3D Camera Slider

'Sketchup
Bracket for Center of EMT
Roller Wheels TPU
Bearings
End Brackets
Camera Shoe
1/4x20 shoe
 4 rail rail track
Roller Wheel
Inline Skate Bearings
Cheap camera sliders
 https://www.youtube.com/watch?v=oCotul5lVnI
https://www.youtube.com/watch?v=W9BrPCVuqCo
The inline skate bearings are a simple inexpensive source for a very high quality bearing.
You can usually get ABEC5 or ABEC7 bearings for about $15-$30 for 16 of them.

 2 bar system
3 bar system  ***
4 bar system