>but don't these suffer from the same problem as a mercury switch ?
>Say the cylinder is mounted horizontally in the veehickle. If it's
>then parked on an angle (hill, verge etc) the angle could be great
>enough for the weight of the ball to hold it steady and not respond
>to small tampering vibrations ?

Guess you are looking to make your own of this style of sensor (for the
cost/time reasons already given)

I would look at having the sensor on a platform that was self levelling (a
damped gimbal mount style of thing) with probably a dish of oil to do the
damping, on a ball solidly mounted on the bottom of the gimbal. Suspect you
could get a 2-5 second damping of movement that would still transmit any
rapid movement to the detection ball, especially if the detection ball
suspension is solidly attached to the car.

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