click to view video

 

The following construction should be understood as temporary but reliable
for hours of continuous operation. Each year I must build props
in less than a month. And these will not be 'repeat performers'.
 Each year new automatronics replaces old, although
parts, like motors, etc are re-used.
 

Lid Drive Motor

The ubiquitous 12 vdc Saturn wiper motor lifts box lid.  It was positioned
right at the top edge of box, on one side,  by (1) plumber's strap.  To
prevent downward force on motor from moving it,  a piece
of wood (2) was butted against bottom of motor.

The rotating arm was made from "hole steel" about three inches long,
and the roller (3)  was a porcelain electric fence insulator bolted to arm,
but free to turn.
 
 
 
 
 

View inside box showing lid contact plate (1) which was a piece of 22 gage sheet metal.
Note skuff mark on this sheet where the roller (2) has rubbed during operation.
This double walled box had been used as a fog chiller, this year it's serving
as a prop.

This arrangement was the quickest/easiest construction method for lifting and dropping
the lid a short distance.
 
 
 

Something learned about d.c. wiper motor operation:

Often you hear that the Saturn motor is rated at 4 amps (running); however, it requires
at least twice that to start,  when under load.  The load in this case is the weight
of the hinged top (lid) plus chains.  The weight of the chains was about twice
that of the lid, itself.

This power supply WAS NOT enough to drive the motor once the chains were
added on top of the lid.  I used a power supply with a rating of 7 - 10 amps and
that one worked fine.

In an automobile, the battery momentarily supplies all the starting current
the motor may need; however, when using a power supply, it must have
enough reserve capacity to supply starting current.   Just something
to remember when applying this very useful motor.
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