bike2

 

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View from  the front of the completed drag racing motorcycle

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View of  the left side of the completed drag racing motorcycle

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Detail of  the drive train assembly - note the gear ratio as compared to the first  model

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In every trial, the Scout based bike pulled away at the beginning

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...but at  the end, the RCX based unit always won the race

This is the second of two motorcycle models using the Lego Mindstorms robotic construction sets. This robot uses the Scout brick from the discovery set.

The major consideration for this design was to use only parts from the discovery set to create a competitive robot to race against our RCX based model. This was accomplished with the exception of the use of the two big front and rear wheels. We also chose to create a completely unique design although many of the lessons we learned in building the first model were incorporated into this design.

The frame on this robot is slightly longer. We used gear drive for this model instead of belt drive since the pulleys are not included in this Lego set. The final design has a gear ratio of less than 1:1 -- this gave the model the ability to accelerate more rapidly than the first model, but limited the achievable top speed. The motor receives structural support partially from the frame and by attachment to the Scout brick.The entire robot is kept upright by the two supporting wheels on each side.

The front fork assembly on this model is also rigid and does not rotate to steer the robot. Half-width supports were used at the point the axle attached as in the first motorcycle model. We reduced the amount of support near the wheel end of the fork by simply using a single frame member with pins. The handgrips and controls were modeled identically to the first model.

The placement and size of the supporting wheels was dictated by the limited choices available with this set. An additional member was added below the frame on each side. This served dual purposes -- it placed the support wheels at the proper height and increased the support at the joining point of two frame members under the Scout brick.

For the creation of the exhaust pipe assembly we used several pieces of flexible tubing and the short axles at the connecting points. The footpegs and driver controls were made of the few remaining parts available.

Programming of the unit was accomplished by use of the Scout software development kit. This program allows programming of the brick with a c style language interface. We created a simple one task program. The robot sets motor motion forward, waits for three seconds, then turns the motor on for fifteen seconds. This was identical to the racing program we created for the first model.

The final step was to take both models to the outdoor course and see how they ran against each other. The course we chose was exactly 36 feet long which is equivalent to about 13 seconds of run time for both of these models. As you can see from the pictures at the left, the Scout based unit always got an early lead from the starting line. In the picture, the starting line can be see immediately to the rear of both bikes.

For each race we ran, the Scout continued to lead for about ten to fifteen feet, but then the higher gear ratio of the RCX caused it to catch up and pass the Scout on each run.

We had a fun time racing these two models against each other and they will be missed as we disassemble them in preparation for our next project.