Over nine consecutive days, he noticed that the times indicated by the clocks were identical, even though one pendulum was swinging to the left and the other to the right.
All these studies have helped to shed light on the secret of self-synchronization in pendulum clocks. The synchronization is due to the clocks transferring energy to each other via the coupling bar in the form of mechanical vibrations. The clocks start moving exactly out of phase, in other words, when the vibrations exerted by one pendulum clock on the coupling bar are exactly cancelled by the vibrations exerted by the other.
Will any pair of pendulum clocks eventually synchronize — or only certain types? And can you synchronize more than two pendulums? Only since the start of this millennium have scientists started shedding further light on these questions. A large ratio indicates a strong interaction between the pendulums, whereas a small ratio corresponds to a weak interaction. A , as Ellicott had observed. At about the same time, James Pantaleon from the University of Alaska Anchorage carried out a fascinating experiment consisting of two metronomes placed on a light wooden board sitting on two empty fizzy-drink cans so the whole system could roll.
He found that the metronomes reached a common rhythm but oscillated in the same direction — rather than in opposite ways as Huygens and Ellis had seen. Our set-up consisted of two metronomes mounted on a rigid metal bar suspended from leaf springs figure 1.
Confirming previous findings, we observed at least two types of synchronized motion. If the bar is relatively light, the metronomes start to oscillate synchronously in the same direction. But if the metal bar is heavier than a certain value, they oscillate at the same frequency but in opposite directions, just as Huygens saw.
The critical transition mass in our experiment was found to be 2. Courtesy: P G M Hamels. It consists of two mechanical metronomes coupled through a metallic bar, which is elastically attached to a fixed support by means of springs.
It appears that a light coupling bar facilitates the onset of complete synchronization because the coupling strength is then relatively large.
A heavier bar, in contrast, has a weak coupling strength, which results in the metronomes oscillating out of phase.
The pendulum in each clock consists of a 5 kg metal mass attached to the lower end of a wooden rod just under 1 m long. Courtesy: Luis Alberto Olvera Cardenas. Consisting of two pendulum clocks coupled through a wooden structure, the clocks end up moving in complete synchronization. The pendulum in each clock consists of a 5 kg metal mass attached to a wooden rod roughly 1 m long. Using this equipment, we noticed that, after about 30 minutes, the pendulums were both oscillating in the same direction and at the same frequency.
The clocks stayed synchronized for as long as potential energy was stored in the weights to drive the escapement mechanism. Indeed, each clock has a device that rewinds the weights roughly every 30 minutes, which means they could keep running for as long as desired. Using this equipment, we confirmed the secret behind the onset of synchronization — first observed by Huygens all those years ago. As he suspected, it is due to the transmission of vibrations — and thus energy — through the wooden structure on which the clocks are attached.
But we have also made some new observations that Huygens never noted. For example, clocks that are placed on the same wooden table and start moving in synchrony are no longer reliable time-keepers, losing 47 seconds per hour, which is almost 19 minutes a day.
In short, no. Under certain conditions, the rotors can revolve synchronously in the same direction but in other cases the rotors start spinning in opposite directions. The latter can be useful as it can cut or even eliminate the vibrations of the common support when the rotors are running. The human body, for example, has many different kinds of oscillating rhythms — including respiration, heartbeat, neuronal activity and blood perfusion — and when these synchronize with each other, very little energy is used.
The generation of epileptic seizures, for example, is closely linked to the abnormal synchronization of millions of neurons see September We therefore believe that a thorough investigation of the synchronized pendulum clocks that Huygens first studied all those years ago could help us to get a better understanding of synchronization phenomena throughout the physical and the biological world.
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Enter e-mail address This e-mail address will be used to create your account. Reset your password. Please enter the e-mail address you used to register to reset your password Enter e-mail address. Registration complete. And the clock keeps the pendulum running! A clock is essentially a motor: a device that uses energy from some source to drive the hands of the clock around and around. The source of the energy varies; it could be a tightly wound spring, or a weight dropping down after being raised to some height.
The energy is dissipated in the friction in the various gears that are used to reduce the speed of the motor for the different hands. The speed of this motor would depend only on the friction in the various gears The role of the pendulum is critical. In part of its motion back and forth, it stops the gear train from moving. As the pendulum moves further in its swing, it releases a tooth of the gear, which rotates a little until another part of the pendulum catches another tooth.
So each swing of the pendulum allows the clock "motor" to rotate only a fixed number of teeth usually one tooth exactly.
Here's a simple example of an escapement :. The next trick is to have the teeth of the gear give a little push to the pendulum as each tooth is released. This compensates for the friction in the pendulum which would otherwise stop the pendulum in a few hours. So the energy source in the clock is keeping the pendulum swinging, as the pendulum regulates the rotation of the gear They do stop without intervention. Grandfather clocks have to be reset.
They are designed so that you can wind them back up. A clock with an eight-day movement required winding only once a week, while generally less expensive hour clocks had to be wound every day. Eight-day clocks are often driven by two weights — one driving the pendulum and the other the striking mechanism, which usually consisted of a bell or chimes. Such movements usually have two keyholes on either side of the dial to wind each one as can be seen in the Thomas Ross clock above. By contrast, hour clocks often had a single weight to drive both the timekeeping and striking mechanisms.
Some hour clocks were made with false keyholes, for customers who wished that guests to their home would think that the household was able to afford the more expensive eight-day clock.
All modern striking longcase clocks have eight-day movements. Most longcase clocks are cable-driven, meaning that the weights are suspended by cables. If the cable was attached directly to the weight, the load would cause rotation and untwist the cable strands, so the cable wraps around a pulley mounted to the top of each weight. The mechanical advantage of this arrangement also doubles the running time allowed by a given weight drop.
They do keep on going with regular rewinding of the driving spring , rising of the driving weight or replacement of the battery. What were you expecting!? Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 6 years, 5 months ago. Active 3 years, 5 months ago.
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