So I was working on some PG188 transmissions- specifically converting them from 775 to 550 motors- and I noticed something that struck me as odd.
The bodies and the endplate on the output shaft side are steel, as are the 550 conversion plates. They are, as we all know, obscenely heavy. But here’s the thing: The endplates that the motors attach to? Plastic. And these are the things that the bolts holding the whole assembly together thread into! And not only that, but the plastic is webbed! What does that gain them? Certainly not weight savings.
My question is, why do they do this? Does anybody know?
Presumably they expect substantial bending loads on the output shaft end, and therefore provide strong support for its bearing.
The webbing is likely intended to maximize stiffness while minimizing material consumption. The motor end shouldn’t be subjected to loads much larger than the bending moment due to the motors’ own mass, so it’s understandably weaker.
There are many other possible considerations that could have driven those decisions, particularly with regard to the economics of mass production. Perhaps someone from AndyMark will see this thread and provide more detailed comments.
I have not looked inside one of these recently. Can someone who has please tell us if the openings in the motor mounting plates are aligned with the motor’s ventilation ports?