Ch4 - Turtle
Turtles are an extremely varied species. We distinguish carnivorous and herbivorous species, terrestrial and aquatic ones. The smallest can weigh merely 142 g, the heaviest – up to 817 kg. The one thing they have in common, however, is the thick shell protecting their bodies.
Turtles are known for their longevity. Sea species can live up to 70 years, tortoises stay alive even 150 years. One of the oldest known specimen belonged to a radiated tortoise species. It died at the age of 188.
Turtle shell looks thick and hard. Appearances are deceptive however, and this shell can be very sensitive. Some of the species love to receive shell massages. The staff of San Diego Zoo discovered that gentle touching makes Galapagos tortoises squint their eyes in delight.
The sluggishness of turtles is widely known. In one hour they can cover a distance of approximately 260 meters. To compare, in the same amount of time a human can easily cross 4800 meters.
Despite their awkward and clumsy appearance, turtles are very agile in water. They can stay underwater for three or even five hours, in record-breaking cases.
When it comes to diving, the current title holder is the leatherback sea turtle. It can dive as deep as 900 meters, and its speed in water is admirable: it swims at 35 km/h.
Sea turtles migrate for thousands of kilometers along specified paths. It is still unknown how they find their way to the beaches they were hatched on, but every couple of years they come back ashore to the exact same spot, to lay their eggs.
All turtles are oviparous. It means females lay eggs, from which young turtles hatch. The sex of the offspring is decided by temperature of the surroundings. If the eggs are laid in a warm place, turtle moms can probably expect daughters. If turtle moms would rather have sons though, they should lay their eggs in a colder spot.
Fate of many turtles has undergone dramatic changes due to human activity. To those animals, humans are the greatest danger. Hotels, roads or restaurants built nearby sea shores disorient female turtles, which lose their tranquil nesting spots. As a result, the number of young turtles continuously drops.
Lights shining from restaurants built by the water pose a threat also to hatchlings. Instinctively, they follow the moonlight to get to the sea, but can get confused by artificial lights. They often arrive to crowded, busy areas, where they end up trampled by pedestrians, or ran over by cars.
In many countries, firefighting employs professional fire-fighters and a volunteers (VFD). Moreover, some organizations establish their own firefighting units: you can find them in airports, railway stations, refineries.
Build
To build this model, you will need LEGO Education WeDo 2.0
Explore
The construction represents a turtle. Each time something suddenly appears in front of it, the turtle gets startled and hides its head.
The model relies on three electronic elements.
1. The motion sensor is placed below the turtle, in the base. The sensor lets the program check if anything appeared in front of the turtle.
2. The motor propels the mechanism, which hides and pulls out the turtle’s head.
3. The hub powers and controls both elements connected to it, in accordance with the created program.
1. The blue bricks are making up the turtle’s body and also limiting the neck movement. Thus, the neck can move only forwards or backwards.
2. The neck slides on the smooth tiles, which pave the space between the blue bricks.
3. The turtle model stands on four thick legs.
1. Just like a real turtle’s shell protects its internal organs, this orange shell protects the mechanism moving the LEGO turtle’s neck.
2. By retracting the neck, the turtle can also hide its head inside the shell.
In order to make the turtle’s neck move, a mechanism changing the motor’s circular motion into reciprocating motion is required. You can find it in this model.
1. Turtles usually move quite slowly, which is why there is a reduction gear installed – it slows down the axle motion.
2. Two small gears rotate and push the white gear racks together with the turtle's head.
3. At the end of the neck brick there is a blockade. The neck cannot move too far, because the blockade will stop the gears and prevent the neck from escaping the rail.
4. On the other end, you can see the turtle’s head and its prying eyes.
Program
Let’s begin the turtle program with the Start Block.
