You'll find them under various name brands, but they all seem to be the same (CLICK HERE). The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam.But a big problem is that you can't throw a Segway in the trunk of your car.
I even carried equipment back and forth from the parking lot.I use them whenever I find the opportunity when tracking shots or subjects.Combined with a hand held stabilizer, you can get smooth long fast dolly like motion.Ideally, a convex curve between the onset and maximum position of lift reduces acceleration, but this requires impractically large shaft diameters relative to lift.Thus, in practice, the points at which lift begins and ends mean that a tangent to the base circle appears on the profile.
Search for Self cam:
These cams are principally used to convert rotational motion to linear motion parallel to the rotational axis of the cylinder.