Product Idea

Wall Clock

This is something I've been working on for quite some time. A mechanical clock, a real timepiece, made only from stock LEGO parts. It's about as precise as an old grandfather clock, and requires absolutely no interaction except the occasional minor adjustment of the big hand. You don't even have to wind it up, the electrical self-winder will do!

Features:

  • 100% original LEGO, including escapement, weight, decorations etc.
  • about 860 parts
  • true second tick, defined by a pendulum ca. 1m in length, resting on a knive-edge bearing
  • easily adjustable escapement made of common LEGO parts
  • separate seconds dial, regular concentrical dial for small and big hand
  • 24 hours display with rising and setting sun and moon symbol
  • moon phase dial, exact to about 1% of the true 29.4 day moon period
  • weight-driven
  • self-winding mechanism, battery box doubles as weight
  • autonomy of more than eight weeks with one set of batteries

Watch the video on flickr!

I wanted to make a pendulum clock that would run long enough to be wound up no more than one or two times a day. That is really hard with only plastic parts, because all the friction in the mechanism eats up a lot of energy. Friction must be reduced to a minium. So all axles are carried in exactly two bearings. The pendulum rests on a knive-edge, and is linked with a flexible coupling to the escapement. The number of gears is reduced as much as possible within the existing LEGO selection. But that wasn't enough for a run time of more than a handful of hours before I had to wind up

To extend the run time, either the weight must be very heavy, which will warp and bend the frame of the clockwork and cause it to stop. Or the weight will have to have a very long path to travel down, which means several meters, and you'd have to cut a hole in the floor.

I solved the dilemma by making the mechanism as sturdy as possible, and using an endless chain on which the weight actually climbs upwards. About every two hours, depending on the precise length of the chain used, the weight will reach the end of the chain loop, and the lever attached to the PF switch will turn on the motor. The complete weight assembly wil now climb up the chain, taking about three seconds, until at the top the switch will be opened again when the lever is runnung against a stop. The process will repeat itself until the batteries run down. My clock is now running autonomously for about eight weeks, and still going strong!

Every other day I need to adjust the clock by two or three minutes, but that is only in comparison to a radio-controlled clock. That precision is okay for a homebrew plastic timepiece. I enjoy the soft, slow tick, and my kids keep looking at the sun and moon slowly rising and setting on the day/night dial. The moon phases change very slowly, but the large 60-tooth turntable has made a full revolution since I last changed batteries (one full moon cycle is half a revolution).

As a Lego set, the building experience would likely be challenging: The mechanism must run more than smooth for the clock to work. But I feel it's quite rewarding to look at that clock, know the time, and to know I have built it myself.

Mr_Kleinstein