What is in this article?:
- Hydraulics make refuse truck quick, quiet, and efficient
- Meeting many challenges
- Changes see quick results
Power-On-Demand hydraulic system helps make the McNeilus ZR Series the fastest side-load refuse truck in the waste reduction industryand with a 15% fuel savings to boot.
Meeting many challenges
McNeilus called on us in early 2009 with the need for a complete hydraulic system for the new sideloader using CANbus controls for optimum performance. McNeilus’s initial thought was to equip the system with traditional fixed-displacement gear pumps, and we responded by specifying hydraulic control valves to complete the system. After evaluating the performance and fuel demands of the prototype hydraulic system on a side-loader during test trials, McNeilus decided to take the road less traveled and equip the truck with a full POD system using piston pumps.
Because the full-eject body is equipped with large telescoping cylinders that run the packing mechanism, the first challenge was to size the pumps to achieve adequate cycle time for the packer cylinders and to fit behind the transmission without interference.
Packer cylinders typically have slow pack extend and retract cycle times due to the high fluid volume required to extend the packing panel during each packing cycle. The trucks are designed for 1000 to 1500 lift cycles per day, and the pack panel extends and retracts twice for each lift cycle. Consequently, instances could occur during routes with frequent stops that the packer panel may not stop running. And in some cases, the packer panel might not keep up with the lift circuit, which would increase route time. A large piston pump would provide the flow required. However its bulky size and cost did not make it an attractive option.
Competitive products equipped on the ZR arm were also causing concerns. A pair of motors on a trolley lift and an over-center valve to control motor movement were wasting energy by generating excessive heat during performance testing. Another problem area was hydraulic fluid leakage due to adapters and fittings that became loose when hoses were extended or twisted during body lift operations.
Full replacements offer system solutions
While considering pump options, we realized that the arm operated quickly during the garbage can dumping cycle and then came to a rest as the packer panel was still extending and retracting to clear the hopper.
This meant that if the arm pump and packer pump could work in tandem while the arm was stationary and the packer was still cycling, the cycle time would improve dramatically. As a result, we selected a tandem 80-cc Eaton 420 Series pump for the application.
Applying the POD load-sensing technology, we designed a custom Vickers MCD manifold with the capability to combine pump flows during packer extend and run independently when the arm must function, resulting in a dramatic reduction in packer cycle time from 17 to 10 sec. Included in the manifold assembly are Eaton’s Vickers solenoid valves, proportional valves, flow regulators, check valves, shuttle valves, and differential pressure sensing logic elements.
Controlling the loader arm proportionally and smoothly was another circuit requirement that benefited from the POD load-sensing technology. A three-section Vickers CMX 100 electrohydraulic load-sense valve was chosen to run the arm reach, grabber, and trolley lift functions due to its capability to precisely manage proportional flow. Using the valve resulted in faster cycle time with less fatigue on the truck structure, along with improved fuel savings by using full POD technology.
To overcome the excessive heat caused by the motor trolley circuit, we teamed up with Tony Montabon, Eaton’s on-site applications engineer at McNeilus, and partnered with McNeilus engineers to evaluate the arm performance and chose Eaton 8.0 in.3 T motors and Integrated Hydraulics’ dual over-center valves as replacement components. Also specified were Aeroquip GH493 half-bend radius, high-pressure hose assemblies that withstand the tight bend radii required as they move in and out during arm reach. The tightbend radii allowed McNeilus to use larger diameter hose assemblies, resulting in a dramatic reduction in wasted heat, thereby improving the efficiency of the circuit.
The STC threadless adapters were specified in locations in which hoses move while the body lift mechanism is activated. This selection was based on their swivel capability when not under pressure and that they use a snap ring to connect the male with the female, which seals on an O-ring to result in a leak-free connection. This is McNeilus’s first application for STC connectors. They are providing leakfree performance and are easy for assembly line crews to install.