Firstly we studied
current pointless boxes to find out exactly how they worked. Which is that the
switch being turned on activates a motor with a gearbox upon it this then turns
a shaft with the arm on it. The arm has a certain profile because of this it
opens the box lid as it moves towards the switch, it then turns the switch off,
the switch going off also triggers the motor to reverse to bring the arm back
to its original position. We would be building upon these principles.
The same motor as used in other pointless boxes would be used, this motor would
be mounted upon and internal rib mounted in the base of the box, the arm would
be custom made by us, and this was due to the different sizing of our box in
comparison to other pointless boxes. We would have to be careful that the
profile of the arm was correct to lift the box lid, but not too fast or too
slow. As with the other pointless boxes our arm would be mounted on the shaft
coming out of the gearbox on the motor. This gearbox gave high torque and low
RPM from the motor; this is exactly what we needed for the arm, as the switch
is quite stiff. When the arm reached the top of its movement, and switches the
main switch off, this would activate a micro switch which would then activate
the second phase of the system. This micro switch would activate a second
motor, which would be slightly more powerful than the other; this is because it
would be powering the movement of the box.
We planned to have the box move roughly 30cm when the second phase was initiated. The motor has a gearbox on it already which again gives high torque and low RPM, but not as low as the other motor. The motor would be connected to a shaft which would power the axle, therefore the wheel. Also upon this shaft would be two cams interacting with micro switches, the first cam would be to turn the motor off after it had travelled 30cm, the second cam would slow the motor down by activating a resistor. This is because we needed to have some form of control over the automation.
The next phase was to design the panels of the box. The top of the box would split in the middle, where the switch would be mounted just over to one side. The other side of the lid would be on hinges so the arm can open it with the correct movement and profile. The sides of the box would be plain and simple. The side panels will all have slots and tabs in so they fit together perfectly and are easier to attach together. The base of the box would be more complicated, with slots needed for the wheels and various mountings needed for the internal workings. The panels themselves would be attached together with glue as this is the simplest and most effective way of mounting each component to one another.
Initially, the group
agreed that the material to be used for the construction of the useless box
would be 2mm clear acrylic. The thickness was sufficient to give the box the
required strength and rigidity, but not too thick so as to reduce internal
space and increase weight. However, after some consideration, it was decided
instead to opt for 3mm thick black acrylic.
The reasons for this
were:
1.) Clear acrylic would show off the internal workings of the device, which detracts away from the personification idea (although this would make the engineering design available to scrutiny)
2.) 2mm thick is a relatively uncommon size; 3mm is much more readily available and therefore considerably cheaper
1.) Clear acrylic would show off the internal workings of the device, which detracts away from the personification idea (although this would make the engineering design available to scrutiny)
2.) 2mm thick is a relatively uncommon size; 3mm is much more readily available and therefore considerably cheaper
This meant that some of
the designs already completed would have to be altered, as they were originally
based around working in 2mm thick material.
