the number of working teeth : 12 overs  

 1 stage gear train only  

quantity main parts : 7  

static / dynamic condition braking possibility  

Pure gear drive  

High-strength

the number of working teeth : 9  (sun gear: 3x3 ) 

High gear ratio : 2~3 stage over 

1 stage : 8, 2 stage : 14, 3 stage : 20

Separate braking system is necessary 

Pure gear drive  

High-strength 

the number of working teeth: 3~5

High gear ratio : 2~3 stage over

1 stage : 6, 2 stage : 10, 3 stage : 14

dynamic condition braking impossibility

Frictional drive  

low-strength