I finally found an instruction guide for my Panasonic RK-T28 cup wheel typewriter. It’s actually the instruction guide for a higher-spec RK-T40, but gives directions on how to change the cup wheel.
I already knew you had to push the print carrier all the way to the right, so that the cup wheel ended up aligned with a small hatch on the underside of the machine.
The cup wheel in the machine has a black plastic lever rather than an exposed looped metal clip, but depressing the lever while pulling the knob upwards doesn’t help. The wheel won’t budge. A black lever and a white lever to the left of the wheel (as pictured below) do not do anything to free the wheel either. So back to square one.
Being able to quickly swap a daisy wheel without all the rigmarole entailed for the above cup wheel is an obvious advantage that the daisy wheel has.
I read somewhere, possibly Panasonic’s own sales literature, that these cup wheels are more durable than daisy wheels. Not sure why, but they’re undoubtedly much slower. The gear wheel and the stepper motor (I guess) that the cup wheel engages, obviously slows things down a lot, perhaps reducing wear and tear in the long run, the cup wheel being, I suppose, the tortoise to the hare of a servo-motor-driven daisy wheel.
NASA won’t be calling me any time soon …