Of all the different types of rides that can
be found at an amusement park, there’s very few that can deliver the same terrifying thrills
as a drop tower. These impressive machines allow riders to
experience a straight freefall from dizzying heights, coming to a safe controlled stop
just moments before reaching the ground. This type of attraction packs a big punch
given its small footprint, with the tallest rides extending to heights in excess of 120
metres, or 400 feet. Modern drop towers also come in a wide range
of design styles with some clever twists that make them even more thrilling, including the
most recent innovation of tilting riders forward so they fall face first. Despite all the variations that exist today,
the original design concept for the freefall ride can be traced back to a single attraction
that was built for the New York World’s Fair in 1939. This ride was known as the Parachute Jump,
and it consisted of a 250-foot steel tower with 12 parachutes suspended from a large
frame with steel cables. Riders would hang below the parachutes in
canvas seats that were hoisted to the top by an electric motor, and a drop mechanism
would release them into a controlled fall as the parachutes slowed the descent. A similar type of wooden structure was used
to train military paratroopers in the Soviet Union as early as the 1920’s, but the technology
was later patented in the United States where it was modified for civilian use as a thrill
ride. This ultimately led to the development of
the first free fall type attraction which was popularized by Swiss ride manufacturer
Intamin in the 1980’s, and they later improved the concept by introducing the first modern
drop tower in 1995. Fast forward to today, and there are now many
ride manufacturers that produce different variations of the drop tower, however they
all rely on one of two fundamental principles; Either electromagnetism, or pneumatics. The original design from Intamin employed
an electromagnetic system, and we’ll start by taking a look at this type of ride first. The tower itself usually consists of a cylindrical
steel structure that is anchored to a large concrete foundation, and this is topped off
with a machine room that houses the electric lift motors. Depending on the configuration, there may
be a single ride gondola that wraps all the way around the tower, or there may be several
smaller gondolas equally spaced around the circumference as shown here. The vehicles travel along rails that are fixed
to the exterior of the structure, and each one is paired with a catch car that is mounted
on the same set of rails above. The catch cars are suspended from the top
of the tower with steel cables, and they can be moved up or down independently using the
lift motors. When the ride is ready to begin, each catch
car is lowered onto the corresponding gondola where a mechanical latch automatically engages
to lock them together. They are then hoisted up to the top of the
tower, and when given the all clear, the latches are disengaged to release the vehicles from
the catch cars. After a brief freefall, the gondolas are brought
to a safe and controlled stop by a magnetic braking system, which is both the most important
and most innovative part of the whole ride. At the bottom of the tower, there are 2 rows
of inert metal plates that run parallel to each set of rails, and these align with permanent
rare earth magnets that are mounted to the ride vehicles. Each gondola has 4 strips of magnets, and
they are arranged in pairs to create 2 thin gaps that are just wide enough for the plates
to pass through. When a gondola drops down the tower, the moving
magnetic field induces closed loops of electric current in the plates called Eddy currents,
and these generate their own temporary magnetic field that opposes the motion of the permanent
magnets. The result is a magnetic drag force that acts
on the gondola opposite to its direction of travel, which is similar to the repulsive
force that you can feel when trying to push two magnets together with matching poles. The magnitude of the drag force is directly
proportional to the amount of current flowing through the plates since this determines the
strength of the opposing magnetic field, and the amount of current is proportional to the
speed of the vehicle. What this relationship tells us is that the
braking force will be highest when the permanent magnets just begin to pass over the plates,
and the force will decrease linearly as the gondola loses speed, thus providing a smooth
non-linear deceleration. This method of magnetic braking is commonly
referred to as Eddy current braking, and it is used quite frequently in the amusement
industry because it converts kinetic energy directly to heat without any need for moving
parts or frictional wear. The system is also completely fail-safe because
it does not rely on an external power source, and the brakes will still function in the
event of a power outage. The only real downside is that magnetic brakes
cannot bring the ride to a complete stop all on their own, since there will be a point
during the deceleration when the magnetic drag force perfectly balances the force of
gravity, and the gondolas will continue to move downward at a slow but constant velocity. In order to prevent a hard landing on the
ground, the ride vehicles simply touch down on hydraulic cylinders that are positioned
around the base of the tower which absorb the remaining kinetic energy. Overall, this type of electromagnetic drop
tower is a safe and dependable ride that is still popular today, however it wasn’t long
after Intamin introduced it that American ride manufacturer S&S developed their own
system using compressed air. These towers usually have a steel truss structure
with a square cross-section, and the ride gondola travels along the 4 corners with small
guide wheels so there is no need for external rails. Inside the tower is a massive air accumulator,
which is basically a storage tank that can hold air under high pressure, and it is surrounded
by 4 smaller pneumatic cylinders called shot tanks. Each cylinder contains a piston that can travel
up and down, and this is connected to a steel cable that exits through small seals at the
top and bottom. The cable passes around a sheave at each end
of the tower where it then connects to the gondola, thus forming a closed loop around
the outside of the structure. As the 4 pistons move in one direction on
the inside of the tower, they pull the cables around the sheaves and drive the vehicle in
the opposite direction on the outside. When the system is depressurized, the gondola
will naturally rest at ground level while the pistons are raised to the top of the shot
tanks, and this is how each ride cycle begins. Once passengers are loaded, a small amount
of air is moved from the accumulator into the top of the pneumatic cylinders, which
pushes the pistons down and lifts the vehicle. The ride computer then weighs the vehicle
by measuring how much air pressure is required to balance it, and this determines how much
air will be used to achieve the desired speed and g-force. Additional air is then released into the cylinders
to lift the gondola to the top of the tower, where it locks into a mechanical brake that
holds it in place before the drop. At this point, the accumulator is pressurized
to its full operating pressure by moving air from an external receiver tank, which is paired
with a large air compressor and drying system in a separate building. When the ride is launched, the compressed
air in the accumulator is released into the bottom of the shot tanks, which shoots the
pistons upward, releasing the holding brake and driving the gondola down towards the ground. As the pistons approach the top of the tower,
the air in the top portion of the shot tanks becomes compressed, thus absorbing the kinetic
energy and slowing the gondola down before bouncing it in the reverse direction just
like a compressed spring. The pistons and gondola then oscillate up
and down several times as the motion is dampened by slowly releasing air from the cylinders,
and the vehicle is lowered back to the starting position once the system in depressurized. One of the benefits of using compressed air
for a drop tower is that the entire ride is controlled by a single pneumatic system that
does not require separate mechanisms for lifting and braking, yet the redundancy of multiple
cylinders and cables still ensures that the ride is fail-safe. The intensity of the ride can also be adjusted
by varying the amount of air that is used for each launch, making it possible to achieve
a drop that is nearly twice as fast as a free fall. The launch can even be reversed by releasing
compressed air into the top of the shot tanks instead of the bottom, shooting the gondola
up the tower with an acceleration in excess of 4 G’s. Regardless of the underlying ride system,
electromagnetic and pneumatic drop towers both offer intense thrills that are unmatched
by any other ride, making them popular installations at amusement parks all around the world. And while the experience of riding a drop
tower may be terrifying, you can be assured that these rides are always designed with
guest safety in mind first. Safety is the number one priority at any amusement
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