Street sweepers may not seem like the most demanding application for mobile hydraulics. But the drives that propel these machines usually work in very dirty conditions and generally don’t receive much preventive maintenance. Therefore, components must provide reliable operation and long life while having a high tolerance for contamination.
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Johnston Sweepers use MS02 and MS05 cam-lobe type motors from Poclain Hydraulics. The motors feature oversized ports for low heat generation and have multiple integrated features for a simple design and to reduce assembly costs.
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Engineers at Johnston Sweepers, Dorking, England, are well aware of these demanding conditions, so they design machines that are simple and rugged. To this end, they collaborated with experts at the UK office of Poclain Hydraulics, Verberie, France, about model CN200 and CN400 compact sweepers.
“The machines are in some cases very poorly maintained and operated by inexperienced drivers who have not had adequate training. It has even been known for people to go directly from sweeping with a broom and shovel to driving one of our machines,” explains Mike Hasler, C 400 chief engineer at Johnston. “The machines’ components must be able to hold up to a lot of abuse.” The Poclain Hydraulics motors went through accelerated endurance testing on Johnston’s grueling proving grounds, equating to five years of extreme use. The results were 100% satisfactory.
Compact but efficient
The CN200 uses two MS02 cam-lobe type motors and the CN400 uses MS05 motors to drive the rear wheels at speeds to 40 km/hr. Empty weight of each vehicle is 2700 and 4600 kg, respectively.
“The smaller CN 200 is definitely the more challenging application of the two,” explains Mark Allport, Johnston’s C 200 technical program manager. “The combination of high traveling speed — up to 40 km/hr — and a small wheel diameter results in the motor having to turning as fast as 480 rpm.” Poclain’s MS02 motors typically rotate at a maximum speed of 280 rpm.
Although it is a single-displacement motor, the MS02 has distribution ports of a twin-displacement motor, allowing more oil to flow through to reduce heat generation. The motor also includes Poclain’s Diamond option, a heat treatment that increases the rotating group’s ability to withstand intermittent overloads.
To assist the operator in maneuvering in busy streets while efficiently cleaning their surface, Johnston sweepers integrate in-house designed controllers. One provides automotive style driving, maintaining constant engine speed in the work mode and allowing the operator to focus on the sweeping functions. The Poclain Hydraulics motors work in harmony with the controller to provide seamless speed variation and smooth shifting from forward to reverse.
Johnston personnel are quite satisfied with motors from Poclain Hydraulics. “Our assembly costs have been greatly reduced with the motors’ integrated brake and bearing support,” says Mike Allport. “We were also very impressed by the level of expertise of Poclain Hydraulics’ engineers and technicians during the machines’ design and testing.”
For more information, call (262) 321 0688 in the U.S., or visit www.poclain-hydraulics.com.