Eaton’s Geroler® Portfolio
Char-Lynn product line
Five things to consider when choosing
the best Geroler motor for your needs
By Todd Degler, Product Manager,
Eaton Hydraulic Motors
When selecting a gerotor or
Geroler motor there are many
items to consider. Performance.
Quality. Reliability. Support.
Cost. Sounds pretty basic, but
with the influx of new entrants
into the market, it is clear not
all manufacturers are the same.
Choosing the wrong one could
lead you down the wrong path
of costly recalls and frustration.
Before selecting your motor,
let’s discuss what sets a gerotor
or Geroler motor apart from the
others on the market.
The gerotor motor, or generated
rotor motor, has been around for
decades. In fact, the first gerotor
motor in Eaton’s Geroler®
Portfolio was manufactured over
65 years ago. Soon after, Eaton
invented the Geroler motor to
meet the needs of the market
and improve upon performance,
reliability, quality and cost while
still providing quality support.
Gerotor and Geroler motors
use what is termed as the Orbit
principle, which is what gives
the motors their tremendous
power density and compact
size. A gerotor motor star has
six teeth and seven lobes.
The spaces among them are
pressure chambers. Pump
fluid flows into these pockets,
creating high pressure in one
chamber and low pressure
in another. This creates an
imbalance of forces, which
causes the gerotor motor star
to rotate, or orbit. A gerotor
motor star orbits multiple times
(image 1) – typically six to eight
times depending on the specific
star and ring geometry – for
each complete single revolution
within the outer ring. Eaton’s
Geroler Portfolio uses the
gerotor principle, but incorporate
Eaton’s advanced Geroler
technology (image 1). Geroler
motors use rollers instead of
lobes which reduce friction,
wear, and improve low speed
performance, extending the
motors life.
Gerotor and Geroler motors
deliver from 10 to 50,000 inch
pounds of torque and can
operate at speeds up to 2,000
RPM. Because of their simple
design and compact size, they
can be used in both mobile
and industrial applications.
However, they are ideal for
mobile applications – especially
agriculture, material handling and
construction – because of their
incredible power density.
machine will cause inconsistent
results. What are the impacts
of decreased product quality on
your business’s reputation?
Ring
Ring
Star
Star
Roll
Gerotor motor
Speed and torque requirements
of the application will determine
the size of a gerotor or Geroler
motor. This will point users into
what displacement (how much
fluid is needed to turn one
revolution) is needed. Speed
and torque can be determined
with the following basic motor
equations. These are the starting
points for finding the right
sized motor.
Theoretical Torque (in-lbs) = CIR
x Pressure differential/(2Pi)
Theoretical Speed (RPM) = GPM
x 231 / CIR
So, when it comes to choosing
which manufacturer’s gerotor
or Geroler style motor to use in
your machine, it’s just as simple
as “Potato, pah-tato”, right?
Not really!
Geroler® motor
Here are five things to
consider when deciding on
the right gerotor and Geroler
motor for your needs
Performance
It is always a good idea to ask
for mechanical and volumetric
efficiency data, but make
sure the test data is over an
extended period of time. Many
manufacturers tune performance
to peak in the first few hours
of operation, but then degrade
quickly. Performance that
degrades quickly will not
do your machine or your
customer justice.
Compare apples to apples.
Hydraulic motor performance
data is not standardized. Be
wary of ratings and test data
that do not include all the
performance test parameters.
“A performance rating without
an oil viscosity is worthless.”
Consider the performance of
not just the product, but also
the team of support. Will they
deliver the product on-time?
Will they provide support in
critical times?
Quality
Does the manufacturer have a
history of consistent quality?
Ask for the quality data and
let the data speak. Some
manufacturers do not have
the process controls to ensure
repeatable performance.
Gerotor and Geroler motor
grinding is not all the same.
Grinding star profiles outside the
capabilities of the form grinding
Look for a manufacturer that
focuses on using high-quality
materials and follows industry
standard manufacturing
processes. Some manufacturers
decrease the cost of their
product by using inferior
materials or speeding up
processes like heat treating and
form grinding.
Consider warranty options.
Does the manufacturer you
choose have a 2-3 year standard
warranty? If not, why?
Reliability
Reliability is quality over time.
Your machine needs both. Look
for a manufacturer that has a
track record of being reputable.
In this game it’s true that
history is the best predictor
of the future.
Can you count on the
manufacturer to be a leader
in technological innovations?
With the time, effort and
resources you’re putting into
developing your machine, make
sure you’re partnering with
a manufacturer that can help
position your business as a
leader in the industry.
Consider where the motor is
made. Is it American-made?
Can you rely on the
manufacturing materials used
and standards practiced in the
manufacturing location?
Support
Consider the long-term
relationship of your business and
the manufacturer. Will you get
the support you need now and
in the future? A product is only
as good as the support system
that surrounds it.
Investigate the manufacturer’s
options for additional support.
Would you benefit from CAD
modeling support or the
creation of a custom solution?
Remember custom solutions
will differentiate your machine
from the competitor.
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Do you just want a part or do
you want a system of solutions?
Some manufacturers have the
know-how and resources to
provide a custom system of
solutions for your machine.
Others can provide a singular
part but may not have the
capabilities to provide insight
and recommendations on
improving the machine’s design.
Cost
Obviously cost is very important.
However cost is really a function
of all the previous above items.
Sacrificing the above items can
provide a lower cost, but what
will that do to your machine
and your customer when
issues arise?
Some manufacturers try to
keep costs low by having a
“one size fits all” approach to
their motor portfolio; however
this compromise often leaves
you with a solution that really
does not work the way it should
on your machine. Look for
quality products that fits your
application, rather than the
cheapest option that will likely
need to be replaced
more frequently.
There’s certainly no shortage
of things to consider when
choosing the best gerotor
and Geroler motor for your
needs. As you consider your
options, think of Eaton. With
the broadest and most unique
Geroler Motors portfolio in the
industry as well as a team that
provides unsurpassed support in
modeling and custom solutions,
Eaton is the manufacturer with
the history and expertise you
can feel proud to partner with.
Learn more about Eaton’s Geroler Motors
Portfolio here.