Our spindle. Main section is stainless, the extended part is aluminum. Two bushings and a shoulder bolt finish off the part.
I can’t make out the spindle part 
I’m assuming it rotates on the two bushings, but where’s the spindle? Or am I just being stupid?
Never mind, I should have looked at your other picture first >.<
http://www.chiefdelphi.com/media/photos/30044?
The term spindle just confused me.
The term spindle is reference to the wheel. However i think the part name you were searching for is rack and pinion which is in reference to the mechanism that turns the robot and is pictured later. The spindles are connected to the wheels and set the robot up for a tie rod connection which could then be manipulated by the rack and pinion. We probaly could of design these to be one part however due to lack of material and four jaw chuck on the lathe we decided to test our tapping skills…