Danfoss BDU User guide

Technical Information

BDU Series

Hydrostatic Transmissions

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Technical Information

BDU Series Hydrostatic Transmissions

Revision history Table of revisions

Date Changed Rev

November 2021 Removed contents of BDP, and aligned revision number along with DAM Hub. 0207

November 2020 Minor update in Hydraulic Fluid, and changed document number from 'BC00000025' and

'520L0935' to 'BC152886484098'

December 2018 Fixed Model Code "H" 0103

May 2017 Fixed typo 0102

June 2016 Convertd to DITA-CMS 0101

Mar 2010 Correction - Drawing AC

Jan 2009 Correction - Text AB

Jan 2006 First edition AA

0104

2 | © Danfoss | November 2021 BC152886484098en-000207

Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU Series Family.............................................................................................................................................................................5

Features and Benefits......................................................................................................................................................................5

Design...................................................................................................................................................................................................6

BDU-06/10S........................................................................................................................................................................................ 8

Pictorial Diagram.........................................................................................................................................................................8

System Schematic.......................................................................................................................................................................8

BDU-10L/21L/21H.............................................................................................................................................................................9

Pictorial Diagram.........................................................................................................................................................................9

System Schematic: BDU-21L................................................................................................................................................... 9

System Schematic: BDU-21H................................................................................................................................................10

Technical Specifications

Features and Options................................................................................................................................................................... 11

Operating Parameters..................................................................................................................................................................12

Fluid Specifications....................................................................................................................................................................... 12

Efficiency........................................................................................................................................................................................... 13

BDU-06S....................................................................................................................................................................................... 13

BDU-10S....................................................................................................................................................................................... 13

BDU-10L....................................................................................................................................................................................... 13

BDU-21L/21H..............................................................................................................................................................................14

Operating Parameters

Overview........................................................................................................................................................................................... 15

Input Speed......................................................................................................................................................................................15

System Pressure..............................................................................................................................................................................15

Charge Pressure..............................................................................................................................................................................15

Charge Inlet Pressure....................................................................................................................................................................15

Case Pressure...................................................................................................................................................................................16

Hydraulic Fluids.............................................................................................................................................................................. 16

Temperature and Viscosity.........................................................................................................................................................16

System Design Parameters

Fluid and Filtration........................................................................................................................................................................ 17

Reservoir............................................................................................................................................................................................17

Control Shaft Force........................................................................................................................................................................17

Independent Braking System....................................................................................................................................................17

Features and Options

Shaft Load.........................................................................................................................................................................................18

Shaft Options...................................................................................................................................................................................18

Shaft Options : BDU-06S/10S/10L............................................................................................................................................ 19

Shaft Options : BDU-21L/21H.................................................................................................................................................... 20

Bypass Valve.....................................................................................................................................................................................21

High Pressure Relief Valve (hprv) and Charge Check (Overpressure Protection)...................................................21

Charge Check Valve with Orifice.............................................................................................................................................. 23

Charge Check with Orifice.......................................................................................................................................................... 24

Optional Integrated Reservoir...................................................................................................................................................25

Filter....................................................................................................................................................................................................25

Fan.......................................................................................................................................................................................................26

Component Selection

Maximum System Pressure........................................................................................................................................................ 27

Input Power......................................................................................................................................................................................28

Unit Life..............................................................................................................................................................................................29

Model Code

BDU : Model Code (A - B - C - D - E)..........................................................................................................................................31

BDU : Model Code (F - G).............................................................................................................................................................32

BDU : Model Code (H - J - K)........................................................................................................................................................33

Recommended Installation and Maintenance

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Technical Information

BDU Series Hydrostatic Transmissions

Contents

Housing Installation......................................................................................................................................................................34

Shaft Installation.............................................................................................................................................................................34

Start Up Procedure........................................................................................................................................................................ 34

Operation..........................................................................................................................................................................................34

Maintenance....................................................................................................................................................................................34

Installation Drawings

BDU-06S : Ports and Dimensions..............................................................................................................................................35

BDU-06S : Control Arm Location.............................................................................................................................................. 36

BDU-06S : Motor Shaft..................................................................................................................................................................36

BDU-10S/10L : Ports and Dimensions.....................................................................................................................................37

BDU-10S/10L : Control Arm Location..................................................................................................................................... 38

BDU-10S/10L : Motor Shaft.........................................................................................................................................................39

BDU-10S : Shaft Configuration..................................................................................................................................................40

BDU-10L : Shaft Configuration and Charge Pumps Displacement..............................................................................41

BDU-21L/21H : Ports and Dimensions....................................................................................................................................42

BDU-21L/21H : Control Arm Location.....................................................................................................................................43

BDU-21L/21H : Motor Shaft........................................................................................................................................................44

BDU-21L/21H : Shaft Configuration and Charge Pump Displacement...................................................................... 45

Optional Fan.................................................................................................................................................................................... 47

4 | © Danfoss | November 2021 BC152886484098en-000207

Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU Series Family

The BDU transmission is a “ Z” style transmission with a variable displacement pump and a fixed

displacement motor. The variable displacement pump features a cradle swashplate with a direct proportional displacement control. Reversing the direction of tilt of the swashplate reverses the flow of oil from the pump and thus reverses the direction of the motor output rotation. The fixed displacement motor uses a fixed swashplate. The pump and motor are of the axial piston design and utilize sphericalnosed pistons which are held against a thrust bearing by internal compression springs. The fluid supply for the BDU-10L/21L/21H transmission is contained in an external reservoir and passes through an external filter prior to entering the transmission and feeding the fixed displacement gerotor charge pump. Excess fluid in the charge circuit is discharged over the charge relief valve back to the charge pump inlet. Constant flow across a small fixed orifice connecting the charge circuit to the transmission housing supplements the cooling flow.

The BDU-06S/10S transmission has a self-contained fluid supply and an integral filter. The fluid is forced through the filter by positive “head” on the fluid in the housing reservoir with an assist by the negative pressure created in the pump pistons as they create a vacuum. Charge check valves in the center section are used to control the makeup flow of fluid to the low pressure side of the loop. A spool type bypass valve is utilized in the transmission to permit moving the vehicle over short distances at low speeds without starting the engine.

Features and Benefits

A complete transmission family to meet the needs of small vehicle application.

•

3 Transmission Frame Sizes: 6, 10, 21

•

PTO Capability on “Z” Style Transmission

•

Cost Effective, Compact, Lightweight Design

•

Low Noise

•

High Efficiency

•

Worldwide Sales and Service

•

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P400202

Technical Information

BDU Series Hydrostatic Transmissions

General Description

Design

Cross-Section (BDU-10S)

1. Tank 7. Spool type bypass valve 13. Shaft seal

2. Built-in filter 8. Cylinder block 14. Input shaft

3. Spring 9. Piston 15. Cooling fan

4. Center section 10. Thrust bearing 16. Cradle swash plate

5. Output shaft 11. Housing

6. Spring 12. Ball bearing

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P400203

1312

Technical Information

BDU Series Hydrostatic Transmissions

General Description

1. Suction Circuit 8. Charge Relief 15. Ball Bearing

2. Working Loop 9. Charge Circuit 16. Shaft Seal

3. Charge Check Valve 10. Output Shaft 17. Input Shaft

4. Spool Type Bypass Valve 11. Center Section 18. Cradle Swash Plate

5. Center Section 12. Cylinder Block 19. Piston

6. Suction Port 13. Thrust Bearing 20. Spring

7. Charge Pump 14. Housing

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Bypass Valve

Cylinder Block Assembly

Input Shaft

Variable Swashplate

Variable Displacement Pump

BDU

Housing

Reservor

Built-In

Filter

(BDU-10S)

Check Valve

Cylinder Block Assembly

Output Shaft

Displacement Motor

P400204

Fixed Swashplate

Fixed

Working Loop (high pressure)

Working Loop (low pressure)

Suction Line

Case Drain Fluid

Control Shaft “b”

Control Shaft “a”

Hydraulic Circuit

ø0.7 ø0.8

P400205

Ø0.7 Ø0.8

Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU-06/10S

Pictorial Diagram

BDU-06S, BDU-10S

System Schematic

1. Ball Check Valve, Option Code. : BB

2. Check Valve with Ø0.7 Orifice, Option Code : 07

3. Check Valve with Ø0.8 Orifice, Option Code : 08

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Bypass Valve

Cylinder Block Assembly

Input Shaft

Variable Swashplate

Variable Displacement Pump

Reservor

Filter

Check Valve

Cylinder Block Assembly

Output Shaft

Fixed Swashplate

Cooling Orifice

Charge Pump

Charge Relief Valve

Displacement Motor

Fixed

P400206

Working Loop (high pressure)

Working Loop (low pressure)

Suction Line

Case Drain Fluid

Control Shaft “b”

Control Shaft “a”

Hydraulic Circuit

Suction Port Drain Port

Ø1.0 Ø1.2

Ø1.0

Ø0.8

Ø1.2

BDU-21L

P400207

Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU-10L/21L/21H

Pictorial Diagram

BDU-10L, BDU-21L, BDU-21H (part of pump)

System Schematic: BDU-21L

1. Ball Check Valve, Option Code. : BB

2. Check Valve with Ø1.0 Orifice, Option Code : 10

3. Check Valve with Ø1.2 Orifice, Option Code : 12

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20.6MPa 17.2MPa 13.7MPa 20.6MPa 20.6MPa

Control Shaft “b”

Control Shaft “a”

Hydraulic Circuit

Suction Port Drain Port

Ø0.8

ø0.85

ø0.7 ×2

BDU-21H

ø0.7 ×2

P400208

1 2 3 4 5

Technical Information

BDU Series Hydrostatic Transmissions

General Description

System Schematic: BDU-21H

1. Check Valve with Relief Valve, Option Code. : R0

2. Check Valve with Relief Valve, Option Code. : R1

3. Check Valve with Relief Valve, Option Code. : R2

4. Check Valve with Relief Valve and Ø0.7 Twin Orifice, Option Code. : RA

5. Check Valve with Relief Valve and Ø0.85 Orifice, Option Code. : RB

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Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

Features and Options

Features Unit

Displacement cm3 [in3]

Pump

Motor

Charge Pump Displacement cm3 [in3] NA NA

Output Speed

Maximum Output Torque (Theoretical) Nm [lbf•in]

Input Power (Maximum) kW [ps]

Weight kgf [lbs]

Control Torque Required to Stroke Pump (Maximum)

Mounting See Installation Drawings Rotation Clockwise or Counterclockwise Suction/Oil Tank Port (SAE O-ring Boss) 7/8-14 UNF 7/16-20 UNF 9/16-18 UNF Other ports See Installation Drawings Shaft See Installation Drawings Bypass Valve OP STD STD STD STD Neutral Valve/Orifice NA/NA NA/OP NA/OP OP/OP OP/OP High Pressure Relief Valve NA NA NA NA STD Filtration W/O built-in External External (Option, Integrated) Reservoir Integrated Integrated External External Space for the oil in the housing cm

Swashplate Angle degree 15 15 15 15 15 Control Shaft degree 15 21 21 22 22

Displacement cm3 [in3]

Swashplate Angle degree 15 15 15 15 15

Rated Maximum

(intermittent)

-1

min

Nm [lbf•in]

BDU-06S BDU-10S BDU-10L BDU-21L BDU-21H

[0.37]

3000 3000 3600 3600 3600

3200 3200 3800 3800 3800

9.8

[87]

1.1

[1.5]

[9]

8.8

[78]

450 550 550 700 700

Product Type & Frame

[0.61]

23.4

[208]

2.2

[3.0]

6.3

[14]

19.6

[174]

[0.61]

1.9

[0.12]

23.4

[208]

3.7

[5.0]

6.5

[14]

19.6

[174]

[1.28]

2.1

[0.13]

49.2

[436]

7.4

[10.0]

[22]

22.5

[200]

[1.28]

3.0

[0.18]

72.1

[639]

11.0

[15.0]

[22]

24.5

[217]

SAE J1926-1 / ISO 11926-1

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Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

Operating Parameters

Parameter Unit

Input Speed

Minimum

Rated 3000 3600

Maximum 3200 3800

System Pressure

Maximum Working

Maximum

Charge Pressure

Charge Inlet Pressure

Case Pressure

Rated

Maximum (Cold Start) 0.7 [10]

min

[psi]

Fluid Specifications

Features Units BD Series

Viscosity

Temperature

bar

Product Type & Frame

BDU-06S BDU-10S BDU-10L BDU-21L BDU-21H

1000 600

-1

105

[1530]

150

[2185]

NA 3 [44] - 5 [73]

NA 0.8 [12] abs

Minimum Continuous 12-60 [66-280] Maximum 1600 [7500] Minimum Maximum Continuous 82 [180] Maximum 104 [219]

[2549]

175

150

[2185]

0.3 [4]

mm2/sec.

[ SUS]

°C [°F]

210

[3059]

210

[3059]

245

[3569]

7 [49]

-10 [14]

100

Efficiency %

3 5 7

Theoretical Output Torpue Nm

40%

50%

55%

60%

65%

70%

45%

0 1000 2000 3000

Output Torque Nm

Output Speed min

-1

P400210

100

5 9 11 13 17

Efficiency %

Theoretical Output Torpue Nm

40%

45%

50%

55%

60%

65%

70%

73%

70%

65%

60%

55%

50%45%

40%

0 1000 2000 3000

Output Torque Nm

Output Speed min

-1

P400211

100

90 80

50 40 30

20 10

5 5 7 9 11 13 15 16 18 20 22

Efficiency %

Theoretical Output Torpue Nm

40%

45%

50%

55%

60%

65%

70%

73%

70%

65%

60%

55%

50%45%

40%

1000 2000 3000

P400212

Output Torque Nm

Output Speed min

-1

Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

Efficiency

Input speed: 3000 min-1, Oil temperature: 50 °C, Full Displacement

BDU-06S

Efficiency (ηv:Volumetric, ηm:Mechanial, ηt:Overall)

BDU-10S

Efficiency (ηv:Volumetric, ηm:Mechanial, ηt:Overall)

BDU-10L

Efficiency (ηv:Volumetric, ηm:Mechanial, ηt:Overall)

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100

90 80 70 60 50 40 30 20 10

11 23 34 46 57 65

Efficiency %

Theoretical Output Torpue Nm

40%

45%

50%

55%

60%

65%

70%

75%

70%

75%

65%

60%

55%

50%

45%

40%

1000 2000 3000

Output

Torque Nm

Output Speed min

-1

P400213

Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

BDU-21L/21H

Efficiency (ηv:Volumetric, ηm:Mechanial, ηt:Overall)

Technical Information

BDU Series Hydrostatic Transmissions

Operating Parameters

Overview

Maintain operating parameters within prescribed limits during all operating conditions. This section defines operating limits given in the table Operating Parameters.

Input Speed

Minimum speed is the lowest input speed recommended during engine idle condition. Operating below

minimum speed limits pump’s ability to maintain adequate flow for lubrication and power transmission. Rated speed is the highest input speed recommended at full power condition. Operating at or below

this speed should yield satisfactory product life. Maximum speed is the highest operating speed permitted. Exceeding maximum speed reduces product

life and can cause loss of hydrostatic power and braking capacity. Never exceed the maximum speed limit under any operating conditions.

Operating conditions between rated speed and maximum speed should be restricted to less than full power and to limited periods of time. For most drive systems, maximum unit speed occurs during downhill braking or negative power conditions.

System Pressure

Charge Pressure

Warning

Unintended vehicle or machine movement hazard.

Exceeding maximum speed may cause a loss of hydrostatic drive line power and braking capacity. You must provide a braking system, redundant to the hydrostatic transmission, sufficient to stop and hold the vehicle or machine in the event of hydrostatic drive power loss.

System pressure is the differential pressure between system ports A & B. It is the dominant operating variable affecting hydraulic unit life. High system pressure, which results from high load, reduces expected life. Hydraulic unit life depends on speed and normal operating—or weighted average— pressure that you can only determine from a duty cycle analysis.

Maximum Working Pressure is the highest recommended Application pressure. Maximum working pressure is not intended to be a continuous pressure. Propel systems with Application pressures at, or below, this pressure should yield satisfactory unit life given proper component sizing.

Maximum pressure (peak) is the highest intermittent pressure allowed under any circumstances. Applications with applied pressures between rated and maximum require factory approval with complete application, duty cycle, and life expectancy analysis.

All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract low loop pressure from gauge readings to compute the differential.

The charge pressure setting listed in the technical specifications is based on the charge flow across the charge pressure relief valve at fluid temperature at 50˚C [120˚F].

Charge Inlet Pressure

Charge pump inlet conditions must be controlled in order to achieve expected life and performance. A continuous inlet vacuum of no less than 0.8 abs bar is recommended. Normal vacuums less than 0.7 abs bar would indicate inadequate inlet design or stricted filter.

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