How do I paint locomotive trucks?

[primavw]

Any tips on painting a set of Loco trucks without completely dismantling them? I have BNSF green trucks that need to be black. They are $15 a pop on Kato's website and I don't feel like dropping the dough unless its necessary. I used search and google and came up with nothing. TIA

[Jeff AKA St0rm]

I take mine apart it is the only way. clean them then prime before you repaint.

[Baronjutter]

I've heard some have the side-frames easily removable without having to actually take the whole thing apart.

[primavw]

They are SD40-2 mid-pro trucks if that helps

[wmcbride]

Any advice on primer? Or will any do?

[peteski]

Truck sideframes are made from a slippery plastic (similar to handrails).  Hobby paints do not adhere to it very well (unless sandblasted first).  They can be painted, but expect the paint to come off after they are handled.  At least that is my experience. 

[ednadolski]

Truck sideframes are made from a slippery plastic (similar to handrails).  Hobby paints do not adhere to it very well (unless sandblasted first).  They can be painted, but expect the paint to come off after they are handled.  At least that is my experience.

Dupli-color adhesion promoter for plastics.  You can find it in automotive supply stores. Apply in several light coats as per directions, followed by a primer and then your paint color.

You can still scratch the paint off or remove it if you try, but it is way better than just putting the paint straight on the plastics.   FWIW, I don't know how well it holds up on plastic handrails, as those might be too flexible for most paints.  (I can't say I have much use for plastic handrails anyway      )

Your other option is grit blasting  (a.k.a the "air eraser").  I have never done that myself; I suspect the results are better but it is way messier and has some cost to set yourself up (esp. with a booth).

Ed

[jimmo]

Dupli-color adhesion promoter for plastics.  You can find it in automotive supply stores. Apply in several light coats as per directions, followed by a primer and then your paint color.

Why would you need a primer when you're painting black over green? It's bad enough adding several coats of adhesion promoter, then primer, then color. That's probably a couple of scale inches thickness of paint in N. I can't even imagine what that will do on already over-scale handrails.

My online research brought out many methods for painting slippery plastics and hands down, the name Badger Modelflex kept coming up. No additives, no primer, no sand-blasting needed. Tamiya paints for Lexan was also mentioned.

[basementcalling]

Why not see if Kato would do a swap for the correct color?

[ednadolski]

Why would you need a primer when you're painting black over green? It's bad enough adding several coats of adhesion promoter, then primer, then color. That's probably a couple of scale inches thickness of paint in N. I can't even imagine what that will do on already over-scale handrails.

You may be able to get away without a primer depending upon your specific paint and colors.   But you should not be putting on the AP so heavily (and I did say "light coats").   I don't see that it accumulates in the same manner as regular paint.

(One scale inch in N is approximately 0.006".   If you put on paint so heavily that you accumulate "a couple of scale inches thickness", then I can't help you much except to suggest that you switch to 1:29 scale  )

The walkways on this model were painted with the several coats of the AP as per the directions on the can, and then airbrushed with the primer and finish color (Polly scale paint, IIRC).   As you can see, there is not enough accumulation to obscure the tread pattern:

Full size image here: http://i119.photobucket.com/albums/o153/ednadolski/Picture021-crop.jpg

My online research brought out many methods for painting slippery plastics and hands down, the name Badger Modelflex kept coming up. No additives, no primer, no sand-blasting needed. Tamiya paints for Lexan was also mentioned.

My experience with Badger Modelflex is that it is terrible on slippery plastics, especially flexible handrails.  It goes on like water, and when dry it flakes off like the film that it is.   But my hat's off if it works for you, I'd love to see some pics.


Ed

[jimmo]

That's a fine looking loco Ed. I'm assuming that it's N-scale, even though it looks like a much larger scale model. I would love to know how you did those handrails.

Does the adhesion promoter have to be brushed on or can it be sprayed?

[peteski]

Does the adhesion promoter have to be brushed on or can it be sprayed?

Spray can or airbrush only. I never seen anybody brushing it on.  The ones I used were fairly viscous clear coatings.  Here are few:



I don't use adhesion promoter coatings. I prefer to sandblast the slippery plastic parts, then airbrush Pactra hobby paint for polycarbonate RC car bodies.  If I can't find it (or ix it) in a correct color, I use gray paint (as sort of a primer), then the top coat it with the correct-colored Accupaint.  That results in a very durable and thin finish.

[jimmo]

Spray can or airbrush only. I never seen anybody brushing it on.  The ones I used were fairly viscous clear coatings.  Here are few:



I don't use adhesion promoter coatings. I prefer to sandblast the slippery plastic parts, then airbrush Pactra hobby paint for polycarbonate RC car bodies.  If I can't find it (or ix it) in a correct color, I use gray paint (as sort of a primer), then the top coat it with the correct-colored Accupaint.  That results in a very durable and thin finish.

I certainly wouldn't brush it on either, I was just wondering because I'm not familiar with the product(s).

Is there any danger of the sandblasted parts to become damaged in the process?

[peteski]

Is there any danger of the sandblasted parts to become damaged in the process?

I suppose if you kept the stream of abrasive blasting the same spot for a long time. I use the Badger sandblaster (which is basically their external mix airbrush with a different nozzle). You sandblast sort of like you would be airbrushing - don't hold it too long over one spot.

Like I mentioned, I've sandblasted the plastic handrails of Atlas/Kato RS-3 and RS-11 without causing any damage.

[ednadolski]

That's a fine looking loco Ed. I'm assuming that it's N-scale, even though it looks like a much larger scale model. I would love to know how you did those handrails.

Does the adhesion promoter have to be brushed on or can it be sprayed?

Thanks jimmo for the kind words.  I had a thread on this loco at this link, and a more up to date handrail build at this link.

I spray on the AP straight from the rattle can.  I make a few light, quick passes, then wait a few minutes, and repeat.  After three passes, the plastic is ready for the first paint or primer coat.  IIRC the instructions recommend painting within 10 minutes of the last AP coat, but check the exact instructions for the specific product that you use.

I have not really been able to find out much about how this stuff is supposed to work.  I suspect that it slightly etches the acetal plastic surface, perhaps similar to how chromic acid would work (but I would not mess with that stuff).

Ed