Milton CAT 390D L - Manual (Page 8)

8
Undercarriage
Strong, stable and durable
Undercarriage
The undercarriage supports the swing bearing and upper structure and is the link that transmits the
reaction forces from digging to the ground. The strength of the Cat undercarriage plays a major factor
in machine stability and durability.
Track Roller Frame
The track roller frame has been improved by installing a longer stroke recoil spring and lowering the
front idler. The longer recoil spring improves durability and service life of the undercarriage, and the
offset idler increases the stability of the machine while working over the front.
Positive Pin Retention 2 (PPR2)
Track links with the PPR2 are provided as standard on the 390D L. The PPR2 is designed to prevent
looseness of the track pin in the track link and to reduce stress concentrations. The PPR2 system
eliminates pin movement for increased service life.
Carrier Rollers
The carrier rollers use a fl oating Duo-Cone seal, which reduces the risk of leaking lubricating oil.