PC35MR vs U35 vs SK75: Hydraulic Flow Rate and Bucket Cycle Time Comparison for 3.5-5 Ton Mini Diggers
What the Pump spec sheet doesn’t tell you – how to read the flow rate correctly.
It was two years ago and I heard it from a regional fleet manager just before he ordered a Kubota U35 for an 8-hour, mid-size pipeline utility team that uses a hydraulic breaker. After 6 weeks its operator was manually cycling the breaker in bursts – not due to the breaker being faulty but due to the aux circuit being starved when the arms are being moved, causing them to also operate in bursts. This loss in productivity was not reflected as a line item. It manifested itself as a blow out in the schedule for a period of three weeks.
I once pulled a fitting off a U35, the fitting was a 3/4″ JIC on the boom side feed as well and the fitting failed to reseat into the boom. Pictures show the fracture face with the characteristic crystal like/granular structure that result is from fatigue, with many cycles of pressure. The operator testified that the machine “rejected itself a little when it was grinding on hard ground.” It wasn’t all in his imagination.
I just had a thought here — of a slightly whacky site foreman who believed that the ‘jerkiness’ in his U35’s was due to contaminated diesel. Two tank drains. For a pump problem.
Data sources for the table above:https://mail.heavyequipmentforums.com/threads/broken-fitting-coupler.92669/
Most operators don’t time their own cycles. They feel them.
The SK75 is faster. Meaningfully faster. However, its operating weight as well as tail swing radius and fuel per hour are in different set of ranges. So, to use an SK75 in a small home excavation, where the equipment is used on a cycle, is a little bit too much like using a 14-inch chainsaw to trim a hedge.
Spec sheets have no expiration dates. Machines do.
