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Friday, August 24, 2018

Rotary Coupling Manifold E45 Bobcat Excavator Remove and Reseal

Mobile Hose Fixers & Hydraulics 
Removes, Reseals and Re Installs Rotary Manifold on Bobcat E45 Excavator in 7 hours.

Have you ever wondered how the high pressure hydraulic oil (at 270 Bar 4000 PSI) that operates most of functions on an excavator can reach the track drive motors and blade while at the same time the cab, operator, boom, dipper, and bucket and the rest of entire top assembly (including counter weight and engine) can continue to rotate in either direction? 

Answer = A Rotary Manifold, Rotary Coupling or Rotary Joint.

To see a great visual explanation on how these rotary couplings work check out this pretty interesting youtube video, for earth mover section skip to 1:15 seconds in.

Heavy equipment rotary coupling starting at 1:15 seconds  

What is a Rotary Manifold ?
Simply explained a rotary Manifold is a large diameter drilled and grooved shaft that rotates in a fixed high pressure cylinder. 

The cylinder barrel has ports drilled along its length and the shaft is specially drilled and grooved to distribute the high pressure oil through to the ports drilled in the cylinder barrel. 

Multiple special seals and O rings are used to isolate each of the individual grooves or sections machined into the shaft. It is very clever and at the same time to so incredibly simple. 

The Symptoms of a Bad Rotary Coupling 
These can Vary from simply annoying to weird  for example
  • Oil leaking on to the ground or into the belly of the machine
  • Strange track drive performance (some operators call it a Lazy Drive) pushing both drive levers fully forward and the machine does track straight and either veers to the left or right and you having to compensate with less power to the more powerful less Lazy Drive
  • Operating one function like the high speed and having the blade move up or down 
  • Having to constantly adjust the blade Up because it keeps creeping down.
All the symptoms above could be indications that the seals in the rotary coupling may have deteriorated or failed. 

There are a series of test that we can carry out to confirm that it is the seals in your machine's rotary coupling that have failed and it is not the track drive motors or cylinder seals on the blade that are the problem.  Contact us with the link below.      

Want us to trouble shoot your Excavator problem or for Bobcat Service Maintenance and Hydraulic Hose Repairs, please click here



Rotary coupling assembly removed from  machine  after disconnecting all hydraulic hoses and removing some adaptors and location bolts 




Grooved and sealed rotary shaft each grove represents a function in this example 8 grooves for 8 functions, for example, Left Track Motor Forward & Reverse Grooves 1 & 2 , Right Track Motor Forward & Reverse grooves 3 & 4 , Track Drives High Speed Mode groove 5, Track Motors Case Drain groove 6,  Blade Up & Down grooves 7 & 8 . 

Total time including draining hydraulic oil tank disconnecting and reconnecting all hoses and testing, 7 hours. (please not rotary coupling seals need to be ordered in advance of job commencing)

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