Now, using the '+' key move the robot arm
downwards until, either the position 255 
is reached, or until the distance of the
centering pin in the hand joint axis is
approximately 3 cm from the base plate.

1. Possibility:
Position 255 is reached - but the distance
to the base plate is obviously larger than
3 cm. By turning the potis in the shoulder
joint counterclockwise (after loosening the
screws) the right distance is set. (then 
retighten the screws).

2. Possibility:
Distance achieved, but position < 255.
Turn the poti clockwise until position
255 can be set.

Position 255 and distance correct: 'Enter'!!