Thames & Kosmos DLX, Руководство по эксперименту, Страница: 22 / 132

Cleaning up with
the bulldozer
YOU WILL NEED
› The assembled bulldozer
› IR remote control
› 5 AA batteries or 5 AA rechargeable batteries
› Boxes (see page 127) or building pieces, etc.
› Masking tape
› Stop watch, note pad, and pen
HERE’S HOW
1. Scatter several boxes or other small objects out across
the floor of the room. These are the things you will be
using the bulldozer to clean up. Just be sure that
nobody slips on them.
2. Mark an area on the floor where all the scattered
objects are to be moved. You could use masking tape,
for example. This way, you will have a clearly
identified target zone.
3. Familiarize yourself with the bulldozer’s controls.
Which touch pad buttons control which motor and
which function?
4. Time to start! Push each one of the scattered objects in
turn into the identified target zone.
5. How about having a bulldozer competition with one of
your friends? To make it fair, each contestant should
start with the same objects arranged in the same
positions. You can use snippets of masking tape to
mark each spot, and write a note on each piece of tape
indicating which object should be placed there.
6. As soon as you have arranged all the bits of masking
tape, place the bulldozer on its marked starting
position.
7. On your marks, get set, go! Use the stop watch
to measure the amount of time each contestant
takes to finish.
WHAT’S HAPPENING
You have probably noticed how the transmission for
the turning movement and for lifting the shovel acts
by way of gear wheels.
This kind of transmission system is known as a
worm drive. It consists of a worm gear (the
“normal” gear wheel) and the worm screw, the
thing that looks a little like the thread of a
screw. A worm drive is often used when shafts
and axles cross, i.e. when they run at right
angles to each other.
In other words: You can use a worm drive to
transfer a turning movement to a different
axis. With the shovel’s lifting mechanism, the
motor shaft runs in the lengthwise direction
of the bulldozer. The worm drive, however,
lets the large gear wheel’s axle run at a right
angle to the lengthwise direction of the
bulldozer.
Another feature of the worm drive is its
relatively large transmission ratio (see
Experiment 8).
EXPERIMENT 2
20