A quick stop at the gym revealed a couple of very interesting points.
My first assumption would have been that rubbing contact in exercise equipment is not important. After all I reasoned, friction is good for a person who needs the resistance to build muscle and stamina.
I was proved wrong. While many of the bearings I saw were plain mostly sealed ball bearings and bushings, there were a few models that utilized fluid bearings.
Pretty groundbreaking stuff considering that using fluid bearings is expensive and it cuts friction down to almost nothing.
But the more I observed, the clearer it became that the design of these machines is very much with the user in mind.
It presupposes that each user will want to adjust the resistance to their taste, rather than rely on the friction of the bearings, which is somewhat unquantifiable, and might degrade over time.
A second very interesting point is that, there is a lot of stress on exercise equipment. Actual physical stress that affects the materials it’s made out of, various components and all the various ways of making a contact joint. More importantly, due to the specific motion of each machine, different, a different set up is used. If there is a pivot point, a plain ball bearing is used, but for a pivot that the axis is offset, a jewel bearing is used. The specific applications are very well thought out, and I honestly am beginning to envy the designers of exercise equipment, mostly because of the specificity of each design. In other words, a design is made with a certain constrain, and those constrains are always followed.
Ofcourse this makes for some boring use of this equipment, since the most fun is to take a design out of context at least conceptually and attempt to reinvent another interesting use for it. Strictly speaking exercise machines are utilitarian machines, physical robots, that cannot function on their own, robots that demand robotic work from humans to reach their intent.