Danfoss RDM Service guide
Service Manual
Cartridge Mount
Reverse Displacement Motors (RDM)
powersolutions.danfoss.com
Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
Revision history Table of revisions
Date Changed Rev
May 2016 new housing 0104
February 2015 update Port locations and gauge installation AC
November 2014 add K Frame AB
May 2014 First edition - Danfoss layout AA
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Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
Contents
General Information
Overview..............................................................................................................................................................................................4
Safety precautions............................................................................................................................................................................4
Symbols used in Danfoss literature............................................................................................................................................5
Basic Design........................................................................................................................................................................................5
Key Features....................................................................................................................................................................................... 6
Schematic Diagrams........................................................................................................................................................................7
Technical Specifications
Overview..............................................................................................................................................................................................8
Features and Options......................................................................................................................................................................8
Specifications.....................................................................................................................................................................................8
Operating Parameters.....................................................................................................................................................................8
Electrical Parameters.......................................................................................................................................................................9
Fluid Specifications..........................................................................................................................................................................9
Features
Output shafts...................................................................................................................................................................................10
Controls............................................................................................................................................................................................. 10
Pressure measurements
Required tools.................................................................................................................................................................................12
Port locations and gauge installation.....................................................................................................................................12
Initial start-up procedures
General ..............................................................................................................................................................................................13
Startup-procedure.........................................................................................................................................................................13
Fluid and filter maintenance
Recommendations........................................................................................................................................................................ 14
Troubleshooting
Excessive noise and/or vibration..............................................................................................................................................15
System operating hot...................................................................................................................................................................15
Motor shifting irregularities....................................................................................................................................................... 15
Minor repair
Shaft seal replacement.................................................................................................................................................................16
Remove the shaft seal.............................................................................................................................................................16
Inspect the components........................................................................................................................................................16
Install the new shaft seal........................................................................................................................................................16
Shifting Valve...................................................................................................................................................................................17
Remove shifting valve.............................................................................................................................................................17
Inspect the components........................................................................................................................................................17
Install shifting valve................................................................................................................................................................. 17
Anti-Cavitation Valve....................................................................................................................................................................17
Remove the anti-cavitation valve.......................................................................................................................................17
Inspect the components........................................................................................................................................................18
Install the anti-cavitation valve............................................................................................................................................18
Speed Sensor installation and adjustment...........................................................................................................................18
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Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
General Information
Overview
This manual includes information for the installation, maintenance, and minor repair of the Reverse
Displacement Motors (RDM). The manual includes a description of the units and their individual
components, troubleshooting information, and minor repair procedures. Performing installation,
maintenance, and minor repair of RDM Motors according to the procedures in this manual will not affect
your warranty.
Performing minor repairs requires the unit to be removed from the vehicle/machine. Thoroughly clean
the unit before beginning maintenance, or repair activities. Since dirt and contamination are the greatest
enemies of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially
important when changing the system filter and when removing hoses or plumbing.
A worldwide network of Danfoss Authorized Service Centers (ASCs) is available for major repairs. Major
repairs require the removal of the unit's endcap, which voids the warranty unless done by an ASC.
Danfoss ASCs are trained by the factory and certified on a regular basis. You can locate your nearest ASC
using the distributor locator at www.powersolutions.danfoss.com.
Safety precautions
Always consider safety precautions before beginning a service procedure. Protect yourself and others
from injury. Take the following general precautions whenever servicing a hydraulic system.
Warning
Unintended vehicle or machine movement hazard
When using the RDM in combination with S45 open circuit pumps with LS or EPC be aware that there will
likely be motor movement as long as the engine is turning. Due to the LS-setting of the pump, a standby
pressure will remain in the system even if the normally closed control is fully energized. Lowest standby
pressures to the motor, 15-18bar or above, may be enough to turn the RDM and has the potential to
cause injury or damage.
Warning
Flammable cleaning solvents
Some cleaning solvents are flammable. To eliminate the risk of fire, do not use cleaning solvents in an
area where a source of ignition may be present.
Warning
Fluid under pressure
Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious
injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing with
hydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, or
components. Never use your hand or any other body part to check for leaks in a pressurized line. Seek
medical attention immediately if you are cut by hydraulic fluid.
Warning
Personal safety
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
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Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
General Information
Symbols used in Danfoss literature
WARNING may result in injury Tip, helpful suggestion
CAUTION may result in damage to product or
property
Reusable part Apply grease / petroleum jelly
Non-reusable part, use a new part Apply locking compound
Non-removable item Inspect for wear or damage
Option - either part may exist Clean area or part
Superseded - parts are not interchangeable Be careful not to scratch or damage
Measurement required Note correct orientation
Flatness specification Mark orientation for reinstallation
Parallelism specification Torque specification
External hex head Press in - press fit
Internal hex head Pull out with tool – press fit
Torx head Cover splines with installation sleeve
O-ring boss port Pressure measurement/gauge location or
Lubricate with hydraulic fluid
specification
The symbols above appear in the illustrations and text of this manual. They are intended to communicate
helpful information at the point where it is most useful to the reader. In most instances, the appearance
of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.
Basic Design
The Reverse Displacement Motors (RDM) are medium power two-position axial piston motors
incorporating an integral servo piston. They are especially designed for operation in open circuit, non
propel applications. With the ability to shift over center, this motor combines reversing functionality and
the simplicity of open circuit design without the need for additional, external valves (HIC’s). For fan drive
system design guidelines refer to Danfoss publication: Hydraulic Fan Drive Systems - Design Guidelines,
520L0926
The RDM uses the existing and proven technology of the Danfoss L/K motor. These motors have been
optimized with regard to options, life, package size and installed cost. The RDM consists of five unique
rotating groups (displacements) in two housings with cartridge mounting flanges. Maximum speeds and
maximum applied pressures for each displacement vary. The standard control is an integrated shift valve
that uses system pressure. The integral servo piston controls motor displacement. The motor is spring
biased to forward displacement and hydraulically shifted to reverse displacement.
Displacement for both directions is set with fixed internal stops. The integrated shifting valve in
combination with large diameter servo piston allows smooth shifting between forward and reverse
rotation. For system protection the motors are equipped with an integrated anti-cavitation and shock
valve. The motor is ideally configured for installations requiring compact packaging and optimized
plumbing with one face of the motor containing all hydraulic porting.
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Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
General Information
K Frame Cross Section
Key Features
1 Servo piston 7 Slipper
2 Bias springs 8 Piston
3 Swashplate 9 Valve plate
4 Output shaft 10 Endcap
5 Shaft seal 11 Cylinder block
6 Bearing
Designed For Durability and Flexibility
•
Designed for open circuit applications
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Five displacements allow the optimum selection of a hydraulic motor to fit your application
•
Uses the existing and proven technology of Danfoss L/K motors, for maximum reliability
Installation and Packaging Benefits
•
Short and compact total installed package
•
High Efficiency - nine piston rotating groups with a positive and negative 18 degree maximum angle
•
Uses system pressure for shifting - no external pressure supply needed
•
Integrated shifting valve enables reversing - no external valves needed, which means less hoses, less
losses providing a simple and clean installation
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12Vdc and 24 Vdc shifting valves
Wide Range of Options
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Fail Safe: Without control signal, the motor is biased to maximum forward speed
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Damped shifting
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Shaft options with dust seal protector
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Integrated system protection - anti-cavitation and shock valve
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High capacity bearings to withstand axial fan forces
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Complimentary to Danfoss Series 45 open circuit pumps with electronic proportional control
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PLUS+1 micro controller with fan drive software available
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Variety of porting options allow for easier system configurations
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Pressure port A (CW rotation)
Pressure port B (CCW rotation)
Cartridge
A
B
L1
reverse
RDM
Cartridge
A
B
L1
reverse
RDM
Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
General Information
Metric O-Ring boss
‒
SAE O-Ring boss
‒
Split flange
‒
•
A speed sensor is available
Schematic Diagrams
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Service Manual
Reverse Displacement Motors (RDM), Cartridge Mount
Technical Specifications
Overview
Specifications and operating parameters for RDM motors are given here for quick reference. For
additional information, see Operating Parameters, Features and Options, and Product Coding.
Features and Options
Mount
Motor type
Displacement
Rotation
Installation position
Porting
Output shafts
Control options
Displacement limiter
Dust seal
High capacity bearing
Speed sensor
Anti-Cavitation-Valve
Cartridge
Inline, axial piston, open circuit, reverse displacement motors
L: 25, 30, or 35 cm3 [1.50, 1.83, or 2.14 in3]K: 38 or 45 cm3 [2.32, or 2.75 in3]
Bidirectional
Discretionary: Housing must always be filled with hydraulic fluid
Split flange - SAE O-ring boss, Metric O-ring boss
Tapered, 0.875 in Dia, 1.5 in/ft taper; Straight key, 0.875 in Dia, with dust seal
Integrated shift valve, 12Vdc/24Vdc
Fixed maximum and minimum displacement limiters available
Standard - refer to Features and Options in the RDM Technical Information manual.
Standard - more options available
Available - refer to Features and Options in the RDM Technical Information manual.
Standard - refer to Features and Options in the RDM Technical Information manual.
Specifications
Parameter Unit LM25 LM30 LM35
Displacement (maximum) cm3 [in3] 25 [1.50] 30 [1.83] 35 [2.14] 38 [2.32] 45 [2.75]
Weight (cartridge and SAE-B) kg [lb] 17.5 [38.6]
Mass moment of inertia of rotating components kg•m
Theoretical torque N•m/bar
2
[slug•ft2]
[lbf•in/1000psi]
0.0017
[0.0012]
0.40
[244]
0.0016
[0.0012]
0.48
[293]
0.0015
[0.0011]
0.56
[347]
KM38 KM45
0.0023
[0.0017]
0.60
[366]
0.0023
[0.0017]
0.72
[439]
Operating Parameters
Parameter Unit LM25 LM30 LM35 KM38
System pressure
Output speed
(at max. disp.)
Case pressure limits Rated bar [psi] 0.5 [7] above outlet pressure, 2 [29] maximum pressure
rated/continuous
maximum 350 [5075] 350 [5075] 325 [4715] 350 [5075] 325 [4715]
rated min-1 (rpm) 3400
maximum 3950
Maximum 2 [29] above outlet pressure, 6 [87] maximum pressure
bar [psi]
260 [3770] 260 [3770] 260 [3770] 260 [3770] 260 [3770]
3500 3600
4150 4300
3600 3500
4000 3900
KM45
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