Painting Brass Key S4 - to strip or not to strip?

[peteski]

Well, after drying overnight after an Acetone bath, I see that not ALL the lacquer was removed.  The truck sideframes are fine, as is the shell, but the frame has a lot of (now discolored) lacquer still left.  Maybe it had a heavier coat?    Gonna try again with Acetone and see what happens.

Since the model is metal, you might want to try some more potent paint strippers, like the stuff available in car parts stores.   Those use chemicals stronger than acetone (like Methylene Chloride) and should easily strip all of the clear coat. Home Depot might carry some of those "real" paint strippers.  I have can of Zip-Strip and it works well. I think another one is called "Aircraft Paint Remover". 

[wazzou]

...I think another one is called "Aircraft psint Remover".

I've found that is the only thing to reliably strip paint from the earlier metal CMW vehicles.

[nickelplate759]

Moved on to real paint stripper - Kleen Strip in a paint can.   Better, but not perfect.  That said, the parts that held on are not where they will be seen, so they got a rinse, a 20 minute vinegar bath and another rinse.  I also discovered that the lacquer was all that was holding on the cab hand rails .   They'll get put back after painting.

[nickelplate759]

OK, it's got a good coat of black Scalecoat II.  Now I have to get it back together.  Most of it is obvious, but the truck contacts are not.  There are four bronze-ish contact springs - two for each truck.  They ride on the top of the wheels.    So far so good, but...
1. two contact springs are wired to the motor - one to each brush.  (circled in green)  They might also be insulated on the bottom with a little clear tape.
2.  two contact springs are not wired to anything (circled in red)
3.  the wheelsets are insulated one side only.  The uninsulated side is means that the truck frame/gearbox is live to the rail on that side.
4.  My notes (see picture) are terrible!

I don't remember how these contact springs mount on to the trucks.  Anyone know?

[peteski]

They might need to be pinched between the gear case and the sideframe. Of course one side has to have insulating strips.

I have serviced another brass diesel. See if the photos I took during reassembly might be helpful.

https://www.therailwire.net/forum/index.php?topic=38297.msg462851

[nickelplate759]

Looks similar enough to be helpful, thank you @peteski .  So it seems that only 4 wheels pick up current on this little beast (2 on each side).  It's odd that the other 4 wheels have these little springs but they aren't connected to anything.   I wonder if I can enhance that with some flexible wire....

[peteski]

Looks similar enough to be helpful, thank you @peteski .  So it seems that only 4 wheels pick up current on this little beast (2 on each side).  It's odd that the other 4 wheels have these little springs but they aren't connected to anything.   I wonder if I can enhance that with some flexible wire....

Are you sure?  Brass models often use the metal chassis for conducting electricity.  So if the wipers are uninsulated, they woudl pass the current to the motor through the metal trucks, and the underframe.

Going back to paint stripping, I'm curious about the Kleen Strip solution you used. I wander if it is a water-based (less potent) stripping solution than the ones I mentioned?

[nickelplate759]

Are you sure?  Brass models often use the metal chassis for conducting electricity.  So if the wipers are uninsulated, they woudl pass the current to the motor through the metal trucks, and the underframe.

Going back to paint stripping, I'm curious about the Kleen Strip solution you used. I wander if it is a water-based (less potent) stripping solution than the ones I mentioned?

I'm not sure yet about the contact.   Kleenex Strip is pretty noxious, no matter the base is.  The fumes are pretty strong.

[peteski]

Actually looking again at the parts in your photo it appears that at least the truck on the top of the photo has insulated kingpin, so its metal frame does not contact the metal chassis.

[nickelplate759]

Actually looking again at the parts in your photo it appears that at least the truck on the top of the photo has insulated kingpin, so its metal frame does not contact the metal chassis.

In fact, both trucks have insulated kingpins.  So the real mystery is why did two of the pickup springs not have any wires to the brushes?  I got this model new back in the 1980s.  The mechanism it is very similar to your example - built by Samhongsa.

[peteski]

In fact, both trucks have insulated kingpins.  So the real mystery is why did two of the pickup springs not have any wires to the brushes?  I got this model new back in the 1980s.  The mechanism it is very similar to your example - built by Samhongsa.

It has been few years since I serviced that brass switcher for Cody, so I don't remember the details.  As for explanation, I have none. Well, maybe the assembler just screwed up? 

EDIT:  I just jogged my memory. Just so we are on the same page.  Only one side pickup on each truck will have wire.  The other pickup is connected to the truck's metal gearbox, and to the insulated kingpin.  The other wire will be attached to the kingpin.  The loco's metal underframe is electrically neutral. 

And since the trucks are directional, each side will have pickup via direct wire to insulated pickup strip on one truck, and kingpin on the other truck (and reverse is true on the other side).

[nickelplate759]

It has been few years since I serviced that brass switcher for Cody, so I don't remember the details.  As for explanation, I have none. Well, maybe the assembler just screwed up? 

EDIT:  I just jogged my memory. Just so we are on the same page.  Only one side pickup on each truck will have wire.  The other pickup is connected to the truck's metal gearbox, and to the insulated kingpin.  The other wire will be attached to the kingpin.  The loco's metal underframe is electrically neutral. 

And since the trucks are directional, each side will have pickup via direct wire to insulated pickup strip on one truck, and kingpin on the other truck (and reverse is true on the other side).

Thanks!  Now it all make sense when I look at the parts I have spread out.  Huzzah!

[nickelplate759]

Next step is to letter this for NKP.   That's a challenge because no one makes the correct striping for the ends in N scale.  The closest I've found is 1/16" Yellow 60-degree chevrons from K4S Decals.  They're really too light in color and about 10% oversize for the older, pre-1958 scheme (NKP striping was 9"), but hopefully close enough to look decent.

The final challenge (besides reassembly) will be installing window glazing. This model has cab interior details soldered to the cab walls. and obstructing part of the rear windows.