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

[peteski]

Even the later-generation Mikados that don't have the bronze strip problem
in the drivers still have a tread resistance often as high as 30 ohms from that black plating. 

At 150 mA, that will drop 4.5 volts.  Allowing for
2 or 3 drivers all conducting at once, it might only drop a volt or 2.   (And since it's getting power from the tender
99% of the time, you'll never notice it).   If you polish off that plating and try it,
the increase in speed at a given voltage is very noticeable (if you run the engine without the tender, that is).

More importantly, the Mikado plating is dead-even and uniform, something I can't really do at home with a
stone-knives-and-bear-skins plating kit.  So even though there is voltage drop through that plating,
it doesn't really matter because it's consistent.

Mine, ahem... is unfortunately not that consistent.    It may LOOK like the plating on the Mikado, but it's clearly not as good.

Funny, when I was talking about Kato locos with plated wheels, I was thinking of diesels. They have all wheels plated (usually 8 or 12) and no tender.  SO you are saying that they all have large voltage drop between the wheels and motor?  I will have to check that out someday.

[parkrrrr]

Nickel-silver is actually an alloy of nickel and copper, so it's more conductive than plain nickel, and less conductive than
copper (or brass).  It would be great if somebody made a nickel-silver plating solution, but I don't know of one.
It does make me wonder if I could mix the nickel plating solution + the copper plating solution and actually have that work.
But something tells me it can't possible be that easy.

I have sent Caswell an inquiry about this to see what they have to say.

They sell a brass plating solution, so it must be possible to plate an alloy somehow. I'd be very interested in hearing their response on this.

[mmagliaro]

Peteski, maybe that plating on the diesels isn't the same as what's on the Mikado drivers.  It doesn't look the same to me.
The Mikado plating, especially in later runs, looks a lot blacker and heavier than it used to.

As for plating nickel silver directly, I don't know if this is possible.  There have been home items, like silverware,
plated with nickel silver, and it is marked EPNS (for electroplated nickel-silver).  That stuff was done, usually, before
the advent of stainless flatware, when people used nickel-silver for its durability.

HOWEVER... another call to Caswell and I may be on to something.  I asked the fellow there how long it should take to
get a black plating on my brass parts.  The way these systems work, the negative electrode is clipped to the brass wheel,
and the positive is a hand-held metal wand wrapped in some gauze on the tip, which you dip in the plating solution.
You swab that onto the part to be plated.
He said it should take "a few minutes". 

I told him mine would turn black almost immediately.  He said if it was that fast, the charge was too high and I was probably
burning the plating, which might explain the conductivity problem.
He suggested I leave about a full inch of gauze hanging off the end of the wand, to reduce the charge at the plating surface.

So... I will strip a wheel and try it that way.  That may be the key here.

[mmagliaro]

Well, that's a bust.

I used a longer bit of wand cloth, and this time I used my own power supply instead of the wall-wart that comes with the kit, so I could run it at lower voltages to see how that would affect it.

At 3.5v (instead of the wall-wart's 4.5), it plates quite nicely.  It goes on more gradually, and I got a really nice,
smooth, shinier black finish.   But it still leaves me with driver treads with a resistance of about 10-15 ohms, and that's just
not going to cut it on a small, light little switcher, unless I am content to let it survive on tender pickup alone, which I am not.

I ordered some copper solution and some plain nickel (not black nickel) solution.
I'll try plating black over copper, like one of the Caswell guys suggested.  I don't hold out much hope for that.
Brass already has a lot of copper in it and the plating is going on just fine.  I think the problem is in the zinc (I suspect)
that they add to get  the black color.

[peteski]

Peteski, maybe that plating on the diesels isn't the same as what's on the Mikado drivers.  It doesn't look the same to me.
The Mikado plating, especially in later runs, looks a lot blacker and heavier than it used to.

I actually don't have that much experience with Kato Mikados. Since B&M never had this loco in the roster I  never bought any complete locos from either the first or the subsequent runs.  I did pick up several complete mechanisms when Kato had a big sale on them.  I didn't know that they went through multiple types of blackeners.  But weren't the tender wheels also blackened?

The only bad experience I had with blackened Kato wheels was documented here, on one specific run of GS-4.   As I documented it there, only the drivers had the problem (and their blackening was different than the rest of the loco and tender wheels). Kato did admit that they used a different blackener on the drivers of that particular run.  But other than that I can't imagine Kato using different formulas of blackener for the steam loco drivers than they use on the rest of their wheels (passenger trucks,Diesel locos, etc.).  But I suppose it is possible.,

Other than the above mentioned problem (where the blackening was totally non-conductive) I never really bothered to measure the resistance of the blackener. Just now I took a random set of new passenger car wheels and when I gently touched the ohmmeter probes to the wheel I was getting a fluctuating reading of 4-20 ohms. When I pressed the probes harder, it would go to zero ohms.  I also took a well-used P42 Diesel from the initial run and I took measurements on the back side of the wheel (where the blackening was undisturbed.  ON that one I was getting few ohm resistance and it was much easier to get zero ohms (as if the blackening layer was thinner).  But it was reliably zero ohms when measured over the tread surface (where the blackening was worn off.

So do see what you mean. - I just never seemed to have a reason to do these measurements (most Katos seem to run reliably).

As for plating nickel silver directly, I don't know if this is possible.  There have been home items, like silverware,
plated with nickel silver, and it is marked EPNS (for electroplated nickel-silver).  That stuff was done, usually, before
the advent of stainless flatware, when people used nickel-silver for its durability.

I suspect that those items were made from nickel-silver and then plated with silver (that is what EPNS seems to indicate). If you look at Wiki entry for nickel-silver it states that N-S was a cheaper substitute for silver which was often silver plated.

I don't see why nickel-silver alloy cannot be used for electroplating. That should be doable.  I wonder if you could just plate the wheel treads with silver?  That should be conductive and not look like brass or copper.

[Chris333]

Could Kato wheels be made of nickle silver and not plated at all (other than the blackening)?

[mmagliaro]

I have seen worn Mikado drivers that seem to have an almost copper-colored metal underneath the black coating, so I don't think they are solid nickel or nickel-silver.

In answer to other questions, no the tender wheels are not blackened.  At least, it doesn't look that way to me and I'm looking at a tender right now.  The faces that show through the frames are black, but that just might be paint.  The treads look pretty darn silver to me.

Silver plating would be great for conductivity.  You know, I shied away from this because I was afraid of the "tarnish", but then I remembered that silver oxide is still conductive (just like nickel-silver, which is why we like it for track rails).  And it is used
on electrical contacts to make them corrosion resistant and highly conductive.   Yeah.... Caswell sells silver plating chemicals too.

[peteski]

Chris might also be onto something: I have couple of very high mileage trucks from a Kato SD90 (or one of the locos with the sprung center axle). the wheel tread shows lots of wear. The blackening is long gone and the shiny metal surface is silver-color (not brass). So maybe those wheels are nickel silver?  Maybe some of the Kato offerings use nickel-silver wheels? Or maybe more recent models use nickel-silver?

I should take a small grinder bit and remove some material from the back of the wheel to see if there is some brass deeper inside.

[Doc Frankenfield]

plating wheels woud hardly be worth the effort especially using the caswell plating.. it is fairly thin and will wear off quickly...
It is howevwr great for details and bright work.

[mmagliaro]

I have heard this suspicion before, about home brush plating being so thin that it wears off.  But doesn't that depend on how long you do it?

I have hit upon a good formula now.  The plain nickel plating solution works a lot better than the "black nickel", which I suspect is just
nickel plating with something added to it to cause an oxidized black layer to form (like metal blackeners work).
With a little experimentation, I found that stright nickel plating solution mixed with the black nickel solution,
(90% nickel solution to 10% black), gets me a slightly darkened looking nickel finish that looks like weathered steel.
And it conducts great.  I can run the engine and get the same performance I get with bare clean brass.

So I have gone through three rounds of plating for several minutes each, and it still conducts and works great.
The question is, how long would you think I have to keep swabbing/brush plating to build up enough?  And how thick is "enough"?
At first, I thought I would need .001" thick plating.  But that seems like much more than necessary.  It also depends on just how hard and durable the nickel is.

[narrowminded]

I have heard this suspicion before, about home brush plating being so thin that it wears off.  But doesn't that depend on how long you do it?

I have hit upon a good formula now.  The plain nickel plating solution works a lot better than the "black nickel", which I suspect is just
nickel plating with something added to it to cause an oxidized black layer to form (like metal blackeners work).
With a little experimentation, I found that stright nickel plating solution mixed with the black nickel solution,
(90% nickel solution to 10% black), gets me a slightly darkened looking nickel finish that looks like weathered steel.
And it conducts great.  I can run the engine and get the same performance I get with bare clean brass.

So I have gone through three rounds of plating for several minutes each, and it still conducts and works great.
The question is, how long would you think I have to keep swabbing/brush plating to build up enough?  And how thick is "enough"?
At first, I thought I would need .001" thick plating.  But that seems like much more than necessary.  It also depends on just how hard and durable the nickel is.

Hi from a sunny vacation spot!  I see what you've been working with and find it interesting.  My main interest in the platings wasn't so much for wheel treads or moving wipers but that was to be tested, too.  All part of a thorough knowledge that I should have in the position I'll be in as a "manufacturer".  Some will be for cosmetics, like black nickel, but I am most concerned about points where conductivity needs to be good but where there's no repeated wiping action like wheel wipers have.  More like a contact that touches but doesn't really move or has very little motion in normal service.  A place where oxide could develop but not have any action that would wear through it, keeping it clean of oxide and conducting low current very well.  A place where you'd like to solder and never look back but just can't get at it or fit it into the tiny space available.  The fixed end of a wheel wiper is an example that ideally has the fixed end just pressing against the frame.  That is a concern to me for the long term that I hope to assure reliable with plating and why I will test all options including localized gold over nickel.  No real wear so I think it would last and on the action end, I think the wiping action on nickel silver wheels with phosphor bronze wiper will be OK.  Might be a little fidgety after sitting for a time but a little coaxing and get it to move will take care of that in a pretty short run time.  But this is also why I'm testing all of them.  As a manufacturer I have to be my own "expert" and so I want to know these things first hand.  I've got a lot of tricks up my sleeve in a lot of areas but at this detail in this service, I just never had to do it. What to do, what NOT to do, and knowing it first hand including options and their effects is what I need to know before to put this thing out for public consumption. 

As far as plating thickness, measure the part before to plate and then after.  With your calipers you probably wouldn't want to call it a certified inspection but at the same time, you should be able to get some sense using a comparative reading with the same tool on the same part, gaining a couple of tenths (splitting one thousandth) and your plate thickness will be half of your diameter reading.  Point is, a half thousandth or even near would suggest a 2 to 3 tenths thick plating.  And for plating that could probably be called a lot.  You should be able to get a measurable reading that gives you a reasonable indication of what you've actually got.  Don't be surprised with a small number. 

[mmagliaro]

I'm afraid I don't have any "before" measurements on these wheels that would be accurate enough to tell how much plating I have on there now.  They are all plated and I really like how they look and how it runs, so I'm not about to strip them again.
(This will all be documented when I finish the photo set and editing for the next project installment).

I have run the engine around the layout for about an hour, and the plating does not show any sign of wear whatsoever.
I know that's not much of a test.  But the plating is at least tough enough that it doesn't just "wear right off".
Whether it will hold up to 100 hours of running, or 500, I have no idea. 

[peteski]

I agree wit narrowminded that plating on the type of items we are discussing will be in a range of micro-meters.  I don't know if there is even 0.001" of chromium plating on a steel bumper of a 1959 Cadillac.   

[narrowminded]

That's very cool and must be very rewarding, seeing it all coming together. 

Nickel is pretty durable.  It also has a fairly hard oxide but will that cause trouble after sitting?  In this service and in the relatively good environment these live in I really don't know.  My suspicions are it will be fine and at worst, might need just a little coaxing to get some action started on the contact faces but just don't know that for sure and wouldn't be surprised at either result.  It's why I'm going to test pretty extensively. 

What did you find was causing the burning and the resultant conductivity issues?  Too much power or sitting your brush in one spot too long?  Maybe a little of both?  Are you using a wiper or just axle to chassis contact?  And what weight did you test at?  These are the areas I have found to be meaningful and have accumulated some data but coincidental as I was working on entirely different issues.  With all of those worked out satisfactorily I have this area left.  Test and accumulate good, honest data that's repeatable, predictable, and therefore useful.   

I REALLY like what you've done and how you've gone about it.

[mmagliaro]

That's very cool and must be very rewarding, seeing it all coming together. 

Nickel is pretty durable.  It also has a fairly hard oxide but will that cause trouble after sitting?  In this service and in the relatively good environment these live in I really don't know.  My suspicions are it will be fine and at worst, might need just a little coaxing to get some action started on the contact faces but just don't know that for sure and wouldn't be surprised at either result.  It's why I'm going to test pretty extensively. 

What did you find was causing the burning and the resultant conductivity issues?  Too much power or sitting your brush in one spot too long?  Maybe a little of both?  Are you using a wiper or just axle to chassis contact?  And what weight did you test at?  These are the areas I have found to be meaningful and have accumulated some data but coincidental as I was working on entirely different issues.  With all of those worked out satisfactorily I have this area left.  Test and accumulate good, honest data that's repeatable, predictable, and therefore useful.   

I REALLY like what you've done and how you've gone about it.

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 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.

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.

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.

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.

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.