Page 1
Technical Information
Axial Piston Open Circuit
Reverse Displacement Motor (RDM)
powersolutions.danfoss.com
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Technical Information
Reverse Displacement Motor (RDM)
Revision history Table of revisions
Date Changed Rev
October 2016 various minor edits 0209
May 2016 corrections to Installation drawings 0208
July 2015 corrections to Installation drawings 0007
May 2015 corrections to Electrical Parameters AG
April 2015 various minor edits AF
February 2015 add Port location and gauge installation AD
December 2014 add K Frame AC
July 2014 Correction to schematic - page 20 AB
May 2014 First Edition AA
2 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 3
Technical Information
Reverse Displacement Motor (RDM)
Contents
General Information
Basic Design........................................................................................................................................................................................4
Key Features....................................................................................................................................................................................... 5
Schematic Diagrams........................................................................................................................................................................5
Technical Specifications
Overview..............................................................................................................................................................................................6
Features and Options......................................................................................................................................................................6
Specifications.....................................................................................................................................................................................6
Operating Parameters.....................................................................................................................................................................6
Electrical Parameters.......................................................................................................................................................................7
Fluid Specifications..........................................................................................................................................................................7
Operating Parameters
Fluids.....................................................................................................................................................................................................8
Viscosity............................................................................................................................................................................................... 8
Temperature.......................................................................................................................................................................................8
Open Circuit Operation..................................................................................................................................................................8
Case Pressure..................................................................................................................................................................................... 8
System Pressure................................................................................................................................................................................9
Output Speed.....................................................................................................................................................................................9
System Design Parameters
RDM application guideline.........................................................................................................................................................11
Installation........................................................................................................................................................................................11
Filtration............................................................................................................................................................................................ 11
Reservoir............................................................................................................................................................................................11
Overpressure Protection............................................................................................................................................................. 11
Series Operation.............................................................................................................................................................................12
Shaft Loads.......................................................................................................................................................................................12
Radial load formula....................................................................................................................................................................... 12
Duty Cycle and Bearing Life....................................................................................................................................................... 12
Hydraulic Equations Helpful for Motor Selection...............................................................................................................12
Name Plate....................................................................................................................................................................................... 13
Product Coding
RDM Model Code........................................................................................................................................................................... 15
Features and Options
Shaft Torque.....................................................................................................................................................................................18
Shaft torque for tapered shafts............................................................................................................................................18
Dust Seal Option.............................................................................................................................................................................18
Output Shafts.................................................................................................................................................................................. 19
Anti-Cavitation Valve....................................................................................................................................................................19
Speed Sensor...................................................................................................................................................................................20
Displacement Limiters................................................................................................................................................................. 21
Motor Rotation................................................................................................................................................................................21
Controls............................................................................................................................................................................................. 22
Installation Drawings
Cartridge (LM/KM) Dimensions.................................................................................................................................................24
Port locations and gauge installation.....................................................................................................................................25
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P108808
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Technical Information
Reverse Displacement Motor (RDM)
General Information
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.
K Frame Cross Section
4 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
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
Page 5
P108731
Pressure port A (CW rotation)
Pressure port B (CCW rotation)
Cartridge
A
B
L1
reverse
RDM
Cartridge
A
B
L1
reverse
RDM
Technical Information
Reverse Displacement Motor (RDM)
General Information
Key Features
Designed For Durability and Flexibility
•
Designed for open circuit applications
•
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
•
12Vdc and 24 Vdc shifting valves
Wide Range of Options
•
Fail Safe: Without control signal, the motor is biased to maximum forward speed
•
Damped shifting
•
Shaft options with dust seal protector
•
Integrated system protection - anti-cavitation and shock valve
•
High capacity bearings to withstand axial fan forces
•
Complimentary to Danfoss Series 45 open circuit pumps with electronic proportional control
•
PLUS+1 micro controller with fan drive software available
•
Variety of porting options allow for easier system configurations
Metric O-Ring boss
‒
SAE O-Ring boss
‒
Split flange
‒
•
A speed sensor is available
Schematic Diagrams
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Page 6
Technical Information
Reverse Displacement Motor (RDM)
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, Reversing 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 forward and reverse displacement limiters available
Standard - refer to Dust Seal Option on page 18
Standard - more options available
Available - refer to Speed Sensor on page 20
Standard - refer to Anti-Cavitation Valve on page 19
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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Page 7
Technical Information
Reverse Displacement Motor (RDM)
Technical Specifications
Electrical Parameters
Description Voltage
12Vdc 24Vdc
Maximum current 1500mA 750mA
Nominal coil resistance 5.3 Ohms 21.2 Ohms
PWM range 70-200 Hz or straight 12Vdc
PWM frequency recommended 100 Hz
Connector Deutsch connector DT04-2P
IP rating IP 65
Ambient temperature limit 80° C (175° F)
Fluid Specifications
Parameter Unit Minimum Continuous Maximum
Viscosity mm2/sec (cSt) [SUS] 7 [47] 12-60 [70-278] 1600 [7500]
Temperature °C [°F] -40 [-40] 82 [180] 104 [220]
Cleanliness ISO 4406 Class 18/13 or better
Filtration efficiency suction filtration β
=75 (β10≥1.5)
35-44
Ratings and data are based on operation with premium petroleum-based hydraulic fluids containing
oxidation, rust, and foam inhibitors.
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Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 7
Page 8
Technical Information
Reverse Displacement Motor (RDM)
Operating Parameters
Fluids
Ratings and performance data for these motors are based on operating with premium hydraulic fluids
containing oxidation, rust, and foam inhibitors. These include premium turbine oils, API CD engine oils
per SAE J183, M2C33F or G automatic transmission fluids (ATF), Dexron II (ATF) meeting Allison C-3 or
Caterpillar T0‑2 requirements, and certain specialty agricultural tractor fluids. For more information on
hydraulic fluid selection, see Danfoss publications:
Hydraulic Fluids and Lubricants, Technical Information, 520L0463,
Experience with Biodegradable Hydraulic Fluids, Technical Information, 520L465.
Viscosity
Maintain fluid viscosity within the recommended range for maximum efficiency and bearing life.
Minimum viscosity should only occur during brief occasions of maximum ambient temperature and
severe duty cycle operation. Maximum viscosity should only occur at cold start. Limit speeds until the
system warms up.
Fluid viscosity limits
Condition mm2/s (cSt) SUS
Minimum 7 47
Continuous 12-60 70-278
Maximum 1600 7500
Temperature
Open Circuit Operation
Case Pressure
Maintain fluid temperature within the limits shown in the table. Minimum temperature relates to the
physical properties of the component materials. Cold oil will not affect the durability of the motor
components. However, it may affect the ability of the motor to transmit power. Maximum temperature
is based on material properties. Exceeding the maximum temperature may result in damage to the unit.
Measure maximum temperature at the hottest point in the system. This is usually the case drain.
Temperature limits
Minimum
(intermittent, cold start)
Continuous
Maximum
- 40° C [- 40° F]
85° C [185° F]
105° C [221° F]
Ensure fluid temperature and viscosity limits are concurrently satisfied.
The motors are designed to operate in open circuits with zero outlet pressure. In open circuits, the
maximum allowed case pressure is 0.5 bar [7 psi] above outlet pressure and 2 bar [29 psi] maximum
pressure. Case drain lines must be plumbed accordingly to insure that case pressure limits are not
exceeded under any circumstances.
Maintain case pressure within the limits shown in the table. The housing must always be filled with
hydraulic fluid.
8 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 9
C
Technical Information
Reverse Displacement Motor (RDM)
Operating Parameters
Caution
Operating outside of case pressure limits will damage the motor. To minimize this risk, use full size inlet
and case drain plumbing, and limit line lengths.
Case pressure limits
Maximum (continuous)
Intermittent (cold start)
System Pressure
The specification tables in each section give maximum pressure ratings for each displacement. Not all
displacements within a given frame operate under the same pressure limits. Definitions of the operating
pressure limits appear below.
Open Circuit Continuous working pressure is the average, regularly occurring operating pressure.
Operating at or below this pressure should yield satisfactory product life. For all applications, the load
should move below this pressure. This will corresponds to the maximum allowable PC setting on the
open circuit variable pump supplying the RDM.
As the RDM will be commonly applied into fan drive systems, the maximum pressure experienced is
generally the pressure at fan trim speed. If this pressure exceeds the continuous pressure rating, a more
thorough duty cycle analysis is recommended.
Maximum (peak) pressure is the highest intermittent pressure allowed.
Maximum machine load should never exceed this pressure, and pressure overshoots should not exceed
this pressure.
0.5 [7] above outlet pressure
2 [29] maximum pressure
2 [29] above outlet pressure
6 [87] maximum pressure
Output Speed
Pressure spikes are normal and must be considered when reviewing maximum working pressure.
The RDM is designed for open circuits. Due to the shifting valve pressure limits the maximum system
pressure is absolute pressure. Differential pressure referenced to to outlet pressure is just relevant for the
maximum case pressure.
Smooth operation and output torque ripple determine the acceptable low speed operating condition.
Generally Danfoss axial piston motors will operate smoothly down to 150 rpm. In some instances, it is
possible to operate smoothly at less than 150 rpm, but performance must be verified for the specific
application. We do not recommend that any axial piston motor be sized to operate continuously at
speeds less than 100 rpm.
Rated speed is the highest input speed recommended at full power condition. Operating at or below
this speed should yield satisfactory product life.
Maximum speed rating is the highest operating speed recommended and cannot be exceeded without
severe reduction of unit life, or without risking premature failure.
Operating conditions between continuous and maximum speed ratings should be restricted to less than
full power and to limited periods of time.
For more information consult Pressure and Speed Limits BLN-9884, when determining speed limits for a
particular application.
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Page 10
W
W
Technical Information
Reverse Displacement Motor (RDM)
Operating Parameters
Warning
Over speed hazard
Especially in fan drive systems, the fan speed and accordingly motor speed is directly related to system
pressure. The maximum system pressure is defined by Pressure Compensator (PC) setting of S45 pump.
To prevent motor overspeed the PC setting needs to be calculated upfront. The maximum fan speed
should be checked at first machine start up.
Warning
Unintended vehicle or machine movement hazard
When using the RDM in combination with S45 open circuit pumps with LS or EPC controls, 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 when the normally closed control is fully energized.
Lowest standby pressures to the motor (15-18 bar, or above) may be enough to turn the RDM and has the
potential to cause injury or damage.
10 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 11
Technical Information
Reverse Displacement Motor (RDM)
System Design Parameters
RDM application guideline
RDM allows immediate reversing from maximum speed forward to maximum speed backward by
supplying voltage to the control valve. In general but especially for load with high inertia the shifting will
influence the system in terms of pressure spikes and possibly noise. To reduce this influence the shifting
should follow some guidelines.
Installation
RDM motors may be installed in any position. The motor housing must always remain full of hydraulic
fluid.
Take care to ensure air is removed and proper fluid level is achieved during system installation and use.
Fill the motor housing and system lines with clean fluid during installation. Connect the case drain line to
the uppermost drain port to keep the housing full during operation.
To allow unrestricted flow to the reservoir, use a dedicated drain line. Connect it below the minimum
reservoir fluid level and as far away from the reservoir outlet as possible. Use plumbing adequate to
maintain case pressure within prescribed limits (see Case Pressure on page 8).
Filtration
Reservoir
To prevent damage to the motor, including premature wear, fluid entering the motor must be free of
contaminants. RDM motors require system filtration capable of maintaining fluid cleanliness at ISO
4406-1999 class 22/18/13 or better.
Consider these factors when selecting a system filter:
Cleanliness specifications
•
Contaminant ingression rates
•
Flow capacity
•
Desired maintenance interval
•
Typically, a filter with a beta ratio of β10 = 1.5 to 2.0 is adequate. However, open circuit systems supplied
from a common reservoir may have considerably higher requirements. Because each system is unique,
only a thorough testing and evaluation program can fully validate the filtration system. For more
information, see Danfoss publication Design Guidelines for Hydraulic Fluid Cleanliness, 520L0467.
The reservoir provides clean fluid, dissipates heat, and removes entrained air from the hydraulic fluid. It
allows for fluid volume changes associated with fluid expansion and cylinder differential volumes.
Minimum reservoir capacity depends on the volume needed to perform these functions. Typically, a
capacity of one half the charge pump flow (per minute) is satisfactory for a closed circuit system reservoir.
Open circuit systems sharing a common reservoir will require greater fluid capacity.
Locate the reservoir outlet (suction line) near the bottom, allowing clearance for settling foreign particles.
Place the reservoir inlet (return lines) below the lowest expected fluid level, as far away from the outlet as
possible.
Overpressure Protection
Reverse Displacement Motors with anti-cavitation and shock valve have internal overpressure protection
against pressure spikes, but the maximum flow across this valve is limited. For flow rates greater than 25
l/min. external relief valves are recommended to maintain system pressure within prescribed limits.
Shock valves are adequate to protect against transient or unusually rapid load application, but excessive
or continuous flow through them adds heat to the system and can damage the fluid. Applications that
are expected to operate near the shock valve setting should use a pressure compensated pump to
minimize the risk of heat build up.
©
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Page 12
T
L
R
e
Mounting flange
90°
R
e
Axis of swashplate
rotation
R
e
270°
180° R
e
90°
R
e
0° R
e
P108737
Technical Information
Reverse Displacement Motor (RDM)
System Design Parameters
Series Operation
These motors may be operated in series configuration as long as system, charge, and case pressure limits
are satisfied. Operating motors in series significantly impacts bearing life. Contact your Danfoss
representative for assistance when applying these motors in series configuration.
Shaft Loads
Reverse Displacement Motors have bearings capable of accepting some external radial and thrust loads.
The external radial shaft load limits are a function of the load position, orientation, and the operating
conditions of the motor.
The RDM has been designed to handle typical external shaft loads from the fan drive and similar systems.
Contact your Danfoss representative to ensure proper selection of bearings and load orientation for
optimum life.
Radial load formula
Me = Re•L
L = Distance from mounting flange to point of load
Me = Maximum external moment
Re = Maximum radial side load
Shaft load orientation
Duty Cycle and Bearing Life
All shaft loads affect bearing life. We recommend tapered shafts or clamp-type couplings for applications
with radial shaft loads.
Knowing the operating conditions of your application is the best way to ensure proper motor selection.
With accurate duty cycle information, your Danfoss representative can assist in calculating expected
motor life.
Hydraulic Equations Helpful for Motor Selection
Use the following equations to compute output power, torque, speed, and input flow. Selecting the right
motor starts with an evaluation of system requirements such as speed and torque. Select a motor that
will transmit the required torque, then select a pump that will meet the flow and pressure requirements
of the motor.
12 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 13
Based on SI units
Input flow Q = (l/min)
Motor speed n = min-1(rpm)
Output torque M = (N•m)
Output power P = (kW)
Based on US units
Input flow Q = (US gal/min)
Motor speed n = min-1(rpm)
Output torque M = (lbf•in)
Output power P = (hp)
Where:
SI units [US units]
Vg = Displacement per revolution cm3/rev [in3/rev]
pO = Outlet pressure bar [psi]
pi = Inlet pressure bar [psi]
∆p = pO - pi (system pressure) bar [psi]
n = Speed min-1 (rpm)
ηv = Volumetric efficiency
ηm = Mechanical efficiency
ηt = Overall efficiency (ηv • ηm)
Vg • ∆p • η
m
20 • π
Q • ∆p • ηt
600
Vg • ∆p • η
m
2 • π
Q • ∆p • η
t
1714
Vg • n
1000 • η
v
Vg • n
231 • η
v
Q • 1000 • η
v
V
g
Q • 231 • η
v
V
g
P108720
Technical Information
Reverse Displacement Motor (RDM)
System Design Parameters
Name Plate
These motors are identified by a name plate affixed to the motor housing. The nameplate contains the
model number, model code, serial number, and country of manufacture.
Serial number
Every unit is identified by a unique serial number. The serial number gives manufacturing location, year
and week built, and a unique sequence number. The serial number in the example is decoded as:
A Ames, Iowa, USA
14 Year 2014
20 Week 20
23456 Sequence number
Model number
A Danfoss model number is issued for every unique configuration. Use this number when placing orders.
Model code
The model code completely defines the options for a specific unit. See Model Code section, for available
options and codes.
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Page 14
Made in U. S. A.
Serial No.
A-14-20-23456
Model Code
Model No./Ident No.
L M 25CN F MD1
N18 S N N BF
F18 NNB FNT
83032051
Technical Information
Reverse Displacement Motor (RDM)
System Design Parameters
Name plate
14 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 15
A
B C1 C2
D
E1 E2
E3
F
G
H1
J
K1 K2
L
M N
Technical Information
Reverse Displacement Motor (RDM)
Product Coding
RDM Model Code
A Frame
Code Description
L Frame size: displacements 25, 30, and 35 cm³ [1.50, 1.83, and 2.14 in³]
K Frame size: displacements 38, and 45 cm³ [2.32, and 2.75 in³]
B Mount
Code Description
M Motor, Variable Displacement-Reversing, Cartridge Mounting Flange
C1 Displacement
Code Displacement
25C 25 cm3/rev [1.50 in³/rev]
30D 30 cm3/rev [1.83 in³/rev]
35E 35 cm3/rev [2.14 in³/rev]
38C 38 cm3/rev [2.32 in³/rev]
45D 45 cm3/rev [2.75 in³/rev]
C2 Speed Sensing Ring
Code Description
N None
S Speed ring installed, L Frame = 41 pulses per revolution, K Frame = 44 pulses per revolution
D Output Shaft
Code Description
F Tapered, 0.875 inch Dia, 1.5 in/ft taper, uses Square key, with dust seal
K Straight key, 0.875 inch Dia, with dust seal
E1 Endcap Porting
Code Description
E Twin Radial, 19mm per ISO 6162 (split flange)
M Twin Radial M27x2 per ISO 6149 (metric ORB)
R Twin Radial, 1 1/16 in-12 O-ring boss
E2 Valving
Code Description
D Anti-Cavitation, Port A, 345 Bar Shock Valve (CW rotation at de-energized valve)
©
Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 15
E Anti-Cavitation, Port B, 345 Bar Shock Valve (CCW rotation at de-energized valve)
Page 16
Technical Information
Reverse Displacement Motor (RDM)
Product Coding
E2 Valving (continued)
Code Description
F Anti-Cavitation, Port A, 280 Bar Shock Valve (CW rotation at de-energized valve)
G Anti-Cavitation, Port B, 280 Bar Shock Valve (CCW rotation at de-energized valve)
H Anti-Cavitation, Port A, 230 Bar Shock Valve (CW rotation at de-energized valve)
I Anti-Cavitation, Port B, 230 Bar Shock Valve (CCW rotation at de-energized valve)
E3 Optional Features
Code Description
1 12 V Integrated Shift Valve
2 24 V Integrated Shift Valve
F Reverse Angle/Displacement Setting
Code Angle % of Max. L25C L30D L35E K38C K45C
N18 18° Reverse 100% 25 cm
N24 14.5°
Reverse
3
79.5% 19,9 cm³ N/A N/A N/A N/A
30 cm
3
35 cm
3
38 cm
3
45 cm
3
G Control Type
Code Description
S Standard
H Supply Orifice
Code Description
N None (standard)
J Drain Orifice
Code Description
N None (standard)
K1 Speed Sensor Connector
Code Description
B None: Housing machined for speed sensor. Port plugged
D Speed Sensor (KPPG 13704); 4.5-8.5V; 4 pin Deutsch DT04 Connector; Option 'C2' must
include a speed ring
K2 Housing Optional Features
Code Description
F None (includes case drain per SAE)
M Metric ORB Case Drain ISO 6149, M18 Option ‘E1’ must be: Twin Radial per ISO 6149 (metric
G SAE ORB Case Drain ISO 11926 2x7/8" PORTS
ORB)
16 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 17
Technical Information
Reverse Displacement Motor (RDM)
Product Coding
L Forward angle/displacement setting
Code Angle % of Max. L25C L30D L35E K38C K45D
F18 18° 100% 25 cm³ 30 cm³ 35 cm³ 38 cm³ 45 cm³
N24 14.5° 79.5% 19,9 cm³ N/A N/A N/A N/A
M Special Hardware
Code Description
NNN None
NNA High capacity ball bearing, recommended for fan drive
NNB High capacity roller bearing, recommended for fan drive
N Special Features
Code Description
FNN Black paint, Danfoss Tag, Layout Q, paint in front of pilot
NNN Black paint, Danfoss Tag, Layout Q
NNT Black paint, Danfoss Tag, Layout T
FNT Black paint, Danfoss Tag, Layout T, paint in front of pilot
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Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 17
Page 18
Dust Seal Option
Retaining Ring
P108749
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Shaft Torque
RDM motors are available with tapered, and straight-keyed shafts.
Shaft torque for tapered shafts
The rated torque is based on the contact pressure between the shaft and hub surfaces with poor surface
contact areas. With an increased quality of the contact areas, the contact pressure between the shaft and
hub is increased and allows higher torque to be transmitted.
When a key is used for orientation of the hub on the shaft in conjunction with poor quality contact
surfaces, the transmitted torque rating will drop significantly. This is due to the key carrying the torque,
which limits the shaft torque carrying capability.
Maximum torque rating is based on an ideal contact area of 100 % and the retaining nut properly
torqued. This allows for the highest contact pressure between the shaft and the hub.
Complete a detailed bolted joint analysis to ensure proper contact pressure, load and torque retention
characteristics are achieved.
Shaft taper: 1:8 per SAE J501
Maximum retaining nut tightening torque: 250 lb•ft (340 Nm)
Any torque in excess of this may lead to shaft damage.
This maximum torque is based on using an SAE J429 Grade 8 standard, non-self-locking nut with a clean/
oiled interface.
Dust Seal Option
The dust seal option has been designed to increase the resistance to airborne particulates which could
contaminate and potentially damage the motor output shaft seal. The speed rating of the dust seal is the
same as the motor speed rating.
Dust seal is standard for all RDM shaft options..
18 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 19
Taper 1:8 Per SAE J501
Except as noted
Nominal Ø 25.4 mm
P108 703E
22.23
[0.875]
90 Max.
[3.543]
35.91 ± 0.63
[1.414 ± 0.025]
58.92 ± 0.88
[2.320 ± 0.034]
3/4-16 UNF Thd.
Gauge Ø
26.5
[1.043]
6.4
+ 0.002
+ 0.05
0
[0.252
]
0
4.084 ± 0.05
[0.161 ± 0.002]
9.17 ± 0.38
[0.861 ± 0.015]
P108750
6.35
+0.05
-0
18.69
0
-0.2
41.7 ± 0.7
64.8 ± 0.55
89 ± 0.8
Full Keyway
Mounting
Flange
22.2 ± 0.025
[1.64 ± 0.03]
[2.55 ± 0.02]
3.5 ± 0.03
[0.875 ± 0.001]
[0.25]
+0.002
-0
[0.735]
0
-0.008
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Output Shafts
RDM motors are available with tapered, and straight-keyed shafts. See the following table for details.
Shaft options
Code Description Torque rating Drawing
F Ø 22.23 mm [0.875 in]
1:8 Taper with Dust Seal Option
(does not ship with key)
Refer to Shaft Torque For Tapered
Shafts pg 17 for information
regarding retaining nut torque.
Continuous
N•m [lbf•in]
N/A 362 [3200]
Maximum
N•m [lbf•in]
K Ø 22.225 mm [0.875 in]
N/A 362 [3200]
Straight Keyed Shaft with Dust
Seal Option
(does not ship with key)
Anti-Cavitation Valve
RDM motors are available with an anti-cavitation valve option. The key application for this option is for
©
Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 19
high inertia loads.
The anti-cavitation valve combines the function of a shock valve and check valve within the same cavity
which is integrated into the endcap. The check valve function provides protection against cavitation
which can occur upon introduction of an overrunning load or due to loss of input flow. In such case, the
system delta pressure becomes negative and the check valve opens connecting the motor inlet and
outlet, effectively short-circuiting the motor. The shock valve function is intended to be used for system
over-pressure protection events of limited duration only. It is not intended for continuous system
pressure limitation.
The shock valve is available with 280 bar or 345 bar setting.
Page 20
Cartridge
A
B
L1
reverse
RDM
P108732
Anti-Cavitation Valve, Port A High Pressure;
CW rotation (de-energized shift valve)
P108734
Anti-Cavitation Valve, Port B High Pressure;
CCW rotation (de-energized shift valve)
Cartridge
A
B
L1
reverse
RDM
9/16-18
57.15 [2.25]
3520
1.52 [0.060]
1
3
2
4
5
6
7
8
9
10
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Because of this option, the high pressure port needs to be predefined to get the correct motor rotation.
Refer to Minimum/Maximum Displacement Setting in the Model Code chapter.
Speed Sensor
RDM motors are available with an optional speed sensor. This hall-effect pick-up senses motor speed and
direction of rotation via a magnetic ring mounted to the cylinder block. The sensor is available with a 4pin Deutsch connector. For more information, refer to KPP Pulse Pick-up Technical Information, 11029257.
Common lead wire configuration (flat end)
Common lead wire configuration (flat end) callouts
Callout Description
1 Speed ring
2 gap approximately half to full turn of thread (maximum)
3 9/16-18 UNF-2A THD (all models)
4 O-ring part number 90042013700
5 Locking nut part number K13988
6 Torque lock nut 13 ± 1.3 N·m
20 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
7 Red
8 White
9 Black
10 Green
Page 21
1
3
2
4
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Specifications
Type
Supply voltage
Output voltage (high)
Output voltage (low)
Maximum frequency
Max. operating current
Load
Peak reverse voltage
Peak transient voltage
Pulses per rev.
Operating and storage temperature
Deutsch® Plug DT series 4-pin assignments
KPPG 13704
4.5 to 8.5 Vdc (regulated)
Supply minus 0.5 Vdc, minimum (no load)
0.5 Vdc Maximum (no load)
15 kHz
20 mA at 1 kHz
15 kΩ to both ground and supply
-15 Vdc continuous
80 Vdc for 2 ms (max.)
41 (LM motor) 44 (KM motor)
-40° to 110° C [-40° to 230° F]
Displacement Limiters
Motor Rotation
Pin assignments
Deutsch® Plug DT series 4-pin
Pin Function
1 Power +
2 Speed
3 Ground
4 Direction
Reverse Displacement Motors can be equipped with optional fixed (non-adjustable) displacement
limiters. Refer to Forward Angle/Displacement Setting in Model Code chapter, for available displacement
settings.
The RDM rotation with a de-energized shifting valve is related to the high pressure port of the motor.
Because of the Anti-Cavitation Valve, this port needs to be predefined. The chart gives the direction of
rotation with respect to the high pressure port of the motor.
High Pressure Port Rotation Valve Option
Flow A CW Anti-Cavitation, port A
Flow B CCW Anti-Cavitation, port B
©
Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 21
Page 22
-150
-100
-50
0
50
100
150
0 100 200 300 400 500 600 700 800 900 1000
Displacement (%)
Current (mA)
RDM Control Characteristics
P108736
24Vdc
12Vdc
Cartridge
A
B
L1
reverse
RDM
P108798
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Controls
Reverse Displacement Motors are designed to operate in two positions: maximum forward and maximum
reverse displacement. The motors are spring biased to maximum forward displacement and hydraulically
shifted to reverse.
Reverse Displacement Motors have an integrated shifting valve to go from forward to reverse rotation.
The shifting valve is a proportional pressure reducing valve using system pressure to pilot the servo
piston.
The proportional controllability can be used to achieve a smooth shifting between forward and reverse
rotation. The diagram below shows the motor control characteristics related to valve current (12 Volt
solenoid).
The shaded portion is indicative of the possible variation in shift characteristics. Variation is caused by
differences in system pressure, speed and temperature.
For information regarding Electrical Specifications see Electrical Parameters on page 7.
The RDM control has a failsafe design. The integrated shift valve acts like an orifice to dampen the shifting
between maximum forward to maximum reverse and back. This feature protects the system components
against fatal damage in case the control signal changes without ramping or if it gets lost immediately
while reversing.
Control orifice, port A high pressure; CW rotation (de-energized shift valve)
22 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 23
Technical Information
Reverse Displacement Motor (RDM)
Features and Options
Control current
Supply Voltage (Vdc) Current Range 0-100% [mA]
12 0-1500
24 0-750
©
Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 23
Page 24
P108800
44.5
68.5 ± 0.8
67 ± 0.3 6.22
83148.3 ± 2.5 ± 0.12
101.6 ± 0.8
2x 37.5
± 0.8
± 0.8
54.6
22
102.1 ± 1.5
77 ± 1.5
± 0.5
2x 86.9
72 ± 0.8
78.3 ± 1.5
108.3 ± 1.5
± 1.5
87.4 ± 0.8
57.4
± 0.8
∅
15.6 ± 0.15 (2x)
78.75 ± 0.2 (2x)
95 ± 0.25 (2x)
4 ± 0.3
∅
(22)
(72)
Center of
Gravity
Center of
Gravity
B
A
F
D
L1
∅
25
Other side (2x)
Maximum allowable
screwhead/washer
Technical Information
Reverse Displacement Motor (RDM)
Installation Drawings
Cartridge (LM/KM) Dimensions
Refer to the table in the following topic Port locations and gauge installation on page 25 for port
identification.
Recommended mounting hardware
Bolt size Grade Torque N•m [lbf•ft]
1/2 inch 5 86 [64]
Use hardened washer under each bolt head.
8 122 [90]
24 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 25
P108844
X1
MA
MB
B
A
F
L1
L1
Technical Information
Reverse Displacement Motor (RDM)
Installation Drawings
Port locations and gauge installation
Pressure measurements can be obtained by installing tee fittings to the connections at the locations
listed in the table below. Recommended gauge sizes are listed.
Twin radial port locations
Port information
Port identifier Metric
X1 ISO 6941-1, M 18x1.5
L1 ISO 6941-1, M 14x1.5
A/B ISO 6941-1, M 27x2
MA/MB ISO 11926-1, 7/16 - 20 System gauge port 600 [10,000]
F ISO 11926-1, 7/16-20 Brake release port -
Inch
ISO 11926-1, 3/4-16
ISO 11926-1, 9/16-18
ISO 11926-1, 1-1/16-12
Pressure obtained Gauge size, bar [psi]
Control signal 600 [10 000]
Case drain 10 [100]
System pressure 600 [10 000]
©
Danfoss | October 2016 L1424445 | BC00000239en-US0209 | 25
Page 26
Technical Information
Reverse Displacement Motor (RDM)
26 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 27
Technical Information
Reverse Displacement Motor (RDM)
28 | © Danfoss | October 2016 L1424445 | BC00000239en-US0209
Page 28
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