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	0104
			'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

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Technical Information
BDU Series Hydrostatic Transmissions
Contents
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

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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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Technical Information

BDU Series Hydrostatic Transmissions

General Description

Design

Cross-Section (BDU-10S)
1
	16
2	15
3
	14
4
5	13
	12
	11
	10
6
8	9
7
	P400202

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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Technical Information

BDU Series Hydrostatic Transmissions

General Description

	1		20
2	2	6	19
			18
		7	17

8

16

9

15

10

3	11		14
	5	12	13
	4

P400203

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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Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU-06/10S

Pictorial Diagram

BDU-06S, BDU-10S

	Bypass
	Valve
	Cylinder			Cylinder Block
	Block		Check Valve	Assembly
Input	Assembly				Output
					Shaft
Shaft
Variable
Swashplate	Variable				Fixed
	Displacement		Check Valve		Swashplate
	Pump			Fixed
				Displacement
				Motor
	BDU	Reservor
	Housing		Working Loop	Working Loop
		B uilt-In	(high pressure)	(low pressure)
		Filter	Suction Line	Case Drain Fluid
		(BDU-10S)			P400204

System Schematic

Control Shaft “b”	Ø0.7	Ø0.8
1	2	3
Control Shaft “a”	ø0.7	ø0.8

Hydraulic Circuit	1	2	3

P400205

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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Technical Information

BDU Series Hydrostatic Transmissions

General Description

BDU-10L/21L/21H

Pictorial Diagram

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

	Bypass
	Valve
	Cylinder			Check Valve	Cylinder Block
	Block
Input	Assembly		Charge		Assembly	Output
			Pump			Shaft
Shaft
Variable
Swashplate	Variable				Fixed	Fixed
		Cooling		Check Valve
	Displacement				Displacement	Swashplate
	Pump	Orifice	Charge		Motor
			Relief
			Valve
		Reservor
				Working Loop	Working Loop
				(high pressure)	(low pressure)
			Filter	Suction Line	Case Drain Fluid	P400206

System Schematic: BDU-21L

BDU-21L
	Control Shaft “b”		Ø1.0	Ø1.2
		1	2	3
	Ø0.8
	Control Shaft “a”		Ø1.0	Ø1.2
Suction Port	Drain Port	Hydraulic Circuit
		1	2	3

P400207

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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Technical Information

BDU Series Hydrostatic Transmissions

General Description

System Schematic: BDU-21H

BDU-21H

Control Shaft “b”

20.6MPa	17.2MPa	13.7MPa	20.6MPa	20.6MPa	ø0.85
				ø0.7
				×2
1	2	3	4		5

	Ø0.8
		20.6MPa	17.2MPa	13.7MPa	20.6MPa	20.6MPa	ø0.85
	Control Shaft “a”					ø0.7
Suction Port	Drain Port	Hydraulic Circuit				×2
		1	2	3	4		5

P400208

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		Product Type & Frame
					BDU-06S	BDU-10S	BDU-10L	BDU-21L	BDU-21H
		Displacement		cm3 [in3]	6	10	10	21	21
					[0.37]	[0.61]	[0.61]	[1.28]	[1.28]
	Pump
		Swashplate Angle		degree	15	15	15	15	15
		Control Shaft		degree	15	21	21	22	22
		Displacement		cm3 [in3]	6	10	10	21	21
	Motor				[0.37]	[0.61]	[0.61]	[1.28]	[1.28]
		Swashplate Angle		degree	15	15	15	15	15
	Charge Pump Displacement			cm3 [in3]	NA	NA	1.9	2.1	3.0
							[0.12]	[0.13]	[0.18]
		Rated			3000	3000	3600	3600	3600
	Output Speed			min-1
		Maximum			3200	3200	3800	3800	3800
		(intermittent)
	Maximum Output Torque (Theoretical)			Nm [lbf•in]	9.8	23.4	23.4	49.2	72.1
					[87]	[208]	[208]	[436]	[639]
	Input Power (Maximum)			kW [ps]	1.1	2.2	3.7	7.4	11.0
					[1.5]	[3.0]	[5.0]	[10.0]	[15.0]
	Weight			kgf [lbs]	4	6.3	6.5	10	10
					[9]	[14]	[14]	[22]	[22]
	Control Torque Required to Stroke Pump			Nm [lbf•in]	8.8	19.6	19.6	22.5	24.5
	(Maximum)				[78]	[174]	[174]	[200]	[217]
	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			cm3	450	550	550	700	700

SAE J1926-1 / ISO 11926-1

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Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

Operating Parameters

Parameter	Unit				Product Type & Frame
		BDU-06S		BDU-10S		BDU-10L		BDU-21L	BDU-21H
Input Speed
Minimum		1000					600
	min-1
Rated		3000					3600
Maximum		3200					3800
System Pressure
Maximum Working		105			150				210
	bar	[1530]			[2185]				[3059]
Maximum	[psi]	150			175			210	245
		[2185]			[2549]			[3059]	[3569]
Charge Pressure	bar	NA					3 [44] - 5 [73]
	[psi]
Charge Inlet Pressure	bar	NA						0.8 [12] abs
	[psi]
Case Pressure
Rated	bar				0.3 [4]
Maximum (Cold Start)	[psi]				0.7 [10]

Fluid Specifications

	Features		Units	BD Series
		Minimum	mm2/sec.	7	[49]
	Viscosity	Continuous		12-60	[66-280]
			[ SUS]
		Maximum		1600 [7500]
		Minimum		-10 [14]
	Temperature	Maximum Continuous	°C [°F]	82	[180]
		Maximum		104 [219]

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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)

<![if ! IE]>

<![endif]>Efficiency %

100
90
80
70
60
50
40
30
20
10
0	5	7
3
	Theoretical Output Torpue	Nm

<![if ! IE]>

<![endif]>Output Torque Nm

10
	40% 45% 50% 55% 60% 65%			70%
						70%
5					65%
					60%
					55%
	40%	45%			50%
0	1000			2000		3000
	Output Speed			min -1		P400210

BDU-10S

100
	90
	80
	70
<![if ! IE]> <![endif]>%	60
	50
<![if ! IE]> <![endif]>Efficiency
	40
	30
	20
	10
	0		(ηv:Volumetric, ηm			:Mechanial,		ηt:Overall)
Efficiency
		5		9	11		13		17
				Theoretical Output Torpue			Nm

BDU-10L

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

	100
	90
	80
	70
<![if ! IE]> <![endif]>%	60
<![if ! IE]> <![endif]>Efficiency	50
	40
	30
	20
	10
	0
	5	5	7	9	11	13	15	16	18	20	22
			Theoretical Output Torpue					Nm

	20	40%	45% 50%	55%	60%	65%		70%	73%
<![if ! IE]> <![endif]>Nm
									73%
<![if ! IE]> <![endif]>Torque	10								70%
<![if ! IE]> <![endif]>Output									65%
								55%	60%
					40%		45%		50%
	0		1000				2000		3000
			Output Speed min -1						P400211

	20	40%	45% 50%	55%	60%	65%		70%	73%
<![if ! IE]> <![endif]>Nm
									73%
<![if ! IE]> <![endif]>Torque	10								70%
<![if ! IE]> <![endif]>Output									65%
								55%	60%
					40%		45%		50%
	0		1000				2000		3000
			Output Speed				min -1		P400212

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Technical Information

BDU Series Hydrostatic Transmissions

Technical Specifications

		BDU-21L/21H
		Efficiency (ηv:Volumetric, ηm:Mechanial, ηt:Overall)
100															50
	90
	80														40
	70													<![if ! IE]> <![endif]>Nm
<![if ! IE]> <![endif]>Efficiency%	60														30
	50													<![if ! IE]> <![endif]>TorqueOutput
	40														20
	30
	20														10
	10
	0
	11			23		34		46		57		65			0
				Theoretical Output Torpue						Nm

40% 45%	50%	55%		60%	65%		70%		75%
										75%
										70%
										65%
								55%		60%
		40%
					45%				50%
			1000				2000		3000
		Output Speed					min -1			P400213

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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.

W 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

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.

Charge Pressure

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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