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Chapter 3 Engineering Design 53
Going Green
Renewable Resources
We use wood and wood products every day.
Wood is used in most houses in the United States
for framing, exterior wall sheathing, roof sheathing,
flooring, trim, and cabinets, Figure A. Think about
the amount of paper consumed in your school in a
year, or even in a day. Wood and wood products are
a valuable part of our daily lives.
Wood is a renewable resource. Renewable
resources are resources that can be replenished
in a reasonable amount of time. If our forests
are managed properly, our forests will never be
depleted. Wise and sustainable forest manage-
ment programs provide for the harvest of this valu-
able resource while using replanting techniques
that ensure the forest will be there for future
generations.
One of the biggest problems with logging, or
cutting trees for timber, is the impact of the massive
harvesting equipment on the forest floor. Skidders,
haulers, and other equipment can tear up the forest
floor, causing increased erosion. The heavy weight of
the equipment can compact the soil and damage or
even kill trees. Until now, most harvesting has been
done with machines using large tires with heavy
tread or tracks. In a harvester, the operator sits in
the cab and uses the machine to cut down, delimb,
and cut trees to desired length for pickup by another
machine. See Figure B.
Engineers are now designing harvesters with
legs. The legs move softly through the woods and
create almost no impact. There are no tires or
tracks to damage the forest floor. A well-protected
driver sits in a climate-controlled cab and oper-
ates the machine with a joystick. The harvester can
move forward, backward, side to side, diagonally,
and rotate in a circle. It can even vary the distance
between the cab and the ground. Typical equipment
requires clearing and leveling paths for travel, while
the harvester can step over obstacles in its path.
Sensors on its feet tell it what the forest floor looks
like so it can adjust accordingly. It can do all this
while minimizing the negative impacts on the rest
of the forest. The trees that are not being cut down
remain healthy.
People often think of technological advance-
ments as having a negative effect on the environ-
ment. Our society needs wood and wood products
to maintain our way of life. Trees are one of our
greatest renewable resources. Selective cutting
can actually improve the overall health of our for-
ests. The walking harvester is an advancement in
design and engineering that allows us to harvest
this valuable renewable resource while minimizing
the negative impacts on the overall health of the
forest. It is important to remember that engineer-
ing designers are often on the forefront when it
comes to renewable resources and environmental
management.
Figure A.
David Lee/Shutterstock.com
Figure B.
Dmitry Naumov/Shutterstock.com