Centre Foot Retracting Mechanism

3D Printed Star Wars R2-D2 R6 Droid

This page is about the 3D Printed Centre Foot Mechanism, check out the main project index for the rest.

There is a YouTube video about this section

The centre foot assembly will need to extend and retract by around 250-280mm. This is so the entire centre foot and its wheels can move completely inside the body of the droid. On top of this we’ll need to keep around another 200mm inside the droid while the foot is extended so that there is something to hold is stable.

For this reason I’ll be building a large assembly that moves up and down which the centre foot is mounted onto. This will move from the bottom to the top of the droid on rails and be driven by some means. I’ve also shaped the bottom of this assembly so that when it’s pushed down to the bottom it ‘homes’ into the rectangular hole to provide added rigidity:

The rollers are mounted on bearings, the red/black parts are printed in Ninjaflex rubber with no infill to make hollow tubes that slots over the white/blue rigid ABS parts. This will provide a much smother linear motion:

The rollers then run on rails at the back/front of the droid:

I’ve build a motor assembly using a ComoDrills 919D 2.5:1 ratio geared motor with further 3:1 reduction using T5 belts:

This turns a piece of M12 studding which winds the centre foot up and down using a hex nut:

This allows the centre foot to fully retract or extend in around 6 seconds on a 15v sypply: