Nickel plating - how to do it, how effective is it?

[peteski]

I gave up on the black nickel entirely.  I did some poking around on the internet and found a plating forum somewhere (yes, there actually is such a thing).  A fellow who was a professional plater for years and is now retired wrote some posts in there about black nickel, and explained that:
1. It is really just nickel plating with some other metal added to it so that a black oxide rapidly forms on the surface. 
2. The black is not durable because it is just an oxide and will scratch off.

Interesting. Sounds like the black nickel is nothing like the dark metallic plating Kato uses on their metal wheels.  I still wonder what they use.

My contact is only through the axles/bearings/frame.  I am not using wipers.


My 2 pickup axles have springs in their bearings as I showed with my last installment.  That is crucial.  They need to be able
to rock and roll a little over real-world track and keep those drivers in solid contact with the rail or it would stall all over the place.

Wipers would accomplish the same thing if they were placed on the tops of the wheels.  They would keep the wheels down in solid contact with the rail.  In fact, I'm sure they would work a lot better because there wouldn't be the rotating contact
point in the bearing, which is good but not perfect.  I bet if I had wipers pressing down on the tops of the drivers,
the engine would crawl.  But I really do NOT want wipers in this thing.

Max,  unless the bearings have some large play in them and the suspension springs are so stiff that they keep the bearings at the bottom end of their travels, I don't see how pickup wipers on the top of the drivers woudl improve the contact with the rails.  The weight of the loco pressing down (through the springs) on the bearings which then are always pressing down on the driver axles, which then press tightly against the rail, already give you maximum contact with the rails.


As far as wipers go, I've seen 3 types:  ones contacting the back of the wheel, ones contacting the tread and the ones contacting the tip of the flange.

I don't like pickup wipers. They all add friction to the mechanism and they all will wear out (since they constantly rub metal against metal without much lubrication.  The amount of rotational resistance they add can vary greatly depending on the type of wiper, its contact area and how much pressure the wiper exerts against the wheel.  But too little pressure and the contact is not reliable.

It seems to me that the wipers with least amount of rotational resistance are the ones which rub the back of the wheel, as close to the wheel center as possible.

I think your model will do just fine in its current configuration.

[mmagliaro]

Generally, the springs in my bearings are very light.  Under normal circumstances, with the engine sitting on level track,
the springs are completely pushed up, that is, completely recessed, and the frame is sitting directly on the bearings,
which is what I want.  If you rock the engine a little bit, however, you can see the spring appear on top of the bearing,
and the wheel stays on the rail.  And that's the whole idea.

Now, why do I say that a wiper on top of the rail would work better?  It's because of the less-than-perfect track of the real world.
When the engine is sitting solidly on all 4 wheels and bearings, sure, everything is great. 

But when it isn't, here's what happens.

In my spring-bearing scheme, the current has to flow from the axle, to the bearing, then through the little spring, to the frame.
There are 3 contact points in the path. (axle/bearing, bearing/spring, spring/frame)  During lucky moments when sides of the bearing are touching the frame, we can forget the spring, so we have two points of contact (axle/bearing and bearing/frame)

With a wiper directly on top of the wheel, the current flows from the wheel rim to the wiper, and that's it.  There is only one contact
point.  Ain't nothin' more reliable than that, as long as the wheel and wiper are clean and the wiper is adjusted right.

I agree with you.  I don't like wipers either.  They bend, they get dirty, they wear, and they put drag on the wheel. 
That's why I'm not using them.  But when they are clean and adjusted, they do provide perfect contact (until they become anything
less than perfectly adjusted, that is).

[peteski]

Now I see what you mean.  But most of the time the bearing will be in direct contact with the metal frame which electrically parallels the spring, reducing number of contact points by 1.  But I do understand that if you used pickup wipers then the number of contact points would be decreased and reliability increased.

[narrowminded]

Thanks, narrow.  I have enjoyed your well-thought advice on my project, and it is helpful, believe me.

I gave up on the black nickel entirely.  I did some poking around on the internet and found a plating forum somewhere (yes, there actually is such a thing).  A fellow who was a professional plater for years and is now retired wrote some posts in there about black nickel, and explained that:
1. It is really just nickel plating with some other metal added to it so that a black oxide rapidly forms on the surface. 
2. The black is not durable because it is just an oxide and will scratch off.

That's basically the information I got from my plating guy as well as research.  What I have entertained and one of my questions and/ or tests may be to use the black nickel for the cosmetics and MAYBE as the base under some strategically placed gold plating.  Gold plate straight on to brass is not considered good as the brass under the thin gold plate makes a poor base.  It will plate OK but is not durable over time.  What is recommended is nickel base and then the gold but then again, nickel alone may be sufficient if it holds up adequately in atmosphere without oxidizing enough to be troublesome.  (The only metal that is KNOWN to be good at extremely low current reliable contact is gold.)  But then, would the properties of the black nickel be sufficient as a base under the gold?  I just don't know and haven't wanted to pester my plating guy until I'm ready with parts and actual test pieces.  In our original conversations I recall asking about the black nickel but I recall him not being sure about it as a gold base but when the time comes, would look into it.  He was VERY comfortable with electroless nickel as it gets in all of the nooks and crannys and in a uniform finish.  I've also had good direct experience with that over brass in my past life.  Great for axle holes, compensation bore, internal corners, and the like.  Then, could I maybe black nickel OVER the electroless nickel or as you just found, maybe dilute the black nickel.  I just don't want bright silver as my chassis base and don't want the ruddy look of tarnished brass, either. I don't think I want black oxide either as it is not so durable and might cause fits with conductivity.  As far as other wheel blackening methods, I don't know this for sure but on a few of my test chassis I used Fox Valley wheels and I suspect that they were black nickel.  Maybe a bit dilute as you learned?  I never actually researched that or even asked.  Maybe that's what I should do when I get off here. They did hold up OK but the treads wore through somewhere in the thousands of hours that they ran and with often cleaning and wiping over time the broader surface finish did seem to wear away some, getting slightly lighter in color but still cosmetically nice.  It was what I would consider to be not durable in the broader world of things durable but still plenty adequate for this service.  I seriously doubt that it's black chrome as I don't believe that's a good conductor.

That is what I found with the Caswell Black Nickel.  So I gave up on that idea.  Adjusting the current (I used my own power supply instead of their wall wart), and putting a longer length of cloth on the wand did not help.  My plating wasn't burning after all.
That black nickel stuff just goes on... well,  BLACK.

How about that!

I tried plating it over a layer of copper, which did not help at all.

Not only was it not durable, but the conductivity was poor - in the neighborhood of 15-30 ohms just touching meter probles
to the rim of the wheel.

As much copper as is in the brass it doesn't surprise me that it had no benefit.

Then I plated with their straight nickel solution.  The difference was night-and-day.  I got a beautiful, hard, silver finish (and zero ohms on the meter).  But I didn't exactly want "bright silver" on my wheels (even though that's the way engines often
come commercially).
So on a whim, I added a "splash" of the black nickel solution to the plain nickel and tried it.  I got a dark weathered-looking
nickel (not unlike Neolube, actually).  The resistance was still zero ohms.

After some experimentation, I decided on a 10:1 mix (10 nickel, 1 black nickel).   (4:1 was still a little too gray for my taste).
That's what I ended up plating with.

That would be expected except for the part about the black nickel.  I wouldn't have expected so much trouble with that but as you arrived at with logical experimentation, a more dilute mixture works well.  That also makes logical sense and may be exactly what some others have done.  I wouldn't want jet black, just that darker, translucent gray.  What will be interesting is how it acts after it has had a chance to oxidize a little.  I wish I knew that but can't help... yet.

My contact is only through the axles/bearings/frame.  I am not using wipers.

The behavior now is this.  I can run it at about 10 mph around the layout, and it runs pretty good.  But when I patch a Kato tender behind it, the performance is absolutely spectacular.  It can crawl crawl crawl all day long, nice and steady without stalling.
It could never do that just on the engine driver pickups alone.  So in spite of all my best efforts, the pickup is still nowhere near
as good as what I can get from a tender.  But I will have a tender, so that's a good thing.
My 2 pickup axles have springs in their bearings as I showed with my last installment.  That is crucial.  They need to be able
to rock and roll a little over real-world track and keep those drivers in solid contact with the rail or it would stall all over the place.

Wipers would accomplish the same thing if they were placed on the tops of the wheels.  They would keep the wheels down in solid contact with the rail.  In fact, I'm sure they would work a lot better because there wouldn't be the rotating contact
point in the bearing, which is good but not perfect.  I bet if I had wipers pressing down on the tops of the drivers,
the engine would crawl.  But I really do NOT want wipers in this thing.

Nice!  I would accept the tender as a viable part of the assembly and call that done.  A quick anecdote that's EXACTLY the same... but different (quote from an Asian professor I once had).  My first foray back into this hobby was a train under a glass top table.  A purchased train set from Bachmann with a Northern.  I did not know nor expect this things notoriously miserable pickup problems.  Afterall, it was an old standard, right?!  Well, after much weeping and gnashing of teeth, I finally figured out the tender pickup idea, fashioned a few axle wipers from brass sheet, hardwired them to the loco chassis and have never had any more trouble with it.  It's a three pole, no creep, noisy geared, miserable model but it is the one we leave running all day every day through the holiday season and it doesn't falter.  It just won't quit.  I oil it about once a month and replaced the motor once.  Also replaced the pilot and haven't replaced the bell, tender stirrups, and who knows what else that has been shredded.  (Kids can be hard on a loco and it has seen a few tumbles to the hard floor.)  It serves a purpose and serves it well... with tender wipers.

Finally, my weight is now at 46 grams.  That is huge considering that I started with the brass chassis that you all saw in the last installment at about 20 grams.  I have loaded it up with tungsten in every conceivable way, but it can still be disassembled.
I took 1/16" thick tungsten plates (you can get them from Pinewood Derby supply places), and I was able to cut and shape them
to really fill cavities well.  Tungsten is awful to cut, but with a Dremel and cut-off wheels, it can be done.  You just have to go slow.
I also found .004" thick tungsten foil and some .031" tungsten rod on eBay - those were spectacular for filling voids with weight that would have been impossible to achieve with lead or tungsten cubes.

And remember, I still have to do all the cosmetics: domes, boiler saddle, cylinders, pilot beam, CAB.  I will be able to add a lot
more weight to this later in the project.

The Walthers 0-8-0 and Bachmann 0-6-0 are both around 46 grams (where I am now) by comparison.
I can push about 9 cars on level track with it.  Not terrible, but I want it to do a lot better than that, even though it's only
an 0-6-0.  But this is overly conservative.  I have no rods on it.  So only one driver set is giving me any pull.
Even though that's the traction-tire geared driver which is responsible for most of the pull, when I get rods on it so that the other 4 wheels can contribute, I bet it will pull a lot better.

You're past the huge hurdles and on the downhhill pull.  

[mmagliaro]

Now I see what you mean.  But most of the time the bearing will be in direct contact with the metal frame which electrically parallels the spring, reducing number of contact points by 1.  But I do understand that if you used pickup wipers then the number of contact points would be decreased and reliability increased.

You'd be surprised.  There are 4 wheels, 4 bearings, in this engine (the other 2 have traction tires, so I'm not considering those).
I'd say that the majority of the time, all 4 paths are not conducting.  If that were true, it would creep a slow as can be without any
help from an attached tender, but it can't.  Most of our engines, I'd wager, are actually sitting on 3 points most of the time.
The frames, trackwork, wheels, etc, are just not made to tolerances nearly close enough to actually have decent pressure on 4 points
at once.  Even within .001" is not good enough.

And that means that at an given moment, with only 2 conductive wheels on each rail, there are probably lots of
times when I have to count on only one wheel completing the circuit.
Thems ain't good odds in N Scale

//////////////////////////////////////////////////////////
narrowminded:
I am not *quite* past the huge hurdles.

1. I need to Loctite the drivers on the axles, properly quartered, make rods and get that working right.  I've made a jig for this,
so I am not too worried about this part, believe it or not, as long as the Loctite doesn't let me down.

2. I need to make tender trucks - wheels, sideframes, and all.
THIS part is going to be brutal.  I have looked at an Andrews-style truck sideframe, which is what I need for this.
And of course, because I am bound and determined, there will be no Shapeways knock-off here.  I have to make 4 truck sideframes,
and make them myself, and they have to hold the wheelsets (which I will turn from nickel silver rod so I don't have to worry about
plating or conductivity!)

The sideframes.... sheer horror.   

[narrowminded]

Generally, the springs in my bearings are very light.  Under normal circumstances, with the engine sitting on level track,
the springs are completely pushed up, that is, completely recessed, and the frame is sitting directly on the bearings,
which is what I want.  If you rock the engine a little bit, however, you can see the spring appear on top of the bearing,
and the wheel stays on the rail.  And that's the whole idea.

Now, why do I say that a wiper on top of the rail would work better?  It's because of the less-than-perfect track of the real world.
When the engine is sitting solidly on all 4 wheels and bearings, sure, everything is great. 

But when it isn't, here's what happens.

In my spring-bearing scheme, the current has to flow from the axle, to the bearing, then through the little spring, to the frame.
There are 3 contact points in the path. (axle/bearing, bearing/spring, spring/frame)  During lucky moments when sides of the bearing are touching the frame, we can forget the spring, so we have two points of contact (axle/bearing and bearing/frame)

With a wiper directly on top of the wheel, the current flows from the wheel rim to the wiper, and that's it.  There is only one contact
point.  Ain't nothin' more reliable than that, as long as the wheel and wiper are clean and the wiper is adjusted right.

I agree with you.  I don't like wipers either.  They bend, they get dirty, they wear, and they put drag on the wheel. 
That's why I'm not using them.  But when they are clean and adjusted, they do provide perfect contact (until they become anything
less than perfectly adjusted, that is).

Worth remembering.  In order to conduct electricity there MUST be a metal to metal contact.  No oil films, non conducting oxides, etc.  Plain metal to metal.  It's what makes this so tough and is compounded when the current isn't high enough to blow through or weight isn't high enough to displace interfering materials.  And oil in a proper bearing prevents any direct metal to metal contact.  It's how and why they work. 

In my project with only four wheels on the track, by far and away this is where the efforts have been expended... once I knew I had motors that could spin a wheel with torques in the micro newton meters torque range and when that number started with a decimal followed by a place holding zero.   Finding that delicate balance in a device that is inherently wrong at the outset.

[narrowminded]

If you want to PM me I may have a couple of ideas or techniques that I stumbled on when working on mine that may be useful in that quest.  I probably won't be back on the board until this Friday or the weekend as I'm on vacation and ready to hit the road again but would be happy to talk to you about this.  It may not be helpful or new but it probably can't hurt.

[peteski]

Most of our engines, I'd wager, are actually sitting on 3 points most of the time.
The frames, trackwork, wheels, etc, are just not made to tolerances nearly close enough to actually have decent pressure on 4 points at once.  Even within .001" is not good enough.

And that means that at an given moment, with only 2 conductive wheels on each rail, there are probably lots of
times when I have to count on only one wheel completing the circuit.
Thems ain't good odds in N Scale

Our (factory made engines) yes. But if your sprung suspension keeps the springs under roughtly 50% compression (in the center point of the suspension's travel) while sitting on a piece of even track then all the wheels will be in fairly good contact with the track (unless the trackwork is really horrendous).  But again, I agree that if pickup wipers were used then the conductivity would be maximized.

[mmagliaro]

Our (factory made engines) yes. But if your sprung suspension keeps the springs under roughtly 50% compression (in the center point of the suspension's travel) while sitting on a piece of even track then all the wheels will be in fairly good contact with the track (unless the trackwork is really horrendous).  But again, I agree that if pickup wipers were used then the conductivity would be maximized.

I know... You'd think so.  But it also depends on just how much spring pressure the little springs can actually exert.
In my case... not much.  I am using those tiny N Scale McHenry coupler knuckle springs.
Or actually, only HALF of one.  And this is something I am considering.
With 46g of weight on the engine now, I may be able to put in a whole spring, or 3/4 of a spring, and get a lot more positive
electrical contact.

I plan to try it.  I also got some springs from D.R. Templemann company.  You can find them on-line.  They had some
stainless steel springs down to .029" in diameter!  (the McHenry springs are .044").
I think these will give me longer, softer springs - i.e. a gentle lift, but useful over a longer distance than 1/2 of a McHenry spring.
Spring-loading drivers in N Scale is a delicate business.

[narrowminded]

Have you ever looked at or thought through spring functions to clearly grasp their characteristics?  I ask because there are generic spring sites that will explain their functions and if you take the time to digest those and a little more time with your gram scale and a bridge rig over your scale with a screw that you can vary the load with, you should be able to come up with a properly planned and applied spring that does exactly what you want, no guessing.  Knowing your weight per axle and getting each spring just bottomed but up in the 80% or 90% range of that would probably have those joints pretty well optimized for your purpose. 

Just quickly, uniformly wound coil springs (which is what you'll be using) will increase force linear for each increment they are compressed.  Compressing a spring more will increase the force at its linear rate all of the way up to its bound state.  If it's a high rate spring but looking for little force and with little action in the mechanism, the force will be accomplished at very little initial compression and will also change force dramatically with very little action.  On the other extreme, if the spring were relatively light force applied to a heavier load, a long spring could be compressed quite a bit, arriving finally at the force required for the load, and then any change in the position of the load would still leave a force closer to uniform on the mechanism.  It's this window that you could play in knowing your loco weight, desired compensation travel, and available spring space.  This may be more than you want  but even just a little time playing with your scale and a way of measurably varying the spring compression travels might get you some sense of an optimum cut length for those springs you are using.  (BTW, cutting any spring increases its rate for distance compressed.  That alone may be useful to optimize.  And if not something you've already known, the theory will get you settled with it.)

[mmagliaro]

I could experiment with springs, I know.  But honestly, it's a little puzzling why a spring that at least reliably flexes the wheel down
so it doesn't lose touch with the rail when I rock the frame up gently shouldn't be good enough.  I know, I could optimize it so I get quick reaction, perfect spring pressure, not too much upward lifting of the engine, etc.  But this is getting a little nuts.

I did... however, think of something.   My phosphor bronze bearings are in a brass frame.  As we know, brass oxidizes happily, and brass is a lousy conductor when it oxidizes.  That's one of the big reasons we don't use brass rails for our track anymore (beside the looks).

Since it won't be too hard to do, I'm going to break out the plating solution and the swab one more time, and plate
the bearing pockets in the frame with nickel.  I'm curious to see if my conductivity/stalling behavior improves.

(... but I do have the base plate cut out for the tender floor...    )

[narrowminded]

Because you can, I would plate those pockets.   But letting the tender pickups do their job, assuming they work properly which they should, is as legit as it gets and if it works I would accept it without batting an eye.

[peteski]

Brass and nickel both oxidize.  I have not done any research about the conductivity or hardness of the oxides.  But if you clean a piece of brass and do not contaminate (like touching it with fingerprints which have salty sweat)  or expose it to caustic or acidic fumes then it should stay relatively clean.

I am also assuming that you will lubricate the areas where the bearings will move in the slots in the chassis. Oily film also prevents oxidation.   I don't know if nickel plating will actually be beneficial in this application.

[mmagliaro]

Brass and nickel both oxidize.  I have not done any research about the conductivity or hardness of the oxides.  But if you clean a piece of brass and do not contaminate (like touching it with fingerprints which have salty sweat)  or expose it to caustic or acidic fumes then it should stay relatively clean.

I am also assuming that you will lubricate the areas where the bearings will move in the slots in the chassis. Oily film also prevents oxidation.   I don't know if nickel plating will actually be beneficial in this application.

So far, neither do I.  I plated the pockets, and it doesn't really seem to run any better or worse.  It's still not nearly as good
as I want it to be.  Let's put it this way.  It can putt around at a modest speed on its own.  With a Kato tender attached to it, it can
*crawl*.

[narrowminded]

I think you are right back here.   https://www.therailwire.net/forum/index.php?topic=37254.msg446883#msg446883

Without a wiper, or a LOT of weight, or a LOT of voltage, I really don't think you are going to get what you want.  It's the simple facts of the matter.  But with a functioning tender picking up you have it covered and don't need it.  I can see where wipers could be hard to fully hide with the spoked wheels and I agree, they would be unsightly.  But it also seems like you don't NEED their help.  If it's working with the all of the tender wipers tagging along and conducting here and there, be happy and call it done!

You might get a kick out of one of the test rigs I'll be using in this next phase of my testing.  I'll be wiring a set of leds to each axle/ wheel combo.  One that wipes the wheel only, insulated elsewhere, and then another wired through the chassis.  I will also be able to insulate an axle so I can test just one axle at a time, isolating the chassis so I can tell if the compensation pickup is working well.  This allows to test wheel pickup only, then wheel to chassis pickup, then compensated axle to chassis pickup.  Each has its own tell by which leds light or don't.  I'm not suggesting that you should do such a thing and in part because I don't think you need to.  In my position I feel I really do need to be pretty expert at these things, therefore the testing and education.  I think you've got good performance covered between weight AND playing the odds with so many chances to get your power.  And there's ample existing evidence that that works including your own experiences with this unit.