[TC28] Desk clock

[ord]

Impressive! It seems like you have achieved your goal of less than 1% error .

[Davidz90]

40 minutes ago, aeh5040 said:

In particular I am reminded of this:

Whoa, this is a little creepy but very cool. Maybe I'll try to incorporate more moving parts with organic feel, to make it more like a kinetic sculpture. So many things to consider, fortunately there's a lot of time left.

27 minutes ago, ord said:

Impressive! It seems like you have achieved your goal of less than 1% error .

Yes, indeed I have. Turned out to be way easier than anticipated, I had no idea that balance wheel can be made so stable so easily; I expected it to be a complete garbage compared to a pendulum, but it's only ~10 times worse. Funnily, this is similar to real wristwatches, which are about 10 times worse than grandfather clocks.

[Berthil]

Good to see you got everything working so good, I expected nothing less from the writer of the 'Guide to LEGO Clocks' book. .

[2GodBDGlory]

4 hours ago, Berthil said:

Good to see you got everything working so good, I expected nothing less from the writer of the 'Guide to LEGO Clocks' book. .

Yeah, I was talking to my Mom about my choice of what to build in this contest, and I think I said something along the lines of, "I could build a clock, but the guy who literally wrote the book on Technic clocks has already started one, and I don't think I can compete with that!"

It's really interesting to see the design without the pendulum!

[Davidz90]

2 hours ago, 2GodBDGlory said:

"I could build a clock, but the guy who literally wrote the book on Technic clocks has already started one, and I don't think I can compete with that!"

Hahaha :D Yeah, I'm pretty predictable, although I chose balance wheel to have some novelty; simple pendulum would be lazy. Frankly, I don't think that I can compete with other entries as well; the musical machine, lathe, calendar, Berthil's clock are all extraordinary (so far, music machine is my favourite). My humble clock probably won't be much more than already shown and I don't have that much time to work on it.

Edited January 20, 2025 by Davidz90

[aeh5040]

On 1/20/2025 at 11:02 AM, Davidz90 said:

Whoa, this is a little creepy but very cool. Maybe I'll try to incorporate more moving parts with organic feel, to make it more like a kinetic sculpture. So many things to consider, fortunately there's a lot of time left.

Personally I kind of like the (humourous?) contrast that the whip (or wishbone) is the only organic looking part. That's what reminded me. Yours is indeed less creepy! 

[Davidz90]

Instead of planning the clock layout, I keep fiddling with the escapement design XD

 

[Davidz90]

I finally have a general idea how the complete clock will look like. It will be gravity powered after all, but with something a little more interesting than just a weight on a string. More to come. But now, a little comparison of accuracy. Escapement makes a good job of maintaining pace despite large torque variation of spring power, but gravity power is still superior:

(embedding images from flickr doesn't seem to work now?)

Edit: Ok, Thanks! 

Edited January 26, 2025 by Davidz90

[aFrInaTi0n]

@Davidz90 IT is BBcode - so everything with [ ] brackets will not work. You need just paste the URLs of pictures (remember to stick to the max resolutions of 1024px)

Testpost with your URL without BBcode pasted as plaintext:

[Davidz90]

The design is more or less finalized. I went for gravity power and electric auto-rewinder to get long running time (probably ~2 days until batteries run dry, it isn't very efficient). What is unique is the overall layout of the clock: it consists of three separate pieces connected with a chain loop. On the top, escapement is located. In the middle, driving weight and auto-rewinder are hanging on the chain. At the bottom, clock face is also hanging on the chain.

This is by far the most silly clock design I have made .

[Davidz90]

I finished fine-tuning the clock. Adding a single 1x1 tile to the balance wheel increases the period by about 0.01 seconds, so this was the smallest correction I could make. That being said, I got very lucky to get a period of 2.0012 s, which is an error of 0.062% or about 54 seconds/day. In other words, after a full day of working, the clock should be late by a little less than a minute.

Here is how the individual periods look like

The curious thing is the upper band around 2.04 s; there is some common occurence that causes the period to be 0.04 seconds longer than average. So far, I have no idea what this is.

Here is the histogram, showning the mysterious upper band as well

And here is clock error

Started out extremely stable, but at ~12 minutes the period increased very slightly and clock started accumulating error at a rate of about 3 seconds/hour. Keeping that rate, after 24 hours the error would be about 1 minute.

That being said, I don't expect the long term performance to be this good. Clock is heavily affected by thermal expansion - not only expansion of the balance wheel makes a bigger difference than identical expansion of a pendulum, but also the whip "spring" is very likely to become softer as the temperature rises. 

 

[aeh5040]

Very interesting data! Can comparing the sound traces of the anomalous periods (perhaps averaged somehow) provide any clues? Or perhaps a slowmo video? (I assume you have ruled out the rewind).

Also, very cool creation (of course)! The hanging face is very neat. Really enjoying the artistry as well as the cleverness.

Edited January 31, 2025 by aeh5040

[Davidz90]

3 minutes ago, aeh5040 said:

Very interesting data! Can comparing the sound traces of the anomalous periods (perhaps averaged somehow) provide any clues? Or perhaps a slowmo video?

Good question. I'll try just that - chop the sound trace into periods and overlap them.  Slomo is an option too, although analyzing the footage in search of the anomalous period (about ~5% of them are anomalous) could be annoying and there's no telling if they can be recognized visually at all.

[Davidz90]

Eureka! The antenna hits the locking piece at some speed, bounces back and then hits it again.

The first hit is louder, but sometimes the second one was registered as the clock tick. The bounce takes 0.043 seconds.

[2GodBDGlory]

That is a super unique clock! Nice job! I like seeing the 24T crown gear being used effectively in there!

[Davidz90]

3 minutes ago, 2GodBDGlory said:

That is a super unique clock! Nice job! I like seeing the 24T crown gear being used effectively in there!

Thanks! Yeah, crown gear is an underrated piece; so much more compact than the equivalent 12:36 with new bevels.

Auto rewinder was surprisingly challenging - for some reason the on/off switch on the battery box needs an absurd amout of force, so a double lever arrangement was needed to make it manageable. In the future, I'll probably replace the current autorewinder with some sleeker 3rd party components.

[Davidz90]

First of all, I'm completely blown away with all TC28 entries. I can't even start to compete with them.

In the meantime, aside from my 100% Lego entry, I tried a proper steel spring for the balance wheel. It makes a huge difference, making lever-type escapements (what is typically used in wristwatches) possible. They keep the advantage of pushing the wheel only in the middle, but in addition are self-starting. Wristwatch must start automatically after a stop and rewind.