There are few things to which we pay as much attention as the passage of time. We don’t want to be late for work, or a date. Even more importantly, we don’t want to age and die. Good time keeping is an all important human activity, and we started to worry about it as soon as we abandoned our hunter-gatherer lifestyle and agriculture and commerce emerged.
Measuring time needs two things: a repetitive process to mark equal increments of time, and a way of tracking and displaying the result. The first timekeeping devices relied of course on the movement of the sun. Ancient Egyptians, around 3500 BC, built obelisks that, by casting a shadow on the ground at different positions, gave an approximate idea of the time. Next came the use of some medium that was consumed at a regular pace: candle, incense, water and sand clocks are examples. A great advancement came with the advent of the mechanical clock, and here is where the escapement mechanism appears.
[Scott] doesn’t have any kids, but he’s the sort of type that likes to get ahead of the game. Of course this means spending time in his garage to build a rocking cradle. Usually, these are acquired from a baby shower and are powered by batteries. Terribly uncool, considering a mechanism to keep a pendulum swinging has existed for hundreds of years now. His latest project is the escapement cradle – a cradle (or hammock) that keeps rocking with the help of falling weights.
The first video in this series goes over the inspiration and the math behind determining how much energy it will take to maintain a swinging pendulum. The second video goes over a very rough prototype for the escapement mechanism with some woodworking that looks dangerous but is kept well under control. The third video puts everything together, rocking a cradle for about 10 minutes for every time the weight is lifted to the top.
Every once in a while we get sent a link that’s so cute that we just have to post it. For instance: this video from [Ludic Science]. It’s a wind-up chicken toy that kicks a pendulum back and forth. No more, no less.
But before you start screaming “NOT A HACK!” in the comments below, think for a second about what’s going on here. The bird has a spring inside, and a toothed wheel that is jammed and released by the movement of the bird’s foot (an escapement mechanism). This makes the whole apparatus very similar to a real pendulum clock.
Heck, the chick toy itself is pretty cool. It’s nose-heavy, so that under normal conditions it would tip forward. But when it’s wound up, tipping forward triggers the escapement and makes it hop, tipping it backward in the process and resetting the trigger. The top-heavy chicken is an inverted pendulum!
And have a look, if you will indulge, at the very nice low-tech way he creates the pivot: a bent piece of wire, run through a short aluminum tube, held in place by a couple of beads. Surely other pivots are lower-friction, but the advantage of using a rod and sleeve like this is that the pendulum motion is constrained to a plane so that it never misses the chicken’s feet.
Our only regret is that he misses (by that much) the obvious reference to a “naked chick” at the end of the video.
Many have tried, but [Christoph Laimer] has succeeded in designing a working, (relatively) accurate clock nearly completely from 3D printed parts. Every gear, pulley, wheel and hand of [Christoph’s] clock is printed. Only a few screws, axles, a weight, and a string are non-printed. Even the crank to wind the clock is a 3D printed part.
[Christoph] designed his clock in Blender. It took quite a bit of design work to create parts that would work and be printable. Even more work was involved in printing over 100 failed prototype parts.
One might think that [Christoph] is using the latest printers from the likes of Makerbot or Utimaker to achieve this feat. It turns out he’s using a discontinued Rapman 3.2 printer. Further proof that even “older” printers are capable of great things! [Christoph] does run his printer rather slowly. Printing a single gear with 0.125 mm layers and a 0.4 mm nozzle takes him 2 or 3 hours.
Mechanically, the clock is gravity powered with an anchor escapement. Rather than a pendulum, [Christoph] chose to use a balance wheel and hairspringassembly to govern the escapement. Even the spring is printed from standard PLA. The weight is suspended from a pulley block. The clock isn’t particularly efficient. 70cm of height will run the clock for only 2 hours.
[Christoph’s] clock has proven to be accurate to within 1/4 second per hour. He hasn’t provided temperature stability data – but being PLA, we’d suggest not getting it too hot!
Electronics are undoubtedly the basis for our modern society. Leaving out transistor-based devices, and a mechanical clock would be one of the most intricate devices man has come up with. As a Mechanical Engineer, I thought it would be a fun challenge to design and build my own gear-driven clock.
Because clocks have obviously been invented, I wouldn’t be starting from scratch, and I don’t think I could have figured out an escapement on my own. I explain my initial clock escapement and gear reduction design thoughts in this post, and originally getting the escapement to work was my biggest fear.
As seen in the first video after the break, the escapement gear is still a big problem, but not really for the reason I expected. The shaft that the gear sits on seems to be bent, so it allows the escapement to “go free” for part of it’s cycle, losing any sense of accurate timekeeping. Be sure to also check out the second video, especially around 1:50 when I show what happens when an escapement gear goes much faster than a normal clock. Continue reading “Designing and Building a Wooden Mechanical Clock”→
Put a case around it and it would be a grandfather clock but for now it’s a pendulum clock made from LEGO pieces. The video after the break shows a great overview of the build. You can see the workings at several different angles, as well as a clip that has been sped up to show the movement of the weights over time. One weight, made from dead AA batteries, drives the clock and the other weight switches the winding motor. That motor acts to automatically wind the clock when the drive weight reaches the end of its rope.
This is a nice departure from the majority of clock projects we see as it utilizes mechanical concepts instead of electronic. Most of [Pmroskelly’s] build details are shared as comments on the Picasa album found at the link above. There are also some other videos such as the one showing how the escapement works.