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A CM Lodestar chain motor with slings and lighting
truss, flown from the ceiling in Alden Hall at WPI.
While lifts provide a fairly effective means to fly equipment, they
have several downfalls. For one, they are typically large and quite
heavy. If used in pairs, two to three people are required to operate
them safely. Safety issues aside, they are simply inconvenient in a
lot of situations. Lastly, lifts take up a lot of floor space. In
typical theatrical uses, the ideal placement of the lift conflicts with
house seating. These are all areas that the chain motor excels in.
If appropriate load-bearing hang points are available in a venue (as
they are in WPI's Alden Hall), the simplicity and convenience of chain
motors makes them an ideal solution for flying lighting trusses and
A chain motor is simply a large electric motor with a gearbox and a
chain drive mounted in one chassis. The chassis of the motor generally
has a large hook mounted on its underside, to which loads are
attached. An extremely heavy gauge chain with a hook at one end
passes through the motor and into a chain bag. The hook of this chain
is generally clipped to the shackle of a wire rope sling, which is
attached to a load-bearing overhead beam. Once the attachment has
been made to an overhead hang point, the motors can have loads
attached for flying.
Several methods exist for the control of the chain motors. The
simplest method uses handheld controls (sometimes called pickles) to raise and lower the motors. Complex computer-controlled
systems exist for automatic flying of equipment. These systems can
control dozens of motors simultaneously. Systems this complex are not
generally necessary for a small number of chain motors.
At WPI, a pair of chain motors with handheld controls are often used
to fly lighting truss. The most common venue for this is Alden Hall,
where several sets of hang points exist for such a purpose. The
following list of instructions should be followed for proper use of
the chain motors:
- Choose a set of hangpoints to use. Three sets exist at
varying distances from the stage.
- Place one chain motor roadcase under each hang point.
Exact alignment isn't necessary at this point.
- Obtain access to the Alden Hall attic. Find the drop ropes
stored in the attic. Tie them off with a figure eight knot to a beam
nearest the hangpoints being used. Drop them through the hangpoint holes.
- In the hall, tie the drop ropes to the wire rope
slings. The wire rope slings should be attached to the chain of the
chain motor by use of a shackle.
- Locate two lengths of 2 inch iron pipe. These are stored
near the drop ropes in the attic. Making sure people are clear of the
chain area in the hall, raise one drop rope. When the wire rope
sling is through the hole, slip the iron pipe through the sling, as in
the figure 4.10. Repeat for the other rope.
- Locate the backup safety cables and attach them to each
wire rope sling. These safety cables are attached to the metal
ceiling beams, and are of appropriate length to attach to the slings
and provide for a backup if the main hang points should fail for any
reason. They should be attached to the wire rope slings using 1-ton
rapid links or heavy duty steel carabiners. This is the last of the
work that needs to be done in the attic.
- In the hall, attach power and control cabling to the chain
motors. Raise each motor out of its roadcase until it is at a
convenient working height. Slings may be attached to the hook of the
motor, either directly, or by the use of a large shackle.
While working with chain motors are fairly straightforward, there are
several points one should be concerned with when working with them:
- Pay close attention to the chain when raising and lowering
the motors. Note any binding, noises, or other problems.
Discontinue use of the motors if the problem appears to be serious.
- Inspect attic rigging frequently. If the motors are to be
flown for long periods of time, inspect daily for any signs of
impending failure in any piece of the rigging.
- Don't fool around with the motors. It's very tempting,
but it should be avoided due to excess wear and tear on the motors.
- Keep the handheld controls out of public access. Don't
leave them lying around so anyone can wander in and use the motors.
- Turn off the power breaker when motors are not in use.
This is to prevent unintentional movement of the motors.
View of a hang point in the Alden Hall attic. The 2 inch
iron pipe passes through the wire rope sling, which comes through the
hole from below. The pipe at the top of the image is not related to
the rigging. Note that the required safety cable is not
shown in this image.
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