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
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
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
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
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
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
RP 960 Series Ordering Information........................................................................................................................................	29

© Danfoss | June 2019

BC00000383en-000103 | 3

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

C 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.

4 | © Danfoss | June 2019

BC00000383en-000103

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.

-100	-75	-50	-25	0	25	50	75	100	mm
9000									4000
8000									3500
						445 daN [1000 lb]
7000									3000
6000						445 daN [1000 lb]
									2500
5000
									2000
4000
3000									1500
							SHAFT
2000									1000
1000					BEARING				500
lb									daN
-100	-75	-50	-25	0	25	50	75	100	mm
									P109320

© Danfoss | June 2019

BC00000383en-000103 | 5

Technical Information

Hydraulic Brakes

Technical Information

Example Load Rating for Mechanically Retained Needle Roller Bearings

Bearing Life L10	(C/P)p [106 revolutions]
L10	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

Vehicle Drive Calculations

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)

6 | © Danfoss | June 2019

BC00000383en-000103

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

© Danfoss | June 2019

BC00000383en-000103 | 7

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

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.

Radius 76 mm [3.00 in]

Torque

1129 Nm

[10000 lb-in]

P109321

© Danfoss | June 2019

BC00000383en-000103 | 9

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.

	Torque	Distance
Side Load =
	Radius
Side Load = 14855 Nm [3333 lbs]

P109322

Hydraulic Equations

Multiplication Factor	Abbreviation	Prefix
1012	T	tera
109	G	giga
106	M	mega
103	K	kilo
102	h	hecto
101	da	deka
10-1	d	deci
10-2	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