The drive train is the part of the robot that is used to transmit the power generated by the
robot into linear motion. There were several methods available to the group when the project
was first started. This section gives a brief insight into a few of the ideas that were
considered for the type of drive to be used.
Firstly the type of prime mover and subsequent linkage/gearing was looked at. In a short space
of time it was agreed that the power would come from electric motors (reasons for this choice
are detailed in future sections). As can be seen from the following sketches there were three
main options open regarding the type of linkage to be used.
The first option was the direct drive i.e. the motor coupled directly to the wheel/drive pulley.
Obviously, this has the advantage of less components and therefore less cost. However it was
very difficult to find an electric motor with the correct speed offering the required power
This led to the second and third options which both involved gearing the motor, either step up
or step down, this means that the motor characteristics can be changed to suit the required
output characteristics. Comparing the two options the gearbox method was the preferred choice.
This was due to a number of factors; Firstly the gear and pulley method required the separate
gears to be aligned correctly, which mean that if there is a small mistake present in the
system it will accumulate to give a large error at the final stage. With the gearbox there is
only one alignment stage thus reducing the chances of errors. The gearbox was also thought to
be far simpler to mount which was felt to compensate for the additional cost.
Once the type of drive had been decided all that remained was to come to a decision regarding
the type of traction method that was to be used. Basically it was seen as a choice between two
methods, either wheels or tracks. The next sketch illustrates the four-wheeled option.
With all four wheels being driven this option had many advantages, it would be simple to
construct, would have a zero turning circle, however all four motors would need to be
synchronised to ensure ease of control. A variation on this theme was the six-wheeled option,
this idea was dismissed as it was too similar to the previous years robot.
It was therefore decided that the team would attempt to construct a tracked vehicle. There were
several reasons for this choice, such as:
Zero turning circle
No more than two drive motors
Once the decision was made the type of track had to be determined as well as the design of the
track. On the design side three options appeared as shown below.
The design that was chosen was the third option i.e. the 'chieftain tank' look-alike, based
mainly on apperarance.
The initial idea was to have metal tracks, however the availability on the commercial market for
the type of track that the robot required was very limited indeed. Through research on the
Internet, it was found that previous metal tracked robots had mostly produced their own tracks.
This was considered for a while with the options of modifying motorcycle chains in some way,
however it was finally decided that the robot would use plastic tracks, which also produced a
large weight saving. The tracks were to be double sided timing belts running on timing pulleys
from the same suppliers.
project progressed the track design changed slightly, loosing one of the freewheeling timing
pulleys due to weight considerations, thus ending with the design shown below.