The simple ball robot is made from the 8BitModule, some 3D printed parts, and a few extra pieces. All parts are shown below.

Start by assembling the mid-frame.

The two continuous servos fit into the slots in the mid-frame. The servos should be orientated so the servo horns are centered in the frame, one label up and one label down.

Wrap the extra servo cables around the pillar to keep it out of the way later.

Next attach the battery holder using two zip ties

The battery holder goes over the top of the two servos and will secure them in place.

The opening of the holder should face away from the wiring.

Now insert a zip tie through the mid-frame, up into the battery holder, then back down through the holder and out of the mid-frame.

Do this on both sizes to secure the holder and the servos. The zip ties should be "zipped" against the mid-frame and the excess removed.

Next add the power cable and switch.

The pre-made power assembly will push through a hole on the mid-frame into which the switch will clip.

Push the wires, battery and power plugs through the hole. It will all fit but can be a bit fiddly.

Once through, push the switch into the hole. It's sized to be tight but the switch will fit snuggly once pushed all the way in.

Now attach the 8BitModule (assuming it's already in the default case).

The module is orientated with the servo connectors towards the servo wires, and the battery connector towards the switch added in the last step.

The holes in the mid-frame and the module are design for M2 screws, but here we'll just use two more zip ties.

One on each end.

Next we'll add the batteries. The ball takes 6 AA batteries (I use rechargeable).

First plug the power connector into the 8BitModule, then slot the batteries into the 3D printer holder. The shape of the holder should stop the batteries from falling out.

Finally, with the power switch off, attach the cable.

Lastly, add the wheels. Unlike everything else, the wheels must be screwed onto the continuous servos using two M2 bolts (nothing else would secure them successfully).

Each printed wheel has a cross shaped depression into which the servo horn will slot.

It can be tricky so align them correctly, but you will feel the two pieces come together correctly. Once mated, use the bolt to secure.

It doesn't matter which wheel goes on first, although obviously once the wheels are attached you can no longer switch out the batteries without detacting them; so make sure they're fully charged.

Finally, attach the second wheel. They are not design to meet, but rather leave a small gap between them to allow tiny fingers (or probably a screw driver) to access the power switch.

All done!