World Athletics@TDK

[No.1 The Hammer Throw] A great parabola drawn by muscle strength and technique

How is it possible to throw a heavy iron ball of 7 kg over 80 meters?

The hammer throw originates in a Scottish traditional sport in which athletes compete by throwing a heavy piece of iron attached to a wooden handle. However, it is said that its origin goes back to a hunting or combat tool called a sling, from the prehistoric era. It is like a webbing strap with an embedded stone at one end. The strap is used to throw the stone by swinging it overhead and releasing it at high speed. It is also seen in the world’s famous Statue of David by Michelangelo, on his left shoulder. With the right technique and experience, the tool has a range of more than 100 meters, which made it a more powerful weapon than a bow and arrow.

In the hammer throw as a track and field event, the hammer is a metal ball attached to a grip by piano wire.

The hammer weighs 7.26 kg for men and 4.00 kg for women, just like the shot put. In competition, athletes throw the hammer from within a small circle of 2.135 meters in diameter, the same as for the shot put. The world record for men’s shot put is 23.12 meters (Randy Barnes, 1990) while the world record for the men’s hammer throw is more than three times that at 86.74 meters (Yury Sedykh, 1986). The difference comes down to the acceleration gained by widely swinging the metal ball which is attached to a piece of piano wire of about 1.2 meters. To throw a hammer, the thrower first swings the object a few times to gain momentum, then they turn their body around to swing it in a circle, gaining centrifugal force by turning three or four times.
After gaining enough acceleration they finally release the hammer and try to keep their balance within the circle (recovery) in order to avoid a foul. This is the series of movements in a hammer throw.

A rhythmical turn that accelerates the hammer

Muscles in the whole body are engaged in accelerating the hammer. Take bowling for example, the bowler moves their body according to the movement of the heavy ball, so that energy is transmitted from the muscles to the ball to give it momentum. The same goes for the hammer throw. Distance cannot be achieved simply by throwing with force.
As indicated in the figure below, the thrower turns his body rhythmically in response to the hammer to accelerate momentum. As the body turns, the hammer starts to revolve around the body following its movement. The thrower uses all of their body’s muscles to pull up and accelerate the hammer before transmitting the gained force to it and releasing it into the air. At the same time, the thrower retains a mental image of its trajectory, according to which the best timing and angle are determined to release the hammer. It is the combination of these three elements, muscle strength, technique, and mental visualization that facilitate the great parabola beyond the 80 meter line.

Small yet powerful, a neodymium magnet that helps minimize HDD

When swinging a heavy hammer, the body goes out of balance due to the centrifugal force. First-class throwers can maintain excellent throwing form by controlling their steps and turns to maintain their balance. With devices with rotating mechanism, such as machine tools and automotive engines, reducing vibrations is an important engineering challenge. However, this vibration mechanism is applied in the vibrator embedded in smartphones etc. A smartphone on silent mode vibrates when an eccentric weight attached to a small motor rotates. Because the center of gravity is offset from the rotating axis, the rotation creates a force that spins the motor, which results in the vibration that shakes the device as a whole. This motor is minuscule, i.e. several millimeters in diameter, and is used a neodymium magnet, the most powerful of all permanent magnets.

One of the major uses for neodymium magnets is the HDD voice coil motor (VCM) mounted in computers and HDD recorders. HDDs can read and write on a disc when used as a magnetic head attached to a swing arm rapidly scanning over the magnetic disc. A VCM controls the movement of the swing arm by means of the magnetic flux between the magnet and the coil.
As HDDs become smaller, the VCM also needs to be smaller with high performance. For this reason a powerful neodymium magnet is indispensable for VCM magnets. Neodymium magnets are not only used in VCMs, but are also used in flat spindle motors that spin magnetic discs at high speeds. In this instance the neodymium magnet is used in powder mixed with plastic to make a plastic magnet. A neodymium magnet is just like the trained muscles of a hammer thrower, it is a small yet powerful magnet with high performance.

Smartphone vibrator
The eccentric weight is placed so that its center of gravity offsets the axis of the driving shaft, which generates vibration. In order to make the motor smaller, a neodymium magnet is used for the internal magnet.

A powerful neodymium magnet helps to make the VCM for the HDD smaller and thinner. The spindle motor also uses a neodymium magnet in the plastic magnet, which is a mixture of a powdered neodymium magnet and plastic.

The NEOREC Series is Based on Neodymium Magnets
The neodymium magnet in the NEOREC series is based on TDK’s magnetic materials technology developed over the years, and the latest sintering technology. TDK offers the series which consists of a variety of products catering to many different uses such as HDD VCM, various motors and actuators, drive motors for HEV/EV etc. We have also developed a neodymium magnet that contains no rare or expensive heavy rare-earth materials (such as Dy and Tb).

Neodymium Magnets