© 2018 by 21Geo, Thomas Dobroth

Speed Reducers

The 21Geo can make speed reducers with a wide selection of speed ratios.  Like all 21Geo devices, the speed reducers are designed so that the pins rotate freely without sliding, so losses will be very small.  Friction is also a cause of wear, so good overall durability is expected. 

Shown is a 105:1 speed reducer.  The system is comprised of two rotary pin systems.  The speed reduction comes from a differing number of pins on each of the rotary systems.  In the case of the 105:1 speed reducer, there are 14 and 15 pins respectively. 

 

The advantages of this speed reducer over devices currently used in robotics are:

  • Low energy loss

  • Proportional Input and Output (no harmonics)

  • High Torque

  • Zero backlash, even at high torque.  

  • Durability.  Current solutions are vulnerable to damage from accidental collisions.  

  • Scaleability

 

Zero Backlash

Normally systems with bearings and pins have a small amount play, called backlash.  That play is problematic with many applications, like robotics.  In the case of a robot that needs to do an insertion, the position of the robotic arm has to be precise.  If there is play in the speed reducer, then the position is uncertain by that amount of play times the length of the robot arm. 

 

To eliminate the play in this speed reducer, the eccentric will need to push into the rotary systems as shown in the figure below.  By doing so, the play in the bearing and the rotary system pins will be eliminated.  Multiple pins will make contact and support the rotor from multiple directions.  If torque is applied from the shaft, the force on some of the pins will increase and others will decrease, but there is never loose movement.   

The speed reducer with no torque.  A flexure keeps pressure on the pins, taking up any play in the system.   

The speed reducer with torque.  The forces on the pins change, but there is never any backlash.  

The speed reducer with torque.  The forces on the pins change, but there is never any backlash.  

The speed reducer with torque.  The forces on the pins change, but there is never any backlash.  

Wide Range of Speed Reduction

21Geo Speed reducers offer a wide range of speed reduction.  The most common speed ratios are:

  • 105:1

  • 91:1

  • 78:1

  • 66:1

  • 45:1

  • 36:1

  • 28:1

  • 21:1

  • 15:1

  • 10:1

Other speed ratios can be considered upon request, and very high ratio reducers can also be considered.  

Example speed reducers are shown below.  

105:1​

66:1​

28:1​

10:1​