Time ball at Sydney Observatory

Made by Maudslay, Sons & Field Ltd in London, England, 1858.

The time ball at the top of the tower at the front of the Observatory was the reason for the establishment of the Observatory and so is of great significance.It is still in its original condition apart from the addition of an electrical motor and some improvements made by HC Russell in the 1870s.

Before radio the only way to convey accurate time was through a visual signal. Accurate time was especially important to ships setting out on a long voyage as they needed to adjust and calibrate their ...


A yellow and black time ball made of cast iron, with a cyliner, piston, rack and pinion lifting mechanism, safety lock, electric motor and ball.

Observatory stock numbers 9 and 10.


The Time Ball consists of a cast iron cylinder, piston, rack and pinion lifting mechanism, safety lock, electric motor and ball. The cylinder is 30cm diameter and 3 m long. Approximately 7 liters of soapy water fills the bottom of the cylinder to act as a buffer for the piston. The piston is a 10cm thick block of rubber with a bleeder valve to adjust rate of descent. The rack extends from the piston to the Time Ball and is 7.5 meters long. A pinion engages into the rack by a slide gear, which enables the electric motor to raise the rack. A large hand wheel is also attached with a pawl gear to prevent back-slipping. The Time Ball is attached to the top of the rack and is raised 2.7 metres.

At 6 minutes to 1PM the pinion is engaged into the rack and the electric motor switched on. It takes approx 2 minutes and 50 seconds to raise the ball to the top of the mast. The safety lock is then engaged and the pinion is disengaged. At precisely 1PM a signal from the atomic clock disengages the safety lock, causing the Time Ball to drop. It drops approx 2 metres immediately and the back pressure in the cylinder causes it to drop the remaining distance at a slower rate.

Carey Ward 10.3.83
Maudslay, Sons & Field Ltd 1858

Cite this Object

Time ball at Sydney Observatory 2017, Museum of Applied Arts & Sciences, accessed 18 November 2017, <https://ma.as/232664>
{{cite web |url=https://ma.as/232664 |title=Time ball at Sydney Observatory |author=Museum of Applied Arts & Sciences |access-date=18 November 2017 |publisher=Museum of Applied Arts & Sciences, Australia}}
This object is currently on display at the Sydney Observatory.

This object record is currently incomplete. Other information may exist in a non-digital form. The Museum continues to update and add new research to collection records.

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