I am familiar with those hydraulic pumps. We used them on the railroad to propel some of the work equipment used.
They were a good pump for stationary hydraulic needs, but due to the variable terrain railroad equipment operates in, we had a lot of problems with them. I guess if the swash plate gets a "jolt" it literally shatters the pump and renders it useless...worse yet it send fragments throughout the entire system...fragments that must be cleaned out of all the pumps, motors, lines and hydraulic coolers.
We lost a lot of pumps because we were trying to propel 150,000 pound machines at 45 mph on varying grades. As the machines encountered downgrades, they would often over-speed and cause cavitation in the hydraulic lines, one split second of this and they would blow a pump. We added in hydraulic accumulators to prevent the split-second cavitation, but they still did not work as designed. One year I went through 6 of these type of pumps at over $30,000 a piece on a single piece of equipment. I ended up going to a New England Railroad before they engineered a solution to the problem.
Those pumps were a nightmare!
These drives do not look that bad however because they are coupled mechanically, unlike the swash plate pumps that require pressure, and back pressure on the swash plates to keep them from shattering. So the mechanical limitations of this does not bother me as much as Steamup's real world figures.
Darn, guess I will have to go back to perfecting my perpetual motion machine!