Frame Building Directions

Safety Warnings (You can be quizzed on these at any time. Make sure you are familiar with them!)

• Safety goggles and close-toed shoes are REQUIRED while using the power drill, pipe cutters, or heat gun
• When using the pipe cutters, make sure your fingers are not on the inside of that pipe and that you never cut at an angle as this can damage/break the blade. Perpendicular cuts only.
• Drill should be unplugged whenever changing drill bits or when the drill is not being used
• Drill can only be used on pipe that is being held in place by a table vise. NEVER HOLD A PIECE OF PVC WITH YOUR HAND WHILE YOU ARE OPERATING THE DRILL
• Never hand another person the drill or pipe cutters directly. Place these items down and let the other person pick them up when they are ready
• Before using a heat gun, get personal training from Mrs. S!

Training Videos

YOU MUST WATCH ALL TRAINING VIDEOS BEFORE BEGINNING THIS TASK.

How to use Pipe Cutters
How to use a Power Drill

Before you build your actual ROV Frame

1. Use the provided PVC to build some potential frame designs (prototypes). Please do not cut PVC for your prototypes. Instead, try to use what is available. 

• Use the motor mount PVC pieces from your kit in your prototypes to approximate where your will want your motor
  

• Focus on the frame but if you want to look at potential tools for the tasks, feel free. Do not permanently modify them until you are sure you want to use them in your ROV
• Show your prototypes to the rest of your team, get their input, you can even take them out to the pool for a quick dip! Pick your favorite prototype to move forward with your ROV development
1. Create a NEAT sketch of the frame you plan on using. You can do an isometric drawing that shows 3 dimensions at one time OR 3 separate views from the front, side, and top

• Your drawing MUST include dimensions for each piece of pipe and the types of joints you will use (i.e. elbow, 4 way connecter, 3 way T, etc). You should also add up all lengths of PVC to get one total number of PVC footage your PVC will use. If you end up using more or less, you will update your drawing and numbers
• You must show your drawing to Mrs. S and add it's image to your daily update. You will then be given PVC to begin constructing your frame!

Helpful Hints about Frame Design

Note: These directions are provided courtesy of MATE. Full pufferfish directions and details can be found here

Frame Design Considerations:  

There is no set MATE frame design.  Building a frame depends on the tools and other systems that are going to be incorporated into the frame, and the tasks that the ROV will be required to do.  MATE does have some guidelines to help when building a frame.  

1. Bigger is not always better.  With a set amount of thrust, a bigger frame will move and turn more slowly, while a smaller frame will move and turn more quickly.  Which is better?  It depends on what the ROV is doing.  Sometimes slow is better.  Consider what your ROV is going to be doing and design accordingly.  
2. Let water flow through the frame.  Don’t plan to use the air inside the pipe as buoyancy.  It is too difficult to prevent the air inside the pipes from leaking out, and then the buoyancy is lost.  The water inside the pipe is also mass, which must be pushed around by the motors.  Consider using tees at the corners so water can flow through the pipes.
3. Build a symmetrical frame.  If a 12 cm length of pipe is cut for one side, a 12 cm length of pipe will probably need to be cut for the otherside.  This is not always the case, but is a good rule to follow.  Not doing this can lead to a PVC frame that does not fit together well and breaks apart too easily.  
4. Place things around the center of the ROV.  If the vertical motor is not near the center of the vehicle, the ROV may pitch (nose up, nose down) when moving up and down.  Heavier items should be kept below the center-point.  Light items (flotation) should be kept above the centerpoint.  Ideally the tether should come out of the top middle or top rear of the ROV.  
5. ½-inch PVC pipe inserts approximately 1.5 cm into a tee, elbow or other connector.  Plan accordingly.  Keep excess PVC to a minimum.  The purpose of the frame is to hold the other systems together in a functional spatial arrangement.  If a length of PVC isn’t needed, don’t insert it.  
6. Pushing the pipe into a tee, elbow or other joint by hand should be enough to secure the connection.  If the connection is still bad, look at the symmetry of the connecting pieces.  If necessary, use a small screw to hold the pipe together instead of PVC glue.  PVC glue makes a connection that is inflexible, brittle and prone to breaking. 
7. PVC can be painted with paint for plastic. Spray paint is one option. You are welcome to paint your frame but no paint will be provided in class. If you bring paint to school, do not carry it with you. Drop it off in the classroom and make sure you coordinate with Mrs. S about where/when to paint since the area must be well protected and ventilated.
8. Another option is to run the motor wires through the frame of the ROV.  This keeps the wires out of sight and out of harm’s way, and they emerge from the vehicle frame at a single strain relief point.  To run the motor wires through the frame, drill a 3/16-inch hole through the ½-inch portion of the motor mount.  Push the wires through this hole and work them through the framework of the ROV, and out through the strain relief.  Note that if you are using screws to hold the frame together, buy short, ⅜-inch screws.  Otherwise the points of the screw can damage the wires inside the PVC pipe.

Thinking about buoyancy

1. Once you have a frame you like, we can figure out how much buoyancy you need! Note: If you are waiting for motors and whatnot, you should STILL go through the buoyancy exercise with Mrs. S!

• Buoyancy should be located at the TOP of the ROV
• Ballast (weights) should be located at the BOTTOM of the ROV
• The greater the separation between the two, the greater the stability of the ROV
• Add enough buoyancy to provide for late additions to the ROV (remember it is better to be slightly positively buoyant to prevent the ROV from sinking in the event of an ROV failure!)
• Use ballast to trim and level the ROV from the front to rear and side to side. Note: I do not have materials for ballast! You must provide your own

More than you ever wanted to know about buoyancy!