Here are a few controllers from my past. The first is my version of the Gorski frame controller. This was originally made with an internal resistor. The ball bearing pivot uses a brass tube that has a screw threaded through the frame along with braces to keep it from snapping off. The trigger is hand made with brass tubing and a nylon insert. It is probably from around 1974 or so.
This next picture is what is left of my Cotton external resistor controller. I am pretty sure I had this at the Bicentennial race at Joel's. I can't remember anything about the handle but you can see that it had 2 external resistors mounted in a box that sat on the track panel. The cinch plug allowed you to switch to different resistance boxes. The very long cable to and from the box added a lot of resistance and made the controllers feel like a higher ohm that they were labeled.
This last design is my first attempt at an electronic controller. You would connect your controller to the brass studs then plug in a small control wire to drive the transistor signal. Very close in layout to today's controllers with the heatsink sitting on the track panel. This never got past a prototype. Early 1990's vintage.
