My mechanical clocks

[Davidz90]

Seeing so much positive feedback and nice comments in my recent clock topic, I decided to revive this one (I hope it's OK) with some new mechanisms.

Grasshopper escapement

This is a type of clock mechanism invented by John Harrison in 1622. The name comes from the fact that the moving parts resemble legs of a grasshopper. Its remarkable property is the fact that the pendulum is in constant contact with the mechanism, so it is driven all the time, instead of short pushes that most other mechanisms deliver.

In my Lego rendition, I tried to simplify the design by tying it directly to the pendulum. The result is a remarkably simple and efficient design:

You can see that the escape wheel (40T gear) moves mostly forwards, but goes back (recoils) for a brief moment. This recoil, caused by the pallet engaging the tooth, causes the other pallet to disengage. To allow this recoil, the resting points of the pallets need to be movable - this is acomplished by the black T-brackets.

And here is an even simpler rendition, designed for very small swing angles:

My goal here was to find out how efficient it can be; I wanted to make a clock that runs for 1000 hours on single rewind. This proved to be a bit too ambitious, in the end I settled on 170 hours:

 

[lcvisser]

Amazing. Clocks are mesmerizing and it’s amazing that you can build them from Lego!

(I have an old mechanical clock, but my girlfriend made me halt it because it’s too loud )

Edited January 15, 2022 by ludovisser

[Davidz90]

34 minutes ago, ludovisser said:

Amazing. Clicks are mesmerizing and it’s amazing that you can build them from Lego!

(I have an old mechanical clock, but my girlfriend made me halt it because it’s too loud )

Maybe you can disable the striking mechanism but keep it running? Or the ticking is the problem?

The amazing thing is that not only you can make a Lego clock, but actually you can match the efficiency and accuracy of "real" grandfather clocks, at least the lower quality ones. 

[lcvisser]

1 hour ago, Davidz90 said:

Maybe you can disable the striking mechanism but keep it running? Or the ticking is the problem?

It’s the escapement that’s loud. The clock has no striking mechanism. Oh well, it still looks good on the wall 

[Davidz90]

Small update on my grandfather clock. Made it bigger (mostly wider) and most importantly, portable. Can be disassembled into few large pieces for transport.

 

[1980SomethingSpaceGuy]

Very nice! Well done!

[Davidz90]

Now something a little different. The striking mechanism that chimes 1,2,3... 12 times depending on the hour:

The basic idea was to use a little additional clock mechanism, where the swinging pendulum acts as a hammer that hits the bell. The challenge was in counting the swings and stopping the pendulum at the right moment.

[lcvisser]

I had to watch this video a couple of times on a big screen to wrap my head around all that is going on here. Amazing! 

[Davidz90]

3 hours ago, lcvisser said:

I had to watch this video a couple of times on a big screen to wrap my head around all that is going on here. Amazing! 

Thanks! Yeah, it took me several weeks and many failed prototypes to get it working. Funnily, I decided to design my own striking mechanism because I felt that existing ones were too large and complicated, and this is supposed to be a "simple" solution (and it really is, with maybe half the amount of moving parts as compared to other solutions).

[GerritvdG]

On 5/15/2022 at 8:26 PM, Davidz90 said:

Now something a little different. The striking mechanism that chimes 1,2,3... 12 times depending on the hour:

Well done, very interesting, keep posting these videos! 
 

How did you get interested in mechanical clocks? 

[Davidz90]

3 hours ago, GerritvdG said:

How did you get interested in mechanical clocks? 

About 7-8 years ago, I have seen some amazing Lego clocks on Youtube and decided to try it myself. Started with very simple things like this one:

...and it quickly escalated from that XD In fact, recently I've written two research papers on grasshopper escapement:

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.103.062208

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.105.055001

so one can say that I went from playing with Lego to doing actual science :D

[Davidz90]

Another striking mechanism, this one is much simpler and I believe that it is the most compact one ever built:

 

[GerritvdG]

37 minutes ago, Davidz90 said:

Another striking mechanism

Excellent idea to use the chain pieces as a pattern! Seems pretty reliable..

Reminds me of a barrel organ :D

[Davidz90]

6 minutes ago, GerritvdG said:

Excellent idea to use the chain pieces as a pattern! Seems pretty reliable

Thanks! This idea is not mine, there are a few designs with threads, the rest is original though. Yes, the thread solution seems to be the most reliable. 

[Davidz90]

For anyone interested, I have made instructions:

 

[Davidz90]

Big project that took me a good portion of the last month. A large (182 cm high) tower clock.

20220608_090635 by David_Z1, on Flickr

The clock face is a plate sandwich under slight tension

20220608_090610 by David_Z1, on Flickr

The case is built like a cabinet, the mechanism can slide in/out like a drawer. This makes working on the mechanism vastly easier. Case is brick built, with four longitudal spars (technic beams) going through its length.

20220608_084451 by David_Z1, on Flickr

 

The video:

 

[Davidz90]

A new escapement design. By using two wheels, I could make it symmetric, whcich should in theory help the accuracy. Initial tests are encouraging, I got a maximum of 0.5 seconds of error in a 6 hour test run.

 

[lcvisser]

That grandfather clock is massive! Is it allowed to stay in the living room? 

 

I built this simple escapement (by Ben van de Waal) once. I never did any performance test on it, but I guess that it has quite some friction due to the two gears meshing. Can you comment on what level of accuracy you think is feasible with LEGO? Is this last one your most accurate one so far?

[Davidz90]

16 minutes ago, lcvisser said:

That grandfather clock is massive! Is it allowed to stay in the living room? 

 

I built this simple escapement (by Ben van de Waal) once. I never did any performance test on it, but I guess that it has quite some friction due to the two gears meshing. Can you comment on what level of accuracy you think is feasible with LEGO? Is this last one your most accurate one so far?

Currently the grandfather clock stays in my room. Couldn't convince my mother that it fits the living room XD

Yes, I think that the last one might be the most accurate. Here are some results I got by recording the sound and measuring the time between ticks:

test_1h_1 by David_Z1, on Flickr

test_1h_2 by David_Z1, on Flickr

First one shows the period. It is intended to be 1.6 seconds and comes very close to this, with about 0.02 second variation. The second plot shows how much clock time differs from reference time.

As for what accuracy is feasible, there is an awesome Lego clock by Kei Abe.

In one month of testing, it never exceeded 12 seconds of error.

[Davidz90]

I rebuilt my clock tower to look a bit like a cathedral. The mechanism features auto-rewinder and hours striking with a large pipe chime.

overview by David_Z1, on Flickr

 

Edited September 19, 2022 by Davidz90

[Davidz90]

Another update. After several orders with unholy amount of black bricks, clock tower became even more massive. Now the mechanism is powered by four 1.5 kg weights, which keep it running for 240 hours (10 days) on a single rewind. Moreover, the clock will be equipped with a working 365 day calendar.

Overview of progress is here:

And here is the calendar mechanism:

and instruction how to do a 1:365 gear reduction:

Also, I figured out an easy way to make 1:12 reduction for clock hands that has very little gear backlash:

 

[GerritvdG]

Thanks for sharing, very interesting those reductions! Good luck to the crane operator 

[Jurss]

Some genious solutions.

Have You considered to make also dial (or what is the name?) out of lego fully? Seems to be possible in this scale.

[Davidz90]

12 hours ago, GerritvdG said:

Thanks for sharing, very interesting those reductions!

Thank You very much!

1 hour ago, Jurss said:

You considered to make also dial (or what is the name?) out of lego fully? Seems to be possible in this scale.

Yes, I had used several Lego dials in the past. The simplest one is probably circle gear rack (it has 12 evenly spaced holes). One can also use #3 connectors to form a 12-gon, although the axles are a little stressed in such configuration. Finally, recently I've made one with plates:

20220608_084527 by David_Z1, on Flickr

Here, I could use Lego dial for hours, but there is no way to do the calendar so I decided to keep style consistent.

[Davidz90]

Another update to the clock tower. Now it is over 2 metres high.

The mechanism includes working calendar (day, month, day of the week), moon phase indicator, striking train (with actual bell tower), additional 24 hour time with sunrise/sunset indicators.