July 28, 2015 | By Alec

While many of us have, at one point or another, finished a cool and original 3D printing project that we’d like to share with the world, you have to be well-prepared to score in 3D printing competitions as popular as Thingiverse’s Make It Float Challenge. The high quality of entries is best illustrated by the amazing first prize winner. For David Choi took home the first prize for designing and 3D printing a complex and fun GO-GO AirBoat that is not only a motorized, propeller-powered payload-sensing boat, but also comes with the most comprehensive guide you’ll have ever seen on Thingiverse.

David Choi, perhaps better known under his web handle Macakcat, is an electronics designer and prototype developer based in Brooklyn, New York. Having extensive experience in developing fun 3D printing projects, he set out to build a fun and floating educational experience that offers unexperienced builders (as well as more experiences ones) a challenge to learn from. ‘I wanted to create an educational piece that one can learn from and expand on, by developing and enhancing fundamental and motivational experiences while building, testing, and playing,’ he says about his entry. ‘Mathematics, physics, and electronics weren't the easiest things for me to learn, but I think with passion you can learn anything, and this can be rapidly fueled by successful, real-world experiments that are made fun.’ This project is therefore especially aimed towards young builders, students and others looking to get more familiar with making.

And in that respect, the GO-GO AirBoat could hardly have been more fun. In a nutshell, it’s a fun little boat that is easily3D printed, but has been equipped with enough motors and sensors to be able to sense how many pennies it has been loaded with. Once enough are on board, the motor comes to life and the propeller sends the boat racing through your bathtub. ‘Load your cargo containers with up to 20 pennies each (US cent tested). The cargo containers are infinitely stackable! GO-GO's cargo bay area can support up to 5 columns of cargo containers. Many combinations of load and weight distribution possible,’ Choi says. It can thus also be used to test different stacking options and to see what it takes to keep the boat afloat.

The GO-GO AirBoat in action.

This is thus especially educational in respect to motors and sensors. And it’s payload-sensing secret is remarkably easy: ‘A floating piston inside the boat's smokestack is free to move with the water level and triggers the motor to drive when a certain depth is achieved. This sensor employs a simple infrared LED, phototransistor, and a Darlington pair transistor amplifier stage for switching of a small DC motor,’ Choi reveals. ‘The depth-sensor trigger point can be mechanically altered using different, floating piston heights of your own creation.’

However, the 3D printing itself is fairly easy. The GO-GO AirBoat only consists of four STL files, all of which can be 3D printed on just about every desktop FDM 3D printer. Choi himself used a MakerBot Replicator 5th Gen in PLA, 3D printing without rafts or supports. Results will be best at 214 degrees Celsius, 0.20 mm resolution, a 10% infill and 3 shells. To ensure a watertight seal, its best to 3D print the first layer at 30 mm/s. Little to no post processing or gluing during assembly is needed.

The main scientific issue behind this cool little boat is obviously the ratio between weight and movement. ‘We want to calculate the maximum number of pennies we can load onto the GO-GO AirBoat before it begins to sink. Hopefully your GO-GO AirBoat will shove off before it reaches this maximum penny value. Since we're loading the pennies into cargo containers, it'd be nice to predict if our next container will lead to a sunken disaster or not,’ Choi explains. ‘Boats float due to their buoyancy in water. Buoyancy is a function of the volume of the fluid displaced and the density of the fluid displaced, along with the local acceleration due to gravity. The less dense object will be more buoyant (float), and the denser object will be less buoyant (sink). In our case, so long as our boat is less dense than the water it displaces, it will stay afloat!’

Recreating the GO-G AirBoat is thus an excellent opportunity for gaining experience with resistors, potentiometers, capacitors, diodes, LED's, DC motors, bipolar junction transistors (BJT's), Darlington pair transistors, phototransistors as triggers, circuit board layout, and soldering – which is probably a major reason for its victory. And through an amazingly detailed set of instructions, all these steps are completely and comprehensively explained. ‘The instructions provide step-by-step calculations and descriptions of how the individual circuits function together as a whole. Use this model as an activity or introduction to subjects such as weight, mass, displacement, density, buoyancy, and center of gravity. Topics covered within the instructions focus on mass, density, and basic algebra. Logic and reasoning skills are exercised to translate calculated values to the real world,’ Choi advises.

The full step-by-step and very educational approach to this problem can be found in the instructional guide attached to the GO-GO AirBoat here. It is well worth checking out even if you don’t decide to recreate this fun little boat, as Choi has written up a very accessible and educational overview of all these engineering steps – perfect as a refreshing course or for people who only discovered their love for making years after leaving school. However, Choi has even prepared a list of further challenges for more experienced engineers, mathematicians and physicists, and computer sciences – so there’s something for everybody to work with. It’s obvious why this entry took home the gold.



Posted in 3D Printing Applications



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