|
 As
part of my job, I was required to ride in a truck in connection with obtaing
a "Pit Driving License" for a huge open pit mine in the Mojave Desert. The
vehicle I rode in was a Terex Unit Rig MT4400 Diesel Electric Mining Truck.
The picture makes it look big, but to put it in some perspective, the tires
are almost twelve feet tall, making the truck about the size of a small two
story house. It has a big 2500HP diesel engine that drives an electric
generator that drives individual electric motors on each wheel. On the
flat, the truck is capable of about 30 miles per hour, which is quite a bit
faster than they drive down in the mine. The truck is rated for a load of
260 tons, but on most loads we carried, the weight went some bit over that.
(The shovel that was loading us had a 100 ton capacity, and when it dropped
its load in the bed of the truck, things bounced around quite a bit!) The
driver’s cab, over the left front wheel, has two roomy seats, is air
conditioned, and is equipped with a good stereo, a touch screen computer so
that the driver can communicate with his dispatch center, and auxiliary TV
so that the driver can see close things on the right. The TV doesn’t work
very well, which means the driver actually can’t see anything on the ground
to the right that is closer than 175 feet. The mine rules say to stay 300
feet behind a Haul Truck, and not to park any closer than 150 feet, which
makes good sense to me. To get in the vehicle, I had to climb up the ladder
on the front, to the right of the radiator. The platform where the driver’s
cabin is located actually is rather like a nice raised patio—it’s big enough
that one could easily throw a party there. My driver’s name was Jay, and
he gave me quite a ride. Going down hills was very interesting, as the
vehicle has two braking systems. For retarding at speeds above 5 MPH, the
electronic controls applies a reverse current to the wheel motors, rather
like with a diesel train, which does a pretty good job of slowing things
down. Below 5MPH, there is a conventional hydraulic braking system that
actually brings the truck to a stop. The transmission is little more than a
switch on the console, and all it does is set forward polarity to the wheel
motors, reverse polarity, or no drive at all. Otherwise, it is pretty
conventional. Well—a little bigger than conventional, maybe.
During what ended up being
a hour and a half on the truck, we carried several loads of dirt from an
area on the wall of the pit where they are digging down to another vein, and
then we took one trip all the way down to the bottom of the mine to pick up
one load of ore. The dirt is pretty normal dirt, but the ore is a different
issue altogether. I suppose weight wise, it is pretty heavy, but the
kernite (a type of borax) we were carrying is very crystalline and white,
and shatters easily into a very fine powder. When the shovel dropped a load
of kernite into the truck ahead of us, a dense white cloud of kernite dust
enveloped the truck and shovel, a cloud so dense we were unable to see the
truck, even though it was only about 150 feet away. The dust dissipated
fairly quickly though, and we moved in for our load. My driver told me that
on a downhill stretch, if the truck got over 35 miles and hour, he would be
just along for the ride as the braking systems would not be able to cope
with that speed. With a heavy load on the back, his limit speed is even
slower. It is funny, though, as those kinds of speed seem plenty fast
enough when you are riding in something so big.
All too soon, my time in
the truck was up. This was the ride of a lifetime. I must say that my
Volkswagen seemed pretty darn small when I got back to the parking lot. Now
I have a dark blue numbered sticker on my hard hat that says “Pit Driving
License,” which will allow me to drive in a place that is unique in my
experience, and I must say it is all rather exciting—this was one of the
better days for a job that normally takes me to the rather dull environment
of corporate offices around the county. |
