Propeller Designs: Week 8

As we we're going to test the first set of propellers that were printed in the diving pool, we encountered a drastic problem. The propeller was connected to the motor shaft through the use of a sleeve that slid onto the shaft. This sleeve held the propeller and was soldered to the motor shaft. However, the bond was obviously not strong enough since during the testing the port motor sleeve fell off of the shaft. We are working to correct this issue by carefully re-soldering the propeller sleeves onto the motor shaft along with another adhesive.
The two other propeller designs have also been constructed and sent to the rapid prototyping machine. The first set of propellers that were printed had a blade length of 10mm while the propellers provided in the kit had a length of 15mm. Therefore, to keep differences in blade lengths consistent, one model has a blade length of 15mm while the other has a length of 20mm. These are shown below in Figure A and Figure B, respectively.

Figure A: 15mm blade length

Figure B: 20mm blade length

James Esser

Daniel Stenger

Propeller Designs: Week 7

After looking at the designs, we reevaluated how exactly we would go about testing to see the differences in propulsion. Instead of testing two separate designs, we chose to modify Design A. Previously, the Pro/ENGINEER files had been in the wrong units and wrong magnitudes. These changes are displayed in the figure below.

We then sent these designs to the rapid-prototyping machine which fabricated the parts in hard plastic. In order to make sure that these propellers stayed on the motor shaft, a hole needed to be drilled in the center. This was done at the machine shop with the drill press and is depicted below.

The next step in testing submarine propulsion is to print out two more sets of propellers. The current propeller blades are shorter than the ones provided in the kit. Therefore, the next set will have the same blade length as the ones provided in the kit. Then the final set will be longer than those provided to us in the kit.

James Esser
Daniel Stenger

Water Capsule: Week 7

The purpose of this project was do use the modified Sea Perch to test water for pH, impurities, and other qualities. Sensors that we looked into for these measurements were all far over budget, and most of the ones available would not be able to operate under water. As an alternative to submarine-mounted sensors, we created a water capture device to retrieve a sample from a specific area in the water and return it to shore for testing.
The capsule is constructed of a three-inch long, half-inch diameter piece of PVC pipe. One end of the pipe is sealed with an end cap an PVC cement. The other end is covered by a sliding cap with a long sleeve that covers most of the pipe. The sliding cap is fitted with a rubber O-ring to prevent water leakage when the capsule is closed. Six holes are drilled into the sleeve, so that when the cap is lifted, water will enter the capsule. The idea is to mount a spring to keep pressure on the cap and keep the capsule closed. A small motor will be used to open the capsule and allow water to enter at the desired moment.

Brian Bucci

Tim Kaack

Justin Goebel

Propeller Designs: Week 6

In order to find the most effective propeller designs, we decided it would be a good idea to design two different propellers and then test the differences between them. To get a basic idea of how a standard submarine propeller looks, we conducted some research and constructed two models in Pro/ENGINEER, which are shown below.

Figure 1: Design A

Figure 2: Design B

The thought behind the Design A was to be able to move the most amount of water as possible. However, the issue with this design is that, theoretically, it will move faster in one direction than the other. Because of this, Design B is curved in both directions that will be able to move the water in both directions giving a better balance of forward and backward motion.

Brian Bucci
Tim Kaack
Justin Goebel
Daniel Stenger
James Esser

Motor Orientation Pictures: Week 5

The following pictures show the changes in motor orientation made to the SeaPerch. In order to remount the motors differently, the original zip-ties had to be cut. Also, more motor wire was required so the butyl rubber tape needed to be pulled back to expose more wire. Finally, the motors were re-positioned and then zip-tied  to the chassis.

Motor Orientations and Propeller Designs: Week 5

Now that the Sea Perch is assembled using all the standard parts, the next step is to optimize propulsion and maneuverability. Our first step was to adjust motor orientation. The two factors that are affected most by changes in motor orientation are the Sea Perch's turn radius and upward/downward movement. The propeller are capable of spinning in forward and reverse directions, but because of their shape, propellers provide more thrust in one direction than the other. The direction that provides more thrust will be referred to as the forward direction.
The vertical movement motor was originally mounted with the propeller's forward direction aiming down. We decided to reverse this for two reasons. The way the Sea Perch was constructed, it's average density was slightly greater than that of water, so it had the tendency to sink slowly. With the forward direction aimed up, the Sea Perch was able to overcome this tendency more efficiently than before. Also, in the original orientation, The propeller itself was located on the top of the Sea Perch, above the motor. When the Sea Perch would ascend to the surface of the water, this propeller would emerge from the water and splash around as it would spin on above the water. This caused instability and minor loss of control. The new motor orientation avoids this issue altogether.
The two side mounted motors are used to control the submarine through turns. Through first-hand testing, we determined that the when the motors were farther apart, the Sea Perch had a smaller turn radius. To implement this advantage into our design, we positioned the motors on the outside of the chassis, as opposed to the inside where the were originally. This added about 3 more inches of space between the two propellers (distance motor shaft to motor shaft), and should give the Sea Perch a smaller turn radius.
Our next approach to improving the Sea Perch is to increase the propulsion the motors are able to exert. To accomplish this, we will be using the 3D printer to manufacture new propellers. We are currently in the process of designing propellers in Pro ENGINEER. We are basing the designs off of research done on propellers and propulsion to come up with designs that maximize propulsion delivered by the propellers.

Brian Bucci
Daniel Stenger
Justin Goebel
James Esser
Tim Kaack

Motor Assembly Update: Week 4

A small packet of epoxy came included in the Sea Perch kit. This epoxy was supposed to be used to attach the metal caps that held the propellers to the metal rods that were spun by the motors. This epoxy, however, was would dissolve when in contact with chlorine, which was unacceptable due to our plans to test the submarine in a pool. We purchased marine glue that would hold up better than the epoxy in nonstandard conditions. This glue was applied to the pieces, and the propellers were tested in water. The glue wan unable to withstand the stress caused by the water resistance, and the pieces separated from each other.
To solve this problem and get the pieces attached once and for all, we decided to use solder to hold the propeller sleeves onto the motor shafts. We placed the sleeves one at a time into a vice, melted solder into them, and plunged the motor shafts into liquid solder, allowing it to cool and form a strong bond. All three propellers were then attached and tested in water. They held up to the resistance and were able to operate without fail.

Brian Bucci
Dan Stenger
Tim Kaack
Justin Goebel
James Esser