Week 9 Post

Between last week's class and now, we tested the submersible in two creeks off campus. Our first test, taking place in Valley Forge park, was mostly to check on the buoyancy. We decided to add some weight and take away some foam for a rough buoyancy test, but the submersible still mostly floated.

Our second test was closer to home, in faster water. We found that the motors were just strong enough to match the speed of the water, even when using the boost motor. It turns out that the boost motor takes away enough power from the side motors that the sub ends up going the same speed.

To compensate for this, Jacob wired two AA batteries into the boost motor circuit. They were wired on a bypass switch to test the difference in power. The 9V-18V boost motor was able to handle the additional 3V over the supplied 12V motors. This was enough to make the sub overtake the water speed.

This is a video of different highlights of our tests.

Week 8 Post

Over the course of the last week, we finished putting the motors together and attaching the motors themselves. We also tested each of the motors in the water and are looking for a larger amount of water to test the maneuverability.

Our fourth propeller is a 7-blade fan for a computer.

We attached it to the boost motor on the rear cross pipe.

The boost motor had to be turned around because the fan is one-directional, so this is the opposite of what it currently looks like.

Week 7 - Motor Waterproofing

Over this week, we waterproofed three of the four motors. The last motor could not be finished because a wire broke and the soldering iron was not available. The wire will be fixed today, and the last motor will be waterproofed and attached to the body.

Flotation Testing

We discovered that the 5" (with 2.5" radius) polyethylene foam noodle could hold a rough weight of 14 pounds  under water without sinking. There are two 5" pieces of pool noodles so the total weight that the two can hold is about 28 pounds. The 5" length will most likely have to be cut down to less than 3 inches.

Various manufacturers' online information regarding pool noodles states that they are 63" in length and can hold between 160-200 pounds of weight. Therefore, 5 inches of pool noodle must be able to hold around 14 pounds before sinking. Below is an image of the 5" polyethylene foam.

5" polyethylene foam

Week 6

This week we finally got the corner pieces for the structure of the submersible, and were able to put it together.  There was some difficulty in this, since some of the pipe pieces didn't fit into the corner pieces very well.  We had to file down the ends of some of the pieces in order to attach them properly.

Our original intention this week was to also put together the motors, and waterproof them.  We were unable to complete this, but should be able to do it this week in lab.  We need to put the lead wires that attach to the motors through the holes in the lids of the canisters, then cover the motors in electrical tape and wax in order to water proof them before putting them in the canisters.  After that the only thing to do for the motors is attach the hardware and propeller to the shafts of the motors.

After that, the only thing we need to do is balance the submersible, and make it neutrality buoyant.

Week 5 Post

This week Jacob finished up the controller box (above).  We also ordered the last pieces we needed, and are waiting for them to be delivered.  The cost of the pieces was $5.72 and with $8.95 shipping, the total was $14.67.  This makes a total cost of $36.04. We still need to find a fourth canister for our fourth motor, which should be done sometime this week.

Week 4: Update

Jacob went out and picked up the fourth motor for the design (above). We've decided that we are going to use the motor as a boost instead of as a strafe motor. After checking a few local hardware stores, we have determined that we will have to get our extra PVC fittings online. We plan on purchasing these today.  These fittings include 4 corner pieces, which allow for a 3 dimensional connection, and a valve that we are planning on using to fill the submersible with water in order to make it naturally buoyant.  If the valve costs to much, we will not be buying it, and will replace it by drilling holes, and filling them with stoppers.  The corner pieces should only cost $1.43 a fitting, making an additional $5.72 for 4 fittings plus tax and shipping.

The wiring of the control box and the submersible should be finished by next week as long as we get the rest of the pieces in time.

Cost of motor: $6.35
Total amount spent so far: $21.37
Estimated final cost will be under $40.