Built for Eurobrick's C-model competition.
The set I've used is 42007 Moto Cross Bike, consisting of 253 parts (extra parts were not used). This choice was just because I had already ordered it, and that it fulfilled my only requirement of having at least a few gears. After a few really simple contraptions I decided to build a clock. I've read about escapement before, but have no experience. Didn't really expect it would work, but where's the harm in trying?
One of the wheels and the small panels with their triangular tips looked like they could make a pinwheel escapement. All the simple solutions where the panels moved together failed. The spokes in the wheel are placed in pairs, and the panels will only fit in the big gaps. This meant that the panels need to move a fairly long distance from each other and with good precision. Of course they also need to do this without much friction as well as be rigid enough to be able to transfer force from the wheel to keep the pendulum going.
Getting the escapement working took a whole day. A second day was spent one making it more reliable and somewhat prettier. After scavenging straight liftarms to increase the length of the pendulum the running time increased from 9 to 13 seconds (using the full length of the chain). There are two gears left that I tried to use for increasing the time further, but it was too much. The mechanism is struggling already. For that reason I also chose the simple (and light) arm that unfortunately doesn't face the same way as the pendulum. Using the other wheel as clock face would have been great, but it was needed to provide enough weight and centering the arm on it would have been difficult anyway.
The weight that drives the clock doubles as counterweight, which makes it possible for the clock to stand on its legs despite the heavy pendulum. Once it runs out of chain it will fall off the table.