Danfoss Hydraulic Brakes User guide
Technical Information
Hydraulic Brakes
BK, AB, FB, SB, RP Series
www.danfoss.com
Technical Information
Hydraulic Brakes
Revision history Table of revisions
Date Changed Rev
June 2019 Spelling and grammatical updates 0103
Nov 2017 Updated SB 930 max. release pressure rating 0102
Mar 2017 First edition 0101
2 | © Danfoss | June 2019 BC00000383en-000103
Technical Information
Hydraulic Brakes
Contents
Technical Information
BK 913 and 915 Series
AB 920 Series
FB 925 Series
SB 930 Series
RP 960 Series
Operating Recommendations..................................................................................................................................................... 4
Oil Type...........................................................................................................................................................................................4
Fluid Viscosity and Filtration...................................................................................................................................................4
Installation and Start-up...........................................................................................................................................................4
Hydraulic Motor Safety Precaution.......................................................................................................................................4
Hydraulic Brake Precaution..................................................................................................................................................... 4
Allowable Bearing and Shaft Loading.......................................................................................................................................5
Vehicle Drive Calculations.............................................................................................................................................................6
Induced Side Load............................................................................................................................................................................9
Hydraulic Equations......................................................................................................................................................................10
Shaft Nut Information...................................................................................................................................................................11
BK 913 and 915 Series Housings...............................................................................................................................................14
BK 913 and 915 Series Technical Information......................................................................................................................14
BK 913 and 915 Series Shafts..................................................................................................................................................... 16
BK 913 and 915 Series Ordering Information...................................................................................................................... 16
AB 920 Series Housings................................................................................................................................................................17
AB 920 Series Technical Information...................................................................................................................................... 18
AB 920 Series Shafts......................................................................................................................................................................19
AB 920 Series Ordering Information....................................................................................................................................... 19
FB 925 Series Housings................................................................................................................................................................ 20
FB 925 Series Technical Information.......................................................................................................................................21
FB 925 Series Shafts.......................................................................................................................................................................22
FB 925 Series Ordering Information........................................................................................................................................22
SB 930 Series Housings................................................................................................................................................................ 24
SB 930 Series Shafts.......................................................................................................................................................................25
SB 930 Series Technical Information.......................................................................................................................................26
SB 930 Series Installation Information....................................................................................................................................26
SB 930 Series Ordering Information........................................................................................................................................27
RP 960 Series Ordering Information........................................................................................................................................29
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C
Technical Information
Hydraulic Brakes
Technical Information
Operating Recommendations
Oil Type
Hydraulic oils with anti-wear, anti-foam and demulsifiers are recommended for systems incorporating
Danfoss motors. Straight oils can be used but may require VI (viscosity index) improvers depending on
the operating temperature range of the system. Other water based and environmentally friendly oils may
be used, but service life of the motor and other components in the system may be significantly
shortened. Before using any type of fluid, consult the fluid requirements for all components in the system
for compatibility. Testing under actual operating conditions is the only way to determine if acceptable
service life will be achieved.
Fluid Viscosity and Filtration
Fluids with a viscosity between 20 - 43 cSt [100 - 200 S.U.S.] at operating temperature is recommended.
Fluid temperature should also be maintained below 85°C [180° F]. It is also suggested that the type of
pump and its operating specifications be taken into account when choosing a fluid for the system. Fluids
with high viscosity can cause cavitation at the inlet side of the pump. Systems that operate over a wide
range of temperatures may require viscosity improvers to provide acceptable fluid performance.
Danfoss recommends maintaining an oil cleanliness level of ISO 17-14 or better.
Installation and Start-up
When installing a Danfoss motor it is important that the mounting flange of the motor makes full contact
with the mounting surface of the application. Mounting hardware of the appropriate grade and size must
be used. Hubs, pulleys, sprockets and couplings must be properly aligned to avoid inducing excessive
thrust or radial loads. Although the output device must fit the shaft snug, a hammer should never be
used to install any type of output device onto the shaft. The port plugs should only be removed from the
motor when the system connections are ready to be made. To avoid contamination, remove all matter
from around the ports of the motor and the threads of the fittings. Once all system connections are
made, it is recommended that the motor be run-in for 15-30 minutes at no load and half speed to remove
air from the hydraulic system.
Hydraulic Motor Safety Precaution
A hydraulic motor must not be used to hold a suspended load. Due to the necessary internal tolerances,
all hydraulic motors will experience some degree of creep when a load induced torque is applied to a
motor at rest. All applications that require a load to be held must use some form of mechanical brake
designed for that purpose.
Hydraulic Brake Precaution
Caution
Danfoss’ brakes are intended to operate as static or parking brakes. System circuitry must be designed to
bring the load to a stop before applying the brake.
To achieve proper brake release operation, it is necessary to bleed out any trapped air and fill brake
release cavity and hoses before all connections are tightened. To facilitate this operation, all motor/
brakes feature two release ports. One or both of these ports may be used to release the brake in the unit.
Motor/brakes should be configured so that the release ports are near the top of the unit in the installed
position.
Once all system connections are made, one release port must be opened to atmosphere and the brake
release line carefully charged with fluid until all air is removed from the line and motor/brake release
cavity. When this has been accomplished the port plug or secondary release line must be reinstalled. In
the event of a pump or battery failure, an external pressure source may be connected to the brake release
port to release the brake, allowing the machine to be moved.
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9000
8000
7000
6000
5000
4000
3000
2000
1000
lb
4000
3500
3000
2500
2000
1500
1000
500
daN
445 daN [1000 lb]
445 daN [1000 lb]
BEARING
SHAFT
-100
-50 -25 0 25 50 75 100
mm
-75
-100
-50 -25 0 25 50 75 100
mm
-75
P109320
Technical Information
Hydraulic Brakes
Technical Information
Allowable Bearing and Shaft Loading
This catalog provides curves showing allowable radial loads at points along the longitudinal axis of the
motor. They are dimensioned from the mounting flange. Two capacity curves for the shaft and bearings
are shown. A vertical line through the centerline of the load drawn to intersect the x-axis intersects the
curves at the load capacity of the shaft and of the bearing.
In the example below, the maximum radial load bearing rating is between the internal roller bearings
illustrated with a solid line. The allowable shaft rating is shown with a dotted line.
The bearing curves for each model are based on laboratory analysis and testing conducted at Danfoss.
The shaft loading is based on a 3:1 safety factor and 330 Kpsi tensile strength. The allowable load is the
lower of the curves at a given point. For instance, one inch in front of the mounting flange the bearing
capacity is lower than the shaft capacity. In this case, the bearing is the limiting load. The motor user
needs to determine which series of motor to use based on their application knowledge.
ISO 281 Ratings vs. Manufacturer's Ratings
Published bearing curves can come from more than one type of analysis. The ISO 281 bearing rating is an
international standard for the dynamic load rating of roller bearings. The rating is for a set load at a speed
of 33 1/3 RPM for 500 hours (1 million revolutions). The standard was established to allow consistent
comparisons of similar bearings between manufacturers. The ISO 281 bearing ratings are based solely on
the physical characteristics of the bearings, removing any manufacturers specific safety factors or
empirical data that influences the ratings.
Manufacturers’ ratings are adjusted by diverse and systematic laboratory investigations, checked
constantly with feedback from practical experience. Factors taken into account that affect bearing life are
material, lubrication, cleanliness of the lubrication, speed, temperature, magnitude of the load and the
bearing type.
The operating life of a bearing is the actual life achieved by the bearing and can be significantly different
from the calculated life. Comparison with similar applications is the most accurate method for bearing life
estimations.
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Technical Information
Hydraulic Brakes
Technical Information
Example Load Rating for Mechanically Retained Needle Roller Bearings
Vehicle Drive Calculations
Bearing Life L
L
10
10
(C/P)p [106 revolutions]
nominal rating life
C dynamic load rating
P equivalent dynamic load
Life Exponent p 10/3 for needle bearings
Bearing Load Multiplication Factor Table
RPM Factor
50 1.23
100 1.00
200 0.81
300 0.72
400 0.66
500 0.62
600 0.58
700 0.56
800 0.50
When selecting a wheel drive motor for a mobile vehicle, a number of factors concerning the vehicle
must be taken into consideration to determine the required maximum motor RPM, the maximum torque
required and the maximum load each motor must support. The following sections contain the necessary
equations to determine this criteria. An example is provided to illustrate the process.
Sample application (vehicle design criteria)
vehicle description 4 wheel vehicle
vehicle drive 2 wheel drive
GVW 1,500 lbs.
weight over each drive wheel 425 lbs.
rolling radius of tires 16 in.
desired acceleration 0-5 mph in 10 sec.
top speed 5 mph
gradability 20%
worst working surface poor asphalt
To determine maximum motor speed
RPM = (2.65 x KPH x G) / rm or RPM = (168 x MPH x G) / ri
KPH max. vehicle speed (kilometers/hr)
MPH max. vehicle speed (miles/hr)
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Technical Information
Hydraulic Brakes
Technical Information
G gear reduction ratio (if none, G = 1)
rm rolling radius of tire (meters)
ri rolling radius of tire (inches)
RPM = (168 x 5 x 1) / 16 = 52.5
To determine maximum torque requirement of motor
To choose a motor(s) capable of producing enough torque to propel the vehicle, it is necessary to
determine the Total Tractive Effort (TE) requirement for the vehicle. To determine the total tractive effort,
the following equation must be used:
TE = RR + GR + FA + DP (lbs or N)
TE Total tractive effort
RR Force necessary to overcome rolling resistance
GR Force required to climb a grade
FA Force required to accelerate
DP Drawbar pull required
The components for this equation may be determined using the following steps.
Step One: Determine Rolling Resistance
Rolling Resistance (RR) is the force necessary to propel a vehicle over a particular surface. It is
recommended that the worst possible surface type to be encountered by the vehicle be factored into the
equation.
RR = (GVW / 1000) x R (lb or N)
GVW gross (loaded) vehicle weight (lb or kg)
R surface friction (value from Rolling Resistance on page 7)
Rolling Resistance
Concrete (excellent) 10
Concrete (good) 15
Concrete (poor) 20
Asphalt (good) 12
Asphalt (fair) 17
Asphalt (poor) 22
Macadam (good) 15
Macadam (fair) 22
Macadam (poor) 37
Cobbles (ordinary) 55
Cobbles (poor) 37
Snow (2 inch) 25
Snow (4 inch) 37
Dirt (smooth) 25
Dirt (sandy) 37
Mud 37 to 150
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Technical Information
Hydraulic Brakes
Technical Information
Rolling Resistance (continued)
Sand (soft) 60 to 150
Sand (dune) 160 to 300
Step Two: Determine Grade Resistance
Grade Resistance (GR) is the amount of force necessary to move a vehicle up a hill or “grade.” This
calculation must be made using the maximum grade the vehicle will be expected to climb in normal
operation.
To convert incline degrees to % Grade:
% Grade = [tan of angle (degrees)] x 100
GR = (% Grade / 100) x GVW (lb or N)
Example: GR = (20 / 100) x 1500 lbs = 300 lbs
Step Three: Determine Acceleration Force
Acceleration Force (FA) is the force necessary to accelerate from a stop to maximum speed in a desired
time.
FA = (KPH x GVW (N)) / (35.32 x t) or FA = (MPH x GVW (lb)) / (22 x t)
t time to maximum speed (seconds)
Example: FA = (5 x 1500 lbs) / (22 x 10) = 34 lbs
Step Four: Determine Drawbar Pull
Drawbar Pull (DP) is the additional force, if any, the vehicle will be required to generate if it is to be used
to tow other equipment. If additional towing capacity is required for the equipment, repeat steps one
through three for the towable equipment and sum the totals to determine DP.
Step Five: Determine Total Tractive Effort
The Tractive Effort (TE) is the sum of the forces calculated in steps one through three above. On low
speed vehicles, wind resistance can typically be neglected. However, friction in drive components may
warrant the addition of 10% to the total tractive effort to insure acceptable vehicle performance.
TE = RR + GR + FA + DP (lb or N)
Example: TE = 33 + 300 + 34 + 0 (lbs) = 367 lbs
Step Six: Determine Motor Torque
The Motor Torque (T) required per motor is the Total Tractive Effort divided by the number of motors
used on the machine. Gear reduction is also factored into account in this equation.
T = (TE x rm) / (M x G) Nm per motor or T = (TE x ri) / (M x G) lb-in per motor
M number of driving motors
Example: T = (367 x 16) / (2 x 1) lb-in/motor = 2936 lb-in
Step Seven: Determine Wheel Slip
To verify that the vehicle will perform as designed in regards to tractive effort and acceleration, it is
necessary to calculate wheel slip (TS) for the vehicle. In special cases, wheel slip may actually be desirable
to prevent hydraulic system overheating and component breakage should the vehicle become stalled.
TS = (W x f x rm) / G (Nm per motor) or TS = (W x f x ri) / G (lb-in per motor)
8 | © Danfoss | June 2019 BC00000383en-000103
Radius 76 mm [3.00 in]
Torque
1129 Nm
[10000 lb-in]
P109321
Technical Information
Hydraulic Brakes
Technical Information
f coefficient of friction (see Coefficient of friction (f) on page 9)
W loaded vehicle weight over driven wheel (lb or N)
Example: TS = (425 x .06 x 16) / 1 = lb-in/motor = 4080 lbs
Coefficient of friction (f)
Steel on steel 0.3
Rubber tire on dirt 0.5
Rubber tire on a hard surface 0.6 - 0.8
Rubber tire on cement 0.7
To determine radial load capacity requirement of motor
When a motor used to drive a vehicle has the wheel or hub attached directly to the motor shaft, it is
critical that the radial load capabilities of the motor are sufficient to support the vehicle. After calculating
the Total Radial Load (RL) acting on the motors, the result must be compared to the bearing/shaft load
charts for the chosen motor to determine if the motor will provide acceptable load capacity and life.
RL = sqrt(W2 + (T / ri)2) lb or RL = sqrt(W2 + (T / rm)2) kg
Example: RL = sqrt(4252 + (2936 / 16)2) = 463 lbs
Once the maximum motor RPM, maximum torque requirement, and the maximum load each motor must
support have been determined, these figures may then be compared to the motor performance charts
and to the bearing load curves to choose a series and displacement to fulfill the motor requirements for
the application.
Induced Side Load
In many cases, pulleys or sprockets may be used to transmit the torque produced by the motor. Use of
these components will create a torque induced side load on the motor shaft and bearings. It is important
that this load be taken into consideration when choosing a motor with sufficient bearing and shaft
capacity for the application.
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Distance
Side Load =
Side Load = 14855 Nm [3333 lbs]
Torque
Radius
P109322
Technical Information
Hydraulic Brakes
Technical Information
To determine the side load, the motor torque and pulley or sprocket radius must be known. Side load
may be calculated using the formula below. The distance from the pulley/sprocket centerline to the
mounting flange of the motor must also be determined. These two figures may then be compared to the
bearing and shaft load curve of the desired motor to determine if the side load falls within acceptable
load ranges.
Hydraulic Equations
Multiplication Factor Abbreviation Prefix
12
10
10
10
10
10
10
10
10
9
6
3
2
1
-1
-2
T tera
G giga
M mega
K kilo
h hecto
da deka
d deci
c centi
Theo. Speed (RPM) (1000 x LPM) / Displacement (cm3/rev)
(231 x GPM) / Displacement (in3/rev)
Theo. Torque (lb-in) (Bar x Disp. (cm3/rev)) / 20 pi
(PSI x Disp. (in3/rev) / 6.28
Power In (HP) (Bar x LPM) / 600
(PSI x GPM) / 1714
Power Out (HP) (Torque (Nm) x RPM) / 9543
10 | © Danfoss | June 2019 BC00000383en-000103
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