But I don't believe that to be the fault of the rail, but other factors as per above.

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1 hour ago, kevinlms said:

I was always under the impression, that the purpose of having a set of copper bus wires underneath, was to reduce the losses at rail joiners and the like, because that is where corrosion, dirt, dust, paint and oxides get in (all definitely non conducting), thus causing poor conduction. Not because of the nickel silver rail itself.

 

I agree with you - but it is a numbers game.  Without resorting to units, the resistivity of NS is about 28, the relative resistivity of copper is 1.7.  If you jumper all your fishplates wih soldered copper, you'd have a well conducting run of NS, but if the layout only has a single feed, you'll have much more voltage drop at the extremes than if you added a couple of extra copper wired feeds.  Practically, it only takes a couple of feeds to assist a small layout beyond the point you can recognise a steady drop off of speed due to these resistances.  As soon as you've put in a couple of section feeds in for DC 'cab control', or even just isolating sidings &c., you've fixed a problem you never knew you had.

 

Bear in mind if you use DCC, then you won't see an issue with voltage drops at all (in theory) as the voltages fed to the motors are locally calculated by the electronics in the decoder.  As long as the DCC feed voltage is high enough to begin, you should never see a variance in your loco speed.

 

I do remember from more than 30 years back that locos on my codged and bodged 4ftx7ft roundy-roundy (with its rusty steel* Hornby settrack, plastic power clips and probably filthy wheels and pickups) would perform noticably better close to the power feed than directly opposite.  While I've witnessed this directly and you state you have not, I think this goes more to proving your point than mine!   :)

 

I'm designing a OO garden layout which may be in the order of 80 metres in extremis, so I've been thinking about these things as they will make a difference for me.  Then again, with DCC, as long as there is some signal,   Almost certainly, YMMV (Your Meterage May Vary.  :D)

 

 

 * For info, the resistivity of mild/carbon steel compared to the other materials above is in the 7-10 range.

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6 minutes ago, FoxUnpopuli said:

 

  While I've witnessed this directly and you state you have not, I think this goes more to proving your point than mine!   :)

 

 

No, we're talking about different things, as I have seen exactly as you described with the distance from the feed. But that is poor conductivity at the joiners, not the rail.

 

What I meant and perhaps wasn't clear, if I take a length of track (for discussion a 3ft length of Peco's finest), then you WILL NOT get any speed reduction within that rail length). The resistance of that rail isn't significant enough to have any voltage drop. If I took 10 lengths of brand new Peco's finest and joined them end to end, using brand new and tight rail joiners, I still doubt that you would be able to measure any significant voltage drop, assuming fed from one end.

However, if you left those sections of track out in the weather for a year, almost certainly your results would be entirely different and as the train went down (the cleaned on top only) track, it would probably progressively get slower or perhaps stop, as it went over the joins (at one join only, nothing beyond).

That would demonstrate that the joiners are the issue and NOT the rails.

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39 minutes ago, FoxUnpopuli said:

* For info, the resistivity of mild/carbon steel compared to the other materials above is in the 7-10 range.

And the figure for graphite please?

 

Andi

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5 hours ago, kevinlms said:

Increasing the resistance between the rail and wheel, will use more power (current) to do the same job?

I think something is wrong with your interpretation of Ohms Law. Increasing the resistance will reduce the amount of current that flows.

 

 

This is exactly what im trying to say, the higher the resistance the more current flow needs to be to run the motor at the same speed, just like using under spec track wire, it does indeed reduce the current flow thats why you will draw more power, i already did this experiment in the late 80s, my flying scotsman without graphite used to draw 0.4 amps, with graphite on the rails it used to draw 0.58 amps, modern nickelsilver track is far superior to the old steel stuff its just the wrong colour.

 

example: putting a 470ohm resistor on an LED vs putting a 4.7k resistor on an led, to make the led with a 4.7k resistor the same brightness as the 470ohm fitted one you need to crank up the power, this is exactly what graphite is doing, its putting a layer of resistance on the track, the path of least resistance always wins.

 

Resistors themselves are made from carbon thats their whole point, to reduce current.

 

electrical contact cleaners boost conductivity therefore simple logic says the loco will run much better and with less power needed, this helps the electron flow and doest hurt it. deoxit will also clean and disperse carbons as the train runs. you dont want any loose particles on the track at all, only a good electrical cleaning fluid once a week. a drop of this stuff on the pickups once a month will increase their lifespan by a very large amount as theres less friction and more conductivity.

 

In the days of steel track carbon was the enemy, it built up very quickly and ruined pickups

 

carbons can wear down and clog certain metals, thats how they do damage to petrol engines.

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@kevinlms One length of flexi, I agree.  Now ten lengths of flexi - a little over 9 metres -  would have significant resistance (a little over 2 ohms for the 18m of rail concerned) in comparison to motor windings (which I wouldn't like to guess at but should be roughly similar).  I'd lay odds that you would indeed notice the slowing of the loco towards the other end of the straight run.  However, this is now a bar discussion only proven by experiementation.  (I do agree with you about the corrosion, however...  but that's actually what the purpose of the thread is, combatting the corrosion layer with nowt but a pencil!)

 

@Graham Radish Well... the layer of graphite is inconsequential as far as resistance is concerned, it's extremely thin.  It's purpose here, and why it works as a concept practically, is that it's being used as an anti-corrosion layer.  The NS rail corrodes at a far lower rate, and the graphite doesn't really transfer as there's so little of it, filling all the microscopic cracks and pores in the surface of the rail.  For a relatively small loss in traction, you remove the need to continually clean corrosion off your track and wheels.  It's a trade-off many people make, and it works just fine.

 

You speak of carbon deposits and carbon film resistors, they are both different material forms of carbon again - apples and oranges. We could diamond coat the track, leving it lovely and shiny, and while the wear resistance would be stellar, it wouldn't really need to be as diamond is a phenomenally good insulator - nothing would be going anywhere.

 

Since you ask, graphite in the same units is around 800, semiconductor carbon about 3500...  and diamond is ... somewhere between 10^13 and 10^20.  Lots.

 

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My rather old copy of Fowler's Electrical Engineer's Pocket Book contains a useful table of  relative conductvities, using Silver (Annealed) as the reference, the conductivity of which is assigned a value of 100.

 

German Silver (the old name for Nickel Silver) comes in at 4.89, and Graphite at a measly 0.062.

 

Out of interest, hard carbon as used in arc lamps (which dates the book a bit) is even worse at 0.019.

 

All of which might suggest that Nickel Silver and Graphite are rubbish as conductors and should never be used as such, but both have their places. NS where corrosion resistance, certain mechanical properties, and easy soldering are required (e.g. model railway rails), and graphite as a way of helping to reduce "micro-arcing" on a rolling contact surface (which brings us to model train wheel/rail interfaces).

 

And, various grades of hard(ish) carbon, often 'doped' with copper and other materials, are of course used as the brushes in rotating machines, and as sliding contacts for some purposes.

 

In short, simply talking about resistivity/conductivity in this context is a red-herring - materials are used as conductors or resistors on a "horses for courses" basis according to the application.

 

(For anyone wishing to back calculate absolute resistivities from the relative conductivities, the resistivity of  annealed silver at 0 degrees C is 1.468 Microhms per cubic centimetre - sorry about the ancient units!)

 

My understanding is that the graphite performs its function of reducing micro-arcing (which is what causes carbonisation of dust , specks of oil etc, creating high-resistance muck), by filling pores and scratches in the surface, thereby improving contact and reducing the number of tiny breaks in contact (it is breaks in contact that cause arcs).

 

As a by-the-way, when designing "real" electrical circuits, a great deal of effort goes into avoiding rolling contact, because it is always a pig to maintain that contact in good order - electrical engineers design for sliding (often what is called 'wiping') contact, because that helps to break through any surface contamination, so model train wheels are on to a loser from the outset. Which might be part of why I'm instinctively drawn to three-rail systems using sliding contact!

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1 hour ago, Nearholmer said:

My rather old copy of Fowler's Electrical Engineer's Pocket Book contains a useful table of  relative conductvities, using Silver (Annealed) as the reference, the conductivity of which is assigned a value of 100.

 

German Silver (the old name for Nickel Silver) comes in at 4.89, and Graphite at a measly 0.062.

 

Out of interest, hard carbon as used in arc lamps (which dates the book a bit) is even worse at 0.019.

 

All of which might suggest that Nickel Silver and Graphite are rubbish as conductors and should never be used as such, but both have their places. NS where corrosion resistance, certain mechanical properties, and easy soldering are required (e.g. model railway rails), and graphite as a way of helping to reduce "micro-arcing" on a rolling contact surface (which brings us to model train wheel/rail interfaces).

 

And, various grades of hard(ish) carbon, often 'doped' with copper and other materials, are of course used as the brushes in rotating machines, and as sliding contacts for some purposes.

 

In short, simply talking about resistivity/conductivity in this context is a red-herring - materials are used as conductors or resistors on a "horses for courses" basis according to the application.

 

(For anyone wishing to back calculate absolute resistivities from the relative conductivities, the resistivity of  annealed silver at 0 degrees C is 1.468 Microhms per cubic centimetre - sorry about the ancient units!)

 

My understanding is that the graphite performs its function of reducing micro-arcing (which is what causes carbonisation of dust , specks of oil etc, creating high-resistance muck), by filling pores and scratches in the surface, thereby improving contact and reducing the number of tiny breaks in contact (it is breaks in contact that cause arcs).

 

As a by-the-way, when designing "real" electrical circuits, a great deal of effort goes into avoiding rolling contact, because it is always a pig to maintain that contact in good order - electrical engineers design for sliding (often what is called 'wiping') contact, because that helps to break through any surface contamination, so model train wheels are on to a loser from the outset. Which might be part of why I'm instinctively drawn to three-rail systems using sliding contact!

Yup but years ago we managed with steel track, and steel is a much lower conductor than modern peco track, but this was before DCC became mainstream, everything was DC then and no one cared about losing power to the trains. most people back then ran their trains at stupid high speeds. i mean does modern track even acquire carbon buildup? the old steel track was horrid for this simply because guess what, yet again its Carbon steel.

 

I think silver would be the ultimate thing to use for track and provide the correct colour to the rails but prices would be steep and this hobby is expensive enough as it is especially when you have certain model shops charging 5 quid for a 2cm piece of plastic.

 

Silver is the king of metals when it comes to high frequencies, therefore would be absolutely ideal, its for this reason silver wires are used for tweeters in loudspeakers and copper for bass, ideally good quality track feeder cable should be silver not copper, copper suffers greater power losses over distance if i remember right, in turn you need more current.

 

No matter what type of carbon it is it all acts as a resistor to electricity and this is never a good thing with model railway track, peco have designed the track the way it is for a purpose and they spent years doing it, its rustproof has better MUCH better electrical stability than steel and is hell of a lot easier to work with, but as i say its the wrong colour! this is very noticeable in OO gauge track and upwards, on garden scale track it looks absolutely horrid. but steel track outdoors is a bad idea on a whole different level, yes real trains run on steel but obviously on a whole different scale and quality and real trains dont have a habit of cutting out when they hit dirt on the track.

carbon deposits can attract dirt big time.

 

Keeping the track clean of as many contaminants as possible is the ideal scenario adding carbon based graphite to me is bad idea, having a high possibility of reacting with the locos pickups is one thing, graphite however is an excellent heat transfer solution, i use graphite pads instead of thermal paste in my computers for years even in my new ryzen 2700x pc. all this said a good metal polish like PEEK will shine that track up a treat in turn boosting performance providing the tracks laid properly. peco designed the track to keep carbons away not add them.

 

Theres a factory just past stoke on trent that manufactures graphite resistors, these are for precision, right down to 0.01 ohm increments for electrical distribution boards etc... where an off the shelf resistor is not good enough or have the wattage rating.

 

Put your multimeter across a builders pencil, it will measure anywhere from 6 to 14 ohms, thats borderline semiconductor territory you may as well paint your track with superglue.

 

Peco silvernickel is top notch for stopping corrosion as you say, 100% agree there certainly are different applications for different materials, try putting a silver kill coil in a PC that has a nickel waterblock and watch what happens, silver is a poison therefore ideal for killing bacteria, however, it will also totally destroy nickel when used with water and corrode it in a matter of weeks. Adding dissimilar metals and using a water based cleaner has a high possibility of doing damage.

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1 hour ago, Nearholmer said:

Which might be part of why I'm instinctively drawn to three-rail systems using sliding contact!

Overhead wires would be a good solution... ;)

Oh and the real pan head contacts are made of...... 

 

wait for it...

 

...

 

Carbon!

 

 

Andi

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I am amused being told that the Graphite doesn't (or rather cannot) work.. but V=IR ( or V/R =I) and some of the statements made don't make any sense when you look at the  resistance "measurements" used

 

We used to have steel rails.. they went rusty, they were a real so and so keeping clean.. no one has mentioned the phosphour bronze  SMP rail (so was in effect "self coloured" rail). The phospour bronze should have been ok but it  never seemed to work as well as the Nickel Silver variety.

 

The application of graphite works. I have used it and seen it used on other model railways. It doesn't affect traction that much (indeed on some locos it seems to have improved it)..It is acting as a "filler" to get rid of the micro cracks on the rails allowing the wheels to be in constant contact with the rails.. hence reducing arcing. 

 

So despite the calculations being used it is not the resistance changes which help - it is the "lubrication" properties of the graphite..

 

If you don't like the idea don't stop others trying it..but , if it doesn't work for you look at other problems which may giving you a problem ..such as incorrectly fitted  pick ups, dirt on wheels, out of square chassis etc...

 

Baz

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To each their own init, for me the negative effects outweigh the positive, all in all a waste of time. this is trying to solve a problem that doesnt exist.

sorry but im taking no chances with thousands worth of locos

 

oh i never said graphite wont work, what i DID say is its pointless and possibly can cause damage, and it WILL attract dirt more, its giving grime a nice home to live.

and do these laws of physics mention possible dissimilar metals damage, crud buildup and the fact that graphite is one of the poorest materials as a low voltage conductor?

 

I can see what people are saying but in reality its the dumbest idea ever

Edited by Graham Radish
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23 minutes ago, Dagworth said:

Overhead wires would be a good solution... ;)

Oh and the real pan head contacts are made of...... 

 

wait for it...

 

...

 

Carbon!

 

 

Andi

What you mean the 20KV overhead wires yea obviously, carbon handles heat very well and model trains are 15v 0.5amp not 20,000v 20amp

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I'm another user of graphite. I have a small H0e layout which generally runs very well, but two locos (out of 7) had a tendency to stick and I'd spent a considerable amount of time on them for little improvement. After using graphite on the rails they now run as reliably as the rest.

I find the argument about extra power usage rather amusing, were talking 6 watts total ( assuming 0.5a @ 12v) not megawatts.

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On 08/08/2020 at 09:44, jcm@gwr said:

How many years did scientists claim that, according to the size of their

wings and the weight of their bodies, it was impossible for bumble bees

to be able to fly!

 

Approximately zero years: https://www.snopes.com/fact-check/bumblebees-cant-fly/

 

18 hours ago, Oldddudders said:

I am reminded of the pasta chef. Every scientist on the planet will tell you that oil and water cannot mix, the former simply sitting on the latter.

 

Nonsense: https://en.wikipedia.org/wiki/Emulsion, and specifically https://en.wikipedia.org/wiki/Emulsion#In_food

 

(Oh, and by no means every chef on the planet adds oil to the water when cooking pasta.  In fact it's generally regarded as unnecessary.  For example: https://www.nigella.com/ask/oil-for-pasta-water.)

 

None of which means that graphite isn't effective at improving the performance of model trains.  But regurgitating pseudo-scientific myths isn't a particularly effective way to proving that it is.

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18 hours ago, kevinlms said:

Nickel Silver (NS) is not a bad conductor for rail, better than brass or steel, the usual alternatives, as the oxide conducts. As you point out, it's weakness for model railways is the colour. Perhaps it is possible to come up with a modified material that looks like polished steel but isn't. I'm no scientist to know if such a product would look better, but work no worse than NS?

 

 

 

C&L have already done this - it's their "HiNi" range of NS rail, that looks a lot more like steel than ordinary NS does.

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Strangely enough once you use the graphite cleaning loco wheels and track becomes a far less regular requirement.

 

It doesn't attract crud (less arcing??) .

 

But it isn't about resistance.. it is about another effect.. and for that we need a chemist or metallurgist...

 

Baz

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1 hour ago, Barry O said:

But it isn't about resistance.. it is about another effect.. and for that we need a chemist or metallurgist...

You mean those giving us chapter and verse so far aren't fully qualified to do so? I am shocked!

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10 hours ago, Graham Radish said:

To each their own init, for me the negative effects outweigh the positive, all in all a waste of time. this is trying to solve a problem that doesnt exist.

sorry but im taking no chances with thousands worth of locos

 

oh i never said graphite wont work, what i DID say is its pointless and possibly can cause damage, and it WILL attract dirt more, its giving grime a nice home to live.

and do these laws of physics mention possible dissimilar metals damage, crud buildup and the fact that graphite is one of the poorest materials as a low voltage conductor?

 

I can see what people are saying but in reality its the dumbest idea ever

Have you ever actually tried it? Your posts are full of theory but I've seen no evidence of any practical experience.

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11 minutes ago, Michael Edge said:

Have you ever actually tried it? Your posts are full of theory but I've seen no evidence of any practical experience.

I think he's just a troll, Mike. You're all wasting your time with this guy.

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2 hours ago, Oldddudders said:

You mean those giving us chapter and verse so far aren't fully qualified to do so? I am shocked!

As a control systems engineer I don't count myself as understanding metallurgy but from my electrical background I think I can hold my own on the electrickery side of things..:D

 

Baz

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