Monday, November 30, 2015

TAV (Terrestrial Aquatic Vehicle)

This is a long overdue post for a fun little science project...  My child came up with the idea for TAV (Terrestrial Aquatic Vehicle) and designed it a few months ago, for a class project in Grade 3. Interestingly, he designed it not for a Science project, but an Economics one! His classroom had a project called "Market Place", where students are supposed to come up with ideas for little stores and businesses: make & sell products, earn (fake) money and then use the money for their expenses including living costs, education, retirement savings, etc. A simulation of real-life economics...

The kid decided to create a Tech company and recruited a couple of his classmates for the project. He came up with the idea for "TAAV - Terrestrial Aquatic Aerial Vehicle".
Once the idea was conceived, the practical work was divided up among the three in the team. The first team member created a simple "terrestrial" version of the vehicle: a plastic water bottle with wheels fitted to the bottom and a propellor in the front attached to a DC motor that helps the vehicle move. The second member - my child - added the aquatic feature to the vehicle, the details of which we will go over below. The third team member added a few more features to the aquatic version, providing more power and stability.

The kids had only about two weeks for the entire project - design through execution - and in the interest of time, the aerial part had to be cut off and set aside for a future phase. Hence, the final product turned out to be TAV(Terrestrial Aquatic Vehicle) rather than the originally intended TAAV(Terrestrial Aquatic Aerial Vehicle)  :)

TAV - The Design Process:


  1. DC Motor
  2. 9V Battery for power supply
  3. Battery snap connector
  4. Switch (to switch the power on & off)
  5. Propellor (used one that came with a SnapCircuits kit)
  6. Small rectangular tin (a spice tin that we emptied out)
  7. 4 Wheels & a couple of axles to hold them (LEGO pieces)
  8. Pieces of thermocol/polystyrene (light material to help with floatation)
  9. Tape for binding materials together


We started off by trying to use the same device created for the Terrestrial version by team member#1 - a plastic water bottle with wheels fitted to the bottom and a propellor in the front, attached to a DC motor - and adding the aquatic features. Quickly found out that the plastic bottle was not stable while floating on water, especially with the weight of the extra attachments of battery & propellor. Plus, stabilizer wings were needed on either side for floatation & balance in water. Hence, a decision to slightly redesign the vehicle was made, to make it more suited for an aquatic environment.

A flat surface provided by a small rectangular spice tin seemed better suited for attaching the wings, as well as for providing a stable surface to mount the battery pack & switch. LEGO wheels and axles were attached to the vehicle to help it move on land. Thermocol/polystyrene pieces from some packing material were tested and proved to be good floatation devices. Wings were made out of these and attached to the spice tin. To balance out the weight of the structure and help it float well, a tail made of thermocol was also added. Tape was used to attach all of the components to the spice tin.  The length of the wings and the tail were determined purely via trial & error.

The next issue was the propellor. The Terrestrial version's propellor was not powerful enough to produce the thrust needed to move across water. We replaced it with a bigger propellor from our SnapCircuits kit. Also, while testing the vehicle in aquatic mode, it was observed that the battery pack and the motor were getting too close to the water and being splashed on. To reduce the proximity to water, an extra piece of thermocol was placed on top of the spice can and the motor & battery were mounted on top of it. Now, things were working smoothly in water. BTW, we tested out the aquatic features of TAV in our bathtub :)

While testing the vehicle on land, the front part of the vehicle had crashed against a chair leg and sent the propellor flying. So, an additional "bumper" made from thermocol was attached to the front of the vehicle, to prevent the propellor from hitting anything. We did not run into any technical issues beyond this point, and testing proved smooth, both for land and water.

A closer look at the machine...

Construction of TAV turned out to be a fun family project... Here are a couple of videos of the machine being tested:  The first one shows the TAV version without the extra "bumper" in front, and without the piece of thermocol on top on the spice tin. The second & third videos show both those additions, while testing out the aquatic features...

Market Place

On the day of Market Place, one of the team members brought in a baby bathtub, and that's what was used to demo the aquatic features of TAV. The demo was set up outside the classroom to provide plenty of space for the vehicle to move on land, and to minimize any spills while showing off the aquatic features. The TAV team sold tickets for the demo of their product, and explained their design of the prototypes. And they made a huge profit auctioning off "kits" to make the TAV, to their classmates after the demo.

At the end of the day, the little tech company did really well. TAV was the second highest earner in Market Place, coming in right after a book and snack store :) And our little CEOs decided to invest part of their profits into developing the next version - TAAV - with the aerial features added in.

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