Lego bricks were used in this semi-automatic CW key project.
The dash lever seen here moves independently of the main lever. Dash contact is made of a narrow strip of steel and two screws. Rubber bands are used as keying springs.
Inside view: the main lever and its bearing.
Left: dot contact (thin strip of steel)
Center: pendulum for dots (more bricks and weight means slower speed)
Right: damper unit to stop pendulum oscillation (off-road Lego tire was selected for best performance)
See & hear how the bug works:
Link to my other homebrew bug project here.