Hydrostatic Transmission Case Drain Flow and Efficiency – Part III

Rexroth A2VSL1000 hydraulic pumpIn my previous articles on hydrostatic transmissions, I described the technique for determining the condition of a hydrostatic transmission using case drain flow, and discussed the role and influence of a flushing valve when doing this.

In response to these articles, some members were still confused about the influence of the charge pump when determining case drain leakage from a hydrostatic transmission.

One reader held the view that, assuming the charge pump relief valve vents into the case of the motor and the motor case drain line is isolated from the pump, then transmission pump leakage is determined by subtracting charge pump flow from the total flow from the pump case.… continue reading »

3 Things About Troubleshooting

The Hydraulic Troubleshooting HandbookDespite his mother’s horror and protestations, my 18 year old son recently bought a motorcycle. It’s a Japanese, hog style machine. Ben would quite like a H.D. but that’s WAY out of his price range. The bike he got is 13 years old with 15,000 km (9,300 miles) on the dial. So he didn’t pay a lot for it. In fact, his bike clothes and safety gear cost almost as much as the used hog.

Anyway, being that he’s 18 and this is his first bike, he’s like a lamb with two tails. Not long after he departed for his third outing on his new machine I get a call.… continue reading »

Hydraulic Troubleshooting Step #1

hydraulic schematic drawingIn The Hydraulic Troubleshooting Handbook, I explain 12 principles which must be adhered to in order to solve any hydraulic problem effectively. Troubleshooting Principle #1 is: check and eliminate the easy things first. The benefits of this mandatory first step are clearly illustrated by a troubleshooting situation I was involved in recently.

The machine in question had a complex hydraulic system, the heart of which comprised two engines driving ten hydraulic pumps. Six of the pumps were variable displacement pumps and four of these had electronic horsepower control.

The symptoms of the problem were slow cycle times in combination with lug-down of the engines (loss of engine RPM).… continue reading »