I'm trying to figure out a "swing arm" design to allow an "arm" attached to a wheel to be pushed down and returning to its original position via a spring.  This would allow rotor magnets at the end of the arm to move from a horizontal position - downwards - and then returning.

The arm on it's return to original position must be prevented from traveling further than the horizontal.
The whole unit must be prevented from moving in the lateral.

Approximate arm dimensions:
Length: 3"  Gap: 1" 

Approximate wheel dimensions:
Diameter: 3"  Height:  3"

Design considerations:

1) attachment methods to the wheel
2) pivot point means for upper arm? (bearing, ball joint etc)
3) restriction of upper arm travel beyond the upper horizontal
4) restriction of entire "arm" unit from lateral movement
5) overall unit design (rectangle, triangle etc)

I guess it's kind of like an automobile front end suspension - but shock absorption is not the goal - only the vertical movement of the upper "swing arm"

Any off-the-shelf items I might use, modify or incorporate?

What would this type of "swing arm" be called?

Any help - designs ideas - comments etc would be greatly appreciated!!!!!

Thanks!

CH