[TC28] Pendulum Clock

[Berthil]

Buidling instruction available on Rebrickable

Making a Technic Pendulum Clock is sitting on my wishlist for years now, so the non-vehicle contest seems like a good moment to have a go at it.

It took me about three days to make a start in Stud.io but I'm already studying clocks for years now. This clock is inspired by the Billion Year clock by Brick Technology and has some similarities in the same way in that a drive train or suspension is re-used in models, all via reversed engineering. I hope that is okay for the competition. In the end a clock is not rocket science, it needs an escapement, a weight and the correct gearing for seconds, minutes and hours (1:60:60:60).

Next is building and testing the mechanisms and adjust weights to let the clock run on time. When that works I will fortify and beatify the frame, like covering up the battery box. Maybe also add a Steampunk vibe as far as that is possible with Technic elements. If time permits I want add some ball action with Zamor Spheres (so no GBC). Im thinking of dropping one ball every hour so that it makes a 'chime' sound, or the exact amount of balls at that hour. That might be too ambitious because it should have a mechanical mechanism like the rest of the clock and get drive from the clock.

If all works out well I might make building instructions for it.

Edited April 10 by Berthil
Rebrickable link added

[Davidz90]

Wow, very interesting. So, gravity power + electric auto-rewidner. I like the oscillator a lot. The part at the top, left to the motor, is escapement?

Good luck with the striking mechanism, chiming the exact number of hours is sure ambitious, such mechanism may take more space than the rest combined!

 

[Berthil]

@Davidz90 Yes, that's the escapement left of the rewinding motor. Since the weight system is on the left, I hope to make a compact ball chime system on the right with maybe a ball storage and tilt system on the back, or if it doesn't obscure the oscillator, on the front. I agree that chiming the hours with the exact amount of balls in a mechanical contraption may take more space than the clock . Also because of contest time restrictions, I'll probably be concentrating on one ball per hour and release all 12 when it is 12 o'clock but maybe have to add an 'AM' mode without dropping balls to not wake up the whole house .

After the contest, I might make a horizontal escapement on top and the elaborate ball chime system as an add-on, as well as more brick-build Steampunk ornaments.

Edited January 7 by Berthil
last remark added

[JunkstyleGio]

Looks intregueing!

Hope to see a video soon!

 

[lcvisser]

Didn’t you make a clock for the pullback contest? 
Anyway, curious to see how this will work, looks suitably complicated!

[Berthil]

After 60 hours of work, a more or less digitally finished Technic Pendule Table Clock. I've added a chime ball drop at the right, every hour a Zamor Sphere should drop with a notable sound on a large tile. So at the right a ball will go up in an hour. Since I have no experience with Zamor spheres, I will build the frame and the chime system first as soon as the Zamor Spheres arrive from Bricklink. So expect a video soon of the working chime system .

The rubber tires act as sound dampening, it does not make the clock a vehicle . If no effect, I'll probably replace them with something else.

On 1/7/2025 at 7:14 PM, lcvisser said:

Didn’t you make a clock for the pullback contest? 

I didn't.

[Davidz90]

Wow, I love the steampunk aesthetics! I'm anticipating a video of the real thing, especially the escapement; there's quite a jump from building it digitally and actually getting it to work reliably.

[Berthil]

A bit of progress on the Clock, finally after Dutch Postal Services took 11 days deliver 3 Bricklink orders.

Unfortunately the clock needs big updates to have a chance to function properly because the escapement doesn't run on its own:

• the pendulum is too short and the escapement runs slightly too fast. I tried to solve that by heightening the pivot point but this also meant adding gears with friction and backlash. This means I have to increase the height of the entire clock, probably by eleven studs. Because of this I have to redesign the weight and ball chime system.
• in the video I'm puling the string to mimic the weight that needs to be added, the string is genuine LEGO (x77ac50) but it is too thin and too short. It's too close to the winding axle and has no momentum. If I help the top gear next to the spindle a little bit with my finger, the escapement runs. I might try a longer and thicker string, and have more windings on the spindle to create more momentum. I might also try and use small track links on a gear now that I know I have to redesign it anyway.

The redesigning of the frame and weight and ball chime system attached is my own fault. I should have checked the timing of the escapement first by building a prototype and test the swing time, but since I used about the same length as in the Brick Technology setup I assumed it was okay and designed too far ahead. As such the ball chime system with the Zamor Sphere works as the video shows, the frame is also sturdy.

 

[Davidz90]

27 minutes ago, Berthil said:

he pendulum is too short and the escapement runs slightly too fast. I tried to solve that by heightening the pivot point but this also meant adding gears with friction and backlash

A neat way to slow the pendulum down without making it longer is to add a secondary mass above the pivot. This method can slow it down considerably.

 Also, You may consider using a more subtle escapement that is less power hungry. Something with regular gear as an escape wheel, for example. The one in the video is extremely inefficient.

[Berthil]

@Davidz90 Thanks for the feedback, I will have a look at it. The top weight I already tried by adding train weights. This slowed it down but also decreased momentum a lot, but I'll give it a go  together with a a more efficient escapement, before disassembling everything.

[Davidz90]

1 hour ago, Berthil said:

Thanks for the feedback, I will have a look at it

Sure! One more thing worth testing is some better pendulum suspension than just an axle. This is also a big source of friction. Just replacing the axle with bar/lightsaber resting on the bottom of technic hole reduces the friction by a factor of 10 or so.

[Berthil]

@Davidz90 Thanks again! The bar is a good tip. I'm also looking at using the Bionicle tooth as a knife suspension. In my setup a Detent escapement system seems to be the best way to go but a Bionicle tooth or light saber suspension system seems hard to integrate, also because I want to keep the pendulum in the middle of the clock without changing all the gearing. Luckily, still almost 6 week until the deadline 

[Berthil]

Small update, but not a visual one. I've experimented with different and more efficient escapements, at least more efficient on paper. I worked on them until deep in the night but none of them work. Mainly because the whole machine has friction, many mechanisms are attached. A robuust and high force escapement system is required instead of a low friction fiddly one. I was very close to giving up but I like the clock very much, so I'm reverting back to the former escapement system and will try to optimize that as much as possible and hope it will work in the finished build. If not, I will find ways to let it work, if needed even with an additional motor and clutch system to overcome the high friction. I'm not giving up.

[Davidz90]

Yeah, multiple mechanisms stealing energy from the escapement is a common and annoying problem. One solution is to add a small power source that powers only escapement, which is then rewinded at regular intervals by the larger power source. Or, in your case, all functions could be attached to electric auto-rewinder instead of the escapement.

Finally, below are some simple escapements that are not as fiddly as the really efficient ones:

 

[Berthil]

@Davidz90 I've already looked at these from the links in your book, the single pin would be most suitable but has a full rotation on every swing right? I need a half rotation because the gearing ratios go into fractions after the escapement instead of whole numbers, and I don't see a way to change that. I could add a 200% gearing but this would only add to the friction already there.

How did you run this amazing clock with all the mechanics behind it, just from the pendulum and weight? I would like to do something similar, but in a table clock without the long pendulum and be able to make building instructions for it.

Edited January 20 by Berthil
amazing clock added

[Davidz90]

41 minutes ago, Berthil said:

I need a half rotation because the gearing ratios go into fractions after the escapement instead of whole numbers, and I don't see a way to change that. I could add a 200% gearing but this would only add to the friction already there.

Yeah, single pin escapement cannot be changed into half rotation easily. Is it half, not quarter? The one on your video has four "teeth". How about Galileo escapement with propeller piece? Going from 4 to 8, You could reduce the gear ratio by 2 somewhere.

45 minutes ago, Berthil said:

How did you run this amazing clock with all the mechanics behind it, just from the pendulum and weight? I would like to do something similar, but in a table clock without the long pendulum and be able to make building instructions for it.

The striking mechanism has its own weight and a low friction trigger. World time rotates only once per 24 hours and calendar only advances by one day every 24 hours, so both of these are very slow and connected to the mechanism through huge gear ratio.

In general, for optimal performance, it is best to use largest gear reduction immediately next to escapement (so one or few 8:40 ratios) and then go from that. Your pendulum seems to have a period of about 0.8 seconds. So 4-toothed escape wheel would make one rotation in 3.2 seconds. For minute hand, 1:1125 ratio is needed. 1125=5*5*5*9, so three 8:40 in a row and then two 8:24.

Also, kind of obvious but avoid adding seconds hand if possible; it uses up a lot of energy.

Forgot to add: the first escapement in the video I linked is very robust and with little tweaking, it can be converted to a knob wheel to have 4-toothed escape wheel.

[Berthil]

@Davidz90 The clock has seconds, minutes, hours, AM/PM and the ball chime. One swing of the pendulum from left to right is one second and half rotation on the escapement. I used the Brick Technology clock mechanism which has substantial downgearing right after the escapement to seconds, and more after that for minutes and hours. I've optimised all axles to support on both sides where it was possible to prevent friction. The prototype build in my video does not have all the planned frame and axle supports yet as it was a short test, so I plan to have less friction in the final build and hope for the best.

Meanwhile I converted the weight string to gears and tread links, I expect better torque distribution to the escapement. It probably means more rewinding which is okay for me, the clock is a showpiece of Technic trying to look like a clock and doesn't have to run a full day on one weight rewind. But it has to run of course. I also added a weight at the top and am very close to 1 second per swing in the current configuration. 

I'll have a look at the suggested escapement and use a knob wheel, thanks. Will adding weight to the pendulum be good for keeping the swing movement going despite an inefficiënt escape mechanism, or is it just adding friction to everything?

[Davidz90]

3 minutes ago, Berthil said:

Will adding weight to the pendulum be good for keeping the swing movement going despite an inefficiënt escape mechanism, or is it just adding friction to everything?

It will definitely be good, especially if you manage to implement some better pendulum suspension.

5 minutes ago, Berthil said:

Meanwhile I converted the weight string to gears and tread links, I expect better torque distribution to the escapement.

Yes, thread links should work better than strings.

6 minutes ago, Berthil said:

The clock has seconds, minutes, hours, AM/PM and the ball chime

Ok. Seconds can be problematic if the seconds hand is heavy and/or not balanced well, so that needs attention. Minutes and hours are usually non-issue. Ball chime may or may not need its own power source, but lifting a ball doesn't seem to take that much power. At any rate, this part could be attached directly to the electric rewinder, especially if the said rewinder activates often.

9 minutes ago, Berthil said:

One swing of the pendulum from left to right is one second and half rotation on the escapement.

This puzzles me. On the video, I see close to one second period (swing left to right and back), which advances the escape wheel by one tooth (=1/4 rotation)?

[Berthil]

I'm a novice when it comes to clocks but am experienced in running mechanisms as frictionless and reliable as possible with designing GBCs. I'm using the Brick Technology clock and you're right, it is a quarter per second so 1:4. I expected the escapement would run without problems, especially after the friction optimisations, but it doesn't in my build. Maybe some magic is applied by Brick Technology.

 

[Davidz90]

10 minutes ago, Berthil said:

Maybe some magic is applied by Brick Technology.

No magic here, just a heavy weight applied almost directly to the escapement axle is just barely enough to keep it running. Also, isn't your mechanism running in opposite direction? In Brick Technology video, the escape wheel is pushing the anchor horizontally at the top and more vertically at the bottom. Or in other words, escape wheel runs counterclockwise with pendulum on the left side and yours runs clockwise. Details like this can matter a lot - I can see that the Brick Technology version runs substantially smoother. In general, with anchor escapement, the geometry needs to be optimized so that the escape wheel spends time mostly pushing the pendulum, not being locked by it.

At any rate, look into the suggested escapement, either with knob wheel or in the original configuration with triangular connector (and appropriately changed gear ratio; shouldn't be too hard to replace 4 with 3 somewhere). It is very forgiving. 

[Berthil]

I just saw a very big mistake on my side, the Brick Technology escapement is run in the opposite direction with a string going under the spindle instead of above. So there is hope 

1 hour ago, Davidz90 said:

Also, isn't your mechanism running in opposite direction?

You've seen it and I also just noticed myself, shame on me. Fun and learning is what the competition is about, they said 

Actually, now that I had some time to think about it, the escapement is symmetrical so it should not matter in what direction it is operated. So I might be less stupid than I thought or I am and am missing something, only gravity could have some influence (push down instead of up). This also means it will not be more efficient when running in the other direction, I will see as I will try of course. Running the weight with a chain in the other direction will not be possible as the chains would need to cross in the same 2D plane or have some construction to run over the weight and to the other side.

Edited January 20 by Berthil
remark added

[Berthil]

Some progress, and an important one! I've tried several other escapements but got the original one running after more friction improvements. I had to add more weight because the weight would stop on the bottom switch occasionally. Next is adding the clock face, hour ring and minutes hand. I expect no problems with friction because these are geared down considerably. The ball drop chime I still need to test by letting the clock run longer, I will do that with a 9V train power supply, the batteries are almost empty here (old ones).

 

[Davidz90]

Very cool, and it seems really accurate too!

7 hours ago, Berthil said:

I expect no problems with friction because these are geared down considerably.

Yes, given rather high-power mechanism, there should be no issues there.

[Berthil]

The build of the clock is finished. Before the contest deadline, not because it was easy, but because I spend a lot of time on it. I still had to do optimisations by replacing a few bevel gears with straight teeth gears for better meshing and less friction, as well positioning the hour ring better for more reliability. I've run the clock for a full day without problems.

The clock is 100% LEGO (over 2000 parts) without stickers and has 67 gears.

Here a short video. I want to add a 12h timelapse of the clock to the video for the final presentation, although I have never done that before. At the end of the video a 5 min run (x20) shows that the clock was accurate by 0.12 seconds after 5 minutes!

 

Edited February 8 by Berthil
photo added

[Good old Lego builder]

Amazing!