Fixing PW Lionel screw hole cracks

Those FM shells develop cracks because the frame is just a tad bit short. I put a small shim between the shell and the frame to fill the gap. IMHO that prevents further damage.
Also, I think it's best to pick up those engines by their trucks.

I would not try the JB Weld.

CW,

Are you attaching the "shim" to the screw hole post/lamp bracket? How thin? Would a square of styrene be good? I'm thinking that without the JB, though, each time the shell is removed would cause that crack to flex and therefore, spread.

Roger

I don't attach the shim to anything, just slip it between the shell and the frame.
A square or rectangle of styrene with a hole punched in the center would be fine. You will have to experiment to determine what thickness to use. The hole can be oversized. I forget how I managed to get the shim's hole aligned with the body & frame screw holes.

I figure that the shim prevents the shell from flexing to the point where the crack will spread.

What do others think?

Rather than JB Weld I would suggest a liquid solvent adhesive like Tenax or Plastruct. It will weld the plastic together. A small drop on the backside is all that is needed. Capillary action will draw it into the crack. 

Pete

You might try some Testors styrene liquid cement on the inside on the cracks.  This liquid cement is very thin solvent and will soak into the crack and weld it shut.  Be careful not to use too much.

C W shim suggestion sounds like good preventative measure.

Charlie

I've never used those products. Going to look into them for sure. Thanks, guys

Roger

If you have room for a shim then glue it to the inside of the shell, it will prevent the crack from enlarging.

The problem with any thin glue is keeping it from coming up to the surface on the OUTSIDE of the shell. It seems that anytime I use a thin glue to try to glue a crack from the inside, some of the glue makes its way to the surface of the outside.

   The solvent cements are the way to go, but they weld vs glue. Take some time to learn to use it on scrap.

    Be sparse with applying, and patient while the chemicals do there thing. Each plastic takes a different time period before it softens. Overkill amounts just mean more softening to the point of melting and drooping if its over used. Thinness means keeping an eye on and good control over any applying; it' as runny as water.

JBw might work, but it doesn't do as well in very small amounts, I use other epoxies and a filler material if its tiny. I've also had it pull away from smooth plastics, like a paint chips on too smooth a surface. Definitely rough it with some coarse sandpaper first, and clean it too.

   A backer on the shell holds the best overall chance at long term success IMO. You might not need a shim after either

   I've seen them live for years after a crack with nothing done but being more careful using it. The mounting solution I liked best was rubber or plastic washer, similar shim and a nylon screw.

Good luck!

The best shim will be a piece of styrene of the proper thickness. Then glue to the shell over the hole using the same solvent cement. It will fill the space and also reinforce the crack. Drill it out after the solvent has set, a few hours is best.

Pete