A steel pipe distribution center reported that a Heli CPD50 heavy-duty electric forklift (5-ton capacity) had a severe "wobble" in the rear end when turning, and the mast would "jam" when lifting heavy coils.
The technician inspected the "Steering Axle." In heavy-duty forklifts, the rear axle is a turntable design. He found that the "Axle Pivot Pin Nut" (the large central nut securing the axle to the chassis) had backed off by 5mm. This allowed the entire rear axle assembly to rock back and forth. The wobble was the axle shifting on its pivot. The nut had loosened because the "Cotter Pin" (split pin) had sheared due to high-frequency vibration.
The mast jamming issue was related to "Chain Tension Asymmetry." The Heli CPD50 uses two lift cylinders and two chains. He measured the chain tension with a gauge. The left chain was 20% tighter than the right. This imbalance caused the inner mast frame (stage 2) to tilt slightly sideways inside the outer rails. When lifting a 4-ton coil, the tilted frame caused the rollers to bind against the rail edge, creating the "jam" sensation.
The repair involved re-torquing the axle pivot pin nut to 500 Nm and installing a new high-strength split pin. For the mast, he loosened the chain anchor bolts, leveled the fork carriage, and re-tensioned both chains equally. He also lubricated the mast rails with molybdenum grease. The steering became stable, and the mast lifted smoothly without binding.
