Replacing springs for Peco points

[Graeme Dunbar]

Graphite conducts electricity and with repeated applications its quite likely that a build up between the point blade & stock rail will occur.   Whilst it may not be enough to affect an analogue controller one may end up with enough graphite on the surface of the sleepers to will give a DCC system a bit of a headache, especially if sparking / arcing and heating occurs this may be enough to melt the plastic parts of the point.

I suspect that will be quite difficult to achieve in practise.

An electronics activity I devised for the local annual STEM festival involved children making their own resistors by drawing on paper with a soft graphite pencil. These were used with a little oscillator/sounder circuit, and with a bit of experimentation it is possible draw rectangles or thick lines to give the notes of a scale.

I've just checked and the best I can achieve with a 6B pencil and some quite absorbent paper is about 2 to 3 kilohms per square. (It does not really matter, but 'per square' is a common way of categorizing the resistance of materials - the longer a resistive material it is the higher the resistance, the fatter, the lower, so for a square it evens out and doesn't matter what size the square is.) I achieved that resistance pressing quite hard and shading in all directions until I thought I was not having much additional effect.

If a small amount of graphite dust settling on sleepers is of concern I might be rather more worried about painting sleepers, especially if a black undercoat is used - carbon black is also conductive and a common pigment. However I doubt it is a concern.

(I had some success making track-circuiting resistors for wheelsets by painting over the insulating bush on wagon wheels but it was a pain to apply the many coats to build up a suitable thickness - surface mount resistors and silver-loaded glue were much simpler.)

If there is a down-side I think it is more likely to be false triggering of track-circuit sensors. That I have seen. When applying graphite directly to rails, some got in the gaps in rails between section blocks (the relatively sharp edges of the rails shaved off bits of graphite and packed the gap). Cleaning out the gaps and filling with a scrap of plastic cured the problem. Any graphite bridging the surface between the rail ends (say about a mm apart) was too thin to be detected.

[B.Meldon]

All that does not help the fact that graphite on the rails reduces adhesion somewhat on grades.
This can be more of an issue with 009 as layouts tend to have more grades than standard gauge layouts.
This was the issue I had when I tried it some years ago now. It took ages to clean it off all the rails and wheels. Never again as far as I am concerned! But I have no doubt that others where all their 009 layouts have no grades will find it very good.

[Graeme Dunbar]

Also, my original suggestion was it may help with conductivity between switch rail and stock rail as opposed to putting it on the rail head. (I do that too, but the layout is level.)

[B.Meldon]

Also, my original suggestion was it may help with conductivity between switch rail and stock rail as opposed to putting it on the rail head. (I do that too, but the layout is level.)

Yes I agree graphite is very good provided all the layouts you intend to run your locos and stock on are flat.
However, it is quite obvious that even a small amount in the point blade gap will enevitably get on the wheels of the locos and stock causing issues on any layouts they run on with grades.

[Julian Evison]

I also put a little bit of graphite in there using a 6B or similar soft pencil (not recommended for DCC users). You need to make sure the blade contacts the stock rail, so have a vey close look at it and improve if necessary.

Why not, Julian?

Graphite conducts electricity and with repeated applications its quite likely that a build up between the point blade & stock rail will occur.   Whilst it may not be enough to affect an analogue controller one may end up with enough graphite on the surface of the sleepers to will give a DCC system a bit of a headache, especially if sparking / arcing and heating occurs this may be enough to melt the plastic parts of the point.

Tom,

Julien has pretty well answered the question. I have read, but can't remember where, of graphite deposits causing sufficient arcing with a DCC system to melt plastics sleepers (because a DCC system always has power to the rails?). I should say immediately that this is only hearsay and I no have personal experience of it (and I note Graeme's observations). However I would hate to advise somebody to do something and then find it caused damage that could have been foreseen.

Julian

[andy1878]

I said it before.

A DCC system should shut down long before there is a risk of melting sleepers.
The supply wiring needs to be able to carry at least the max output current of the controller. If it doesn't allow the tripping current to flow a continuous current could flow, this could do serious damage.

So I'll expand.
A dcc system supplies all the rails all the time [unless switched externally-you may want to isolate a siding or 4]. So it has to provide enough juice to run what ever is on the layout. All decoders comsume some power, so given enough it could overload whilst every thing is stationary.
In order to provide enough power to run train the system may well deliver 5 or more amps. This can do significant damage if allowed to flow across a short. The dcc needs to detect this and shutdown PDQ.
If the wiring is inadequate a current of, say 4.5 amp could flow in a short circuit situation and the dcc system won't trip and the risk of damage occurs.
Graphite could cause a short that could create such a situation.
009 layouts tend not to have significant numbers of locos in action at any one time and we can use ally get away with smaller dcc systems NCE power cab is good for about 2Amp Arduino hosted dcc++ex 1.5 amps. This very much reduces the risk.
Make sure your dcc trips instantly on fault.
A derailment on a turnout can be disastrous if it doesn't.

All of which is nowt to do with change the spring.
Which for the record I remove. So I can have slow acting motion.

I hope it goes without saying that power supply to the dcc also needs to be up to the task. If it's not the dcc could never achieve trip current.

[Graeme Dunbar]

I took a look to see what I could find relating to arcing of rails treated with graphite. I found a few results that appear to concur with this example:

"Less is more in this case

If you've been following the technology revelations around Graphene, microscopic-thin layers of graphite and their wonder properties, then you will understand that more is not better when it comes to applying the graphite. You just want the smallest amount of graphite on the rails - if you can see it, then it's too much. Graphite, when applied in a very thin layer, does wonders for conductivity. Graphite also reduces arcing, which is why it's used in motor brushes as well. By reducing the arcing, that reduces the formation of nickel-silver oxide, which is most of what's in the "black gunk" that builds up on your rails. Applied properly the graphite will almost invisibly do its magic, it won't build up, and you will be amazed at how you no longer need to clean the track as often as you once needed to.

Joe Fugate​
Publisher, Model Railroad Hobbyist magazine"

https://forum.mrhmag.com/post/fighting-dirty-rails-with-graphite-12200279

On a more general note regarding arcing, I found this from the motor manufacturer Maxon relating when to choose motors with precious metal brushes and when choose graphite:

"If your application does not require the rigor of graphite brushes, for example, a blower, precious metal brushes should be the leading choice. This cost efficient solution is typically utilized in designs with continuous operation with lesser current loads. Although this brush selection is more sensitive to induction arcing, maxon motor's DC motors with precious metal brushes feature CLL, capacitor long life, which utilizes an RC filter between commutator segments to suppress brush spark."

https://drive.tech/en/stream-content/precious-metal-vs-graphite-brushes

[B.Meldon]

As I said graphite is good if all the layouts you run your locos and stock on are flat.

But on layouts with grades it is not good at all, and I do known this from experiance.
Even a tiny amount will make the locos slip.

All my layouts have grades so it is useless for me, and took it took me ages to get it all off when I did try it as it is very hard to see once it is on the wheels!

[Hugh Norwood]

I think this thread has drifted rather.....

[andy1878]

I think this thread has drifted rather.....

As your first reply offered, very sensibly, a different solution than the OP was looking for.......

sorry folks but I can not resist:

Hugh started it.