Painting San Juan Trucks

You might read through this thread from another forum site...

https://dieseldetailer.proboar...dhering-paint-delrin

I haven't personally tried any of the techniques/materials offered, but they seem to present some effective alternatives.

Prior to finding these more exotic strategies, some of our (LHS) modelers seemed to have success in handrail painting with Pactra (lacquer) brand paints.  We stock them, as well as Tamiya's version, in the RC area.....they're especially preferred for custom painting RC car bodies, which take a LOT of abuse/flexing.  Of course, those bodies are typically molded in clear plastic, and the paint schemes applied to the inner surface of the body.  That protects the paint from most abrasion in the rough-and-tumble the cars go through.  But, the paint seems to survive the flexing, too.  Now Delrin, Celcon, other acetal variants of the slippery plastic, are not hardly the same as polycarbonate.  However, as you may have experienced in the 'School of Hard Knocks'...like most of us...lacquer paint is overly aggressive-to-ruinous on common hobby plastics, like styrenes.  So maybe, as a couple of the forum entries cited above point out, it is part of the best alternative for getting good paint adhesion to the slipperies.

Good ventilation when painting is always prudent.  But, when using lacquers, it's ESPECIALLY important.  The lacquer solvent is quite a liver-eater in extended exposure/inhalation, which figured into the demise of some mid-century hobby paints, like Floquil's original formulation of railroad color paints.

Of course, the upside of the 'slippery plastics' is its resistance to handling breakage and moldability in very thin/lengthy cross sections....a BIG PLUS in the historical refinement of our hobby.  So, not every improvement is a panacea.....as with treatments for many viruses!

Good Luck!.....and let us know if you can find/verify a technique/material satisfying to the most important of critics....yourself!

KD

Have not been able to get anything that sticks over time or from bumps on Delrin

I have not yet found a paint that will stick well to those Engineering plastics.    On the other hand, with metal axles in those journals they sure roll well

I have painted many Athearn plastic trucks which are slippery plastic, with various model paints and it stays on OK as long as you don't hit with somehitng like a scraper or sharp finger nail.

I found some youtube videos that show some acids will etch Delrin including sulphuric and phosphoric. I could try that on some sprues with some battery acid I have. I m not sure this is actually Delrin but it sure is slippery and its not affected by solvent cements.

Pete

Delrin is a brand name for an Engineering plastic.   These are used for bearings in many applications.    Slide bearings on weld guns on assembly lines for example.   They also can injection molded with very fine detail.    I think the hand rails on Red Caboose GP9s and Weaver RS3s and GP38s were made with an engineering plastic.

The generic version is acetal plastic. Delrin is Duponts brand name. Its become a descriptor just as many refer to copies as xeroxes. San Juan used a mix of plastics in these trucks. The bolsters can be welded with solvent cement. Acetal is a good choice for the sideframes and axles as the trucks are very free rolling. 

 I am a bit surprised many have not used them.

Pete

Have you posed your question to the vendor/maker?

Simon

Wash in soap and water then a rattle can of dark grey auto primer. Not perfect but sticks pretty well.    

Internet search for the PDF:  henkel-loctite-design-guide-plastic-bonding.pdf

Jump to pages 14-15 and read about acetal homopolymer (Delrin...etc.), surface prep and bonding.

Thanks,

Old Goat

Appreciate the link OG. Very interesting. Today I tried battery acid (sulphuric) and rust remover (phosphoric) with no effect. I don't currently have access to the real stuff. I will play around for a while before applying paint.

Pete