MGI Zip Navigator compatible rear 4th wheel

In case you have lost or broken the 4th wheel for your zip navigator golf buggy you can now 3d print your own replacement part. 

The original part is out of stock as I am uploading this model

Hardware needed:

• 1 M8×90mm partially threaded bolt
• 1 M8 locking nut
• 2 Ball bearings with an outer diameter of 22mm and inner diameter of 8mm
• 2 10mm long bearing spacers of an appropriate diameter for the bearings

Assembly

Assembly is pretty straight forward, look at image 3 for the basic overview. The tolerances are quite tight so putting everything together might take some force. 

1. Push the bearings into their holes. A dowel might be necessary to force them in
2. Make sure that the bolt can go through the holes made for it. 
3. Push or hammer the wheelcaps into place
4. Place the bearing spacers in the right spot in the wheel
5. Holding it in the orientation that it will be used, position the wheel inside the mount and push the bolt through it
6. Screw the nut on with enough pressure that everything is held firmly together, but still spins freely

Modifications

The wheel can be extended up to 15mm further from the buggy by changing the variable mount_rod_depth in the OpenSCAD customizer.

The OD of the bearings can be changed by changing the variable bearing_hole_D in the module wheel. The thickness of the bearings/length of the bearing spacers can be adjusted with the variable bearing_hole_depth in the module wheel (assuming 10mm spacers, the spacers will extend 5mm from the wheel).

The size of the required bolt (which should equal the ID of the bearing) can be changed by changing the variable axle_D in the module mount/body

The code is not made to automatically adapt to other changes than these, if you want to make other changes you need to know what you're doing — my code is pretty confusing.