Repairing a Slot Car Chassis

by Matt Agnew

Recently, I bought a Scalextric Ferrari F430 to participate in a club race. I figured it would be a great idea to open up the car, just to make sure everything looked race-ready inside. As I GENTLY tried to pry the motor out, the chassis snapped on both sides right under the motor mount. As there is a lot of stress on this area when inserting the motor, I knew I couldn't just put glue in the crack and hope for the best. There's just not enough surface area for the glue to bite into.

Luckily there was enough room between the motor mounts and the tires that I could glue some patches on the side of them without interference. I used some Plastruct .040" (1 mm) styrene sheet from the local hobby store.

Basically I wanted to get as much surface area as I could without interfering with the fit of the motor in the chassis pockets. The pieces were cut out with scissors and then trimmed with a file and my Radio Shack sheet metal nibbling tool. Much safer than trying to hold the piece and trim it with a sharp craft knife.

After I was happy with the fit of the patches, I glued the chassis back together with cyanoacrylate (super) glue. I've had bad experiences applying this stuff from the bottle and always use an applicator, here a sliver of bamboo kitchen skewer. I've also been known to use cut-off ends of guitar strings - the wound strings seem better.

Using the accelerating spray isn't needed, but it sure saves one from having to hold the chassis in position as it dries. The chassis wants to spring open a bit. If the crack isn't closed when the glue dries, you'll never get the motor to line up properly.

After the superglue is dry, file off any lumps. You want the patch area to be as flat as possible.

Superglue is great for setting things up, but lousy in a slot car environment. As it is brittle, you risk the glue cracking on one of the many impacts that (especially my) slot cars receive. 5-minute two-part epoxy is much better. Test clamp everything BEFORE mixing up the epoxy to make sure everything fits. I used some clear polycarbonate scraps as clamping cauls as the epoxy doesn't like to stick to it. You could also use popsicle sticks waxed up or covered in wax paper. If you don't have handy wee clamps like these, clothespins will probably suffice. You don't want too much pressure otherwise you squeeze all the epoxy out! Give the epoxy more than five minutes to cure - I left it half a day.

Word to the wise - be really careful of the taillight module - the new surface mount LEDs are very fragile and I knocked one off the board with very little effort. These are not easily repaired, if it is even possible. Reassemble the car carefully, remembering to hold your breath when snapping the motor back into place.

In hindsight, the vertical pieces of the patch probably don't do much in the way of stiffening, but I'm sure they made it easier to clamp everything up.

How's it run? Pretty good, all things considered. We did about 400 laps on it that night and it didn't seem to be any worse for wear, other than being one-eyed from the rear!

This same procedure could be used just about anywhere on a slot car chassis; I've seen broken guide supports fixed in a similar fashion.