Dual speed focuser for 5 mm shaft (5:1)

Inspired by DrRobot's version I've remade mine for friction drive as well. But using printed TPU tyres instead of o-rings.

Required hardware: 

• 3 pcs 40 mm countersunk M3
• 3 pcs M3 nuts (hex and/or heat-set)
• 2-4 pcs M4 hex nut
• 2-4 pcs M4 8 mm grub screw (one can be up to 12 mm)
• 3 pcs 3 mm steel rods, 20-25 mm long
• 1 pcs 3 mm steel rod, ~ 35 mm (needs to be slightly less than 3 mm to fit into bearings, some dremel tools seems to have 2.9 mm shafts)
• 2 pcs 676zz bearings
• 1 pc 6704zz bearing (somewhat optional, I've provided a model that can be printed to at least hold the gear case in place)

The sun gear is made out of a ~2.9 mm dremel tool shaft, flattened on one side for knob attachment, and a 5 mm printed cylinder glued to it. The planet gears consist of an ~8 mm plastic wheel (PETG/PLA) that will need to be drilled for a smooth bore slightly larger than their steel rod axis. The wheels gets a 1 mm thick TPU tyre (I'm using 40D TPU, softer should probably be fine). The tyre model has all three tyres stack on top on each other, to be printed in one go then cut into 8 mm pieces. It also has a built in 1.2 mm raft to avoid any elephent footing. Both the wheels and tyres are somewhat oversized (OD is supposed to be 10 mm), but sanding the gear case to a smooth out surface might reduce its ID (nominally 25 mm). When not sufficiently tight I'd get a lot of slipping. With the provided sizes I'm not able to physically notice any slipping, altough the actual ratio is about 6:1 (rather than 5:1). But use slicer to scale the models if needed.

The bearing lock attaches to a 5 mm shaft with 1-3 M4 grub screws. The focuser I'm modifying has 5 mm of M4 thread at the end, so I'm also inserting a >5mm ⌀ M4 heat insert at the bottom. A single grub screw should be sufficient if the shaft has a flat spot, the extra screws is mostly for balancing to get rid of any wobbling. To hold the gear case in place I've made a simple arch that matches my telescope tube in curvature and distance to the focusing shaft. Other attachments could be made, the case is 17 mm deep, 29 mm ⌀ with a 4.5x2 mm key.

All models are made with 0.2 mm layers in mind.

• Friction drive instead of gears
• M3 driving the sun gear
• 693zz bearings (3x8x4) instead of 676zz
• Attaches onto 5 mm shaft 
• Overall wider