Actually what would be difficult would be to mass produce cheap plastic pressure plates with a smooth enough surface and precise enough pressure to press against the film and still allow the tiny spring-loaded claw to properly perform a pulldown without slipping or tearing perfs. Try pushing down a S8 pressure pad and sliding the film over it with your finger, it's horribly sticky. The pressure of a Standard 8 pressure plate that does actually press on the film (with a highly polished metal surface and twice the width) is only about 50 grams.
The reason S8 film isn't constantly pulled through by the take-up and blurring every frame is in the cartridge design and the take-up clutch. Within the cartridge the film bends sharply around a pin before being taken up, which provides enough resistance to make the take-up spindle slip until the claw feeds another frame of film through and relieves the friction going around the pin.
The outer rails in the gate guide the film but at certain points also rest upon the plastic tabs in the cartridge pressure pad that extend out either side of the film at the gate aperture and also (looking at the cartridge) at top right and bottom left. You will find cutouts at these positions in the taller, sloping side-rail guides of the gate where the surface has been machined down to something like 0.17 or 0.18 mm (0.15 mm film thickness plus room to move) higher than the inner rails upon which the film rests. The precision is in the camera gate, not the cartridge, which just needs the pressure pad area under the film and its extending tabs to be flat.
Edited by Dom Jaeger, 29 April 2013 - 04:06 AM.