What is the first thing a mechanic should do before disassembling a
used orbital motor (discarding the answers like wash hands, wear
protective gear, clean the working place and such...)? I ask this
question because the step I am going to discuss in this post is often
skipped, and although most of the times this doesn't produce negative
consequences, it potentially CAN.
Before opening any used orbital motor one should always confirm its timing
(the relation of the shaft rotation to the direction of the port oil
flow), which is a five second step and can easily be done by turning
the input shaft and noticing the port that creates suction.
The reason you shouldn't skip this simple
check is very simple - most surely your client will want the repaired
motor to be timed the way it was before! Practically all orbital motors
can be timed in two manners, but not all
orbital motors that crash on your shop bench will be timed according to
the standard manufacturer timing pattern (to top it up, the timing
pattern can differ between brands and motor models). Once you have the
motor disassembled, there's no way of telling "which way" it was timed,
which means that if you skipped the "timing check" and re-assembled the
motor "by the book", there's a small (but real) chance that after
delivering it to your client the motor will start turning the other way
- something that can create a hazard and will definitely make you look
like an amateur fool.
I am not sure if it is universally accepted, but I call motors that follow standard Danfoss pattern - right motors, and all the other - left motors. The majority of orbital motors on the market are "right" motors, by the way.Sometimes
machine manufacturers will opt for purposefully timing an orbital motor
"the other way" to allow for a more compact piping layout (when
two hydraulic motors
drive the same function, one of them being
"right" and the other one "left"). Sometimes a motor can have a
long "history" of interventions before ending up at the final owner
already re-timed. In any case it is always a safe practice to check the
timing before starting the disassembly, especially when you deal with an unknown brand or a motor that has a reference plate missing.
The same principle can be applied to radial piston
motors, that also can be "right" and "left". Due to the often large
size and the fact that the pistons inside can be retracted it is often
easier to check the timing by turning the motor with compressed air,
rather than by turning the shaft. In most cases, due to the distributor
design, it will be possible to mark its position during disassembly and
thus define timing, but again not always, so checking the timing before disassembly still remains a good practice.
It's always better to say "I did" than "I should have done"!