About Lego Clock Chronograph

[kotax]

I am not an English speaker so I use a translation site. So the text may be strange in places.
I'm trying to build a chronograph with Lego, but I don't really understand how the reset works. So if anyone knows how the reset works or how to make one, I would love to know.

[Davidz90]

Hi and welcome to the forum!

 

Usually, in real clocks chronograph uses a whole set of special-shaped cams to do the job; see: https://www.fratellowatches.com/understanding-the-mechanical-chronograph/#gref

That is difficult to do with Lego. However, a simpler option is to use a weight on a string or a pullback motor attached to the chronograph hand. Then, you need some sort of a clutch to:

1. Connect the hand to the clock. Hand goes forward and lifts the weight or winds up the pullback motor.

2. Stop the hand.

3. Disconnect the hand from the clock. Weight/pullback motor resets it.

[kotax]

8 minutes ago, Davidz90 said:

こんにちは。フォーラムへようこそ!

 

通常、実際の時計のクロノグラフでは、特殊な形状のカムのセットを使用して機能します。詳しくは、  https ://www.fratellowatches.com/understanding-the-mechanical-chronograph/#gref をご覧ください。

レゴでそれを実現するのは難しいです。しかし、もっと簡単な方法としては、紐に重りを付けたり、クロノグラフ針にプルバックモーターを取り付けたりする方法があります。そして、以下の機能を実現するために、何らかのクラッチが必要になります。

1. 針を時計に接続します。針が前進して重りを持ち上げたり、プルバックモーターを巻き上げたりします。

2.手を止めます。

3. 針を時計から外します。重り/プルバックモーターが針をリセットします。

Oh, this is a good idea. How do you attach the weight?

[Davidz90]

Two ways:

1. Weight on a string, hanging from a spool

2. Weight on a lever, connected to the hand with some high gear ratio.

[kotax]

I see, so that's how you did it. I will try to make it your way. Thank you very much!

7 minutes ago, Davidz90 said:

2つの方法:

1. 糸巻き機から吊るされた紐の上の重り

2. レバーに重りが付いており、高いギア比で手に接続されています。

I see, so that's how you did it. I will try to make it your way. Thank you very much!

[kotax]

I was looking up videos of clocks with chronographs made out of Lego. Then I found this video.

How does the chronograph reset in this video work?
 

[Davidz90]

It seems that by pushing a button, he pushes some lever to a horizontal or vertical position. The lever is connected to the hand with some large gear ratio.

[kotax]

Thank you for your thoughts. Could you please tell me how to make the reset part of this video?

[Davidz90]

Unfortunately, I have no idea how it looks exactly.

However, here is a mechanism I have built just now:

I hope this will give You some ideas.

[kotax]

Oh, this is great! Thank you for taking the time to do this. I did not have this idea. I will take it as a reference. I may have another watch-related question like this. Please let me know if you do! Thank you very much!

Edited April 21 by kotax

[Davidz90]

6 minutes ago, kotax said:

I may have another watch-related question like this. Please let me know if you do!

Sure, feel free to ask.

[Davidz90]

I have found one more good explanation of how this works:

 

[kotax]

Sorry for the delay in replying. This is a nice video. I will watch this to get a better understanding. Thank you very much.

[kotax]

On 4/21/2025 at 10:59 PM, Davidz90 said:

Unfortunately, I have no idea how it looks exactly.

However, here is a mechanism I have built just now:

I hope this will give You some ideas.

I made this mechanism that you thought of. However, there was one problem. When the hand turns one revolution and a bit, it stops. I think this is caused by the blue technic pin, is there any way to solve this problem?

[Davidz90]

4 hours ago, kotax said:

I made this mechanism that you thought of. However, there was one problem. When the hand turns one revolution and a bit, it stops. I think this is caused by the blue technic pin, is there any way to solve this problem?

This is intended. There is no need for more than one rotation unless there are two hands.

[kotax]

17 hours ago, Davidz90 said:

これは意図された動作です。両手がない限り、1回以上の回転は必要ありません。

What is the mechanism if there are two hands?

[Davidz90]

4 hours ago, kotax said:

What is the mechanism if there are two hands?

There is no standard. Usually chronographs have only one hand that counts to 60 seconds. When using the same dial, second hand could show up to 60 minutes. But for that a completely different mechanism than the one I've built would be needed. Resetting would get rather complicated.

[kotax]

I see, can you please tell me how to create a reset mechanism in that case?

18 hours ago, Davidz90 said:

標準はありません。通常、クロノグラフは60秒までカウントする針が1本しかありません。同じ文字盤で、秒針を60分まで表示することも可能です。しかし、そのためには私が作ったものとは全く異なる機構が必要になります。リセットはかなり複雑になります。

I see, can you please tell me how to create a reset mechanism in that case?

[Davidz90]

4 hours ago, kotax said:

I see, can you please tell me how to create a reset mechanism in that case?

Frankly, I have no idea.

[kotax]

22 hours ago, Davidz90 said:

Frankly, I have no idea.

I understand. I will try to make it in my own way. Thank you very much.

[aeh5040]

It seems that in principle two hands would be no different - it is simply a matter of gearing. In practice friction and backlash might be problematic though.

Edited April 30 by aeh5040

[Davidz90]

34 minutes ago, aeh5040 said:

It seems that in principle two hands would be no different - it is simply a matter of gearing. In practice friction and backlash might be problematic though.

Exactly. A reset mechanism that pulls the faster hand back by several rotations and puts it exactly at 0 seems really difficult to do reliably.

It seems that adding a slip clutch between hands and using some lever arrangement like in the gray video, that independently forces both hands to 0 position, may be a better approach here. 

[kotax]

On 2025/5/1 at 午前1時14分, Davidz90 said:

まさにその通りです。早針を数回転戻して正確に0に戻すリセット機構を、確実に実現するのは非常に難しいように思えます。

この場合、両手の間にスリップ クラッチを追加し、灰色のビデオのように、両手を独立して 0 位置に強制するレバー配置を使用するのが、より良いアプローチであると思われます。 

Sorry for repeating myself. If I were to make this, could you tell me exactly how to make it?

[Davidz90]

1 hour ago, kotax said:

Sorry for repeating myself. If I were to make this, could you tell me exactly how to make it?

Chronograph with two hands seems to be rather problematic to do and I don't know how to make such a mechanism reliable. Besides, I have never seen chronograph with two hands. What exactly is your goal?

[kotax]

17 hours ago, Davidz90 said:

二針クロノグラフはなかなか難しそうで、どうやって信頼性の高い機構にすればいいのか分かりません。それに、二針クロノグラフなんて見たことがありません。具体的に何を目指されているのですか？

I would like to make a watch with a chronograph second hand, a 60-minute totalizer and a 12-hour totalizer on top of it, as shown in this video. So the total number of chronographs will be three.