I love it when a plan comes together, but sometimes there's no particular plan and I end up happy anyhow.  I had earmarked the windshield of a spare set 1580 for a Rail Rider, but there were no further forethought.  An old gray base color seemed like a natural match, and after hours of throwing parts at a 9V train motor, what do you know, a bunch of them actually stuck.

Video: LEGO Rail Rider Blast ⏩ Classic Space racing train MOC