Real-Life Math
Math skills are very important for crane operators. They need them
to figure out whether the crane can safely handle a specific weight. An unstable
crane is an operator's worst nightmare -- it might tip over.
"You
definitely need all the basic math skills," says Ross Kerr, general manager
of a company providing crane safety courses. "For one thing, you need math
when you're using the load charts to figure out how much a crane can
lift."
You are a crane operator working on a downtown construction
site. It's been a busy morning. Your job is to use the crane to remove
buckets filled with wet cement from a cement truck. Then you move the buckets
through the air to a concrete form where a workman is waiting.
The
workman grabs the bucket and positions it over the concrete form. When the
bucket is perfectly positioned, he opens a lever at the bottom of the bucket
and wet cement pours into the concrete form. When he has finished, you move
the empty bucket back to the concrete truck and repeat the process.
After
lunch, your supervisor has another job for you. He wants you to lift a diesel
generator to the top of the roof. It will be used as a source of backup power
when the building is complete.
The diesel generator is much heavier
than a bucket of cement. Before hoisting it on to the crane, you need to make
some adjustments. To do this, you need to understand the concept of torque.
Torque
is the twisting force of the crane. When a crane lifts a weight into the air,
the natural inclination of the crane is to twist, moving the weight toward
the operating tower where the crane operator sits.
Two things prevent
this. First, there is a counterweight -- usually a slab of concrete -- at
the other end of the crane. This produces torque in the opposite direction,
which helps balance the crane.
Second, the mechanism that attaches
the operating tower to the crane helps prevent twisting.
Every crane
has a load chart that tells the operator the maximum weight that the crane
will carry at a particular radius. The radius is the distance between the
operating tower and the item to be lifted. Every crane has a carrier that
you can use to move the item closer to, or farther away from, the operating
tower.
To find out the torque, you multiply the radius by the maximum
weight. This tells you how much of a twisting force the crane can bear without
tipping over.
Torque = maximum weight x radius
Right
now, you are operating a crane with a radius of 100 feet. On this particular
crane, with a radius of 100 feet you can safely carry 17,980 pounds. The diesel
generator weighs 25,000 pounds. You need to figure out how much to increase
or reduce the radius so that the crane can safely handle the heavier weight.
(Hint:
even though you calculate torque by multiplying the maximum weight by the
radius, it is a constant figure that does not change no matter what adjustments
you make to the crane).