When cutting sections of a roadway with a heavy-duty, diesel-powered concrete saw, the blades and machine must safely and powerfully work together with the material being cut. But occasionally, thermal expansion of the concrete causes the blade to pinch in the kerf of the cut.
That’s when a little 10-inch-diameter clutch located on a Husqvarna diesel-powered flat saw provides a level of safety unavailable on most competitive machines. The clutch, made by Warner Electric, South Beloit, Ill., allows the operator to disengage the blade drive while leaving the engine running. This allows the operator to free the blade by moving the large saw using the power drive.
It’s a safety benefit that is also an ergonomic and convenience benefit, because flat saws can weigh up to 1500 pounds and moving them with the power drive, without the blade spinning, significantly reduces operator fatigue.
“When operating a saw without a clutch, the operator must shut the saw engine off and manually move the machine,” says Don Meister, senior design engineer, Husqvarna Construction Products, Olathe, Kan. “Or the operator has to move the saw while the engine is running and the 60-inch saw blade is rotating, which presents a safety issue.”
The clutch also allows the saws to meet European safety requirements.
The Model SF1000 clutch has been manufactured by Warner Electric, an Altra Industrial Motion company, for more than 15 years. The same basic clutch fits different model saws with various engine sizes (ranging from 48 to 84 hp), with only small changes in the armature spring configuration needed between models. The armature is modified so the spring orientation is outward to bolt directly to the flywheel, and the flange-mounted field bolts directly to the face of the gearbox.
The clutch is supplied in three pieces, which is mounted into the drivetrain during saw assembly. The field coil attaches to the stationary gearbox, the armature attaches to the engine flywheel, and the rotor attaches to a hub wheel, which is attached to the input shaft.
Custom hubs and flywheels were designed into the saws to adapt to the clutch. Depending on the model, flat saws generate 50, 60, or 100 foot-pounds of torque. The static torque rating of the clutch is 200 foot-pounds. Actual test results range from 720 to 940 foot-pounds of torque at 25º F, and 840 to 1050 foot-pounds at 70º F.
“This is a modified standard Stationary Field Clutch, but the robustness of design and its ability to provide more torque than normally necessary provides the maximum safety in operation,” says Gary Haasch, Warner Electric product and engineering manager.
“We’ve done extensive testing with this basic product over the years, but the testing for this particularly application was done primarily by Husqvarna,” says Haasch. Testing involved dynamometer, high-speed, low-speed, and field testing, according to Meister. “We’ve sold thousands of saws with the clutch and have had excellent results.”
David Brooksbank is director of marketing at Altra Industrial Motion, Braintree, Mass.