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44 Manual – Gear Units and Gearmotors

5 Efficiency of gear unitsProject Planning for Gear Units

5 Project Planning for Gear Units5.1 Efficiency of gear unitsGeneral information

The efficiency of gear units is mainly determined by the gearing and bearing friction.Keep in mind that the starting efficiency of a gear unit is always less than its efficiencyat operating speed. This factor is especially pronounced in the case of helical-worm andSpiroplan® right-angle gearmotors.

R, F, K gear units The efficiency of helical, parallel shaft and helical-bevel gear units varies with thenumber of gear stages, between 94 % (3-stage) and 98 % (1-stage).

S and W gear units

The gearing in helical-worm and Spiroplan® gear units produces a high proportion ofsliding friction. As a result, these gear units have higher gearing losses than R, F or Kgear units and thus be less efficient.

The efficiency depends on the following factors:• Gear ratio of the helical-worm or Spiroplan® stage• Input speed• Gear unit temperature

Helical-worm gear units from SEW-EURODRIVE are helical gear/worm combinationsthat are significantly more efficient than all worm type gear units. The efficiency mayreach η < 0.5 if the helical-worm or Spiroplan® stage has a very high ratio.

Self-locking Back-driving torques on helical-worm or Spiroplan® gear units produce an efficiency ofη’ = 2 - 1/η, which is significantly less favorable than the forward efficiency η. Thehelical-worm or Spiroplan® gear unit is self-locking if the forward efficiency η ≤ 0.5.Some Spiroplan® gear units are also dynamically self-locking. Contact SEW-EURODRIVE if you wish to make technical use of the braking effect of self-lockingcharacteristics.

Do not use the self-locking effect of helical-worm and Spiroplan® gear units as solesafety function for hoist or incline applications.

Manual – Gear Units and Gearmotors 45

5Efficiency of gear unitsProject Planning for Gear Units

Run-in phase The tooth flanks of new helical-worm and Spiroplan® gear units are not yet completelysmooth. That fact makes for a greater friction angle and less efficiency than during lateroperation. This effect intensifies with increasing gear unit ratio. Subtract the followingvalues from the listed efficiency during the run-in phase:

The run-in phase usually lasts 48 hours. Helical-worm and Spiroplan® gear unitsachieve their listed rated efficiency values when:• the gear unit has been completely run in,• the gear unit has reached nominal operating temperature,• the recommended lubricant has been filled in and• the gear unit is operating in the rated load range.

Churning losses In certain gear unit mounting positions (→ Sec. "Mounting positions and important orderinformation"), the first gearing stage is completely immersed in the lubricant. Consider-able churning losses occur in larger gear units and high circumferential velocity of theinput stage. Contact SEW-EURODRIVE if you wish to use gear units of this type.If possible, use mounting position M1 for R, K and S gear units to keep the churninglosses low.

Worm Spiroplan®

i range η reduction i range η reduction

1 start approx. 50 ... 280 approx. 12 % approx. 40 ... 75 approx. 15 %

2 start approx. 20 ... 75 approx. 6 % approx. 20 ... 30 approx. 10 %

3 start approx. 20 ... 90 approx. 3 % approx. 15 approx. 8 %

4 start - - approx. 10 approx. 8 %

5 start approx. 6 ... 25 approx. 3 % approx. 8 approx. 5 %

6 start approx. 7 ... 25 approx. 2 % - -

7 start - - approx. 6 approx. 3 %


5 Oil compensatorProject Planning for Gear Units

5.2 Oil compensatorThe oil compensator allows the lubricant/air space of the gear unit to expand. Thismeans no lubricant can escape the breather valve at high operating temperatures.SEW-EURODRIVE recommends to use oil compensators for gear units and gearmotorsin M4 mounting position and for input speeds > 2000 rpm.

The oil compensator is suppled as assembly kit. It is intended for mounting onto thegearmotor. However, if installation space is limited or if the compensator is intended forgear units without motor, it can be mounted to nearby machine parts.

59648AXXFigure 7: Oil compensator

Gear unit Motor Package no. Dimension a [in]

Dimension b [in]

Dimension c [in]

R27 ... R67F37 ... F67K37 ... K67S37 ... S67

DT80 ... DV132 0045 627 6 3.35 7.80 1.59

R77 ... R87F77 ... F87K77 ... K87S77 ... S87

DT80 ... DV100 0045 648 9 3.35 7.80 1.59

DV112 ... DV132 0045 628 4 3.35 11.93 1.59

DV160 ... DV180 0045 649 7 3.35 11.93 1.59

R97 ... R137F97 ... F107K97 ... K107S97

DT80 ... DV100 0045 629 2 3.35 7.80 1.59

DV112 ... DV132 0045 650 0 4.92 11.93 1.59

DV160 ... DV250 0045 630 6 4.92 11.93 1.59

R147F127K127

DV132 0045 631 4 4.92 11.93 1.59

DV160 ... DV280 0045 632 2 4.92 11.93 1.59

R167F157K157 ... K187

DV160 ... DV180 0045 633 0 4.92 11.93 1.59

DV200 ... D315 0045 634 9 4.92 11.93 1.59

b

c

a


5Multi-stage gearmotors (→ GM)Project Planning for Gear Units

5.3 Multi-stage gearmotors (→ GM)General information

You can achieve particularly low output speeds by using multi-stage gear units or multi-stage gearmotors. This means an additional second gear unit, usually a helical gear unit,is installed in front of the gear unit or between gear unit and motor.The resulting total reduction ratio may make it necessary to protect the gear units.

Limiting the motor power

You have to reduce the maximum output motor power according to the maximumpermitted output torque on the gear unit (Ta max). For this purpose you first have todetermine the allowable motor torque (TN allowable).You can calculate the allowable motor torque as follows:

Use this allowable motor torque TN allowable and the load diagram of the motor to deter-mine the associated value for the motor current.Take suitable measures to prevent the continuous current consumption of the motorfrom exceeding the previously determined value for the motor torque TN allowable. A suit-able measure is, for example, to set the trip current of the protective circuit breaker tothis maximum current value. Besides, a protective circuit breaker can compensate for abrief overload, for example during the motor’s starting phase. A suitable measure for in-verter drives is to limit the output current of the inverter according to the determined mo-tor current.

Checking brake torque

If you use a multi-stage brake motor, you will have to limit the braking torque (TB)according to the maximum permitted motor torque TN allowable. The maximum permittedbraking torque is 200 % TN allowable.

TB max ≤ 200 % TN allowable

If you have questions on the starting frequency of multi-stage brake motors, pleaseconsult SEW-EURODRIVE.

Avoiding blockage

Blockage on the output side of the multi-stage gear unit or multi-stage gearmotor is notpermitted. The reason is that indeterminable torques and uncontrolled overhung andaxial loads may occur. This may destroy the gear units.

G M

59717AUS

T =TN allowable ηtotal

a maxi total

Consult SEW-EURODRIVE if blockages of the multi-stage gear unit or multi-stage gear-motor cannot be avoided due to the application.


5 Service factorProject Planning for Gear Units

5.4 Service factorDetermining the service factor

The effect of the driven machine on the gear unit is taken into account to a sufficient levelof accuracy using the service factor fB. The service factor is determined according to thedaily operating time and the starting frequency Z. Three load classifications are takeninto account depending on the mass acceleration factor. You can read off the servicefactor applicable to your application in Figure 8 . The service factor determined from thisdiagram must be smaller than or equal to the service factor according to the selectiontables.

Load classification Three load classifications are distinguished:(I) Uniform, permitted mass acceleration factor ≤ 0.2(II) Non-uniform, permitted mass acceleration factor ≤ 3(III) Extremely non-uniform, permitted mass acceleration factor ≤ 10

00656BXXFigure 8: Service factor fB

* Daily operating time in hours/day** Starting frequency Z: The cycles include all starting and braking procedures as well as changes from

low to high speed and vice versa.

T f Ta • b a max

fB

0 200 400 600 800 1200 14001000

24* 16* 8*

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.2

1.3

1.4

1.5

1.6

1.7

1.8

Z [1/h] **

(III)

(II)

(I)


5Service factorProject Planning for Gear Units

Mass acceleration factor

The mass acceleration factor is calculated as follows:

"All external mass moments of inertia" are the mass moments of inertia of the drivenmachine and the gear unit, scaled down to the motor speed. The calculation for scalingdown to motor speed is performed using the following formula:

"Mass moment of inertia at the motor end" is the mass moment of inertia of the motorand, if installed, the brake and the flywheel fan (Z fan).Service factors fB > 1.8 may occur with large mass acceleration factors (> 10), highlevels of backlash in the transmission elements or large overhung loads. Contact SEW-EURODRIVE in such cases.

Service factor: SEW fB

The method for determining the maximum permitted continuous torque Ta max and usingthis value to derive the service factor fB = Ta max / Ta is not defined in a standard andvaries greatly from manufacturer to manufacturer. Even an SEW service factor of fB =1, the gear units afford an extremely high level of safety and reliability in the fatiguestrength range (exception: wearing of the worm wheel in helical-worm gear units). Theservice factor may differ from specifications of other gear unit manufacturers. If you arein doubt, contact SEW-EURODRIVE for more detailed information on your specificdrive.

Example Mass acceleration factor 2.5 (load classification II), 14 hours/day operating time (readoff at 16 h/d) and 300 cycles/hour result in a service factor fB = 1.51 according toFigure 8. According to the selection tables, the selected gearmotor must have an SEWfB value of 1.51 or greater.

JXJnnM

= Mass moment of inertia scaled down to the motor shaft= Mass moment of inertia with reference to the output speed of the gear unit= Output speed of the gear unit= Motor speed

Mass acceleration factor =All external mass moments of inertia

Mass moment of inertia on the motor end

J = JX ( )nnM

2


5 Service factorProject Planning for Gear Units

Helical-worm gear units

For helical-worm gear units, two additional service factors will have to be taken intoconsideration besides service factor fB derived from Figure 8 . These are:• fB1 = Service factor from ambient temperature• fB2 = Service factor from cyclic duration factor

The additional service factors fB1 and fB2 can be determined by referring to the diagramsin Figure 9 . For fB1, the load classification is taken into account in the same way as forfB.

The total service factor for helical-worm gear units is calculated as follows:

Example The gearmotor with the service factor fB = 1.51 in the previous example is to be a helical-worm gearmotor.Ambient temperature ϑ = 40°C → fB1 = 1.38 (read off at load classification II)Time under load = 40 min/h →cdf = 66.67% → fB2 = 0.95The total service factor is fBges = 1.51 • 1.38 • 0.95 = 1.98According to the selection tables, the selected helical-worm gearmotor must have anSEW fB service factor of 1.98 or greater.

00657BXXFigure 9: Additional service factors fB1 and fB2

Contact SEW-EURODRIVE in case of temperatures below -20 °C (-4 °F) (→fB1).

fBges = fB • fB1 • fB2

fB2

-20 0-10 20 40 6020 8030 100 %ED40 50°C

fB1

1.0 0.6

1.2 0.8

1.4 1.0

1.6

1.8

(III)

(II)

(I)

ED (%) =Time under load in min/h

60• 100


5Overhung and axial loads (→ GM, → MM, → GK)Project Planning for Gear Units

5.5 Overhung and axial loads (→ GM, → MM, → GK)Determining overhung load

An important factor for determining the resulting overhung load is the type of transmis-sion element mounted to the shaft end. The following transmission element factors fZhave to be considered for various transmission elements.

The overhung load exerted on the motor or gear shaft is calculated as follows:

Permitted over-hung load

The basis for determining the permitted overhung loads is the computation of the ratedbearing service life L10h of the anti-friction bearings (according to ISO 281).For special operating conditions, the permitted overhung loads can be determined withregard to the modified service life Lna on request.The permitted overhung loads FRa for the output shafts of foot-mounted gear units witha solid shaft are listed in the selection tables for gearmotors. Contact SEW-EURODRIVE in case of other versions.

G M

M M

G K

Transmission element Transmission element factor fZ Comments

Gears 1.15 < 17 teeth

Chain sprockets 1.40 < 13 teeth

Chain sprockets 1.25 < 20 teeth

Narrow V-belt pulleys 1.75 Influence of the tensile force

Flat-belt pulleys 2.50 Influence of the tensile force

toothed belt pulleys 1.50 Influence of the tensile force

FR = Overhung load in lbTd = Torque in lb-ind0 = Mean diameter of the installed transmission element in inchfZ = Transmission element factor

FR =T 2

dd

0

•• fZ

The values refer to force applied in the center of the shaft end (in right-angle gearunits as viewed onto the B-end output). The worst-case conditions are assumedas regards the force application angle α and direction of rotation.• Only 50% of the FRa value specified in the selection tables is permitted in mounting

position M1 with wall attachment on the front face for K and S gear units.• Helical-bevel gearmotors K167 and K187 in mounting positions M1 to M4: A

maximum of 50% of the overhung load FRa specified in the selection tables in thecase of gear unit mounting other than as shown in the mounting position sheets.

• Foot and flange-mounted helical gearmotors (R..F): A maximum of 50% of the over-hung load FRa specified in the selection tables for torque transmission via flangemounting are permitted.


5 Overhung and axial loads (→ GM, → MM, → GK)Project Planning for Gear Units

Higher permitted overhung loads

Exactly considering the force application angle α and the direction of rotation makes itpossible to achieve a higher overhung load. Higher output shaft loads are permitted ifheavy duty bearings are installed, especially with R, F and K gear units. Contact SEW-EURODRIVE in such cases.

Definition of force application point

Force application is defined according to the following figure:

Permitted axial loads

If there is no overhung load, then an axial force FA (tension or compression) amountingto 50 % of the overhung load given in the selection tables is permitted. This conditionapplies to the following gearmotors:• Helical gearmotors except for R..137... to R..167...• Parallel shaft and helical-bevel gearmotors with solid shaft except for F97...• Helical-worm gearmotors with solid shaft

59824AXXFigure 10: Definition of force application point

FX = Permitted overhung load at point x [lb]FA = Permitted axial load [lb]

0° 0°

X

FX

FA

α α

Contact SEW-EURODRIVE for all other types of gear units and in the event ofsignificantly greater axial forces or combinations of overhung load and axial force.


5Overhung and axial loads (→ GM, → MM, → GK)Project Planning for Gear Units

On the input side: Overhung load conversion for off-center force application

Important: only applies to gear units with input shaft assembly:Consult SEW-EURODRIVE for off-center force application on the drive end.

On the output side: Overhung load conversion for off-center force application

The permitted overhung loads must be calculated according the selection tables usingthe following formulae in the event that force is not applied at the center of the shaft end.The smaller of the two values FxL (according to bearing life) and FxW (according to shaftstrength) is the permitted value for the overhung load at point x. Note that the calcula-tions apply to Ta max.

FXL according to bearingservice life

FxW from theshaft strength:

F = FxL Ra •a

b + x[lb]

F =xWc • 103

f + x[lb]

FRa = Permitted overhung load (x = l/2) for foot-mounted gear units according to the selection tables in [lb]

x = Distance from the shaft shoulder to the force application point in [in]a, b, f = Gear unit constant for overhung load conversion[in]c = Gear unit constant for overhung load conversion[in]

02356BXXFigure 11: Overhung load Fx for off-center force application

x

x

FRa

FRaFX FxL

d d

l

l/2


5 Overhung and axial loads (→ GM, → MM, → GK)Project Planning for Gear Units

Gear unit constants for overhung load conversion

Values for types not listed are available on request.

Gear unit type a[in]

b[in]

c[lb-in]

f[in]

d[in]

l[in]

RX57RX67RX77RX87RX97RX107

1.712.072.382.893.414.04

0.931.081.201.321.441.67

1.342.141.736.8112.6621.86

1.351.56

01.932.122.45

0.7501.0001.2501.6252.1252.375

1.571.972.363.153.944.72

R07R17R27R37R47R57R67R77R87R97R107R137R147R167

2.833.484.194.655.395.816.636.848.5310.0611.2413.5215.8317.72

2.052.703.213.664.214.435.265.266.567.708.4810.1811.6913.58

0.410.581.381.102.163.342.353.517.5010.5318.2354.3476.56111.52

0.430.670.46

00.590.71

00000

1.181.30

0

0.7500.7501.0001.0001.2501.3751.3751.6252.1252.3752.8753.6254.3754.750

1.571.571.971.972.362.762.763.153.944.725.516.698.278.27

F27F37F47F57F67F77F87F97F107F127F157

4.314.866.046.727.148.5010.3513.7814.7017.4220.16

3.333.884.865.345.566.537.9911.0211.3613.2916.02

1.000.951.584.863.656.9710.5318.5037.4483.6492.93

000

1.260000000

1.0001.0001.2501.3751.6252.0002.3752.8753.6254.3754.750

1.971.972.362.763.153.944.725.516.698.278.27

K37K47K57K67K77K87K97K107K127K157K167K187

4.866.046.687.148.509.9212.5614.7017.4620.0424.4728.37

3.884.865.305.566.537.569.8011.3613.3315.9119.5522.07

1.251.586.023.656.8114.5224.7848.9473.55

104.44166.39269.06

00

1.22000000000

1.0001.2501.3751.6252.0002.3752.8753.3254.3754.7506.2507.500

1.972.362.763.153.944.725.516.698.278.279.8412.60

W10W20W30

3.343.884.31

2.553.093.52

0.320.390.53

000

0.6250.7500.750

1.571.571.57

S37S47S57S67S77S87S97

4.675.125.917.248.8211.0812.85

3.884.134.725.877.058.7210.09

0.531.181.892.694.6614.8722.48

0000000

0.7501.0001.2501.3751.7502.3752.875

1.571.972.362.763.544.725.51


5RM gear unitsProject Planning for Gear Units

5.6 RM gear unitsProject planning You must take into account the higher overhung loads and axial forces when planning

projects using RM helical gearmotors with extended bearing housing. Observe the fol-lowing project planning procedure:

02457BUSFigure 12: Project planning for RM gear units


5 RM gear unitsProject Planning for Gear Units

Permitted over-hung loads and axial forces

The permitted overhung loads FRa and axial forces FAa are specified for various servicefactors fB and nominal bearing service life L10h.

fBmin = 1.5; L10h = 10,000 h

fBmin = 2.0; L10h = 25 000 h

na [1/min]

< 16 16-25 26-40 41-60 61-100 101-160 161-250 251-400

RM57FRa [N] 400 400 400 400 400 405 410 415

FAa [N] 18800 15000 11500 9700 7100 5650 4450 3800

RM67FRa [N] 575 575 575 580 575 585 590 600

FAa [N] 19000 18900 15300 11900 9210 7470 5870 5050

RM77FRa [N] 1200 1200 1200 1200 1200 1210 1210 1220

FAa [N] 22000 22000 19400 15100 11400 9220 7200 6710

RM87FRa [N] 1970 1970 1970 1970 1980 1990 2000 2010

FAa [N] 30000 30000 23600 18000 14300 11000 8940 8030

RM97FRa [N] 2980 2980 2980 2990 3010 3050 3060 3080

FAa [N] 40000 36100 27300 20300 15900 12600 9640 7810

RM107FRa [N] 4230 4230 4230 4230 4230 4230 3580 3830

FAa [N] 48000 41000 30300 23000 18000 13100 9550 9030

RM137FRa [N] 8710 8710 8710 8710 7220 5060 3980 6750

FAa [N] 70000 70000 70000 57600 46900 44000 35600 32400

RM147FRa [N] 11100 11100 11100 11100 11100 10600 8640 10800

FAa [N] 70000 70000 69700 58400 45600 38000 32800 30800

RM167FRa [N] 14600 14600 14600 14600 14600 14700 - -

FAa [N] 70000 70000 70000 60300 45300 36900 - -

na [1/min]

< 16 16-25 26-40 41-60 61-100 101-160 161-250 251-400

RM57FRa [N] 410 410 410 410 410 415 415 420

FAa [N] 12100 9600 7350 6050 4300 3350 2600 2200

RM67FRa [N] 590 590 590 595 590 595 600 605

FAa [N] 15800 12000 9580 7330 5580 4460 3460 2930

RM77FRa [N] 1210 1210 1210 1210 1210 1220 1220 1220

FAa [N] 20000 15400 11900 9070 6670 5280 4010 3700

RM87FRa [N] 2000 2000 2000 2000 2000 1720 1690 1710

FAa [N] 24600 19200 14300 10600 8190 6100 5490 4860

RM97FRa [N] 3040 3040 3040 3050 3070 3080 2540 2430

FAa [N] 28400 22000 16200 11600 8850 6840 5830 4760

RM107FRa [N] 4330 4330 4330 4330 4330 3350 2810 2990

FAa [N] 32300 24800 17800 13000 9780 8170 5950 5620

RM137FRa [N] 8850 8850 8850 8830 5660 4020 3200 5240

FAa [N] 70000 59900 48000 37900 33800 31700 25600 23300

RM147FRa [N] 11400 11400 11400 11400 11400 8320 6850 8440

FAa [N] 70000 60600 45900 39900 33500 27900 24100 22600

RM167FRa [N] 15100 15100 15100 15100 15100 13100 - -

FAa [N] 70000 63500 51600 37800 26800 23600 - -


5RM gear unitsProject Planning for Gear Units

Conversion factors and gear unit constants

The following conversion factors and gear unit constants apply to calculating the permit-ted overhung load FxL at point x ≠ 1000 mm for RM gearmotors:

Additional weight RM gear units

Gear unit type a b cF (fB = 1.5) cF (fB = 2.0) FF

RM57 1047 47 1220600 1260400 277

RM67 1047 47 2047600 2100000 297.5

RM77 1050 50 2512800 2574700 340.5

RM87 1056.5 56.5 4917800 5029000 414

RM97 1061 61 10911600 11124100 481

RM107 1069 69 15367000 15652000 554.5

RM137 1088 88 25291700 25993600 650

RM147 1091 91 30038700 31173900 756

RM167 1089.5 89.5 42096100 43654300 869

Type Additional weight compared to RF with reference to the smallest RF flangeΔm [kg / lb]

RM57 12.0 / 26.4

RM67 15.8 / 34.8

RM77 25.0 / 55.1

RM87 29.7 / 65.5

RM97 51.3 / 113.1

RM107 88.0 / 194.0

RM137 111.1 / 244.9

RM147 167.4 / 369.1

RM167 195.4 / 430.8


5 Drives for overhead trolley systemsProject Planning for Gear Units

5.7 Drives for overhead trolley systemsSpecial gearmotors with integrated coupling are required for operating overhead trolleysystems. SEW-EURODRIVE offers a range of drives for overhead trolley systems. Youwill find detailed information on this topic in the "Drives for Overhead Trolley Systems"catalog.

Type designation Drives for overhead trolley systems have the following unit designation:

Division into two groups

Drives for overhead trolley systems are divided into two groups:

Technical data The following technical data apply to overhead trolley drives:

03138AXXFigure 13: Drive for overhead trolley systems

Type Description

HW.. Overhead trolley drive based on Spiroplan® gear unit

HS.. Overhead trolley drive based on helical-worm gear unit

HK.. Overhead trolley drive based on helical-bevel gear unit

Group Drives

Drives for overhead trolley systems according to VDI 3643 guideline (C1 standard)

HW30HS40 (up to motor size DT80)

Drives for heavy duty overhead trolley systems

HS41 / HS50 / HS60HK30 / HK40 / HK50 / HK60

Type Ta max[lb-in]

FRa[lb]

Gear ratiosi

Shaft end

d[mm] l [mm]

HW30 620 1259 8.2 - 75 2025

3535

HS40 1060 1461 7.28 - 201 2025

3535

HS41 1640 2248 7.28 - 201 25 35

HS50 2660 3372 7.28 - 201 3035

6070

HS60 5310 5620 7.56 - 217.41 45 90

HK30 1770 2248 13.1 - 106.38 25 35

HK40 3540 4159 12.2 - 131.87 3035

6070

HK50 5310 5620 13.25 - 145.14 45 90

HK60 7260 8992 13.22 - 144.79 55 110

5 project planning for gear units - sew eurodrive...48 manual – gear units and gearmotors 5...

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