TECH TIP 11 | RELEASED 02.28.2022 | VERSION 1.0
INTRODUCTION
The planetary slip drive rotation utilizes both a mechanical parking brake and a hydraulic valve
braking system.
There are three parts to the rotation system on a Digger Derrick to protect the unit from structural
overload of the boom or rotation system.
1. The parking brake is used to lock the boom in position when the rotation system is not being used
such as road travel. The mechanical brake, located on top of the planetary gearbox, is either full
on or full off. There is typically no lubricant in this mechanical parking brake.
2. The rotation port relief valves limit the maximum side force that the rotation system will generate
when rotating the boom.
3. The slip drive protects the boom when winching or while digging or setting screw anchors when a
side load is generated.
When rotating, digging, or winching, a hydraulic pilot signal is sent to release the mechanical parking
brake. During any of these operations, a sequence valve located in the rotation slip drive hydraulic
manifold performs the braking. If a side load exceeds the sequence valve setting, the slip drive will
slip by back-driving through one of the two sequence valves. The Old-Style valve was used up until
1/1/2016. Anything after that date will have the New Style valve as shown below.
New Style
Old Style
Planetary Slip Drive Test & Adjustment
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