This document describes a technique which is a reliable and effective way to get not only a perfectly straight chassis, but a chassis with minimal parasite internal tensions, which are left from the cooling process of the injected material, under normal manufacturing conditions where cooling happens quickly.

No slot car chassis is perfect out from the box. Care in mold making, plastic injection, and storage can make the difference between a good chassis and a warped one, but there is always room for improvement.

The principle is very simple: keep the chassis as straight as possible, heat it up, and cool it down slowly, in water, which is very important as it:

has a thermal inertia which slows down the cooling process

acts as a thermostat, thus preventing the chassis to be burnt as it will get no hotter than 100° C

floats the chassis, helping the parts that are not clamped to stay the way they should without
bending under their own weight.