subs in schools build manual - rearea.org.au › wp-content › uploads ›...

Submarine Build Manual Produced for Schools by SAAB Australia

Re-‐Engineering Australia Foundation Ltd PO Box 136 Castle Hill, NSW 1765 www.rea.org.au

UNCLASSIFIED

UNCLASSIFIED

Title Page

Subs in Schools Build Manual

Document No: DMS#354545 Issue: 1.0 26 02 2015 Approval: FINAL Page 1 of 55

Saab Australia Pty Ltd ABN 88 008 643 212

COPYRIGHT All rights reserved. Intellectual Property rights in this document are owned by Saab Australia Pty Ltd [Saab]. Use of this material is not permitted without prior written consent of Saab.

UNCLASSIFIED Saab Australia Pty Ltd DMS#354545 | Issue 1.0

FINAL | 26 02 2015 Page 2 of 55

UNCLASSIFIED

T A B L E o f C O N T E N T S

Introduction 4 1.1 Purpose................................................................................................................ 4 1.2 Scope ................................................................................................................... 4

Parts Inventory 4 2.1 Mechanical Parts ................................................................................................. 4 2.2 Electrical Parts ................................................................................................... 12 2.3 Required tools .................................................................................................... 17

Overview 24 3.1 Introduction ........................................................................................................ 24 3.2 How it works ...................................................................................................... 24 3.2.1 Buoyancy ...................................................................................................... 24 3.2.2 Mechanicals .................................................................................................. 27 3.2.3 Electronics .................................................................................................... 27

Building Instructions 30 4.1 Manufacturing Instructions................................................................................. 30 4.1.1 Metal Board with Electronics ........................................................................ 30 4.1.2 Submarine body and mechanical parts ........................................................ 38 4.1.3 Tubing and water tight cylinder..................................................................... 44 4.2 Assembly Instructions ........................................................................................ 47

Shortcomings 54 5.1 Warping of the 3D printer................................................................................... 54 5.2 3D printing extrusion problems with PLA. .......................................................... 54 5.3 3D printed parts did not fit together. .................................................................. 54 5.4 3D printer area not large enough for printing the larger parts. .......................... 54 5.5 Canola oil on the 3D printing platform. .............................................................. 54

Future Work 55 6.1 Preventing the relays and pumps from overheating. ......................................... 55

Improvements 55 7.1 Solutions regarding motor and servo submerged in water ................................ 55

List of Figures Figure 1 The completed submarine, labelled ........................................................ 24

Figure 2 Positions where to drill on metal sheet .................................................... 30

Figure 3 Circuit layout ............................................................................................ 31

Figure 4 Pump with servo extension ..................................................................... 32

Figure 5 Valve with 2-pin servo extension ............................................................. 33

Figure 6 Series with servo extension ..................................................................... 34 Figure 7 Power harness ......................................................................................... 35

Figure 8 Layout of electronics................................................................................ 36

Figure 9 Channels ................................................................................................. 37

Figure 10 Modified servo arm .................................................................................. 38


FINAL | 26 02 2015 Page 3 of 55

UNCLASSIFIED

Figure 11 Method A layout ....................................................................................... 39

Figure 12 Method B layout ....................................................................................... 39 Figure 13 Control rods for method A ....................................................................... 40

Figure 14 Control rods for method B ....................................................................... 41

Figure 15 Threaded rods for Method A ................................................................... 42

Figure 16 Threaded rods for Method B ................................................................... 42

Figure 17 Collar holes to drill ................................................................................... 43

Figure 18 Collars in control surfaces ....................................................................... 43 Figure 19 End cap for bladders ............................................................................... 45

Figure 20 External wiring ......................................................................................... 45

Figure 21 End cap for servos and motor ................................................................. 46

Figure 22 Holes in PVC pipe ................................................................................... 46

Figure 23 Submarine tail .......................................................................................... 47

Figure 24 Joining tail-2-a to tail-2-b ......................................................................... 47 Figure 25 Method A ................................................................................................. 48

Figure 26 Method B ................................................................................................. 49

Figure 27 Control rods layout .................................................................................. 50

Figure 28 Head ........................................................................................................ 51

Figure 29 Modified arm for head ............................................................................. 51

Figure 30 Head layout ............................................................................................. 52 Figure 31 Support rails ............................................................................................ 52

Figure 32 Completed Submarine ............................................................................. 53

Figure 33 Rough illustration of motor inside water-tight container .......................... 55

List of Tables Table 1 Mechanical Equipment ............................................................................ 11

Table 2 Electrical Equipment ................................................................................ 16 Table 3 Required tools ......................................................................................... 23


FINAL | 26 02 2015 Page 4 of 55

UNCLASSIFIED

Introduction

1.1 Purpose Provide a complete set of instructions for the school students undertaking the Subs In Schools program to build a remote control submarine.

Document the materials needed in addition to the material provided by REA to build a working submarine.

1.2 Scope Provide a complete inventory of the parts needed to build a remote control submarine. Specify a list the tools required and a complete set of manufacture & assembly instructions (assuming no prior knowledge).

Parts Inventory

2.1 Mechanical Parts

Part Number

Name Quantity Source Description Illustration

1. PVC Drain Pipe

1 REA Inner diameter: 100 mm Length: 1000 mm

2. Acrylic

Tube 1 REA Outer diameter: 80 mm

Length: 700 mm

3. Water Tight

End Caps 2 REA Diameter: 80 mm


FINAL | 26 02 2015 Page 5 of 55

UNCLASSIFIED

4. Inflatable Air Bladder

2 REA

5. Flexible

PVC Tubing 1 REA Inner diameter: 4 mm

Length: 500 mm

6. Tin Metal

Sheet 1 REA Width: 70 mm

Length: 400 mm Thickness: 0.55 mm

7. Cable Ties 15 Elsewhere Length: 300 mm


FINAL | 26 02 2015 Page 6 of 55

UNCLASSIFIED

8. Bonding Agent

1 Elsewhere For rubbers and plastics

9. Metal Rod -

Control Rod 1 Elsewhere Connect to control

surfaces. Diameter: 3/32” Length: 600mm

10. Metal Rod –

Drive Shaft 1 Elsewhere For the drive shaft

Diameter: 1/8” Length: 100 mm

11. Thread End

Rod 2 Elsewhere Connect servo to control

rod. Diameter: M3x0.5 (This is the “metric coarse” for threaded objects, major diameter: 3mm and pitch diameter: 0.5mm)

Length: 300mm


FINAL | 26 02 2015 Page 7 of 55

UNCLASSIFIED

12. 10mm x 1/4" Collet

2 Elsewhere Motor to drive shift connector Length: 42mm

13. Ball links 2 Elsewhere Inner diameter: 3/32”

14. Collar 8 Elsewhere Inner Diameter:3/32”

Securing control surfaces to control rods and securing brass to servo rods in head.

15. Neodymium

Magnets 22 Elsewhere Diameter: 4mm

16. Servo Arm 3 REA


FINAL | 26 02 2015 Page 8 of 55

UNCLASSIFIED

17. Propeller 1 REA

18. 1-to-10 Gear

Box 1 REA Comes with propeller

19. Thin Screws 6 Elsewhere Diameter: 2.5mm

Length: 20mm For connecting the tail together and connecting the 3D printed parts to the PVC pipe.

20. Nuts For

Tail 8 Elsewhere Diameter: 2.5mm

21. Thick

Screws 2 Elsewhere Diameter: 3mm

Length: 10mm For securing the motor into the tail.


FINAL | 26 02 2015 Page 9 of 55

UNCLASSIFIED

22. Silicone sealant

1 Elsewhere Aquarium sealant

23. Lead

Sheeting 1 Elsewhere Buoyancy Correction.

(Weigh down parts that are too light.) WARNING: Lead is poisonous. Use gloves and wash hands thoroughly after handling. Do not touch your face or food while handling lead.

24. Foam 1 Elsewhere Bouyancy Correction. (Lift up parts that are too heavy.)

Parts specific for method A


FINAL | 26 02 2015 Page 10 of 55

UNCLASSIFIED

25. A.i Hollow Brass Tubing

1 Elsewhere Inner Diameter: 3/32” Length: 80mm

26. A.ii Collar 4 REA Diameter:3/32” Prevent the brass tubing from sliding off the control rods. Collars that come with propeller can be used but the hole needs to be enlarged with a 2mm drill piece.

Parts specific for method B

25.B.i Screws For Servo Rods

2 Elsewhere Diameter: 2.5mm Length: 10mm

26.B.ii Nuts For

Servo Rods 2 Elsewhere Diameter: 2.5mm


FINAL | 26 02 2015 Page 11 of 55

UNCLASSIFIED

Table 1 Mechanical Equipment

27.B.iii Collar 4 REA Diameter:3/32” Keep control rods joined together. Collars that come with propeller can be used but the hole needs to be enlarged with a 2mm drill piece.


FINAL | 26 02 2015 Page 12 of 55

UNCLASSIFIED

2.2 Electrical Parts Part

Number Name Quantity Source Description Illustration

1. AXI-24007 Electric Motor

1 REA 55 turn

2. NiMH Cell Battery

1 REA 3000 mAh 6 Cell 7.2 V

3. Servo 3 REA


FINAL | 26 02 2015 Page 13 of 55

UNCLASSIFIED

4. Speed Controller

1 REA

5. Receiver + Transmitter

1 REA

6. External On/Off Switch

1 Elsewhere

7. Electrical Relays

3 REA


FINAL | 26 02 2015 Page 14 of 55

UNCLASSIFIED

8. Electrical Valves

2 REA

9. Electrical Pumps

2 REA Rolling pump

10. T-Connector Female

6 Elsewhere


FINAL | 26 02 2015 Page 15 of 55

UNCLASSIFIED

11. T-Connector Male

6 Elsewhere

12. 2-pin 200mm Servo Extensions

9 REA Length: 200mm Male to Female If 2-pin extension cables are not available 3-pin extension cables can be used. Cut the third wire off.




FINAL | 26 02 2015 Page 16 of 55

UNCLASSIFIED

Table 2 Electrical Equipment



15. Power Wire 1 REA Length: 100 mm of black wire Length: 100 mm of red wire


FINAL | 26 02 2015 Page 17 of 55

UNCLASSIFIED

2.3 Required tools

Name Usage Illustration

Hand Held Drill • Drilling out the cable tie holes on the tin metal sheet

• Making holes for the air bladder tubing on the water tight end caps

Centre Punch • Prevent Hand Held Drill from wandering.

Claw Hammer • Used with Centre Punch

• Bending control rods to the correct shape


FINAL | 26 02 2015 Page 18 of 55

UNCLASSIFIED

Drill Press • Drilling into the side of the collars

Soldering Iron • For soldering electrical parts (such as the switch)

Solder • For connecting the wires together.


FINAL | 26 02 2015 Page 19 of 55

UNCLASSIFIED

Safety Glasses • protects eyes from debris when drilling

• Protects eyes from flux when using the soldering iron

• Protects eyes from debris when cutting with the band saw

Heat Gun • Heating the heat shrink

Hack Saw • Cutting metal rod

Pliers • Holding metal rods while soldering

• Bending rods


FINAL | 26 02 2015 Page 20 of 55

UNCLASSIFIED

Spanner • Securing bolts

Side Cutters • Cutting wires to the correct length

• Cutting servo arms

Wire Stripper • Stripping wires

Tin Snips • Cutting the sheet of tin to the correct length

• Cutting amounts of Lead sheeting for Buoyancy correction.


FINAL | 26 02 2015 Page 21 of 55

UNCLASSIFIED

Band Saw • Cutting the PVC pipe to the correct length

Phillip Screw Driver

• Screwing in the servos in the servo holders

• Screw tail parts together


FINAL | 26 02 2015 Page 22 of 55

UNCLASSIFIED

Vice • Bending control rods and threaded servo rods

Metal File • Removing rough ends on control rods and end caps

Rubber Gloves • Protect hands when using super glue.

Silicone gun • Holds silicone sealant


FINAL | 26 02 2015 Page 23 of 55

UNCLASSIFIED

Table 3 Required tools

permanent marker • For marking directions on magnets

Computer • For editing and creating the 3D models

3D printer • Printing the tail and head of the submarine


FINAL | 26 02 2015 Page 24 of 55

UNCLASSIFIED

Overview

3.1 Introduction The Subs in Schools program, challenges year 10-12s to build a fully functional remote control (R/C) submarine. The program aims to create an exciting and fun learning environment for students. This manual provides students step by step instructions on how to build a baseline model. If time permits, students are encouraged to go beyond the baseline model and be innovative. Some of the problems they will face when designing the submarine will be real challenges faced by engineers building a full scale submarine. It will expose them to scientific and construction challenges that will provide opportunities for creativity.

The baseline submarine will have two air bladders for ascent and descent, six control surfaces to adjust the direction, and a propeller for thrust.

Figure 1 The completed submarine, labelled

3.2 How it works The control surfaces are used the manoeuvre the submarine in the water. Each control surface is connected to a metal rod which is attached to a servo. A servo has an arm that moves in a circle. When the servo moves, the corresponding control surfaces move accordingly.

The motor pushes the submarine forwards and backwards in the water. The air bladders control the buoyancy of the submarine to let it go up and down.

3.2.1 Buoyancy To understand how a submarine works you first need to understand how buoyancy works. The force exerted upwards by the water is called the buoyancy force. This force is equal to the weight of the fluid displaced:

𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝐹𝐵𝐹𝐵𝐹 = 𝑤𝐹𝑤𝑤ℎ𝑡 𝐵𝑜 𝑡ℎ𝐹 𝑜𝑓𝐵𝑤𝑓 𝑓𝑤𝑑𝑑𝑓𝐵𝐵𝐹𝑓

Note: Buoyancy is measured in newtons (N)


FINAL | 26 02 2015 Page 25 of 55

UNCLASSIFIED

Remember from your physics classes that weight is directly proportional to mass and the acceleration of gravity:

𝑊𝐹𝑤𝑤ℎ𝑡 = 𝑚 × 𝑤

Using this definition the buoyancy force is equal to the mass of the fluid multiplied by the acceleration due to gravity.

∴ 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝐹𝐵𝐹𝐵𝐹 = 𝑚𝑓𝑓𝑓𝑓𝑓 × 𝑤

∴ 𝐵 = 𝑚𝑓𝑓𝑓𝑓𝑓 × 𝑤

Now density is defined as:

𝐷𝐹𝐵𝑑𝑤𝑡𝐵 =𝑀𝐵𝑑𝑑𝑉𝐵𝑓𝐵𝑚𝐹

Or using symbols:

𝜌 =𝑚𝑉

Rearranging this gives:

∴ 𝑚 = 𝜌 × 𝑉

Therefore for a fluid the mass is equal to:

∴ 𝑚𝑓𝑓𝑓𝑓𝑓 = 𝜌𝑓𝑓𝑓𝑓𝑓 × 𝑉

Substituting this equation into Equation 1 gives:

∴ 𝐵 = 𝜌𝑓𝑓𝑓𝑓𝑓 × 𝑉 × 𝑤

Where: ρ = Density (kg/Litres) m = Mass (Kg) V = Volume (m3)

Where: m = mass (Kg) g = gravitational acceleration (m/s/s) Weight (N)

Equation 1

Where: B = Buoyancy Force (N)


FINAL | 26 02 2015 Page 26 of 55

UNCLASSIFIED

Example:

Imagine if I threw a basketball into a pool of water. If the volume of water displaced by the basketball is one litre then what is the buoyancy force acting on the basketball?

To answer this equation we first need to convert 1 litre into m3.

Therefore 1 litre is equal to 0.001 m3:

𝑉 = 0.001 𝑚3

But what is the density of water (𝜌𝑤𝑤𝑤𝑤𝑤)?

The answer is in the definition of a litre. 1 litre is defined as the volume of 1 kg of water at ‘standard temperature and pressure’. This translates to 25°C under atmospheric pressure of 1 atm. This means that 1 litre of water approximately has a mass of 1kg. Therefore:

𝑚𝑜𝑓 𝑤ℎ𝑤 𝑤𝑤𝑤𝑤𝑤 = 1 𝑘𝑤

∴ 𝜌𝑤𝑤𝑤𝑤𝑤 =𝑚𝑉

=1

0.001= 1000 𝐾𝑤/𝑚3

So we know 𝜌 and V. g at sea level is approximately 9.8 m/s2. Therefore the total upwards buoyancy is equal to:

𝐵 = 𝜌𝑓𝑓𝑓𝑓𝑓 × 𝑉 × 𝑤

𝐵 = 1000 × 0.001 × 9.8

Litres m3

Volume Conversion

÷ 1000

× 1000


FINAL | 26 02 2015 Page 27 of 55

UNCLASSIFIED

𝐵 = 9.8 𝑁 𝐵𝑑𝑤𝐵𝐹𝑓𝑑

What is interesting about this finding is that the force of displacing 1 litre of water is also equal in magnitude to the weight of a 1 kg object.

Now it’s your turn. What is the buoyancy force if the basketball displaced 2 litres of water? What if it was 3 litres? You should notice the trend continuing. The buoyancy of displacing 2 litres is equal to the weight of a 2kg object and the buoyancy of displacing 3 litres is equal to the weight of a 3kg object.

Neutral buoyancy is when the buoyancy force is equal to the gravitational weight of the object. In the above example neutral buoyancy is achieved if the basketball weighs 1 kg. If the ball weighed less than 1 kg it would float on the surface of the water. If it weighted more than 1kg then it would sink in the water. If it weighed exactly 1 kg then the ball would hover in the water.

Summary: To achieve neutral buoyancy in water the mass of the object in kilograms must equal the volume of the object in litres. This result only applies for water. That is:

𝑀𝐵𝑑𝑑 (𝑘𝑤) = 𝑉𝐵𝑓𝐵𝑚𝐹 𝑓𝑤𝑑𝑑𝑓𝐵𝐵𝐹𝑓 (𝐿𝑤𝑡𝐹𝐹𝑑)

3.2.2 Mechanicals

The submarine contains two air bladders and an acrylic water tight cylinder. By using pumps, air from the cylinder can be blown into the air bladders, causing them to inflate. This creates positive air pressure in the bladders and negative air pressure in the cylinder. As the bladders expand they displace a greater volume of water and therefore the buoyancy of the submarine increases. When the buoyancy of the submarine exceeds neutral buoyancy the submarine rises in the water. When the submarine is ready to descend into the water, valves in the submarine release the air back into the water tight container. This causes the bladders to contract hence the buoyancy decreases. When the buoyancy is below the neutral buoyancy the submarine descends.

Remember buoyancy is equal to the volume of water displaced. It is not equal to the amount of air in the submarine. By making the air take up a greater volume in the submarine it can change the buoyancy of the submarine accordingly.

3.2.3 Electronics The battery provides power to all electrical components. The receiver picks up radio waves from the transmitter (controller). The receiver can then send signals to the pumps, servos and valves. The battery can be recharged by disconnecting the wires between the battery and power harness. Because this wire is outside the water tight container it means that the battery can be recharged without having to open the water tight container.


FINAL | 26 02 2015 Page 28 of 55

UNCLASSIFIED

3.2.3.1 Battery The battery stores an electrical charge. When the circuit is completed, negatively charged electrons travel from the negative terminal of the battery to the positive terminal. These moving charges release energy. The amount of energy can be calculated from two quantities, voltage and current:

𝐹𝐵𝐹𝐹𝑤𝐵 = 𝐵𝐵𝐹𝐹𝐹𝐵𝑡 × 𝑣𝐵𝑓𝑡𝐵𝑤𝐹

These two quantities are best explained with a water analogy.

An electrical current is a flow of charged particles. In a river current is a flow of water particles. Because of these similarities electrical circuits can be related to a flowing river. A battery is like a hill. Water travels from the high ground to the low ground. In a similar way electrons travel from areas of high negative charge to low negative charge.

Current can be thought of as the amount of water going down the hill. In electrical circuits the current is simply the number of electrons that past a certain point in the circuit.

Voltage can be viewed as the difference between the high ground and the low ground. If there was a high difference between the high ground and the low ground then we would expect the hill to be quite steep. If the hill was steep them we would expect the water particles to be pushed by gravity more and hence travel faster down the hill. In electrical circuits the voltage is the electrical potential difference between the positive and negative terminals of the battery.

3.2.3.2 Power Harness The power harness connects all the electronic parts to the battery.

3.2.3.3 Receiver and Transmitter The Transmitter is the controller. The controller sends radio waves through the water to the receiver. The receiver picks up these waves and can decode these signals. Each button and direction on the joy stick corresponds to a channel. For example channel 1 on the receiver is normally the backwards and forwards motions on the right joystick. Each channel on the receiver has three pins. Three wires (normally red, black and white) are connected to these three pins. The black and red wires provide power to the part connected to the receiver and the white wire sends the signal. The only exception is the channel that goes to the speed controller. In that special case the black and red wires power the receiver instead of the receiver powering it. This is how the receiver gets its power.

3.2.3.4 Electrical Valves Valves have an inlet and outlet. When the valve is powered on air is allowed to flow from the inlet to the outlet.

3.2.3.5 Electrical Pumps Just like valves, electric pumps have an inlet and outlet. When the pump is powered on air is sucked in from the inlet and blown out the outlet.


FINAL | 26 02 2015 Page 29 of 55

UNCLASSIFIED

3.2.3.6 Electrical relays An electrical relay is an electrical switch. When it receives a signal (from the white cable) it turns on the connection. The receiver is not powerful enough to power the electrical valves and pumps by itself. The receiver sends a signal to an electrical relay. The electrical relay then switches on another circuit that connects the battery directly to the valves. In other words instead of powering the valves with the receiver it is powering the valves with the battery.

3.2.3.7 Speed Controller Unlike valves which are either on or off the motor can rotate at many different speeds. The speed controller decodes the signal from the receiver and adjusts the power to the motor according to the signal. This allows the motor to spin at a wide variety of speeds. The speed controller also powers the receiver.

3.2.3.8 Servo A Servo is similar to a motor however it knows how many degrees it has rotated to a much higher precision level. This makes it ideal to move the control surfaces of the submarine. It also can be powered directly from the receiver and does not need a speed controller or a relay.


FINAL | 26 02 2015 Page 30 of 55

UNCLASSIFIED

Building Instructions

4.1 Manufacturing Instructions The Build instructions will be separated into four sections: metal board with electronics, mechanical parts, tubing and pressure bladder, and assembly.

4.1.1 Metal Board with Electronics 1. All electronic parts will be attached onto a tin metal sheet. Using tin snips cut a

70mm by 400mm rectangle from the sheet of tin metal.

2. Clamp the rectangular tin sheet onto a block of wood. Using a drill, cut the holes as outlined in Figure 2. A drill has a tendency to wander if it does not start in an indentation. To prevent this from happening, a centre punch can be used. Position the centre punch over the point and gently tap the end with a mallet. This should leave a small indentation in the metal.

Figure 2 Positions where to drill on metal sheet

3. The electrical parts will be connected as outlined in the circuit in Figure 3. Instead of soldering wires between each part, servo extension cables will be used. This allows for each electrical component to be unplugged from the circuit. Begin by cutting a 2-pin 200mm servo extension wire in half with side cutters. Separate the two wires from each other and strip both sides. This can be done using wire strippers. Keep both halves (the side with the male connector and the side with the female connector).


FINAL | 26 02 2015 Page 31 of 55

UNCLASSIFIED

Figure 3 Circuit layout

4. Feed heat shrink onto the side with the male connector. Now solder the 2-pin male connector onto the terminals of a pump. If you are uncertain on how to solder then follow the method outlined below:

a. Prepare the wire. This involves stripping the wire and sliding on heat shrink. If the wire you are soldering is stranded then twist the end to keep the strands together. A small vice can be used to hold the wire/part you are soldering.


FINAL | 26 02 2015 Page 32 of 55

UNCLASSIFIED

b. Tin the ends. Heat up the wire with a soldering iron. Apply solder to the wire. If the wire is hot enough, the solider will melt onto the wire. Use the soldering iron to spread out the solder evenly across the surface. If you are having problems getting the solder onto the wire then try lightly sanding the metal first. This can remove impurities on the metal. Make sure to tin both connections (the wire and the terminals of the pump).

c. Solder together. With both ends tinned you shouldn’t need to apply any extra solder. Heat up the terminal and when the solder is starting to melt push the tinned wire onto the terminal. When the solder has set the wire should be connected to the terminal. If not, repeat steps b and c.

d. Reinforce the connection. Slide heat shrink over the solder point and heat with a heat gun. You’ll see it shrink and wrap the wire tightly. This prevents other wires from touching the exposed solder points.

Hints: It is a common mistake to forget to put on the heat shrink before soldering. Try to get into a habit of preparing the wire first before soldering. If you do forget then heat the solder and pull the wires apart.

Refer to Figure 4 for the completed pump with a 2-pin servo extension attached.

Figure 4 Pump with servo extension

5. Repeat the previous two steps with the other pump, making sure to retain the servo connectors with the female end.


FINAL | 26 02 2015 Page 33 of 55

UNCLASSIFIED

6. Cut and strip the ends of the two valves. Cut a 200mm servo extension in half and strip both ends. The two valves will be controlled from the same button on the transmitter. To achieve this we will connect the two valves in parallel. This means when one is powered, so is the other. As seen on Figure 5 the two valves are connected to one relay. The electrical valves are not directional, therefore it doesn’t matter which side is positive and which is negative.

Take one wire from each of the valves and solder them together. Now solder the negative wire from the male extension to this. Don’t forget to apply the heat shrink before soldering. Repeat for the positive wire and the other two valve wires. Hang onto the side with the female connector. Refer to Figure 5.

Figure 5 Valve with 2-pin servo extension

7. Next we want to attach servo extensions to the relays. Each relay should have two 2-pin and one 3-pin connector. The 3-pin connector is for powering the relay and sending signals. We’ll be leaving this alone. One of the 2-pin connectors will be connected to the power supply and the other will be connected to a part that requires power such as a pump or valve. When a signal is sent to the relay, the power supply powers the pump or valve.

Cut and strip the end connectors off the two 2-pin connectors (do not cut the 3-pin connector). Repeat for the other two relays.


FINAL | 26 02 2015 Page 34 of 55

UNCLASSIFIED

8. Cut another 200mm servo extension in half and strip the wires. Split the red and black wires apart on both ends and slide heat shrink onto each wire. Solder the side with the male connector to a 2-pin connector from a relay. Solder the female side of the servo extension to the other 2-pin connector.

These connections are directional so make sure to join the black with black and the red with red. Reinforce the connection by heating the heat shrink around the points soldered. Refer to Figure 6. Repeat for the other relays.

Figure 6 Relays with servo extension

9. We will connect the male 2-pin connector from each relay to a power harness. From following the previous steps you should have three spare servo extensions with female heads. Cut and strip one red and one black 70mm power cable.

We need to attach the female servo extension cables to the power cables. The easiest way to do this is to coat the ends of the three female wires and power cable with solder. Then press each servo extension cable onto the power cable with a soldering iron. Make sure not to heat the solder too much otherwise the other servo extension cables will fall off in the process.

Slide on heat shrink to the black and red power cables and then solder a male T-connector to both ends of the power cable. Be careful, T-connectors are directional. Look for the plus symbol on the T-connector; this is where the red power cable will be connected. Reinforce the connection by heating the heat shrink around the points soldered. Refer to Figure 7.


FINAL | 26 02 2015 Page 35 of 55

UNCLASSIFIED

Figure 7 Power harness

10. Solder a female T-connector to the other end of the power harness.

11. Warning: Because the battery stores large amounts of energy, you should take extra care in ensuring the battery does not short-circuit.

Short-circuiting is connecting the positive and negative end of the battery together without putting a load in the circuit. This destroys the battery and has the potential to start a fire.

To ensure we do not short-circuit the battery, start by only cutting and stripping the negative wire from the battery. Slide on heat shrink and solder the negative terminal to a female T-connector. Reinforce the connection by heating the heat shrink around the point. Repeat for the red wire on the battery.

Instead of opening and closing the water-tight cylinder to recharge the battery a cable will be fed out of the cylinder that will connect straight to the battery. This is achieved by cutting and stripping two red and two black 200mm power cables. Grab a black and red wire and solder a female T-connector to one end and a male T-connector to the other end. Repeat for the other black and red wires.


FINAL | 26 02 2015 Page 36 of 55

UNCLASSIFIED

12. Attach the battery using two cable ties. Refer to Figure 8 for the layout.

Figure 8 Layout of electronics

13. Next, position the speed controller and receiver on the tin sheet. Note the orientation as outlined by Figure 8. Secure both parts with a single cable tie making sure to also feed the 3-pin connectors from the relays through the cable tie.

14. Using a cable tie for each electrical relay, secure the three relays to the metal sheet making sure to face the 3-pin connectors towards the receiver.

15. Plug the 3-pin connectors from the three relays into channels 6, 8 and 9 of the receiver. Be careful that you put it in the right orientation. Refer to Figure 9 for what each channel does.

Electric pumps Relays Receiver

Electric Valves

Battery Speed Controller

Back

Front


FINAL | 26 02 2015 Page 37 of 55

UNCLASSIFIED

Figure 9 Channels

16. Attach the electrical pumps and valves by securing each part with a cable tie. Refer to Figure 8 for more details.

17. Connect the speed controller to Ch 1 of the receiver.

18. Connect each pump to a relay, and the third relay to the two electric valves (joined in parallel).

Ch 1

Ch 2

Ch 3

Ch 4

Ch 5

Ch 6

Ch 7

Ch 8

Ch 9

Speed Controller / Motor

Tail Elevation

Tail Yew

Head Elevation

Valves

Front Pump

Back Pump

Batt


FINAL | 26 02 2015 Page 38 of 55

UNCLASSIFIED

19. Connect the 2-pin male extension cables from the servos to the female on the power harness. Refer to Figure 8 for the complete circuit layout.

4.1.2 Submarine body and mechanical parts 1. Using a 3D printer, print out all the submarine body parts. This should include:

• four tail parts

• two head parts

• four tail control surfaces

• two front control surfaces

• fin

• servo holder head

• servo holder tail

• pressure hull spacers

• support rails for the metal sheet

Refer to Figure 32.

2. Cut and drill the three servo arms along the lines outlined in Figure 10. Make sure to keep the offcuts which will be used later. You can smooth the edges by filing them down with a metal filer.

Figure 10 Modified servo arm

3. The control surfaces of the sub will be jointed to rods. These rods will then be jointed to the threaded servo rods. There are two methods for preparing the rods. Method A involves bending the rods with pliers and using hollow brass rods to join servo pairs. Refer to Figure 11.


FINAL | 26 02 2015 Page 39 of 55

UNCLASSIFIED

Figure 11 Method A layout

Method B involves bending the rods with a hammer, soldering collars to the bend rods, and securing the servo rods with screws. Refer to Figure 12.

Figure 12 Method B layout

Hollow brass rod Bend control rod

Screw

Bend control rod

Bend control rod


FINAL | 26 02 2015 Page 40 of 55

UNCLASSIFIED

Method A:

The metal rods will be bent to the shapes outlined in Figure 13.

Figure 13 Control rods for method A

Prepare the rods for the control surfaces by cutting them to the right lengths. A hacksaw can be used to cut the rods and a metal filer can be used to remove any sharp edges. Once this is done bend the rods as outlined in Figure 13. This can be done with wire bending equipment. If such equipment is not provided a vice can be used instead:

a. Put the pair of rods in the vice with the bend points level with the top.

b. Using a pair of pliers, bend the first rod by 90°. Then bend the other rod to approximately the same angle.

c. Move the rods in the vice for the next bend point and repeat steps a and b.

Note: Putting the pair of rods in the vice at the same time ensures the dimensions of the rods are the same.

Method B:

Using a hacksaw cut two 45mm metal rods and remove the shape edges with a metal filer. The rods will need to be bent to the shapes outlined in Figure 14.

Horizontal Tail Rods

Vertical Tail Rods

Right Head Rod

Left Head Rod

Quantity: 2 Quantity: 2 Quantity: 1 Quantity: 1


FINAL | 26 02 2015 Page 41 of 55

UNCLASSIFIED

Figure 14 Control rods for method B

Note: It is best to bend the rods from the outer edges and work your way towards the middle bends.

Follow the steps below for each bend:

a. Secure part of the rod in a vice with the bend points level with the top. For bends greater than 45° position the bend point such that it is just inside the vice.

b. Take a hammer and hit the exposed end of the rod until it bends. Stop hammering if the angle exceeds 45°. If the rod is bent too much at a single point it has a chance of breaking. Untighten the vice and move the rod slightly higher in the vice. Secure and continue hammering. This will allow you to achieve bends greater than 45°.

4. Next we want to bend the threaded servo rods to the correct shapes. If you selected Method A then refer to Figure 15 otherwise refer to Figure 16 for Method B. The rods can be cut to the correct length with a hacksaw and filed down with a metal filer. They can be bent either with pliers or a vice and hammer.

Right Head Rod

Left Head Rod

Quantity: 1 Quantity: 1 Quantity: 1 Quantity: 1


FINAL | 26 02 2015 Page 42 of 55

UNCLASSIFIED

Figure 15 Threaded rods for Method A

Figure 16 Threaded rods for Method B

5. Next we will prepare the control surfaces so they can be assembled. A collar will be glued into each control surface. To ensure that the collar moves with the control surface a small rod will be inserted with the collar. Using a drill press, drill 2.5mm holes into the sides of the collars. Refer to Figure 17 for the details.


FINAL | 26 02 2015 Page 43 of 55

UNCLASSIFIED

Figure 17 Collar holes to drill

6. From the 3/32” rod, cut six 6mm length rods. This can be done using a hacksaw and vice. To increase the surface area that comes into contact with the collars, file the edges to remove any sharp edges.

7. Glue collars and rods into each control surface making sure to rotate the collar such that the bolt can be accessed through the small hole on the side of each control surface. Refer to Figure 18.

Figure 18 Collars in control surfaces

8. With a 3mm drill piece, drill a hole into the propeller so that the 1-to-10 gearbox fits in the hole.


FINAL | 26 02 2015 Page 44 of 55

UNCLASSIFIED

9. Cut the female end of an 800mm servo extension cable. On the side with the male connector strip the wires. The switch has three pins. Solider the red wire to the middle pin and the black wire to either of the side pins.

10. Place the switch into the fin and secure in place with the nuts that came with the switch.

4.1.3 Tubing and water tight cylinder 1. All cabling from the servos and motor will be fed through a hole on a water-tight

end cap. The other end cap will have holes for the air bladders. Each air bladder will need two holes in the end cap. One for pressurising the bladder and the other for releasing the pressure back into the water-tight container. These holes will be sealed up with silicone sealant afterwards.

We will start with the air bladder end cap first. To determine the location of the four holes that need to be cut out, lay the metal plate with the attached electronic parts inside the cylinder. This should give you a rough idea to where the holes will be positioned to minimise bending of the tubing. Mark these four spots with a permanent marker.

2. Using a centre punch and 10mm drill piece, cut out the marked holes from the end cap. Remove the rough edges with a metal filer.

3. Measure out the tube lengths that will be fed through the end cap. Make sure to leave at least 50mm coming out of the end. Cut the tubes with a pair of side cutters and lay them out. With a piece of masking tape, mark where each tube exits the end cap.

4. With the four tubes positioned correctly, it is time to seal up the end cap. To ensure that the end cap is water tight, we will apply silicone sealant to both sides of the end cap. Using a silicone gun, fill in the holes created in step 2 on the outer side of the end cap. A popsicle stick can be used to spread out the silicone into the hard-to-reach places. Leave to set. Refer to Figure 19.


FINAL | 26 02 2015 Page 45 of 55

UNCLASSIFIED

Figure 19 End cap for bladders

5. While the silicone is setting, drill a 25mm hole in the centre of the other end cap. A unibit (sometimes called a ‘step drill bit’) can be used to achieve such a large hole.

6. Feed all the wiring through the hole and position the wires to get a rough layout of where everything will go. Refer to Figure 20 for the external wiring circuit. With the wires correctly positioned, mark their positions with masking tape.

Figure 20 External wiring

7. Test to see if the silicone has set on the first end cap. If the tubing wobbles around in the holes, wait. When the silicone has set, turn the end cap over and fill in the holes from the other side.

8. The second end cap will also need to be sealed. While holding the wires in place, fill in the hole with the silicone sealant on the outer side. Just like on the other end cap, a popstick can be used to push the silicone into areas that are hard to reach. Leave to set and then fill in the other side with silicon. Refer to Figure 21.


FINAL | 26 02 2015 Page 46 of 55

UNCLASSIFIED

Figure 21 End cap for servos and motor

9. Drill three holes in the PVC pipe. Refer to Figure 22.

Figure 22 Holes in PVC pipe


FINAL | 26 02 2015 Page 47 of 55

UNCLASSIFIED

4.2 Assembly Instructions 1. Tail-1-a with tail-1-b, and tail-2-a with tail-2-b, will be secured together with

screws to form two larger parts. Refer to Figure 23 and Figure 24 for clarification.

Figure 23 Submarine tail

Figure 24 Joining tail-2-a to tail-2-b

2. Repeat step 1 with tail-2-a and tail-2-b.


FINAL | 26 02 2015 Page 48 of 55

UNCLASSIFIED

3. The two tail parts will be joined together with magnets. There are 12 holes on the printed parts for the magnets. Because you will be dealing with super glue and directional magnets make sure the magnetic pairs attract each other before applying glue. Remember to wear disposable gloves when handling super glue.

Glue magnets in pairs. After gluing the first magnet, work out which direction it pair will need to face. Mark the side that attracts with a permanent marker. Make sure that the side with the mark on it is facing towards the other tail part. The 3/32” rod can be used to hold the magnets while gluing.

4. The control surfaces will be controlled by the servos. Place two servos in the motor servo casing and secure each motor with four 2.5mm screws. Attach the modified arms to the servos and connect the threaded rods. Refer to Figure 25 if you followed method A and Figure 26 if you followed method B.

Figure 25 Method A


FINAL | 26 02 2015 Page 49 of 55

UNCLASSIFIED

Figure 26 Method B

5. Screw the two ball links onto the ends of the threaded rods.

6. Carefully place the motor servo casing into the submarine making sure not to bend the servo rods. Then follow the method that is correct for you:

Method A:

a. Referring to Figure 27, position the rods into their respective hole on the body of the submarine with the collars.

b. Connect the two ball links to the control surface rods and slide the hollow brass tubing over the control surface pairs.

c. Prevent the hollow brass tubing from sliding off by tightening the collars.


FINAL | 26 02 2015 Page 50 of 55

UNCLASSIFIED

Figure 27 Control rods layout

Method B:

a. Referring to Figure 26, place the collars in the tail of the submarine. Slide on the 4 control rods and tighten the grub screws in the collars. To ensure the grub screws cut into the rods well enough to grip, make sure the screws are well done up tight, then back off and tighten again (possibly a few times).

b. Bolt the two ball links to the collars.

7. With the motor servo casing in place, attach the drive shift via a collar to the motor and insert the motor into the motor servo casing. Screw the motor into place with two 3mm screws.

8. Join the propeller to the 1-to-10 gear box and tighten the grub screw. Attach this to a collar which is connected to the motor shift.

9. Glue the magnets into the ten holes found on head-1 and head-2. Remember you are dealing with super glue so wear gloves and ensure the magnets are glued in the correct direction. Refer to Figure 28. Use a whiteboard marker to make sure the magnet pairs attract each other. Refer to step 3 for more details.


FINAL | 26 02 2015 Page 51 of 55

UNCLASSIFIED

Figure 28 Head

10. Screw and bolt one of the off-cuts of a servo arm to the servo in the head of the submarine using a washer. Refer to Figure 29.

Figure 29 Modified arm for head

11. Insert the two control rods with their collars into the head of the sub. Slide the two servo brackets onto the servo and attach this to the control rods. Secure the servo holder to the head with two 2.5mm screws. The layout of the head can be seen in Figure 30.


FINAL | 26 02 2015 Page 52 of 55

UNCLASSIFIED

Figure 30 Head layout

12. Attach the brass tubing to the control rods. Secure in place by tightening the grub screws.

13. Attach the support rails to the metal sheet. Refer to Figure 31.

Figure 31 Support rails

14. Slide the metal sheet with the electronics into the pressure hull. Connect the tubes and cables and push the end caps on.


FINAL | 26 02 2015 Page 53 of 55

UNCLASSIFIED

15. Slide the spacers onto the pressure hull and insert into the PVC piping. Slide the cable for the switch through the middle hole in the PVC pipe and connect this to the corresponding cable from the pressure hull. Connect up the 3 servos, motor, switch and two bladders.

16. Attach the tail and head to the PVC pipe. Bolt them into place with a 2.5mm screw. Place a drop of super glue onto the two edges of the fin and attach to the PVC pipe. Your submarine should now look like Figure 32.

Figure 32 Completed Submarine


FINAL | 26 02 2015 Page 54 of 55

UNCLASSIFIED

Shortcomings

5.1 Warping of the 3D printer Description: Parts printed from the 3D printer sometimes were noticeably affected by warping. This caused the 3D parts not to fit together.

Solution: The following changes were made to reduce the effects of warping:

1. Reduce the temperature of the filament head from the default (215°C) to 210°C.

2. Calibrate the build platform. Levelling the build platform before the 3D print ensured that the head started with the correct Z height.

5.2 3D printing extrusion problems with PLA Description: During printing, the filament would sometimes have difficulties coming out of the filament head. As a result gaps in the layers would form, reducing the overall strength of the printed parts. This could be due to the heat rising from the head causing the PLA to soften where the drive gear grips are.

Solution: Dipping a sponge in canola oil and then dabbing the filament with a sponge seemed to prevent the heat from rising into the filament and hence preventing the filament from softening around the drive gear grips. A sponge holder can be printed that sits on top of the extruder. The sponge can then be dipped in oil and placing it in the sponge holder where it can coat the filament as it is fed through the extractor.

5.3 3D printed parts did not fit together Description: PLA is very sensitive to heat and as a result expands when heated. This results in printed parts increasing in size and no longer able to fit in the PVC pipe.

Solution: When designing the parts allow for a 1mm gap between any joints.

5.4 3D printer area not large enough for printing the larger parts Description: The tail and a couple of the other parts had dimensions that were too large be printed by the MakerBot 5th gen 3D printer.

Solution: The 3D printer parts were scaled down to fit the dimensions of the 3D printer. The tail on the other hand was far too long to be printed as a single piece. To achieve an appropriate length the tail was printed as two separate pieces and glued together in the assembly process.

5.5 Canola oil on the 3D printing platform Description: The filament would occasionally not stick to the 3D printing platform due to a layer of canola oil on the build platform. This resulted from the solution in 5.2.

Solution: During the process of inserting a new filament, stop the filament from touching the build platform. A ruler can be used to collect the filament as it is fed through the extractor.


FINAL | 26 02 2015 Page 55 of 55

UNCLASSIFIED

Future Work

6.1 Preventing the relays and pumps from overheating When the two relays attached to the pumps are closed, the pumps connect directly to the battery. Adding a resistor to each pump would limit the current to the pump and hence reduce the heat produced.

Improvements

7.1 Solutions regarding motor and servo submerged in water The motor and servos are suspended in water for the submarine to be operational. This is not ideal as impurities in the water have the potential to conduct electricity and thus cause the motor and servos to short-circuit. A possible solution would be to redesign the motor to lie inside the water-proof cylinder. A hole for the drive shift will have to be created in the water proof cylinder. An oil-based substance such as wax could form a layer between the water and the inside of the water proof cylinder. This would prevent water from entering the cylinder temporally and allow for the movement of the drive shift. Refer to Figure 33 for more details.

Figure 33 Rough illustration of motor inside water-tight container

Oil based substance Motor

Plastic layer

Drive shift Water-proof container

subs in schools build manual - rearea.org.au › wp-content › uploads ›...

Documents