What shoudl i know about Resin Kits?

Discussion in 'HO Scale Model Trains' started by green_elite_cab, Oct 11, 2005.

  1. green_elite_cab

    green_elite_cab Keep It Moving!

    I got a Walthers guard sation, made out of resin, is there anythign special about resin i should be careful with?
  2. MasonJar

    MasonJar It's not rocket surgery

    We had an interesting presentation lat night at the club, in part about resin kits. It focussed on rolling stock, but also touched on buildings.

    The main points to remember according to the presenter are (in no particular order):

    - newer resin formulations are easy to drill, older ones are harder due to different fillers
    - resin replicates very fine detail, so be careful when handling
    - must be thoroughly cleaned before painting to remove any mould release (special "resin prep" does not work better than dishwashing liquid, but is more expensive)
    - not all parts will be square
    - use bracing inside the structure to help keep it square
    - regular hardware store superglue is good for assembly
    - use a large flat file to square up edges and corners
    - when gluing, "tack" one part of the joint with a very small amount of glue, check for fit, and then finish the gluing
    - small voids in castings can be filled with baking soda and then soaked with superglue
    - some sort of primer coat is recommended before final colours

    I have done a few small resin buildings, and the only other thing I would add is that if you intend to light the building, paint it black inside, or line it with aluminum foil - the resin is translucent and light will leak right through the walls and roof.

    Hope that helps.

  3. dsfraser

    dsfraser Member

    MasonJar has given you good advice.

    I would hold off on the "large flat file". Use some #400 grit wet-dry sandpaper (used wet) on a piece of plate glass, otherwise you will end up removing too much material. Resin sands very quickly, and files even quicker . . .

    Get hold of a piece of flat steel, even a cookie sheet will do, and use rectangular magnets to hold parts in place, and keep them square, while you build the beast.

    The catalyst used for polyurethane resin contains isocyanides. That's iso-CYANIDEs. When you're sanding it dry or filing it or milling it, wear a mask to avoid inhaling particles. Your wife and your grandchildren will thank you. Better yet, sand it wet, don't file it, and that will eliminate the dust problem. Clean up afterwards.

    Sometimes you will encounter resin parts that aren't straight, or flat. Run them under a hot tap, between 180° and 200° F. The resin quickly softens with exposure to heat, and you can then bend parts to their proper shape.

    Once it has cured, polyurethane resin is impervious to hydrocarbons, so you can use any type of paint on it, and you can't glue it with conventional model cement. You do need to clean it before painting. Most manufacturers use a silicone-based mould release that does a very good job of keeping resin from sticking to RTV, and keeps paint from sticking to resin. Warm water and Sunlight will remove it.

    The main thing is to take your time. Make sure the parts are flat. Make sure your joints are square. Wash the parts before attempting to glue them.

    Finally, know that preparing parts for resin casting is difficult. Casting parts in resin is also difficult. Casting parts in resin is also very expensive. If you're really good, you'll only suffer a 20% failure rate, so you'll only waste $10 for every $50 worth of material you buy. And while I don't know about what Walthers has set up, I do know that 99% of resin kits are produced by individuals working in their garage, or basement, who spend time away from their families and their own hobby interests, and who rarely do more than break even on their efforts. That's why they don't last more than a few years, if you've ever wondered.

    How do I know this? I've built many model of aircraft and tanks from vacuform and resin kits. I've poured gallons of resin. I've designed complete kits and aftermarket accessory kits for same. Now I've moved in to the realm of trains, designing photoetch, resin parts, and explorig stereolithography as a means of creating masters. I keep getting sucked into it — I have a dozen projects in front of me, but it gets my creative juices flowing, and I end up spending my time on new products rather than building stuff for my own layout. I need to learn to not answer the phone.

    Anyway resin kits are simple, except that you have to use CA rather than styrene ement. Don't be shy. Build a few, and a whole new world will open up to you.

    Scott Fraser
    Calgary, Alberta

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