NXT Wind-up Ballerina

Fun Projects for your LEGO^® MINDSTORMS^® NXT!

Wind-up Ballerina

Building:
Program:

Note: Make sure that the two pulley wheels and their cross hole in the middle are lined up exactly as shown here, then pegged together.

Connect the three motors to the NXT brick as follows:

Wind-up Ballerina Programming

Use the Ballerina program for the Wind-up Ballerina.

Using the Wind-up Ballerina

Make sure the transmission shifting lever starts out vertical (straight up and down), as shown in the picture to the right, by adjusting the motor position using the handle attached to the transmission motor.
Run the program, then turn the wind-up lever clockwise to wind up the model. The motor will resist your winding, as if there were were a real spring inside, so it will be a little hard to wind. Winding counter-clockwise (which is easy) will not do anything.
As the ballerina turns, the wind-up motor will slowly turn counter-clockwise, as if unwinding. To wind it up more while it is turning, you can can overpower the motor and force it to turn clockwise, just like a real wind-up spring.
Try winding the model until the Stop sign appears, indicating that is fully wound. Then next time try winding a couple more turns past that.

Challenges

OK, so my ballerina looks sort of like a cave man drawing. Can you do any better, or think of something else interesting to replace it with? If you used some parts that pivoted on low friction (gray or beige) pegs, then they might fly outward when the motor switched into high gear.
Learn how the 2-speed transmission works, and see if you can use the basic idea in another model that you design.
See if you can figure out how the Ballerina program uses the rotation sensors of the wind-up and ballerina motors to make the wind-up and wind-down behavior seem realistic.

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