Chapter 6

The clutch, before the motor

The clutch is what pushes the filter disc: a printed ASA hub with a co-printed TPU tyre around it, gripping the motor shaft on its milled flat through a grub screw. It goes in now, before the motor: once it is on the shaft it cannot be lifted off - the roof of the box is a millimetre above it - so it is put in place first, from the middle of the collar, and the motor comes up into it. Its insert is already in, from chapter 2.

Step 1 Slide the clutch in from the middle of the collar

• The wheel is not in yet, so the middle of the collar is empty. Lower the clutch into it from the telescope side, flat, tyre down, hub collar up.
• Slide it outwards, level, through the gap in the collar ring, until it sits over the arm where the motor shaft will come up.
• Turn it so its four holes stand over the four holes in the arm: the motor screws go through them, later, from above.
• It just rests on the arm for now. The motor comes up into it next.