Cuckoo clock

A cuckoo clock made for the Setechnic’s clock contest, features a standard clock with a cuckoo.


The clock has a standard minute-hand and second-hand with 1/60 gear ratio composed of  worm/24t, 20/20t and 16/40t. There is not hour-hand because of the available place. The pendulum mechanism is not a vertical pendulum but a double horizontal pendulum with two masses (61mm wheels). The escapement wheel is composed of two 6-tooth wheels. The accuracy is +-10% for 1 second because of play. The autonomy is rather good, with 50cm string, a 5/1 ratio before the escapement wheel and 150g of counterweight, the autonomy is 30min. With a pulley and 1m of string and 300g, it may be reach 1h of autonomy.


Concerning the cuckoo, it is powered by a weight lifted up by the minute-hand (one time each hour), when it reaches a special point, it falls down and make the cuckoo get out . The mechanism is simple and has no need to be lifted. Consequently, the clock has one counterweight to power all functions. The counterweight can be easily lifted up thanks to the sliding wheel.


Despite the fact that the cuckoo out mechanism has a non-linear motion, I think that it doesn’t get out enough time. The ideal behaviour must be a normal behaviour during the lifting and a viscous behaviour during the fall in order to slown down the cuckoo. To finish, I will certainly create the building instructions !

The building instructions are available. You can watch them by browsing my website or

Download the Zip Archive of the Clock’s instructions, 5 mo, ZIP.

Design in 2011

(11) Comments


    is it possible to modify this say to have an arm that moves forward and back with the second hand, (like the cuckoo but more frequent) and also instead of having a weight having tension of rubber bands instead?

    This is just brilliant. I was just creating a model in order to teach children time reading but with 3 NXT motors. This model is far better.
    Thanks for the inspiration.

    You should have a close look to the escapment wheel. In order to obtain a good functionning, the escapment wheel must be at a correct distance of the double pushing lever. So try to modify the distance by sliding the two escapment wheel on them axle.

    Because the cuckoo clock is the most advanced clock I did so I prefer to make building instructions for advanced creation.

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