Applications Manual

Selection of Driveline Components

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Applications Manual
Selection of Driveline Components

Revision history

2 | © Danfoss | July 2015

Table of revisions
Date

ChangedRev

July 2015

Minor edits

0304

April 2015

Minor edits

CC

December 2014

Corrections to the equations

CB

November 2013

Major rewrite - Danfoss layout

CA

July 1997

Second edition

B

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Applications Manual
Selection of Driveline Components
Contents
Introduction
Applications Manuals......................................................................................................................................................................4
Selection of Driveline Components
Introduction........................................................................................................................................................................................5
Design Goal.........................................................................................................................................................................................5
Sizing Procedure...............................................................................................................................................................................5
Machine Corner Power (CP)..........................................................................................................................................................6
Variable or Fixed Motor..................................................................................................................................................................8
Motor Selection.................................................................................................................................................................................9
Final Drive Selection..................................................................................................................................................................... 11
Input Gearing...................................................................................................................................................................................13
Pump Selection...............................................................................................................................................................................14
Continuous Pressure.....................................................................................................................................................................16
System Sizing Flow Chart............................................................................................................................................................17
Sizing Flow Chart...................................................................................................................................................................... 19
Equations.......................................................................................................................................................................................... 23
Definition of Terms........................................................................................................................................................................25
Tractive Effort
Tractive Effort.................................................................................................................................................................................. 26
Acceleration
Acceleration..................................................................................................................................................................................... 30
Charge Pump Sizing
Introduction..................................................................................................................................................................................... 33
Charge Pump Considerations....................................................................................................................................................33
Charge Pump Sizing Worksheet............................................................................................................................................... 36© Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Introduction

Applications Manuals
Content included in these manuals
These applications manuals provide design theory and detailed calculations for building hydraulicallypowered machines.
The original document was written as one manual with four sections.
The current set of manuals includes the four documents listed below. The section numbers from theoriginal document are listed in parenthesis after the current document title.
• Selection of Driveline Components BLN-9885 (originally Section 1)• Pressure and Speed Limits for Hydrostatic Units BLN-9884 (originally Section 2)• Transmission Circuit Recommendations BLN-9886 (originally Section 4)• Fluids and Lubricants 520L0463 (originally Section 3)
Other Reference Manuals• Hydraulic Fan Drive Systems Technical Information 520L0824• Hydraulic Fan Drive Systems Design Guidelines 520L0926

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

Introduction
This section presents a method of sizing driveline components for typical closed loop hydrostatictransmissions. Although the method was developed for propel systems, it may be used for winch, or reel,applications, or other circuits with very slight modifications. The terminology used in this procedure also
tends to reflect off-highway mobile applications.
It is assumed that the specific functional requirements of the application have been defined, and that thefundamental design parameters have been established for each mode of operation. These typically
include vehicle speed, gradability, useful life, vehicle weight, and drive configuration. It is also assumed
that required engine power has been established.
Design Goal
The goal of this design method is to optimize the performance and cost of the driveline system byselecting appropriate driveline components. Smaller hydraulic components cost less than larger
components, but they have lower torque capability.
Hydraulic unit life is highly dependent on system pressure. Establish maximum and continuous pressure
based on the required life of the driveline. Danfoss document Pressure and Speed Limits for Hydrostatic
Units BLN-9884 covers this subject in detail.
The figure below Driveline Element Selection shows the components typically found in a closed loophydrostatic drive system as well as the design parameters and degree of design flexibility associated witheach component. Because driveline design includes so many variables (each dependent on the others),
and because final component selection is ultimately limited by product availability, several iterations of
this procedure may be required before arriving at the optimum system.
Sizing Procedure
The sizing procedure starts with values for the machine maximum torque and required speed. Fromthese values, a hydraulic motor size can be selected. This motor selection is then made compatible withratings of available output gear drives. From a motor size, a pump size can be established. The pumpmust be capable of accepting the required input power, and it must be compatible with the pump drive
mechanisms. It must also be large enough to provide sufficient flow to the drive motor to attain therequired speed.

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Driveline Element Selection
DrivingElement

DesignParameter

DesignFlexibility

Engine

Power
Speed

No

Gearing

Ratio

Sometimes

Pump

Size
Pressure
Speed

Yes

Motor

Size
Pressure
Speed

Yes

Gearing

Ratio

Usually

Load

Speed
WeightNo

Optimizing the size of the hydraulic units depends on selecting the correct gear ratios. By matching machine
corner power with motor corner power, the required unit sizes can be quickly determined. The gear ratios canusually be adjusted to provide some optimization of hydraulic unit component size.
Along with the equations presented throughout this document, a sizing flowchart is included to assist
with sizing. The flowchart details the sizing procedure and includes numerous design check steps tovalidate the calculated sizing values.
Design limits for associated mechanical components are not identified.
Machine designers should verify that the design parameters are met for all driveline components.
The steps outlined in this manual are designed to guide you in component selection. For further
assistance, contact your Danfoss representative for help interpreting and verifying your results.
Machine Corner Power (CP)The first step in the sizing process is to determine the value referred to as Machine Corner Power (CP).
The concept of Corner Power is abstract and is normally not an attainable value of transmission power. It
is useful in the design process because it provides an indication of transmission component size and ratio
requirements. Corner Power is representative of the maximum torque and the maximum speed (at fullload) that the machine is required to have. These two values of maximum speed and maximum torque(or Tractive Effort) never happen at the same time, but the purpose of Corner Power is to capture both
values to define an operating envelope for the machine and to aid in the selection of the hydraulic motor.
Refer to the Machine Corner Power graph below for an illustration of the concept.
The concept of Corner Power also applies to hydraulic motors. As demonstrated in the topic Motor
Selection on page 9, the maximum corner power of a hydraulic motor represents the maximum torqueand maximum continuous speed capabilities of that product. Equations are provided in the Motor
Selection topic that allow you to select the appropriate motor based on the machine’s corner power.
The equations for calculating Corner Power are provided below. For rotary drives (work function), theinput values to the equation are the required maximum output torque and the maximum output speed
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Applications Manual
Selection of Driveline Components
Selection of Driveline Components(at full load) of the machine. For propel drives, the input values are maximum tractive effort andmaximum vehicle speed (at full load).
For multi-speed drives (e.g. work mode and travel mode), corner power must be calculated for all ranges.
Tractive Effort
Tractive Effort refers to the amount of force available at the wheel or wheels of the vehicle and represents
the maximum possible pull a vehicle could exert, if it had no resistance to movement.
Ideally, tractive effort or output torque requirements should be derived from actual tests of the machine.
However, for establishing tractive effort design values, an analytical approach based on machineparameters and functional modes of operation has been used successfully.
The topic Tractive Effort on page 26 describes tractive effort in more detail.
Machine Corner PowerMax System Pressure

CP

OutputTorqueFull Load Speed

Part Load Speed

HP Out(Approx. 0.70 HP In)

No Load, High
Idle Speed (NLHI)

Rated Speed

Output Speed

BLN-9885-4

Machine Corner Power (CP) is determined by estimating the maximum torque and maximum output
speed required. It is normally greater than actual transmission output power. Maximum output speed isassumed to be at engine rated speed. However, under part load conditions slightly higher speed may beobtained.

W Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.

W Warning
Check to ensure that maximum motor speed is NOT exceeded under dynamic braking conditions, whenengine speed can exceed No Load High Idle (NLHI) ratings.

SI System

US System

TQ • ND
1) Machine CP =9549

Machine CP =© Danfoss | July 2015

TE • S
3600

Rotary Drives
Machine CP =Description

TQ • ND
63 025CP = machine corner power
kW (hp)
TQ = maximum drive output torqueNm (in lbf)
ND= maximum drive output design speed rpm

TE • S375

TE = maximum vehicle tractive effort
S = maximum vehicle design speed

Propel Drives
Machine CP =N (lbf)kph (mph)

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Variable or Fixed Motor
Because the machine corner power is an expression of maximum torque (tractive effort) and maximum
vehicle speed, it can be used to establish the effective Transmission Ratio (TR) required to satisfy system
demands.
The effective Transmission Ratio (TR) is the ratio of the required vehicle corner power divided by theavailable power from the machine’s prime mover (engine). This ratio is similar to the ratio spread of asimilarly sized mechanical transmission and indicates the amount of hydrostatic ratio which is required.
Systems with high transmission ratios normally benefit from variable, or two-position, drive motors.
For drives with variable load cycles, determine the normal input power (available power) to thetransmission by deducting the average power dedicated to other functions from the maximum engine
power available to the drive.
A Transmission Ratio (TR) greater than 1.0 means that there is not enough engine power available tomeet all of the operating requirements at the same time.
• Typically, machines with high transmission ratios have high torque (Tractive Effort) requirements at
low speed and high speed requirements at low torque (Tractive Effort). In this case, a large fixed
motor would satisfy the high torque requirements, but operating the same motor to meet the
maximum speed requirement could exceed the speed limit of the motor and require a large
displacement pump. For high transmission ratios, use a variable displacement motor; it can be usedat high displacement to satisfy the maximum torque requirement and then shifted to a smaller
displacement to satisfy the machine’s maximum speed requirement. A fixed motor could be usedwith a multi-ratio gearbox for machines with a high transmission ratio, but usually a variable motor
will be the most cost effective solution.
• If the transmission ratio is low, that means that there is probably enough engine power available toachieve the maximum torque and speed requirements simultaneously. In those cases, a fixed motor issuitable for the task.
• In cases of extremely high transmission ratio, a variable motor may not satisfy the need. In thesecases, a multi-speed gearbox may also be required. Some applications use 2-speed, 3-speed, or 4speed gearboxes to meet the vehicle requirements; but a 2-speed gearbox is most common.
The rule for selecting a fixed or variable drive motor is as follows:• If TR is greater than 4, use a variable motor,• If TR is less than 2, use a fixed motor,• If TR is between 2 and 4, evaluate both variable and fixed motors for suitability,• If TR is greater than 14, use a multi-ratio gear box between the motor and the final drive.
There is no direct relationship between transmission ratio and final drive ratio. The final drive ratio is
calculated based on the displacement of the motor that has been chosen, the maximum pressure, theloaded radius of the wheels, and the required maximum tractive effort.
The transmission ratio is only used to help determine the motor type, not the motor size. Refer to the
topic Final Drive Selection on page 11 to calculate the Final Drive Ratio (FD).]

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

SI / US System
2)

TR =

Description

Machine CP
HP

TR < 2, use fixed displacement motor

TR = effective transmission ratio
HP = normal input power

kW (hp)

HP = 0.7 * Available prime mover power

TR > 4, use variable displacement motor
TR > 14, use multi-ratio gearbox

Motor Selection
Calculate the required motor corner power from machine corner power and driveline efficiency using
equation (3) Required Motor CP. This establishes the minimum motor size capable of meeting the power
requirement of the machine. For multi-speed drives, use the largest corner power for each of theoperating ranges.
For transmission circuits using multiple drive motors, the required motor corner power should beinterpreted as the required corner power at each motor.
Use equation (4) Maximum Motor CP to calculate the maximum motor corner power based on the design
maximum pressure and the design maximum speed and the desired life of the motor.
Design maximum pressure is the maximum pressure at which the motor is intended to operate to meetthe required life. The design maximum pressure may or may not be the same as the maximum pressure
rating published in the product literature. Published ratings for maximum pressure assume the pressure
will occur for only a small percentage of the operating time, usually less than 2% of the total, and will
result in “normal” life. For applications in which the maximum pressure will occur over a significant
portion of the duty cycle, or applications in which additional life is required, the design maximum
pressure should be assigned a value less than the published rating for maximum pressure.
Design maximum speed is the maximum speed at which the motor is intended to operate to meet therequired life. Although speed has less effect on life than pressure, lower operating speeds will have theeffect of increasing life. The value for the design maximum speed must never exceed the maximum
speed rating published in the product literature; and will usually be less, to allow for motor speed
increases as a result of reduced-load, or no-load, conditions (see Machine Corner Power graph).
Danfoss document Pressure and Speed Limits for Hydrostatic Units BLN-9884, provides additional
information concerning pressure and speed limits with respect to component life.
Ideally, values for the design maximum pressure and design maximum speed would be used in Equation(4) Maximum Motor CP to determine motor CP capability. However, this is difficult at this stage of thesizing process because both the motor displacement and final drive ratio are unknown. Despite thislimitation, the next step is to choose a logical motor displacement based on the required motor CP. The
table Hydrostatic Motor Corner Power Chart can be used as an aid in preliminary motor selection. You
should choose a motor with a motor CP at least as large as the required motor CP calculated using
Equation (3) Required Motor CP.
Equation (A) Design Check serves as a design check to ensure that a motor with sufficient corner power
capability is selected. Motor selection based on corner power results in the smallest motor capable oftransmitting the required machine power while achieving system life requirements.

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

SI System

US System

3) Required Motor CP =4) Maximum Motor CP =A ) Design Check:

Machine CP

Required Motor CP =Machine CPE•#E•#DM • NM • PM

Description

Maximum Motor CP =600 000

Maximum Motor CP ≥ Required Motor CP

CP = corner power

kW [hp]

E = final drive efficiency(%/100)# = number of motors

DM • NM • PM
396 000

DM = maximum motor displacement

cc [in 3 ]/rev

NM = design maximum speedrpm

PM = design maximum pressure

bar [psi]

For variable motor systems, the transmission CP is determined only by the motor. For various pump sizes,
actual applied motor CP may be varied by adjusting the minimum motor angle.
For fixed motor systems, the transmission CP is ultimately determined by the pump speed anddisplacement. Although the fixed motor CP must be large enough to accommodate the maximum loadand speed, the pump must be large enough to drive the motor at the required design speed.
An additional sizing exercise may be required for fixed motor systems after pump selection has beenmade.
For either variable or fixed motor systems, it may be necessary to increase the motor size if proper output
gearing is not available. Gearing must accommodate both the desired transmission ratio and maximum
motor speed, in addition to meeting the torque requirements.

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

Hydrostatic Motor Corner Power Chart
Fixed

Motor
Series 15
Series 40 - M25
Series 40 - M35
Series 40 - M44
Series 40 - M46
LV/LC25
LV/LC30
LV/LC35
KV/KC38
KV/KC45
Series 90 - 55cc
Series 90 - 75cc
Series 90 - 100cc
Series 90 - 130cc
H1B060
H1B080
H1B110
H1B160
H1B25051V06051V08051V11051V16051V250

Variable

Max
Speed
Max
Max
Working at Max Cont Speed at Max Speed at Cont Speed Corner Corner
Pressure Pressure Angle
Max Angle
Min Angle at Min Angle Power Power(psid)
(rpm)
(rpm)
(rpm)
(HP)
(kW)
(psid)
(rpm)
4500
5000
5000
5000
5000
6000
5000
4350
6000
5000
7000
7000
7000
7000
7000
7000
7000
7000
7000
7000
7000
7000
7000
7000

4350
4350
4350
4350
4350

6525
6525
6525
6525
6525

------------------------------4250
3950
3650
3400

4000
4000
3600
3300
3600
---------------3900
3600
3300
3100
----------------------5300
4850
5000
5000
5150
5300
5200
5050
5100
4700

------4200
3900
4500
4400
4450
4500
4650
4500
4600
4250

7250
6600
5950
5250
4500
7000
6250
5600
5000
4250

5900
5300
4800
4250
3650
5600
5000
4500
4000
3400

42
77
97
112
128
---------------231
291
356
435
-------------------------------

31
57
72
83
95
---------------173
217
266
324
-------------------------------

CornerPower(HP)

CornerPower(kW)------113
132
160
102
103
106
163
156
273
344
------382
457
570
734
985
363
432
534
691
917

------84
99
119
76
77
79
122
116
204
256
------285
341
425
547
734
270
322
398
515
684

These values for corner power capability are based on maximum pressure and maximum speed ratings.
Refer to Pressure and Speed Limits for Hydrostatic Units BLN-9884 for detailed information on ratings ofunits and expected life.
Final Drive Selection
After the motor is initially sized, calculate the required final drive ratio. One of two approaches can betaken to determine this ratio. Both take into account the design maximum and continuous pressures
allowed to meet the life requirements of the machine (see Pressure and Speed Limits for Hydrostatic Units
BLN-9884).
The two methods are as follows:© Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
1. Using the Sizing Flow Chart on page 19, size the final drive ratio using the design maximum pressure
and the maximum torque requirement. Use equation (5) Required FD on the following page for thiscalculation. After the pump is sized and all speed conditions have been met, estimate the continuouspressure, using the Sizing Flow Chart on page 19, and compare it with the maximum designcontinuous pressure.
2. As an alternate method, calculate the final drive ratio required for all modes of operation (travel
mode, work mode, etc.). Calculate the final drive ratio from the assumed pressure and torquerequirements for each operating mode. For worst case or intermittent modes of operation, use thedesign maximum pressure along with the tractive effort or torque requirement to obtain a value forthe final drive ratio. Use the design continuous pressure for typical or continuous modes of operation,and calculate required final drive ratios for these modes as well. Select the largest final drive ratio
from the values calculated for the various operating modes.
For variable or two-position motors, only final drive ratios from those modes utilizing maximum motor
displacement can be calculated, since the motor minimum displacement is not yet known.
The next step is to check motor speed limits using the limits obtained from Pressure and Speed Limits for
Hydrostatic Units BLN-9884, or the respective Technical Information manual.
Motor speed will usually be satisfactory unless the final drive ratio is significantly higher than required(Gearbox limits must also be met). Equation (6) NMR=FD•NMD is used to determine the required motor
speed at maximum motor displacement based on the final drive ratio calculated in equation (5) Required
FD. For fixed displacement motors, the maximum motor displacement referred to in the equation is
simply the displacement of the motor. For variable motors, use the displacement at the maximum
swashplate angle. Use design check (C) NMR ≤ NML to ensure that the speed limit of the motor is notexceeded. If a variable motor is specified, use equation (7) NVR=FD•NMD and design check (D) NVR ≤ NVL
to determine if the speed required at the minimum motor displacement exceeds the maximum reduced
angle speed limit. As explained in Pressure and Speed Limits for Hydrostatic Units BLN-9884, the maximum
speed limit of a variable motor increases with decreasing angle, up to a certain value (the maximum
reduced angle speed limit or cutoff point on the speed/angle curve). At low swashplate angles (i.e., below
the angle cutoff point), a decrease in angle does not result in a greater maximum speed limit.
Note that reduced angle speed limits cannot be checked until the pump displacement and minimum
motor displacement have been established. (This will be done in subsequent steps of this procedure.)
However, if the speed exceeds the limit associated with the smallest possible swashplate angle (i.e., at thecutoff point of the speed/angle curve), then increase the motor’s maximum displacement and recalculate
the final drive ratio.
Refer to Pressure and Speed Limits for Hydrostatic Units BLN-9884 for more information concerning speed
limits.
Both SM (vehicle speed required at max angle) and SV (vehicle speed required at min angle) are customer
defined conditions

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

SI System

US System

Description

Rotary Drives
5) Required FD =Torque • 20π
DM • PM • E • EM

Required FD =Torque • 2 π
DM • PM • E • EM

Propel Drives
Required FD =TE • LR • 20 π
DM • PM • E • EM • #Required FD =Torque • 2 π
DM • PM • E • EM • #DM = max motor displacementE= final drive efficiency

cc (in3 )/rev(%)/100

FD = final drive ratiod’lessE M = motor mechanical efficiency(%)/100
LR = wheel loaded radius
mm (in)
NMD = non-propel design speed at max angle rpm
NML = motor speed limit at max angle
NMR = req'd motor speed at max angle

rpm
rpm

NVD = non-propel design speed at min angle rpm
B)

Design Check:FD ≥ Required FD
Rotary Drives6) NMR = FD • NMD

NMR = FD • NMD
Propel Drives

NMR =

C)

FD • SM • 2650
LR

Design Check:

NMR =FD • SM • 168
LR

NVR = req'd motor speed at min angle
NVL = motor speed limit at min angle
PM = maximum pressure
SM = vehicle speed req'd at max anglerpm
rpm
bar (psid)kph (mph)

SV = vehicle speed req'd at min angle

kph (mph)

TE = vehicle tractive effort
TQ = max drive output torqueN (lbf)Nm (in•lbf)#= number of motors

NMR ≤ NML
Rotary Drives

7) NVR = FD • NVD

NVR = FD • NVD
Propel Drives

NVR = FD • SV • 2650
LR
D)

Design Check:

NVR =FD • SV • 168
LR

NVR ≤ NVL

Input Gearing
The use of input gearing is usually customer defined and determined by the machine configuration. For
vehicles with multiple hydraulic systems, use of an input splitter box is common. Splitter boxes areusually available with various ratios to accommodate pump speed requirements. For machines with onlya single hydrostatic system (or machines utilizing tandem pumps) a direct drive pump may beappropriate, in which case the pump speed is the same as the prime mover speed.
Use equation (8) NP = NE•IR to determine the relationship between the prime mover speed, pump speed,
and input gear ratio.

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Selection of Driveline Components

SI / US System
8)

NP = NE • IR

Description
NP = maximum pump design speed
NE = prime mover design speed
IR = pump input ratio

rpm
rpm

Pump Selection
Pump sizing consists of selecting a pump that will meet the flow (speed) requirements of the motor, or
motors, in the system.
Use equation (9) to determine the required pump displacement. This calculation is based on an assumed
pump input speed. Select a pump displacement at least as large as the calculated displacement. Also,check that the desired pump speed does not exceed the rated maximum speed for the pump. If the rated
speed limit is exceeded, choose a different pump and calculate the input speed required and thecorresponding input ratio using equations (10) and (11).
With a pump displacement selected, calculate the actual motor speed. The actual speed will usually beslightly higher than the required motor speed because the pump that is selected will usually have adisplacement slightly greater than the calculated displacement.
Fixed Motor
For a fixed motor, determine the actual motor speed and compare with its rated maximum speed using
equation (12) and design check (G). Note that equation (12) includes a calculation for an overrunning
condition. An overrunning condition is characterized by a speed increase at the pump (and consequently
the motors), typically by as much as 15%. The condition is especially common during downhill operation.
Not only is there an increase in pump speed, but during either downhill operation or vehicle deceleration
using hydrostatic braking; the motor becomes the pump and the pump becomes the motor. The net
result is that the motor will turn faster for any given pump speed than what would be experienced during
normal propel operation.
A 15% increase in engine speed is just an estimate; check with the engine manufacturer for specificdetails concerning the engine’s ability to provide dynamic braking and its maximum, or [not-to-exceed]
operating speed.

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Selection of Driveline Components

SI / US System
9)DPR = NMR

Description• DM • #NP • EVP • EVM
D)

Design Check:DP ≥ DPR

E)

Design Check:

NP ≤ NPL

10)

NPR = DM • NMR • #DP • EVP • EVM

11)

12)

IR = NPRNE
Without Overrunning Condition:
NM = DP • NE • IR • EVP • EVM
DM • #

cc (in3 )/rev
DM = max motor displacement
cc (in3 )/rev
DP = max pump displacement
cc (in3 )/rev
DPR = required max pump displacementIR= pump input ratio
dimensionless
NMR = required motor speed at max angle
rpm
NE = prime mover design speedrpm
NM = design maximum speedrpm
NML = motor speed limit at max angle
rpm
NP = max pump design speedrpm
NPL = pump speed limit at max angle
rpm
NPR = required pump speedrpm
EVP = pump volumetric efficiency%/100
EVM = motor volumetric efficiency%/100#= number of motors
dimensionless
Assume EVP = EVM = 95% for first pass thru
the sizing exercise

With Overrunning Condition:
NM =DP • NE • IR • 1.15
EVP • EVM • DM • #G)Design Check:

NM ≤ NML
Variable Motor
For a variable motor, the procedure for assuring that the rated maximum speed is not exceeded issomewhat more involved.
The steps are as follows:
1. Determine if the rated maximum speed is exceeded using the method above, reference equation(12).
2. Determine the minimum motor displacement using equation (13).
3. Calculate the angle associated with this displacement using equation (14). Select an available
minimum swashplate angle using design check (H) and determine the actual motor speed using
equation (15).
4. Determine the reduced swashplate angle speed from Pressure and Speed Limits for Hydrostatic Units
BLN-9884, or by using equation (16). Use design check (I) to ensure that the minimum angle speed
limit is not exceeded.
The Sizing Flowchart below details the above procedure.

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Selection of Driveline Components

SI / US System
DP • NE • IR • EVP • EVM
NVR • #

13)

DV =

14)

All Swashplate Motors:
TANV = TANM • (DV / DM)
AV =ARCTAN (TANV)All H1B andSeries 51 Bent-Axis Motors:
SINV = 0.53 • (DV / DM)
AV =ARCSIN (SINV)
Note: Sin 32º = 0.53, 32º = Maximum
angle of H1B and S51 bent axis motors

H)

Design Check:AV ≥ Min Available

IF “YES”, then proceed; IF “NO”, increase pumpdisplacement in Equation 13

15)

Without Overrunning Condition:
NV =DP • NE • IR • EVP • EVM
DV • #

With Overrunning Condition:
NV =DP • NE • IR • (1.15)

DescriptionAV= min angle for a variable motor
degrees
DM = max motor displacement
cc (in 3)/rev
DP = max pump displacement
cc (in 3)/rev
DPR = req'd max pump displacemnt
cc (in 3)/rev
DV = min motor displacement
cc (in 3)/revIR= pump input ratio
dimensionless
NE = prime mover design speedrpm
rpm
NM = motor speed at max angle
rpm
NML = motor speed limit at max angle
rpm
NMR = req'd motor speed at max angle
rpm
NV = motor speed at min angle
rpm
NVL = motor speed limit at min angle
rpm
NVR = req'd motor speed at min angle
rpm
NP = max pump design speedrpm
NPL = pump speed limit at max angle
SINM = sine of motor at max angle
dimensionlessdimensionless
SINV = sine of motor at min angleSV= vehicle speed req'd at min angle
kph (mph)
TANM= tangent of motor at max angle
dimensionless
TANV = tangent of motor at min angle
dimensionless
EVP = pump volumetric efficiency
%/100
%/100
EVM = motor volumetric efficiency
dimensionless#= number of motors
Assume EVP = EVM = 95% for first pass thru the sizing exercise

EVP • EVM • DV • #NOTE: 1.15 is an estimate of engine max speed capability,
contact engine supplier for additional information

16)

All Swashplate Motors:
NVL = NML • DM / DV

Series 51 Bent-Axis Motors:
NVL = NML • (0.53 / SINV)I) Design Check:
NVL ≤ Max Reduced Angle ValueIF “YES”, then proceed

Continuous Pressure
The final (but crucial) step in the procedure is to estimate the continuous pressure based on thecomponents selected.
The Pump Selection graph below shows the relationship between system pressure and system flow for ahydrostatic pump. The figure shows that the continuous system pressure usually occurs near maximum
pump flow and normal input power.
The Sizing Flow Chart on page 19 equations provide a check to ensure that the continuous pressure is
below the pressure required to meet the design life.
16 | © Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Pump Selection
System Pressure Line
Defined byEngine PowerMax

Full Load Speed
SystemPressureContinuous

Output Flow

Rated

NLHI

Continuous system pressure at maximum pump flow may be estimated from the normal input power tothe drive. For many systems, the continuous pressure determined in this manner is a good indicator of
typical system pressure experienced in the drive.

SI System

US System

17) PC = HP • 600 000

PC = HP • 396 000

DP • NE • IR

DP • NE • IR

Propel, Motor at Max Angle18) FD = NML • LR

FD = NML • LR

2650 • SM

168 • SM

Non-Propel, Motor at Max Angle
FD = NML

FD = NML

NMD

NMD

Description
DP = max pump displacement
cc (in 3)/revFD= final drive ratio
HP = normal power input to drive
kW (hp)IR= pump input ratioLR= wheel loaded radius
mm (inch)
NE = prime mover design speedrpm
NMD = non-propel speed at max angle rpm
NML = motor speed limit at max angle rpm
NVD = non-propel speed at min angle rpm
PC = estimated continuous pressure bar (psid)
SM = vehicle speed req'd at max angle kph (mph)SV= vehicle speed req'd at min angle kph (mph)Propel, Motor at Min Angle
FD = NML • LR
2650 • SV

FD = NML • LR
168 • SV

Non-Propel, Motor at Min Angle
FD = NML

FD = NML

NVD

NVD

System Sizing Flow Chart
The flowchart is designed to be used as a sizing algorithm to assist in the selection of systemcomponents. It provides a concise step-by-step run-through of the sizing process. It is intended toaccompany the previous sections and to expand the equations presented with the text.
The symbols used in the flowchart are explained in the box below. The equations used to calculate thequantities are included following the flowchart, along with the definitions of the symbols.
Be aware that the flowchart does not consider any torque/speed limits associated with various
mechanical components, e.g., pump drives or final drive gearboxes.
Use the flowchart on the following pages to assist in sizing a hydrostatic transmission. The number of theequation required to complete this calculation is shown at the lower right corner of the boxes (X). Thisequation can be found in the tables following the flowchart.

© Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

X = Number of equation required tocomplete this calculation
A list of equations follows the
Sizing Flow Chart(X)

Y

18 | © Danfoss | July 2015

Y = Flow chart reference numbers(numbers that jump to otherreference points on the
flowchart).

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Sizing Flow Chart

Determine
TE or Torque

Begin by calculating the required effort or torque.

Yes

Multi-speed
Drive?

Calculate
Machine CP
for All Speeds (1)For multi-speed drives, machine corner (CP) power must be
calculated for each drive.

No
Calculate
Machine CP (1)SelectLargest CP
Value

Calculate
Transmission
Ratio
(2)

Yes
TR > 4?

Transmission Ratio (TR) indicates the need for a fixed orvariable motor.

Use MVNo
Yes

TR < 2?

Use MFNo
Try bothMF and MV

CalculateRequired
Motor CP

(3)

FDR
1.0
“Direct Drive”

Sizing begins at the motor. First, determine the required
motor corner power.

No

1© Danfoss | July 2015

Yes

LSHT

Yes

No

1A

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
1A

1
Select a likely motor displacement andeither calculate its corner power capability
or use the Motor Power Capabilities table.
If this value is less than the required
corner power, select a larger motor.

Select a
Motor
Size (DM)2A

Select a
Motor
Size (DM)Calculate
Motor CPCalculate
Motor CP(4)(4)

CP ≥ Required?

No

CP ≥ Required?
Yes

Yes
Determine
Required Final
Drive Ratio (FD)No

2Determine the final drive ratio (FD) required.
This calculation is based on the maximum
motor displacement.

(5)

2
FDR
1.0

(5)

Select FD≥ RequiredFD

3

Calculate the required motor speed
at maximum angle and comparewith the maximum speed limit allowed.

Calculate Required
Motor Speed (NMR)
at Max. Angle(6)

NMR ≥ NML?

Yes

Increase
Motor
Size

NMR ≥ NML?

Yes

Calculate Required
Motor Speed (NVR)
at Min. Angle(7)

No
Establish
Pump Speed
(NP)

No
(8)

4

20 | © Danfoss | July 2015

NVR ≥ NVL
at Smallest Possible
Angle?

Yes

Increase
Motor
Size

No

No

MV?

Calculate Required
Motor Speed (NMR)
at Max. Angle
(6)

Yes

For variable motors, calculate the required
motor speed at the minimum angle andcompare with the maximum speed limit at
the smallest possible motor angle. Notethat at this point in the sizing procedure,
the required minimum angle is unknown,so the reduced angle speed limit is also
unknown. However, the unknown speed
limit will be less than the speed limit at
Establish
Pump Speedthe smallest possible motor angle.
(NP)

4

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
4

Calculate Pump Disp.
Req'd (DPR) for Motor
Max. Angle Speed

Determine Pump Displacement.
(9)

Choose Pump
Disp. (DP) ≥Required (DPR)

5Overrunning
Condition?

Yes

Increase
NP by 15%

Yes

ChooseDifferent
Pump Size

Check for the possibility of a overrunning condition(e.g., vehicle in downhill mode). If so, increase speed by 15%.

No

NP ≥ NPL?

CalculateRequired
Pump Speed

Determine
New Pump
Drive Ratio

(10)

(11)

No
Calculate ActualMotor Speed (NM)at Motor Max. Angle

NM ≥ NML?

(12)

Yes

Using the displacement for the pump selected, determine theactual motor speed and compare with the rating. This step isrequired since the pump selected usually has a displacement
slightly higher than the displacement required.

2

No

MV?

No

Yes

Convenient
Angle ≤ AV

Calculate
ActualMotor Speed(NV) at Motor
Min. Angle

No

(15)

S elect

Increase
Motor Size

Calculate
Motor Min.
Disp. (DV)Determine
Min. Motor
Angle (AV)

(13)

(14)

Yes

5

Increase
Pump
Disp.

Determine
Speed Limit for
Reduced Angle(16)

AV ≤ Min.
Available?

No

NV ≥ NVL?
Yes

6© Danfoss | July 2015

2

Increase
Motor
Size

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

62

Estimate
Continuous
Press. (PC)

Increase
Motor Size

Continuous pressure can be estimated based on the
input horsepower.

(17)
No
Yes

CP ≥ Continuous
Limit?

Can FD be
Increased?

No

END

If the final drive can be increased to reduce pressure, calculate
the largest final drive that will keep motor speed under limits.
Reselect a final drive no larger than this value.

Yes
CalculateMaximumFD(18)

ChooseFD ≤ Maximum

3

22 | © Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Equations

S te pE q u a ti o n s R e q u i r e d

C o m m e n ts

Me tric S ys te m
1

Machine CP =TE • SU S S ys te m
Machine CP =TE • S

3600
Machine CP =TQ • ND

Machine CP =TQ • ND

9549
2

TR

Propel Drive

375
Non-Propel Drive

63025= Ma c hine C P

S a me0.7 • Available power3

R e quire d Motor C P = Ma c hine C P

S a meE •#4Motor CP=

5

Required FD =0.95 • DM • NM • PM
600 000

Motor CPTE • LR • 0.02π
0.95 • DM • PM • E • #Required FD =TQ

Required FD =Required FD =• 20 π

=0.95 • DM • PM • E
6

NMR = FD • SM • 2650
LR
NMR = FD • N D M

7NVR = FD

• SV • 2650
LR

0.95 • DM • NM • PM
396 000
TE • LR • 2 π
0 . 9 5 • DM • PM • E • #TQ • 2 π

Propel Drive

Non-Propel Drive

0 . 9 5 • DM • PM • E
NMR = FD • S • 1 6 8LR
S a me
NVR = FD • SV • 1 6 8P rope l D rive

N on-P rope l D rive
P rope l D riveLR

NVR = FD • N D V

S a me8

NP = NE • I R

S a me9

DPR = NMR • DM • #S a meN on-P rope l D rive

(0.95)2 • NP
10

NPR = DMDP

• NMR • #S a me• (0.95)2(choose DP ≥ DPR)
11IR

= NP RNE© Danfoss | July 2015

S a me

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components

S te pE q u a ti o n s R e q u i r e d

C o m m e n ts

Me tric S ys te m
12

NM

=

DP • NE • IR • (0.95) 2

U S S ys te m
S a meN orma l Ope ra tion

O ve rrunning C onditions

DM • #NM=DP • NE • IR • 1 . 1 5(0.95) 2 • DM • #S a me13

DV=DP • NE • IR • (0.95) 2
NVR • #Same

14

TANV =TANM

S a meA ll S wa s hpla te Motors

AV

Arctan (TANV)
S a meH1B & Series 51
Bent Axis Motors

15

16

17

=

• ( D V / D M)

AV=

Refer to Technical
Information manualNV=DP • NE • IR • (0.95) 2
DV • #

S a meN orma l Ope ra tionNV=DP • NE • IR • 1 . 1 5(0.95) 2 • DV • #S a meO ve rrunning C onditions

NVL =NML • (DM / DV) 1/2

S a meA ll S wa s hpla te Motors

NVL =Refer to Technical
Information manualS a meH1B & Series 51
Bent Axis Motors

NVL≥

Reduced Angle ValuePC=

HP • 600 000

PC=DP • NE • I R
18

FD

=

NML • LR
2650 • S M

FD

=

N ML
N MD

S a meFD=

NVL • LR
2650 • S V

FD

NV L
NV D

S a me=24 | © Danfoss | July 2015

• 396 000

D P • NE • IR

FD

FD

HP

=

NML • LR
1 6 8 • SM

Propel,Motor at Max Angle
N on-P rope l,
Motor a t Ma x A ngle=

NVL • LR
1 6 8 • SV

Propel,Motor at Min Angle
N on-P rope l,
Motor a t Min A ngle

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Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Definition of Terms
The following list of terms describe the variables used in the sizing equations:© Danfoss | July 2015

AV

Minimum angle for a variable motor

DegreesCP

Corner power

kW [hp]DM

Maximum motor displacement

cc [in3]/rev

DV

Minimum motor displacement

cc [in3]/rev

DP

Maximum pump displacement

cc [in3]/rev

DPR

Required maximum pump displacement

cc [in3]/rev

EFinal drive efficiency%

FD

Final drive ratio—

HP

Normal power input to drive

kW [hp]IR

Input ratio (pump speed /prime mover speed)—

LR

Wheel loaded radius (rolling radius)

mm [inch]

ND

Design speed for non-propel rpm—

NMD

Non-propel design speed at motor max angle

rpm

NVD

Non-propel design speed at motor min angle

rpm

NE

Prime mover input speed (engine, electric motor)

rpm

NML

Motor speed limit at maximum angle

rpm

NPL

Pump speed limit

rpm

NVL

Motor speed limit at minimum angle

rpm

NM

Motor speed at maximum angle

rpm

NP

Pump speed

rpm

NV

Motor speed at minimum angle

rpm

NMR

Required motor speed at maximum angle

rpm

NPR

Required pump speed

rpm

NVR

Required motor speed at minimum angle

rpm

PC

Estimated continuous pressure

bar [psid]PM

Maximum system pressure

bar [psid]

S

Maximum vehicle speed

kph [mph]

SM

Vehicle speed required with motor at max angle

kph [mph]

SINM

Sine of motor maximum angle

—

SINV

Sine of motor minimum angle—

SV

Vehicle speed required with motor at min angle

kph [mph]TE

Tractive effort requirement

N [lbf]

TANM

Tangent of motor maximum angle—

TQ

Torque requirement (non-propel)

Nm [in lbf]

TR

Transmission ratio

—

TANV

Tangent of motor minimum angle—

BLN-9885 | BC00000245en-US0304 | 25

Applications Manual
Selection of Driveline Components
Tractive Effort

Tractive Effort
For vehicle propel drives, motion resistance and required tractive efforts are directly related to vehicle
weight. For a particular class or type of vehicle, the ratio of tractive effort to vehicle weight is relatively
constant. This term is commonly called a pull ratio and it is a convenient design parameter.
The elements constituting a particular class or type of vehicle are machine function, drive configuration,
grade, and terrain. Values for motion resistance contributing to pull ratio requirements have been
estimated and are listed in the table Pull Ratio Requirements for Vehicle Propel Drives below. To establish
the required pull ratio, sum the motion resistance values for machine function, drive configuration, grade
and rolling resistance. Calculate required tractive effort from pull ratio and vehicle weight.
PR = MF + DC + GR + RR
where:
PR = Pull ratio
MF = Machine function motion resistance
DC = Drive configuration motion resistanceGR = Grade motion resistance
RR = Rolling resistanceTE = (PR) (WT)
where:TE = Vehicle tractive effort (lb)
WT = Vehicle weight (lb)
The tractive effort to weight ratio, or pull ratio, is the sum of all expected demands on vehicle motion
resistance. We recommend verifying the calculated tractive effort values by testing an actual vehicle.
To determine Machine Function (MF) motion resistance, consider all functions and modes of operation
separately. Usually, the functions performed in the worst ground conditions predominate. For
transmissions with multi-speed mechanical gearboxes, designers should consider the functions
performed for each speed range. This usually requires examining several possible work situations andselecting the one with the highest rolling resistance and/or grade.
The pull ratio listed for propel forces main work drive in the table Pull Ratio Requirements for Vehicle
Propel Drives below is approximate. For propel drives which interact with work functions (cutters,
planers, etc.), make an accurate determination of the required motion resistance by testing a working
machine.
Transport mode should be used only for specific modes of operation in which traveling or carrying is the
only requirement. It is assumed that the vehicle operates at a relatively constant speed in the transportmode.
The component of pull ratio due to Drive Configuration (DC) results from geometry effects whensteering. The particular form of drive for the vehicle affects motion resistance. Skid steer configurations
imply turning with differential side-to-side torque and no variable geometry. Dual path variable steer
geometry configurations are usually wheeled machines with a single trailing pivot or caster wheel.
Single path track or single path wheel configurations imply a geometry adjustment of the groundengaging elements to achieve steering.
Grade motion Resistance (GR), or Gradability, is a function of terrain slope. Select the maximum grade atwhich the particular machine function is performed. The maximum grade is assumed to be intermittent,with the average grade one-half to two-thirds of maximum.
Rolling Resistance (RR) affects motion resistance depending on the condition of the terrain. Rolling
resistance values listed here are typical and may vary depending on location, particular conditions and
26 | © Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Tractive Effort
drive configuration. These may be adjusted with more specific data. These values apply for typical rubber
tired vehicles. High flotation tires and tracked crawlers may show somewhat lower values in poor terrain.
Vehicle weight (WT) is the maximum weight for the function being considered. For most vehicles, this is
the loaded weight. Empty weight may be appropriate for some transport modes. For shuttle andtransport vehicles, maximum weight is the gross combined weight of the power unit plus any towed
trailer or wagon. For drawbar vehicles, maximum weight is only the weight of the power unit.
Simulating a trailer load: If we make the assumption that the coefficient of rolling resistance is the samefor the vehicle and the trailer, then the weight of the trailer and its load can be added to the weight of thevehicle. If the coefficient of rolling resistance is different, then pro-rate the trailer weight before adding itto the vehicle weight with the following formula:

Typical minimum design values of pull ratio for some common vehicles have been determined and arelisted in the Minimum Tractive Efforts Requirements table below. These values may be useful forchecking intended tractive effort requirements. Vehicle performance testing is highly recommended toverify suitability in an actual working environment.
Pull Ratio Requirements for
Vehicle Propel Drives
Machine Function
MF
Dozing (All Wheel / Track Drive).90
Drawbar (All Wheel / Track Drive).80
Drawbar (Single Axle Drive).60
Dig and Load (All Wheel / Track Drive) .50
Propel Forces Main Work Drive.30 (Typ)
Stop and Go Shuttle.15
Transport (No Work Interaction).00
Drive Configuration
Skid Steer Track
Skid Steer Wheel
Dual Path Variable Steer Geometry
Single Path Track
Single Path Wheel

DC
.40
.30
.20
.10
.00

Grade (Intermittent)
10% Grade
20% Grade
30% Grade
40% Grade
50% Grade
60% Grade

GR
.10
.20
.29
.37
.45
.51

Rolling ResistanceSand
Wet Soil, Mud
Fresh Deep Snow
Loose Soil, Gravel
Grassy Field, Dry Cropland
Packed Soil, Dirt Roadway
Pavement
Steel on Steel Rails

RR
.25
.20
.16
.12
.08
.05
.02
.004

Pull ratio may be used to determine tractive effort in vehicle propel drives. Pull ratios are based on
working vehicle weight. In general, this is loaded weight. For vehicles having a separate transport mode,
empty weight may be appropriate.
© Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Tractive Effort
Minimum Tractive Effort Requirements
Assumed Operating Conditions
Vehicle Type

Function and Terrain

Crane, Tracked
Crane, Wheeled
Crawler Dozer
Crawler Loader
Excavator, Tracked
Farm Tractor, 2WD
Farm Tractor, 4WD
Garbage Packer
GraderHarvesting Machine
Harvesting Machine
Harvesting Machine
Commercial Lawn Mower
Lift Truck, Cushion Tire
Lift Truck, Pneumatic Tire
Lift Truck, Rough Terrain
Locomotive, Switcher
Log Feller, Dual Path Steer
Log Forwarder, Wheeled
Mining Scoop, Wheeled
Paver
Road Planer
RollerSkid Steer Loader
Snow Groomer
Soil Stabilizer
Street Sweeper
Trash Compactor
Wheel Loader, Articulated

Transport in Wet Soil
Transport in Wet Soil
Dozing, Wet Soil
Dig and Load, Loose Soil
Transport in Wet Soil
Plow in Loose Dirt
Plow in Loose Dirt
Crane, Wheeled
Grading Wet SoilHigh Speed, Grassy Field
Low Speed, Mud
Climb Obstacle
Mow on Grassy Field
Stop and Go, Pavement
Stop and Go, Gravel
Stop and Go, Loose Soil
Shuttle Rail Cars
Accelerate With Load, Wet Soil
Transport in Wet Soil
Scoop in Gravel, RockPaving on Firm Soil
Plane Highway
Roll Packed Soil
Dig and Load, Loose Soil
Grooming Snow on Steep Slope
Stabilize Wet Soil
Dump Load in Loose Soil
Blading Uphill
Dig and Load, Loose Soil

Minimum Pull Ratio

Working Grade

Loaded

30%
30%
10%
10%
40%
15%
15%
15%
15%
15%
15%

.89
.49
1.60
1.12
.97
.82
1.02
.27
.65
.23
.35
.45
.37
.22
.32
.52
.19
.65
.49
.72
.45
.52
.30
1.02
1.07
.65
.22
.94
.62

30%
5%
5%
25%
3%
10 %
30 %
10 %
10 %
10 %
10 %
10 %
60 %
15%
10%
30 %
0%

Empty (Ref)

1.30

1.25

.80

Pull ratio and tractive effort requirements are based on typical vehicles being operated in normal fashion.
Specific requirements may vary. Vehicle testing is recommended to verify that performance is satisfactory
and that sufficient life of the driveline components will be obtained.
Pull Ratio
TE
F2
R
O

F1
WT
O

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Applications Manual
Selection of Driveline Components
Tractive Effort
Derivation of Maximum Gradability

Given :TE = Tractive Force of Vehi cle, N (lbf)
WT = Weight of Vehi cle, N (lbf)
RR = Coefficient of Rolling Resistance, d' lessFind :
θ = Gradabiltiy Angle, degrees
Normal Force, F1 = WT * Cos θ, N (lbf)
Tangential Force, F2 = WT * Sin θ, N (lbf)
Rolling Resistance Force, R = RR * F1 = RR * WT * Cos θ, N (lbf)
Maximum Gradability occurs when force uphill balances forces downhill :TE = R + F2 = RR * WT * Cos θ + WT * Sin θ(1 ′ X )TE = RR *WT * X + WT * (1 ′ X )(TE ′ RR *WT * X ) = (WT ) * (1 ′ X )(TE ′ WT )′ (2 * TE * RR *WT * X ) + ((1 + RR )*WT * X ) = 0
2

Let X = Cos θ, Sin θ =

2

2

2

2

2

2

2

2

Solve Quadratic Equation for " X":
X=
X=

)

(

2 * TE * RR *WT ± 4 * TE 2 * RR 2 *WT 2 ′ 4 * 1 + RR 2 *WT 2 * TE 2 ′ WT 2()
(1 + RR )*WT

(

2

)

2 * 1 + RR *WT)2

RR * TE ± WT 2 * 1 + RR 2 ′ TE 2
2

Gradability, % = 100 * Tan θ = 100 * Tan Cos ′1© Danfoss | July 2015

(

2

(
)
(1 + RR )* WTRR * TE ± WT 2 * 1 + RR 2 ′ TE 22

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Applications Manual
Selection of Driveline Components
Acceleration

Acceleration
Vehicle acceleration and deceleration times are often ignored during a vehicle transmission sizing
proposal. This data is important to know especially for high inertia vehicles. An acceptable tractive force
for steady state running may be inadequate for calculating acceleration time. Tractive force minus rolling
resistance is the force left for calculating acceleration on level terrain.
A simple formula for calculating average acceleration or deceleration time on level terrain is:t = (W) (V) (g) (F)t = time (seconds)
W = Vehicle weight (lbs.)
V = Vehicle velocity (ft. per sec.) V = (MPH) (1.467)
g = Gravity (32.2 ft. per sec. per sec.)
F = Drawbar pull (lbs.) (tractive force minus rolling resistance)
Available tractive force will change with vehicle speed due to engine power and/or pump and motor
displacement and power train ratio. Calculating acceleration time requires a summation of forces as theychange with vehicle speed. For example, air resistance may be a factor at high vehicle speeds.
Rolling resistance will have an effect on any vehicle’s ability to accelerate as well as the ability to transmit
all available force to the wheel before wheel slip.
Deceleration time is calculated by this same method, if only engine dynamic braking is used. Tractive
force will vary with pump displacement and the capability of the engine to absorb torque.
Large centrifugal type loads or long conveyor belt drives may also have acceleration time requirements
and should not be overlooked during the equipment selection stage.
An example is attached using computer generated (P-Cubed) performance data.

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Applications Manual
Selection of Driveline Components
Acceleration

Prime Mover Speed (rpm):
Input Power (hp):

Delta System Pressure (psid)

2800
200

5500

Limiting Pressure (psid):
Charge Pressure (psid):

5500

5500

4961

5500
348

4012

3356

2871

2477

2000

1800

H1P165 - H1, 10.07cir, 18deg Max Angle, 1.59cir charge pump
Pump Drive Ratio:
1.00
Pump Drive Efficiency (%):
100
Swashplate Angle (deg)
2.8
5.0
7.4
9.5
11.7
13.8
15.9
Displacement (cir)
1.50
2.70
4.00
5.20
6.40
7.60
8.80
Displacement (cc )
24.6
44.2
65.5
85.2
104.9
124.5
144.2
Input Shaft Speed (rpm)
2800
2800
2800
2800
2800
2800
2800
Torque at Shaft (in-lb)
1646
2718
3877
4502
4502
4502
4502
Actual Flow (gpm)
10.3
24.8
40.5
55.8
71.5
87.0
102.3
Power Loss (hp)
33.7
34.8
35.9
32.2
26.1
23.3
22.2
Charge Pump Loss (hp)
6.44
6.44
6.44
6.44
6.44
6.44
6.44
Volumetric Efficiency (%)
57
76
84
88
92
94
96
Torque Efficiency (%)
87
92
94
94
94
93
92
Overall Efficiency (%)
49
70
78
83
87
88
89

18.0
10.07
165.0
2800
4502
118.6
22.2
6.44
97
91
89

18.0
10.07
165.0
2800
3724
119.2
20.0
6.44
98
90
87

18.0
10.07
165.0
2800
3398
119.5
19.1
6.44
98
89
87

Total Pump Flow (gpm)

118.6

119.2

119.5

Final Drive Ratio:
Final Drive Efficiency (%):
17.0
17.0
17.0
6.10
6.10
6.10
100.0
100.0
100.0
1900
2207
2226
2650
2261
1794
5.8
6.5
6.2
98
98
99
95
94
92
93
92
91
16367
13962
11078
292
340
342
1091
931
739

6.5
95
17.0
6.10
100.0
2234
1598
6.1
99
91
90
9865
344
658

Final Drive Ratio:
Final Drive Efficiency (%):
17.0
17.0
17.0
6.10
6.10
6.10
100.0
100.0
100.0
1900
2207
2226
2650
2261
1794
5.8
6.5
6.2
98
98
99
95
94
92
93
92
91
16367
13962
11078
292
340
342
1091
931
739

6.5
95
17.0
6.10
100.0
2234
1598
6.1
99
91
90
9865
344
658

Rolling Resistance (lb):
200.0
200.0
165.5
159.8
158.4
126.7
40.2
41.6
38.7
80
79
77
2182
1862
1477
26.09130.30530.564
2296
2667
2690
1483
1162
777
4.24
3.32
2.22

700
151.0
113.2
37.7
75
1315
30.670
2699
616
1.76

Pump 1

10.3

24.8

40.5

55.8

71.5

87.0

Final Drive Case 1
Motor 1

90M100 - Series 90, 6.1cir, 17deg Max Angle, AxialPiston
Rolling Radius (in): 15.00
Coeff. Rolling Resistance:
0.02
Weight Carried by Motor/Wheel (lb): 17500
Rolling Resistance (lb):350
Swashplate Angle (deg)
17.0
17.0
17.0
17.0
17.0
17.0
Displacement (cir)
6.10
6.10
6.10
6.10
6.10
6.10
Displacement (cc )
100.0
100.0
100.0
100.0
100.0
100.0
Shaft Speed (rpm)
162
432
726
1015
1317
1610
Torque at Motor Shaft (in-lb)
5047
5085
5121
4634
3743
3119
Power Loss (hp)
3.5
4.9
5.9
6.0
5.5
5.5
Volumetric Efficiency (%)
83
92
95
96
97
98
Torque Efficiency (%)
95
95
96
96
96
96
Overall Efficiency (%)
79
88
91
93
93
94
Torque at Wheel (in-lb)
31162
31401
31619
28613
23113
19260
Wheel Speed (rpm)
25
67
112
156
203
248
Tractive Force (lb)
2077
2093
2108
1908
1541
1284

Motor 2

90M100 - Series 90, 6.1cir, 17deg Max Angle, AxialPiston
Rolling Radius (in): 15.00
Coeff. Rolling Resistance:
0.02
Weight Carried by Motor/Wheel (lb): 17500
Rolling Resistance (lb):350
Swashplate Angle (deg)
17.0
17.0
17.0
17.0
17.0
17.0
Displacement (cir)
6.10
6.10
6.10
6.10
6.10
6.10
Displacement (cc )
100.0
100.0
100.0
100.0
100.0
100.0
Shaft Speed (rpm)
162
432
726
1015
1317
1610
Torque at Motor Shaft (in-lb)
5047
5085
5121
4634
3743
3119
Power Loss (hp)
3.5
4.9
5.9
6.0
5.5
5.5
Volumetric Efficiency (%)
83
92
95
96
97
98
Torque Efficiency (%)
95
95
96
96
96
96
Overall Efficiency (%)
79
88
91
93
93
94
Torque at Wheel (in-lb)
31162
31401
31619
28613
23113
19260
Wheel Speed (rpm)
25
67
112
156
203
248
Tractive Force (lb)
2077
2093
2108
1908
1541
1284

Total Vehicle Performance

Vehicle Weight (lb):
Input Power (hp)73.1
Output Power (hp)26.0Power Loss (hp)47.2
System Efficiency (%)
36
Tractive Force (lb)4155
Vehicle Speed (mph)2.228
Vehicle Speed (fpm)
196
Drawbar Pull @ 0% Grade (lb)3455
Gradeability (%)
9.94© Danfoss | July 2015

35000
120.8
69.8
51.0
58
4187
5.938
523
3487
10.03

Coeff. Rolling Resistance:
172.3
200.0
200.0
118.0
149.3
156.4
54.3
50.7
43.6
69
75
78
4216
3815
3082
9.971
13.94318.085
877
1227
1591
3516
3115
2382
10.11
8.95
6.83

0.02
200.0
159.4
40.6
80
2568
22.106
1945
1868
5.35

102.3

BLN-9885 | BC00000245en-US0304 | 31

Applications Manual
Selection of Driveline Components
Acceleration

Drawbar pull
(lb)
3455
3455
3487
3516
3115
2382
1868
1483
1162
777
616

Assumes average force between two speedsTime toCumulative
Speed
Speed
accel
Time
(mph)
0.000
2.228
5.938
9.971
13.94318.08522.10626.09130.30530.56430.67032 | © Danfoss | July 2015

(ft/sec)
0.000
3.267
8.709
14.62520.44926.52532.42238.26644.44744.82744.983

(sec)
0.000
1.028
1.704
1.836
1.909
2.403
3.016
3.791
5.081
0.425
0.244

(sec)
0.000
1.028
2.732
4.568
6.477
8.880
11.89615.68720.76821.19321.437Accel(ft/sec 2 )
0.000
3.179
3.208
3.235
2.866
2.192
1.719
1.364
1.069
0.715
0.567

g's
0.000
0.099
0.100
0.100
0.089
0.068
0.053
0.042
0.033
0.022
0.018

BLN-9885 | BC00000245en-US0304

Applications Manual
Selection of Driveline Components
Charge Pump Sizing

Introduction
The charge pump is a critical component of the hydrostatic transmission. Without charge flow andcharge pressure, the transmission will cease to function.
The primary function of the charge pump is to replenish fluid lost through leakage. In closed circuit
hydrostatic systems, continual internal leakage of high pressure fluid is inherent in the design of thecomponents used in such a system, and will generally increase as the displacement of the system’s
pumps and motors increase. This make-up fluid from the charge pump is added to the low pressure sideof the closed circuit to keep the lines full of fluid and avoid cavitation at the pump.
In addition to the primary function of replenishing fluid, another major function of the charge pump is toprovide charge pressure to help return the pistons and keep the slippers against the swashplate.
Another function of the charge pump includes providing fluid for servo pistons on those systems having
servo-controlled transmissions. If an Electronic Displacement Control (EDC) is used, the charge pumpprovides flow for the operation of a pressure control pilot valve (PCP). Charge flow also provides atransfer medium for heat dissipation. If the charge pump is used for auxiliary functions, then it must also
be sized to provide this additional flow.
The Charge Pump Functions illustration shows the functions that the charge pump may be required toprovide in a given application.

Charge Pump Considerations
As a rule of thumb, the charge flow requirement for a simple hydrostatic circuit is approximately 10% of
the total displacement of all units in the system. However, this guideline is only an approximation for a
simple system containing high speed piston components. The best way to size a charge pump is toindividually consider each demand imposed on the charge pump. Many of these requirements do notoccur in a simple hydrostatic circuit.
To properly size a charge pump, each of the following factors must be taken into account:© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304 | 33

Applications Manual
Selection of Driveline Components
Charge Pump Sizing

•
•
•
•
•
•
•

System Pressure, and rate-of-change of system pressure (ΔP)
Input Speed
Minimum operational input speed
Line size, length, and Effective Bulk Modulus of the fluid
Control requirements
Non-Danfoss components
Type of loading

The System Leakage graph shows how system pressure and input speed affect leakage in the system. The
graph shows that leakage increases with both higher system pressure and higher input speed. Changes
in pressure have a greater effect on leakage than changes in speed. However, the affects due to changes
in speed are greater at higher system pressures.

The Charge Flow and Leakage graph shows why it is important to also know the “minimum pump input
speed”. In addition to the curves showing leakage, the figure includes curves for two charge pump sizes
and their respective flows. (Charge pump #1 has the larger displacement.) The figure shows that for agiven system pressure and charge pump size, system leakage varies at a rate different than that for
charge flow. .

Disregarding for the moment all other charge pump requirements, other than leakage; for a given speed
and pressure (and temperature) a charge pump has a flow curve which intersects the system leakage
curve. At low speeds and high pressures, the potential system leakage may exceed the flow that the
34 | © Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Charge Pump Sizing
charge pump is capable of providing. Furthermore, the charge pump’s Volumetric Efficiency decreases
with decreasing speed. Therefore, even though leakage rate may be greater at high pump input speeds,
the largest charge pump displacement may be required at a reduced input speed. Both extremes of
speed need to be checked for charge flow requirements. In many cases, the low input speed operational
requirement will predominate in the final charge pump size selection.
If a larger charge pump displacement is selected due to a low input speed, then the case flow rate at thehigher speeds will be greater and larger case drain lines may be required to keep case pressure within
limits.
Make sure that all components with potential leakage are considered. Any component connected to thecharge flow (i.e., connected to the low pressure side of the hydrostatic loop) must have its leakage value
included in the total available charge flow. In addition, if these same components also create large drops
in pressure, additional charge flow may be required for cooling.
The maximum flow required for the “control requirements” for servo-controlled pumps is dependent on
the stroke rate and the servo volume. Normally, the flow required is in the range of 2 to 8 lpm [1/2 to 2gpm]. In any case, servo flow must be included in the charge pump sizing requirement when applicable.
If an Electrical Displacement Control (EDC) is also used, a small amount of additional charge flow isrequired, usually 2 to 4 lpm [1/2 to 1 gpm]. This flow rate is needed for operation of the Pressure Control
Pilot Valve (PCP), which regulates the position of the control spool of the displacement control. Thisadditional flow requirement does not apply to hydraulic or manual displacement controls.
In some applications, special considerations for “cooling flow” requirements are not necessary. Charge
pump flow necessary to make up for leakage may be sufficient for cooling. More often, additional cooling
flow is required and a loop flushing shuttle valve is specified. The charge pump displacement must thenaccommodate this additional requirement for charge flow.
The “type of loading” can also require additional charge flow. Particularly, if the load is erratic or cyclical, abulk modulus effect can occur. Bulk modulus is the inverse of a material property, Compressibility, which
is defined as the amount that a fluid compresses for a given pressure increase. At low pressures, theamount of this fluid compression is small, and for this reason fluids are usually thought of as being“incompressible”. The pressures that can occur in hydrostatic systems, however, are of a magnitude thatthe influence of fluid compressibility can be significant. .
The bulk modulus effect occurs when rapid system pressure spikes compress the fluid in the highpressure side of the system. This results in an instantaneous reduction of the return flow rate into the lowpressure side of the system. This reduction of return flow rate must be provided by the charge system, inorder to maintain proper charge pressure in the low pressure side of the system.
The degree of bulk modulus effect in a given system will depend on several factors. These are, the lengthand diameter of the pressure conduits (which determine the volume of fluid subjected to the highpressure spikes), the rate of rise of the pressure spike, the magnitude of the pressure spike, and the bulk
modulus of the fluid.
Because the bulk modulus effect is so easily overlooked, and because it often results in a tremendous
increase in required charge flow, a section has been included in Fluids and Lubricants 520L0463. An
example calculation is provided below to bring special attention to this topic.

© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304 | 35

Applications Manual
Selection of Driveline Components
Charge Pump Sizing

The required charge pump displacement is the one which is able to provide flow for all of the above
requirements. If the required charge flow exceeds the capability of all available charge pumpdisplacements, then a gear pump (or some additional charge flow source) must be used. Most Danfoss
pumps include an auxiliary pad to mount gear pumps of various displacements.
After the charge pump displacement is selected, a system must be tested to be certain that charge flow
and pressure requirements are met.
Use the Charge Pump Sizing Worksheet below to size a charge pump. Each of the charge flow
requirements is included. The sum of the required charge flows represents the total flow required if all
charge flow demands need to be met simultaneously. In reality, this is usually not the case. For example,
it may be that for a particular system, a bulk modulus effect may never occur while an auxiliary function is
active. Each application needs to be reviewed carefully to determine how much charge flow is required.
Charge Pump Sizing Worksheet
Leakage:"Pump" refers to hydrostatic pump, not the charge pump. Actually, only a portion of all inefficiencies canbe attributed to crossport leakage between high and low system loops. Since the charge pump needs toreplace only fluid leaking past the rotating kits (i.e. case flow), the calculations below are conservative. Ifcase flow values are available, they should be used instead of the equations below.

36 | © Danfoss | July 2015

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Applications Manual
Selection of Driveline Components
Charge Pump Sizing
System Pressure

psi

Pump
SeriesFrame Size
Speed
Volumetric Efficiency
Leakage

RPM%
gpm

Motor #1
SeriesFrame Size
Speed
Volumetric Efficiency
Leakage

RPM%
gpm

Motor #2
SeriesFrame Size
Speed
Volumetric Efficiency
Leakage

RPM%
gpm

Total Leakage

gpm
lpm

Pump Flow =Pump Flow =Pump Disp, cir * Pump RPM Pump Efficiency, %
, gpm
*
3
100
231 in /gal
Pump Disp, cc * Pump RPM
1000 cc/liter

Pump Leakage =Pump Leakage =*Pump Efficiency, %
100

, lpm

Pump Disp, cir * Pump RPM
Pump Efficiency, %
, gpm
* 1′
3
100
231 in /gal
Pump Disp, cc * Pump RPM
1000 cc/liter

* 1′

)
)

(

Pump Efficiency, %
100

, lpm

Motor Speed(Pump Flow, gpm )* 231 in 3 / gal (Motor Efficiency, %/100) , RPM

Motor Speed =(Pump Flow, lpm )* 1000 cm3 / liter (Motor Efficiency, %/100) , RPM(

Motor Disp, in 3 /rev * # Motors

MotorLeakage =

(

(

)
)

Motor Disp, cm3 /rev * # Motors

Pump Flow# Motors* 1′

Motor Efficiency, %100, gpm (lpm)

Note : Consult product technical information bulletinsfor values of Volumetric Efficiency.

© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304 | 37

Applications Manual
Selection of Driveline Components
Charge Pump Sizing

38 | © Danfoss | July 2015

BLN-9885 | BC00000245en-US0304

Applications Manual
Selection of Driveline Components
Charge Pump Sizing© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304 | 39

Applications Manual
Selection of Driveline Components
Charge Pump Sizing
2 Position Control: Step Response, seconds
Step response has been tested with a 2-Position control (de-energized max. angle) at delta p = 30 bar. 210 bar and 400 bar and orifices for Servo M4 & M5
For Max. to Min., current went from zero to max, then back to zero current.

Orifice diameter
60cc
Max  Min (s)30 bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)210 bar(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)400 bar(100%  20%)Min  Max (s)(20%  100%)

w/o
0.22

1.2
mm
0.47

0.8
mm
1.13

Orifice diameter
110cc

0.6
mm

Max  Min (s)1.70
30 bar

0.21

0.52

1.00

1.56

0.14

0.26

0.58

0.85

0.15

0.25

0.45

0.71

0.13

0.21

0.46

0.65

0.15

0.20

0.33

0.51

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

210
bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

400
bar

(100%  20%)Min  Max (s)(20%  100%)w/o

1.2 mm

0.8 mm

0.6 mm

0.56

1.40

1.94

3.60

0.44

1.13

1.89

3.59

0.22

0.45

0.80

1.38

0.21

0.41

0.92

1.67

0.22

0.33

0.58

0.97

0.22

0.31

0.69

1.25

Orifice diameter
80cc
Max  Min (s)30 bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)210 bar(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)400 bar(100%  20%)Min  Max (s)(20%  100%)

Orifice diameter

w/o

1.2
mm

0.8
mm

0.6
mm

0.30

0.61

1.50

2.80

160cc
Max  Min (s)30 bar

0.40

0.71

1.50

2.70

0.14

0.30

0.74

1.32

0.19

0.34

0.73

1.16

0.11

0.23

0.57

1.00

0.14

0.27

0.54

0.90

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

210
bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

400
bar

(100%  20%)Min  Max (s)(20%  100%)

250cc
Max  Min (s)30 bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

210
bar

(100%  20%)Min  Max (s)(20%  100%)
Max  Min (s)

400
bar

(100%  20%)Min  Max (s)(20%  100%)w/o

1.2 mm

0.8 mm

0.6 mm

0.48

1.32

2.62

4.36

0.50

1.30

3.03

4.92

0.27

0.68

1.25

2.10

0.28

0.71

1.61

2.57

0.31

0.50

0.90

1.47

0.24

0.56

1.24

2.04

w/o

1.2 mm

0.8 mm

0.6 mm

0.55

1.56

3.28

5.59

0.62

1.46

3.52

5.94

0.32

0.72

1.38

2.21

0.31

0.72

1.64

2.73

0.33

0.53

0.97

1.50

0.25

0.55

1.24

2.03

Orifice diameter

P10890540 | © Danfoss | July 2015

BLN-9885 | BC00000245en-US0304

Applications Manual
Selection of Driveline Components
Charge Pump Sizing
Proportional Control: Step Response, seconds
Step response has been tested with a Proportional control (de-energized max. angle) at delta p = 30 bar. 210 bar and 400 bar and orifices for Servo M4 & M5
For Max. to Min., current went from zero to max, then back to zero current.
060cc
Max  Min (s)(100%  20%)30 barMin  Max (s)

0.47

0.96

1.59

Max  Min (s)(100%  20%)Min  Max (s)Orifice diameterw/o

1.2 mm

0.8 mm

0.6 mm

0.51

1.27

1.76

3.27

0.95

1.37

0.40

1.03

1.72

3.26

0.25

0.43

0.68

50%  20% (s)

0.20

0.34

0.69

1.11

20%  50% (s)

0.21

0.27

0.42

0.62

20%  50% (s)

0.18

0.34

0.68

1.16

0.24

0.31

0.53

0.84

0.20

0.41

0.73

1.25

0.23

0.32

0.46

0.65

0.19

0.37

0.84

1.52

50%  20% (s)

0.20

0.19

0.27

0.39

50%  20% (s)

0.18

0.16

0.29

0.45

20%  50% (s)

0.20

0.20

0.24

0.32

20%  50% (s)

0.19

0.20

0.37

0.61

0.28

0.27

0.43

0.65

0.20

0.30

0.53

0.88

Min  Max (s)(20%  100%)

Min  Max (s)30 bar

(20%  100%)

Max  Min (s)(100%  20%)210 barMin  Max (s)(20%  100%)

Max  Min (s)(100%  20%)Min  Max (s)

0.24

0.26

0.38

0.49

0.20

0.28

0.63

1.14

50%  20% (s)

0.23

0.21

0.24

0.33

50%  20% (s)

0.33

0.31

0.21

0.33

20%  50% (s)

0.21

0.20

0.22

0.27

20%  50% (s)

0.24

0.18

0.33

0.56

w/o

1.2 mm

0.8 mm

0.6 mmw/o

1.2 mm

0.8 mm

0.6 mm

0.36

0.78

1.39

2.28

0.52

1.15

2.08

3.58

(20%  100%)080cc
Max  Min (s)(100%  20%)Min  Max (s)400 barOrifice diameter(20%  100%)160cc
Max  Min (s)(100%  20%)Min  Max (s)Orifice diameter

0.30

0.59

1.45

2.35

0.42

1.03

2.12

3.74

50%  20% (s)

0.17

0.30

0.50

0.89

50%  20% (s)

0.27

0.48

0.84

1.45

20%  50% (s)

0.16

0.37

0.53

0.95

20%  50% (s)

0.35

0.48

0.90

1.52

0.16

0.40

0.56

0.97

0.40

0.58

1.05

1.64

0.27

0.31

0.67

1.16

0.28

0.58

1.15

1.91

50%  20% (s)

0.18

0.18

0.20

0.34

50%  20% (s)

0.43

0.31

0.45

0.67

20%  50% (s)

0.17

0.20

0.25

0.43

20%  50% (s)

0.49

0.38

0.53

0.81

0.19

0.34

0.40

0.69

0.53

0.49

0.75

1.18

0.32

0.25

0.50

0.86

0.24

0.46

0.87

1.43

50%  20% (s)

0.17

0.20

0.15

0.24

50%  20% (s)

0.56

0.39

0.35

0.50

20%  50% (s)

0.13

0.20

0.19

0.33

20%  50% (s)

0.57

0.43

0.45

0.68

w/o

1.2 mm

0.8 mm

0.6 mm

0.58

1.29

3.12

4.68

(20%  100%)

Max  Min (s)(100%  20%)Min  Max (s)(20%  100%)

Max  Min (s)(100%  20%)400 bar

0.30

110cc

0.50

(100%  20%)210 bar

0.6 mm0.20

Max  Min (s)30 bar

0.8 mm0.04(100%  20%)400 bar

1.2 mm50%  20% (s)(20%  100%)

Max  Min (s)210 barOrifice diameterw/oMin  Max (s)(20%  100%)

30 bar

(20%  100%)

Max  Min (s)(100%  20%)210 barMin  Max (s)(20%  100%)

Max  Min (s)(100%  20%)400 barMin  Max (s)(20%  100%)

250cc
Max  Min (s)(100%  20%)30 barMin  Max (s)

0.50

1.14

2.89

4.93

50%  20% (s)

0.28

0.53

0.98

1.63

20%  50% (s)

0.23

0.48

1.00

1.76

0.24

0.55

1.12

1.74

0.24

0.56

1.27

2.27

0.42

0.43

0.46

0.66

(20%  100%)

Max  Min (s)(100%  20%)210 barOrifice diameterMin  Max (s)(20%  100%)50%  20% (s)20%  50% (s)Max  Min (s)(100%  20%)400 barMin  Max (s)(20%  100%)50%  20% (s)20%  50% (s)© Danfoss | July 2015

0.55

0.92

0.19

0.41

0.82

1.24

0.19

0.43

0.97

1.72

0.55

0.50

0.35

0.49

0.48

0.78

P108906

BLN-9885 | BC00000245en-US0304 | 41

Applications Manual
Selection of Driveline Components
Charge Pump Sizing

42 | © Danfoss | July 2015

BLN-9885 | BC00000245en-US0304

Applications Manual
Selection of Driveline Components
Charge Pump Sizing© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304 | 43

Products we offer:

•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

Bent Axis Motors
Closed Circuit Axial Piston
Pumps and Motors
Displays
Electrohydraulic Power
Steering
Electrohydraulics

Danfoss Power Solutions is a global manufacturer and supplier of high-quality hydraulic andelectronic components. We specialize in providing state-of-the-art technology and solutions
that excel in the harsh operating conditions of the mobile off-highway market. Building on
our extensive applications expertise, we work closely with our customers to ensure
exceptional performance for a broad range of off-highway vehicles.
We help OEMs around the world speed up system development, reduce costs and bringvehicles to market faster.
Danfoss – Your Strongest Partner in Mobile Hydraulics.

Hydraulic Power Steering

Go to www.powersolutions.danfoss.com for further product information.

Integrated Systems

Wherever off-highway vehicles are at work, so is Danfoss. We offer expert worldwide support
for our customers, ensuring the best possible solutions for outstanding performance. And
with an extensive network of Global Service Partners, we also provide comprehensive global
service for all of our components.

Joysticks and Control
Handles
Microcontrollers andSoftwareOpen Circuit Axial Piston
Pumps
Orbital Motors

Please contact the Danfoss Power Solution representative nearest you.

PLUS+1® GUIDE
Proportional Valves
Sensors
Steering
Transit Mixer Drives

Comatrolwww.comatrol.com

Local address:

Turollawww.turollaocg.com
Hydro-Gear
www.hydro-gear.com
Daikin-Sauer-Danfoss
www.daikin-sauer-danfoss.com

Danfoss
Power Solutions (US) Company
2800 East 13th Street
Ames, IA 50010, USA
Phone: +1 515 239 6000

Danfoss
Power Solutions GmbH & Co. OHG
Krokamp 35
D-24539 Neumünster, Germany
Phone: +49 4321 871 0

Danfoss
Power Solutions ApS
Nordborgvej 81
DK-6430 Nordborg, Denmark
Phone: +45 7488 2222

Danfoss
Power Solutions Trading(Shanghai) Co., Ltd.
Building #22, No. 1000 Jin Hai Rd
Jin Qiao, Pudong New District
Shanghai, China 201206
Phone: +86 21 3418 5200

Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products
already on order provided that such alterations can be made without changes being necessary in specifications already agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.

© Danfoss | July 2015

BLN-9885 | BC00000245en-US0304