06 - Constructing - Construire - 06

1 Curves for smooth driving

At the interchanges of motorways, how can one make a road which is smoother and safer for more efficient driving?

In a car, when one is travelling at a constant speed and the steering wheel is turned uniformely, the trace which the car makes is called "clothoid".
This trace reduces the centrifugal forces and gently links a straight line with a curve.
Using the clothoid design makes driving easier and more efficient. This curve is also used for railways, subways, roller coasters…

2 The genius of bridges

How can one build longer and more daring bridges?
The first bridges used wood and stone. Iron, steel and concrete bridges appeared later.
New problems arrose: the dynamic behaviour of suspension bridges, the complexities of managing road construction.
Now computers and their calculability power allow these problems to be resolved, step by step, achieving bridges which beat all records.
Storeboelt East Bridge in Denmark (with a span of 1624 m), Millau's viaduct in France (343 m high)...

3 The rotary engine, Revolutionary!

Piston engines work in an up and down motion. For rotary engines, energy is produced through rotation.
How does compression and combustion occur in these types of engines ?
The volume of gas in each chamber changes extremely as the rotor moves, eventually causing combustion in the engine. The housing is in the shape of an “epitrochoid”, a curve traced by a point inside a circle as it rolls around the outside a fixed circle.
A triangular rotor rotates around a broad bean-like housing, all of its vertices touching the housing at any time.
The space between he housing and the rotor is divided into three chambers.

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