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Gearbox Selection Examples

Gearbox Selection Examples

Gearbox Selection Example – 1

Available Data About the Project

Driven machine type:                                         

Drive type:                                                    

Motor speed:                                                       

Speed of driven machine nd:                                   

Torque required for driven machine Md:             

Daily operation time:                                               

Number of start-ups per hour:                             

Operation time in an hour:                     

Operation environment:                

G.box input speed= Motor speed:                    

G.box output speed:

Bucket Elevator

Electric motor

1460 rpm

23 rpm

9000 N.m

24 hours

Continous

60min (FD: 100%)

Closed, 20°- 25°C

1460 rpm

23 rpm 

 

The gearbox will be connected to the motor by hydraulic coupling and to the driven machine by elastic coupling.

Gearbox types, which are selected by the technical staff, are DA3 and DK3 models.

Calculations           

Power Piş required for driven machine: 

 

           Mdiş (N.m) . n (rpm)          9000 . 23

P =   _________________   =  _________ =  21.7 kw

                        9550                         9550

 

 

Gearbox transmission ratio: i = n1 / n2 = 1460 / 23 = 63 / 1   

           

Operation Safety Factor F:        

Motor factor  fm : 1.0 for electric motors.

Driven machine factor  fiş : 1.5 for elevators.

Start-up factor  fdk : 1.0 for a machine operating continuously.

Daily operation time factor  ft : 1.25. 

Thus F  =  1 . 1.5 . 1 . 1.25  =  1.875 

Power gearbox should transmit: Pre = F . P = 1.9 . 21.7 = 41.2 kw. Nominal power Pn for selected gearbox should be greater than Pre. Pn > Pre

In power table of DA3 model gearbox, it is stated that the nominal power DA3-500 model gearbox can transmit is 55 kw for ninput = 1500, noutput = 24 rpm. Thus, DA3-500 model gearbox is suitable for this project.

Thermal power of DA3-500 model gearbox is Pt = 75 kw Since Pt > Pre,  DA3-500 model gearbox can transmit power Pre without cooling.

In the power table for DK3 model, nominal power of DK3-400 model gearbox is stated as 55 kw under same operating conditions.  Since Pn > Pre, DK3-400 can also be used for this project.

 

Gearbox Selection Example – 2

Available Data About the Project

Driven machine type:                                     

Drive type:                                                      

Motor speed:                                                         

Speed of driven machine niş:                                     

Torque required for driven machine Td:                 

Daily operation time:                                              

Number of start-ups per hour:                              

Operation time in an hour:                       

Operation environment:             

Gearbox and motor connection:

Pulley ratio:                                                                

Gearbox input speed                     

Gearbox output speed

 

Belt Conveyor

Electric motor

1450 rpm

60 rpm

1800 N.m

10 hours

At most 5

50min (FD: 80%)

Open, 25°- 30°C

V-belt pulley

1.5 / 1

1450 / 1.5 =960 rpm

60 rpm 

 

Gearbox is mounted on conveyor shaft.

DG2 model shaft mounted gearbox is suitable for this project.

 

Calculations           

Power Piş required for driven machine: 

 

           Mdiş (N.m) . n (rpm)          1800 . 60

P =   _________________   =  _________ =  11.3 kw

                        9550                         9550

 

Gearbox transmission ratio: i = n1 / n2 = 960 / 60 = 16 / 1     

           

Operation Safety Factor F         

Operation safety factor can be taken from the table on page 17 as 1.5, for a conveyor  which is a machine driven by electric motor, operating 10 hours daily, with medium shock loading.

Power gearbox should transmit: Pre = F . P = 1.5 . 11.3 = 17 kw.

Nominal power for selected gearbox should be greater than power Pre. Pn > Pre.

In power table of DG2 model gearbox, it is stated that for ninput = 1000, noutput = 63 rpm, the nominal power of DG2-250 model gearbox can transmit is 20 kw. DG2-250 model gearbox is suitable for this project.

Thermal power of DG2-250 model gearbox is Pt = 40 kw (from thermal power table.)

Since Pt > Pre, DG2-250 model gearbox can transmit power Pre without cooling.            

 

Gearbox Selection Example – 3

Available Data About the Project

Driven machine type:

Motor power:

Motor speed:

Speed of driven machine niş:

Torque required for driven machine Mdiş:

Daily operation time:                                              

Number of start-ups per hour:                              

Operation time in an hour:                     

Operation environment:                   

Chain sprocket ratio:                                                  

Gearbox input speed = Motor speed:                   

Gearbox output speed:

Drying Mills

15 kw

1460 rpm

24 rpm

4650 N.m

10 hours

At most 5

60 min (FD: 100%)

Open, 25°- 30°C

2.5 / 1

1460 rpm

24 x 2.5 = 60 rpm

 

Motor is directly connected to gearbox. Gearbox is connected to drying mill with chain sprocket.

DMA3 model, heavy industry type motor gear is suitable for this project . 

           

Calculations           

Power P required for driven machine: 

 

           Mdiş (N.m) . n (rpm)          4650 . 24

P =   _________________   =  _________ =  11.7 kw

                        9550                         9550

 

Operation Safety Factor F       

Operation safety factor can be taken from the table on page 17 as 1.5, for a drying mill which is a machine driven with electric motor, operating 10 hours daily, with medium shock loading.

Since a motor with 15 kw power is connected to gearbox, safety factor in motor selection is Pm / Pd = 15 / 11.7 = 1.3

 

In the power and selection table of DMA3 model gearbox , it is shown that for 15 kw power and 60 rpm gearbox output speed, DMA3-120 model gearbox with 1.8 service factor should be selected. The nominal power DMA3-120 model gearbox is

Pn = 15 . 1.8 = 27 kw.

 

Actual safety factor based on power required for driven machine P is Pn / P = 27 / 11.7 = 2.3.

Motor gear is selected with a safety factor greater than necessary.

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