Ch7 - Dragonfly
Dragonflies have a distinctive body shape: their abdomens are narrow and elongated, their resistant torsos winged, their heads well-formed and fitted with two enormous eyes. Dragonflies also have long, thin legs that allow them to tread on the ground and seize their prey in flight.
These beautiful, colorful insects are counted among the best fliers in the animal world. In one second they can cover a distance equal to 100 times their body length. They fly quickly, sometimes they happen to fly backwards, also hovering in the air is not a problem for them.
Dragonflies’ wings are very important in recognizing their species. Scientists patiently examine veins on the wings to confirm the variety they are dealing with.
Those wings are quite special. Most insects can fold their wings in a way they adhere to their torsos. Dragonflies are unique in this area – even when they are not flying, their wings remain unfolded or pointed upwards.
Dragonflies’ wing span varies depending on the species. The largest known dragonflies have a wing span of 19 cm, the smallest merely 2 cm. However, we know of extinct species, which prove that dragonflies used to be much bigger. For example, their wingspan could reach up to 75 cm.
Dragonflies are considered to be very primitive animals that have not changed much over time, whether it comes to their physique or behavior. Scientists claim that dragonflies have already lived on Earth 300 million years ago. In comparison to the modern species, they used to be bigger. Nonetheless, the morphology of their bodies stayed practically the same.
The dragonflies’ lifestyle also remained similar. They are still dangerous predators, just as they were in ancient times. It applies to both adult dragonflies and their larvae – naiads, which live in water reservoirs. To sum up, they did not change much in the evolution process.
The dragonflies', and all other animals', ability to fly is connected with various adaptation mechanisms, which were reflected in their bodies. In the process of evolution, different animals developed different flying techniques and apparatuses, which actually make it possible.
Birds, amazing fliers, have transformed their forelimbs into wings; their feathers, as many scientists claim, used to be scales of reptiles – ancestors of birds from ancient times.
Flying mammals also exist – bats. They developed webbed wings, which start from the fingers of their forelimbs and end at the side of their torso and rear limbs; at first glance they look similar to birds’ wings.
Many well-known flying species belong to the largest animal group – insects. In this group we also find species, which were the first to possess the ability of active flight. In a way, dragonflies were pioneers in this area.
Build
To build this model, you will need LEGO Education WeDo 2.0
Explore
The dragonfly model shows the agility and unpredictability of the real insect’s movement via a complicated gear mechanism.
This model relies on two electronic elements.
1. The hub powers and controls elements connected to it, in accordance with the program created.
2. The motor propels the whole mechanism and makes the dragonfly actually move.
The first gear mechanism is responsible for changing the axis of rotation from horizontal to vertical, as well as for increasing power at the expense of speed.
1. The motor propels a small cogwheel, which transfers power to a larger one. It decreases the speed of rotation.
2. The first transmission also elevates the axis of rotation.
3. The second transmission is angular. It means the axle can be set vertically; moreover, this gear slows down the axle rotation.
1. A sturdy arm connects the dragonfly to the base. Two long beams with holes constitute an indispensable chassis for all cogwheels of the upper gear mechanism.
The upper gear transmission transfers drive through the arm and to the dragonfly, so that it can rotate around its own axis.
1. At the end of the axle, there is a small cog installed. It is a start of the second gear transmission and the spin axis of the arm as well.
2. Despite using five cogwheels, the rotation speed does not change. The first and the last gear have the same size; the middle ones merely transfer the drive.
3. The insect is fixed on a tilted axle to resemble a real dragonfly.
The long vertical axle, the arm's spin axis, channels drive from the base to the arm. The arm itself is quite heavy, so the axle must have additional support to stay vertical.
1. The long axle goes through three plates with holes. They ensure it will not slant away.
1. The dragonfly turns on the arm attached to the base, and also around its own axis.
2. This element limits the insect's rotation. The drive from the motor is transferred from the first to the last axle. Once the dragonfly reaches the blockage, the whole arm starts to move.
1. You can arrange the colorful wings as you wish.
2. Just like a real dragonfly, this model has a long, striped abdomen.
Program
This is the Start Block. It begins the program for the dragonfly model.
