Android 12 Linear Actuators
This page is about Android 12’s linear actuator assembly, check out the project index for the rest.
As with the rest of the android, most of the parts will be 3D printed, so my initial work is to design the pieces in CAD. I’m using Autodesk 123D, which is free software. This page is about the development of the linear actuators which will replace at least the thigh assembly of the Android.
There is a YouTube video about this.
I hacked one of the servos for continuous rotation, there are more details in the video above. I’ve used some cheap gears which I got from Mindsets Online – they are quite soft plastic so I bored out the hole of one of the medium ones to fit the servo shaft and secured it with a washer and the original servo screw. Chain is also available which fits the gears, so I’ll use this to drive a carriage up and down in a linear motion using linear bearings:
I’ve designed some 3D parts in Autodesk123D which is free software, you can check out my CAD tutorials.
These parts consist of a carriage which holds the linear bearings, it travels up and down two 8mm diameter stainless steel bars which are clamped between the 3D printed parts. The bottom of the assembly clamps the M6 studding which already make up the Android’s legs:
The slider potentiometer will replace the internal potentiometer which is normally found in the servo for position feedback. This means that the whole assembly can still be driven to a specific position and will function exactly as a normal servo.
Here are some pictures of the whole assembly, check out the video above for testing. The slide pot needs a new piece to hold it in place, but of you hold it in place by hand then the actuator can be driven as a normal servo to any position:
Here are the final drawings for the output hinge and the piece that’ll hold the potentiometer:
Check out the next section to see the parts fitted to the android.