A trailing arm assembly for a suspension includes at least first and second cast components. The rotary dispenser comprises a top-mounted knob atop a clover-shaped disc, the disc being connected to a rod in a spindle-type manner. A heat-sink member uses the composite material. The first power source switch is turned off by the power source controller when the power source is on. The shank flange excels in homogeneity and dimension stability, and has a high rigidity which can assure a smooth and stable action of the hammer.