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Robot Wars 1999/2000

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DRIVE TRAIN
INTRODUCTION
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.
TYPE
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 output.

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.


TRACTION METHOD
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:
    Uniqueness
    Improved traction
    Zero turning circle
    No more than two drive motors
    Appearance.

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.


TRACK TYPE
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.

As the 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.


DRIVE TRAIN