A Few Words About Slot Car Bodies
Technical History - Bodies
It seems a contradiction that the body of a slot car, vintage or modern, is among the most ephemeral of components, an expendable item not unlike tires and braid, and yet is the single most important identifying part. If it is true that the clothes make the person, then it is likewise true that the body makes the slot car. Even in the "old days" we didn't speak of the "car with the blue motor", or the "car with chrome plated chassis", so much as referring to it as the "Yellow Lola T-70". Indeed, when speaking of "Ready-to-Run" cars it is very difficult to separate the product as a whole from the body as a part.
Although modern slot car bodies are mere wisps of exotic plastic and paint, and most are a standard actual size, hardly recognizable as the prototype they represent, this was not always so. Up through 1966, almost all slot car bodies were accurate scale representations, if not scale models, and through 1965 chassis were built and motors were selected to fit the individual body. During and after 1966, rules increasingly allowed variances from scale (beginning with body width and tire sizes) to accommodate the realities of slot car physics, which unfortunately is utterly indifferent to the disciplines of scale modeling.
Slot car bodies, especially scale bodies, are notoriously difficult to fabricate from scratch at a workbench. In the early 1960s a few brave and skilled scratch builders (Jose Rodriguez among them) would carve blocks of soft wood (commonly balsa) into scale size shapes that represented the prototype they were modeling, and then paint and race them! Most racers on the other hand simply adapted the cheap and plentiful supply of injection molded hard plastic static model bodies.
By the end of 1962, some entrepreneurial types such as Bob Braverman were producing handmade fiberglass copies of their carvings, and the "body business" came into being. Now builders had a choice (albeit small) of bodies purpose-built for slot racing. Looking for an easier way, another bright individual decided to try vacuum-forming heated plastic (usually thick, opaque styrene) over (or into) a custom mold made especially for the purpose.
This worked surprisingly well, but all the bodies up to that point were not much lighter than the injection molded hard plastic static model bodies they replaced, and because they were opaque, still had to be painted on the outside, leaving this meticulous work exposed to the rigors of competitive racing. The only real advantage "purpose-built" slot car bodies had, especially the open top sports cars with driver positions close to the rear axle, was that the interior could be shaped to fit the relatively large motors underneath, usually by making it flush, or nearly flush, with the body itself.
Searching for something thinner (e.g.: lighter) to vacuum-form slot car bodies from, manufacturers discovered newer and tougher classes of plastics, including "Butyrate". Butyrate was tough enough to make a sturdy body only 1/32" (.032") thick! The fact that plastics like Butyrate are commonly transparent is probably a happy coincidence, for now slot car bodies could be painted on the inside, so paint jobs lasted the life of the body. Even so, some manufacturers such as Hawk didn't catch on to the transparency thing right away, and made their bodies out of tinted plastic.
A few manufacturers tried forming their clear plastic bodies by pressure-forming (a.k.a. blow molding), as opposed to vacuum-forming, in a manner similar to the way plastic bottles are made. With blow-molding the fine details (body lines, grilles, scoops, gas caps, etc.) are molded into the outside of the body (where they belong) and stand out much better. Unfortunately, negative molds are considerably more difficult and expensive to make than positive molds, so the blow-molding process didn't work out so well economically for making slot car bodies.
Always looking for lighter and lighter, it wasn't long before bodies were being vacuum-formed out of .020", and then .015" thick clear plastic. They weren't nearly as sturdy as bodies made of .032" , but their lighter weight contributed significantly to the car's overall performance, and they were cheap, plentiful and easy to replace when inevitably damaged during racing.
Meanwhile, a new and incredibly tough plastic called Polycarbonate, trade name Lexan, which had been developed by General Electric in 1953 and patented in 1955, was becoming more available for industrial and private use. Model Products Corporation (MPC) experimented with it, making bodies out of thick Lexan in the middle of 1966, but the major slot car body manufacturers such as Lancer and Dynamic still pretty much ignored it until after 1968.
Lexan plastic is so tough that bodies could be made from .010" thick material, and would still be nearly "bulletproof". The only real downside was that it is very difficult to get the enamel paint used for painting Butyrate bodies to stick to Lexan (and at .010" thickness, sanding the inside of the body to get the paint to stick was problematic at very least) but somehow we all muddled through.
Today it is not uncommon to see serious competition slot car bodies made of Lexan only .007" thick, weighing less than 1/4 of their mid sixties .032" thick counterparts.
I hope you find this information and these lists helpful in identifying and choosing period-correct bodies for your scratch building projects. Just remember, generally speaking the older the body, the more scale (shorter, narrower, taller... and heavier) it will be.