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Mechatronics Learning Studio

 

The Mechatronic Airboat

 

Simon Dube, Isabelle Gilbert, Mireille Gascon, Dept. of Mechanical Engineering, University of Ottawa

 

 

 

Introduction

An airboat is a flat bottomed vessel usually used in swamp and marshy area where the water is shallow. It is made of three main parts which work together: the propeller produces a column of air, air passes across the rudder which deviates the air column and the hull keeps those two components out of the water. For the first part of our project we wanted to build an air boat from material that you would usually find in your household so to minimise the cost.  Then, we established a second goal to make it more reliable, powerful and efficient.

 

Prototype 1

We used an air hockey table fan as the propeller and we powered it with a direct current brushed motor from a toy car powered by six 1.5V batteries in series. Two switches were installed as they work together to invert the direction of the current our airboat the possibility to reverse. We also use a potentiometer to adjust the power given to the motor to be able to adjust the speed of the watercraft. You can find potentiometers in the household switches that adjust the lights intensity or the sound volume.

For the rudder, two galvanised stainless steal plates were attached in parallel with each other. The steal plates move from left to right to steer the boat with the help of a direct current brushed motor taken from another toy car. The motor contains a plastic gear inside to reduce the speed and increase the torque. Also it would complete a full rotation but stops once it is turned at the max due to the geometry creating resistance. We sealed the space between the rudder and the propeller to maximise the effect of the air column.

For the hull a Styrofoam board was use as it is light and easy to carve its shape which is flat bottomed. The Styrofoam board floated perfectly, but all the weight was in the back and we wanted to make sure it would not tip, so, weight was added at the front of the ship to level it. The propeller and the rudder were installed on the hull. This prototype isn’t perfect. Its major deficiency is that the remote control is not wireless and the thick wire interfered with the steering of the boat. So without the wire, we believe we would have had a much better control of the airboat.

 

Prototype 2

After we had achieved our original goal to build our project out of materials found at home only, we decided to come up with a second goal which was to make it more powerful, more efficient, but most importantly, to make it wireless. So we went and bought a wireless remote, we chose the “TACTIC TTX240” as it was recommended to us by the dealer. It is a 2.4 GHz transmitter, so there is no interference by the FM/AM radio frequencies. The remote also came with the matching receiver in which all the components of the airboat (propeller motor, servo motor powering the rudder) will be connected to.

We also got a more powerful motor that propels the propeller and a servo motor to control the rudders more precisely. We decided to keep the original design since we found that it was efficient even with the mediocre equipment. We constructed the tunnel that would hold the propeller and the rudder out of an aluminum sheet. This way, it was lightweight but sturdy enough. But with testing, we realised that it wasn’t sturdy enough, so we had to add an aluminum bar around to prevent it from wiggling from side to side. We mounted the motor on a bracket and riveted it in the wind tunnel. The bracket is made of metal which helps to dissipate the heat created and released by the motor. We then used O-rings and glue to attach the propeller to the motor. We had purchased a two blade propeller because we learnt that the fewer blades there are on a propeller, the more efficient it is. But using more blades on a propeller allows reducing the diameter of the propeller and still getting an equal thrust. We decided to go with the more efficient one since size wasn’t an issue for this prototype. The propeller we chose has a diameter of 8 inches and a pitch of 8 inches. The pitch represents the angle of the blades; it is calculated by measuring the distance travelled by the propeller in a gelatine substance when completing a full rotation. The higher the pitch, the higher the thrust will be but the harder it’ll be for the motor to turn the propeller. To be able to control the speed of the motor, we also had to get an electronic speed controller “ElectriFly C-25” that will be connected between the receiver and the actual motor which is a “Titan 550 Motor 12t”. While adding this to our circuit, the power source must now be connected to the ESC instead of the receiver.

For the rudder, we built it using the exact same design as we did for our original design with the only difference being that we used more bars on the plates to act as a skeleton to give it more strength and rigidity. We also used the servo motor “HiTEC servo HS-311” to turn the rudders to allow a better, more accurate control of the steering as mentioned earlier.

As for the power source, we purchased an “Onyx 1800mAh 7.2V NiCD” battery pack with the charger as they are more efficient than AA batteries and more convenient since it’s rechargeable.

All the electrical components except for the motor and servo motor are stored in a plastic container to prevent water from coming into contact with them causing a malfunction. We also decided to add a wireless camera mounted on the cover of the plastic container on the watercraft to be able to control the airboat without having to keep eye contact with it. One has to simply connect the receiver to a television. The camera we got is the “DIY Security Camera Kit” due to our low budget so the quality isn’t the best but is sufficient for its purpose on our project. The camera itself uses a 9 volts battery which is also stored in the container.

The hull is once again made out of a Styrofoam board because of its floatability, stability and lightweight. The mechanical components were installed in the stern of the boat while the electrical components in the container were installed in the bow of the ship to balance the weight. The airboat still tilts backwards but this is better as it provides better aerodynamics to help the boat to “get out of the water” while in motion.

 

 

Poster

(Prototype 2)


 

(User Guide)

Mechatronic Airboat

It is strongly recommended to read this manual entirely before using this watercraft! Damage from modifications or misuse will void the warranty!

Warranty and repair

This product comes with a one year limited warranty. This manufacturer warrants this product to be free from defects in materials and workmanship for a period of one year from the date of purchase. During that period, the manufacturer will, at its option, repair of replace without service charge any product deemed defective due to those causes. You will be required to provide a proof of purchase (receipt). This warranty does not cover defects due to abuse, misuse, alterations or accidents.

 

Transmitter

The transmitter requires 4 “AA” batteries. Non-rechargeable alkaline or rechargeable nickel-cadmium (NiCd) or nickel-metal hybrid (NiMH) cells can be used. Do not mix old and new batteries. The vehicle does not include an “AA” battery charger so one will need to be purchased if choosing the rechargeable batteries.

To install the batteries, slide the battery door on the bottom of the transmitter open. Install the batteries in the holder as shown on the battery door. Close the battery door.

IMPORTANT: Do not operate the watercraft with weak batteries as it could result in possible loss of control!

Press the power switch to turn the transmitter on. The LED should also turn on. If it doesn’t, check the batteries to make sure they are firmly in place. If the LED blinks, the batteries are weak and should be replaced. When in operation, the antenna should be rotated to its full upright position.

Watercraft

The included battery should be charged for at least four hours the first time then requires a 3 hour charge time using the charger which is also included. Once fully charged, plug the battery to the vehicle in the right direction; black connected to black and red connected to red. Turn the device on by pressing on the push button until the blue light turns on. The watercraft will make a beeping sound.

Once the transmitter and the watercraft are turned on, make sure all systems are operating according to the movement of the transmitter’s controls:

            Steering: Turn the steering wheel left and right, then; make sure that the rudder turns in the desired direction. If it doesn’t, reverse the position of the Steering Reversing switch. The Steering trim is used to adjust the direction of the rudders and the Steering rate adjusts the limits to which the rudders can turn on each side.

            Throttle: Squeeze the throttle trigger and get familiarized with its rate. If it isn’t to the users preferences, adjust it using the throttle rate knob.

The transmitter/receiver have a Fail-safe function which will automatically center all servo motor (rudder) if the receiver loses signal from the transmitter and regains its normal operation once the signal is regained.

Once the watercraft is not in use, turn the transmitter off, turn off the receiver by pressing on the push button, and disconnect the battery to make sure the battery doesn’t drain unnecessarily.

To use the camera, the receiver must be plugged in to a power source and also plugged into the video/audio of a television. If only “snow” is appearing, use the knob to adjust the receiving frequency until u get the signal from the camera.

Troubleshooting

Does Not function; Make sure the remote and the watercraft are on.

Remote/watercraft turned on but the light doesn’t come on: check the batteries and replace/recharge if necessary.

Interference or the rudders glitching: Out of range, operate model more closely.


 

Step by Step (the Assembling)

 

Materials:

  • Propeller      

  • Two motors (one being a servo motor preferably)       

  • Electronic speed controller     

  • Power source

  • Wires

  • Bracket

  • Wood or metal to build the frame

  • Plates (for the rudders)

  • Remote control and its receiver     

  • A wireless camera, its receiver and a television

  • Foam board

1. Assemble the propeller to the motor making sure it is turning in the right direction. Mount it on a bracket measuring its height to make sure the base is high enough that the propeller can turn freely.

 

 

(Prototype 2)

 

2. Build the frame for the rudder. For our first prototype we used wood for the frame and wrapped it with plastic to enhance the air tunnel. For our second prototype we used an aluminum sheet bend in a square shape as the frame. It also serves the purpose of the air tunnel. Make sure the frame is big enough to hold the propeller. (should be bigger than the diameter of the propeller)

 

(Prototype 1)

 

 

(Prototype2)

 

3. Build the rudders. The rudders of both our prototype were made of two plates. We recommend adding bars on the plates to add stiffness. Connect your motor to the rudders using a plastic bar so your rudders move from left to right simultaneously. Assemble to the base. Also add the propeller.

 

 

 

(Prototype 1)

 

(Prototype 2)

 

4. Your motors will need power source. For our first model, we connected the motor directly to 6 AA batteries in series. The second motor used to control the rudders was powered by only 3 AA batteries. Our second model required an electronic speed controller to which the battery pack will be connected to. This battery pack will also supply power to the servo motor used to steer the watercraft.

 (Prototype 1)

 

 

(Prototype 2)

 

(Prototype 2)

5. Build your own remote control if a premade wireless remote control was not purchased. Switches and a potentiometer will be required to vary the speed and rotational direction of motors.

 

(Prototype 1)

6. A camera can be added on the boat. We used a wireless security camera as it wasn’t pricy. The receiver needs to be hooked up to the television.

(Prototype 2)

7. Once everything is assembled you get one cool air boat!

 

 

 

(Prototype 1)

 

(Prototype2)


 

Prototype 2:  Electric Circuit