The heavy load is at TDC and BDC so the mechanism is already moving quickly then which is good for hydrodynamic lubrication. In fact, a wrist pin is your worst example but they seem to work fine.
I'm ok with this design. On ships for the rudder we run a system called a Rapson Slide. Older systems used to have a square block on the slide and it was quite durable. Newer foreign built systems got a cylindrical roller and they are now sloppy and prone to failure. It's been so bad most designers have moved away from the Rapson Slide. This Scotch yoke design is not unlike the old Rapson side with the flat contact points. In fact, it's quite similar to a crosshead in a recip steam engine or slow speed diesel. Higher than normal lube pressures help, the slow speed diesels use high pressure lube for their wrist pins and cross head.
I'm having a hard time picturing that and a 6" diameter piston working with about 5" of stroke at 6000rpm. The piston can be lighter, but that won't make up for the extra mass in that thing. There was a response talking about using exotic materials for weight, I think that'd be a necessity.
If you went to Mahle with money in your hand they'd likely be willing to sign a contract and build what you ask regardless of the viability.
It's easier to visualize how to develop significant oil pressure in a closed circular bushing than an open linear bearing, but I suppose it's possible.
There's a pretty thorough examination of Scotch Yoke lubrication at
This SAE paper is also interesting, though I'm not willing to spend the bucks to get a copy from SAE...
It's an indictment of the patent system, IMHO, that a patent was awarded in 2019 for a design approach that's been discussed in open literature for a long time.
It's an indictment of the patent system, IMHO, that a patent was awarded in 2019 for a design approach that's been discussed in open literature for a long time.
