4/5/2559 Underwater Glider
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Underwater Glider
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We set out to build an underwater glider that would essentially have automated movement up and down through the water. This up and down movement
was to be controlled with a ballast system created by the push and pull of various syringes. In short, the glider was to rest just above neutral buoyancy
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with the syringes empty, meaning it would float. Then when the motor pulled the syringes and they filled with water, the glider would dive. Once the glider
reached a desired depth, the motor would push the syringes to empty them back out and the glider would rise up. To keep the glider from turning or
tipping over, the glider would house an accelerometer attached to a servo holding weight. Whenever the accelerometer (and glider) became offbalanced,
the weight would pivot to straighten the glider out. We also added a single, much smaller syringe so that we could obtain water samples at different
depths in bodies of water for an environmental studies lab to examine.
Step 1: Ballast Control
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Starting at the front of the glider, we first worked on the ballast system. We purchased three 60cc syringes and a 20cc syringe for the test from the Tractor
Supply Company. We decided that the push/pull motion would be done by stepper motors directly connect to long threaded bolts. The syringes would sit
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in a fixed position at the front of the glider with the open ends facing the front.
Step 2: Syringe Mount
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We bought an 18" x 4" diameter clear acrylic tube, with 1/8" walls. This would serve as the main body of the glider. We also purchased 24" worth of 4"
PVC pipe and a Qwik Cap to seal the back. We attached about 12" of PVC to the back of the sub to house the electrical components, and also attached
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about 2" of PVC to the front to make the glider sit flat on a table during construction. Using the 3D printer, we fabricated a syringe holder that would also
serve as the front end cap, fitting the inside of our 4'' diameter acrylic tube. Later application of silicone caulk would provide a waterproof seal in the front
of the glider. As seen in the picture, the syringe mount would securely hold the three ballastcontrolling syringes as well as the smaller, sample syringe.
Step 3: TNut Attachments
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With all four syringes mounted in the 3Dprinted mount, we fabricated a tool that would uniformly push and pull the three ballast syringes. The tool also
housed a tnut which would hold the threaded bolt attached to the stepper motor and provide the push/pull motion when turned. In a similar fashion, we
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attached a tnut to the smaller syringe making it moveable with a threaded bolt attached to a smaller, separate stepper motor.
Step 4: Stepper and Servo Motor Mounts
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Working our way towards the middle of the glider, next was the mounting of the stepper and servo motors. Using sheets of plastic cardboard, we created
a sort of shelf to fit inside the tube. We mounted the two stepper motors to the plastic using premade mounts. Because of limited space in the tube, we
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fabricated a pulley system for the smaller stepper motor so that the motors could sit at the same alignment, yet turn threaded rods at different alignments
(to match the setup of the syringes in the mount). This alignment change can be seen in the picture of the side view. In order to attach the servo motor to
the plastic cardboard, we simply cut a hole the size of the motor and glued it in. The position of the weight on the servo was strategically placed in the
middle of the glider to maximize stability control. All the wires from the three motors were directed towards the back of the glider.
Step 5: Connecting Mech