Deja vu all over again
Hi Robert,
Thanks, now I remember watching that video a few years ago, it all makes sense to me now. I guess the use of the term "crankshaft" had me a bit mystified, since there are no conecting rods or pistons, or even cylinders involved.
From my automotive restoration work, I believe that the pin that connects the "crank" to the trunnion would be called the "trunion pin". At least that's what it's called in the ball-and-trunion type of U-joint in my vintage cars.
One big advantage to the offset design of the Unimatic pulsator mechanism is that it utilizes helical gears. Those are the gears with diagonal teeth, such as the one you are rotating with your finger in the video. Helical gears tend to run much quieter than "straight" gears, although they can be a bit more finicky about proper clearances and such. While I can envision a setup where the motor rotation is translated to a vertical linear movement using straight cut gears, it would be noisy and probably more bulky than the Unimatic design.
The shared characteristics of the Unimatic design to a ball-and-trunion U-joint and certain aspects of a differential is perhaps not too surprising, considering Frigidaire's General Motors connection of the time. Although modern automobiles use cup-and-cross u-joints in combination with splined shafts to achieve power transfer with freedom of motion, until the 60's the ball-and-trunion could still be found in cars (my '64 Valiant has one up front by the transmission, and my '50 Plymouth has one at each end of the driveshaft).
