Based on the main F shape, you can now create a conveyor belt. Copy (Cmd/Ctrl + C) the ‘F_outline’ and Paste (Cmd/Ctrl + F) the new path on top of it, naming it ‘ConveyorBelt’. Change the stroke colour to yellow.
Open the Stroke panel on the right-hand side, bring down the Option menu, tick the Dashed Line box and set the stroke to 3pt. Then open the Appearance window, double-click on 3D Extrude & Bevel Options, change the Extrude Depth to 20pt to make the belt wider and more visible. Send the ‘ConveyorBelt’ path backward to behind the ‘F_outline’ path
by hitting Cmd/Ctrl + [.
Again copy the F_outline path and paste the path behind it (Cmd/Ctrl + B), send it to the back (Shift + Cmd/Ctrl + [). Nudge the position gently until it resembles the screengrab.
Make the ‘F’ layer invisible. On a new layer, use the Ellipse tool (L) to draw a circle on the stage. Hold down Alt/Opt as you draw, to create a perfect circle shape (or Alt/Opt + Shift to draw the circle from a central point). Change the colour as shown here.
Repeat step 2 to apply the same 3D effect on the circle path. Next create a smaller circle. Name it ‘WheelShade’, then click Effect > 3D > Rotate Options; set the position to Isometric Left again. Duplicate the ‘WheelShade’ path (Cmd/Ctrl + C, Cmd/Ctrl + B) and resize it as shown.
Now use the Gradient tool (G) to add some lighting. Repeat these steps to add a few bits and bobs to the wheel to make it more detailed. Group them together by hitting Cmd/Ctrl + G.
Use the Rounded Rectangular tool, Rectangular tool (M), and Ellipse (L) to draw up some random shapes, as if you were creating technical patterns for a device’s accessories. Repeat Step 2 to convert these to 3D, play with Extrude Depth to achieve the best result.
You can also change them to any colour you want. However, if you’re using the Extrude & Bevel effect, don’t apply the Gradient effect before you expand them (Object > Expand Appearance) since the the 3D effect in Illustrator won’t be able to generate a colour selection of its shadows and highlights.