Weight minimum

[POWERSTROKE]

Let's say I rebuild an 8 day cuckoo that runs on 1260g. When testing, what are you happy with as a minimum weight that it runs on? How much less than the given factory weight?

 

[R. Croswell]

Let's say I rebuild an 8 day cuckoo that runs on 1260g. When testing, what are you happy with as a minimum weight that it runs on? How much less than the given factory weight?

Nothing less than the factory spec. It is what it is for a reason.

 

[leeinv66]

The reason being to ensure the clock runs consistently. That said, most weight driven clocks will run on these than the factory specs.

 

[POWERSTROKE]

I'm saying for testing purposes for leeway. What would you be happy with a rebuild running on before you throw the factory weight back on.

 

[leeinv66]

It depends on the clock. An 8 day cuckoo isn't a precision movement, so you wouldn't expecting it to run on much less than the factory weight. But a quality movement, say a Vienna regulator for instance, I've had them running on a single drop at a few ounces with out the motion works fitted. Still, I run all my clocks with the factory weight on the test stand before I call them good.

 

[POWERSTROKE]

So is 1000 good for something that takes 1264

 

[wow]

Why would you want to use less weight?

 

[R. Croswell]

So is 1000 good for something that takes 1264

That depends on what the something is. Perhaps a better way to evaluate if the weight is sufficient for testing is to check that there is sufficient overswing with the factory weight. The smaller the weight the less the overswing and when the overswing approaches zero the clock will become unstable and is about stop. This then begs an answer to the question how much overswing is enough. Someone here suggested that if the overswing is visually obvious then it is probably OK.

In your example, if you reduced the weight by 20% from 1264 to 1000 and the clock still runs, you can probably be confident that the 1264g weight is producing sufficient overswing. The only way to get the complete picture is to reduce the weight until the clock refuses to run, and that includes running through the activation of the strike train if it is a striking clock.

RC

 

[Vernon]

It sounds as if Powerstroke is wanting to duplicate the same test as is done with spring driven movements where you wind a little just beyond the springs shuffle.
Vernon

 

[R. Croswell]

It sounds as if Powerstroke is wanting to duplicate the same test as is done with spring driven movements where you wind a little just beyond the springs shuffle.
Vernon

I believe so. By whatever method that seems to work, we need to make sure the clock will run for a long time after it leaves the shop even if neglected by the owner. When I rebuild a 30 hr. wooden works movement that normally runs 3.5 lbs. I test with 1.0 lb. 1.5 lb. and 2.0 lb. weights. 1.5 is great, over 2.0 and something is probably not up to par. 1.0 lb. and it run but will probably stop before striking. I like to run my own on 2.5 lb. OG weights to reduce stress on 190-year-old wooden clocks.

One thing to keep in mind is that a weight will always produce the same driving force, just after winding until it runs down, even if it gets dirty, now or 100 years later. Springs require an extra margin of safety because the power falls off as they run down and get dry or dirty. So we can cut it a little closer for weight driven clocks.

RC

 

[POWERSTROKE]

I don't think I could get an 8 day cuckoo to run in 1/2 of the prescribed weight.

 

[R. Croswell]

I don't think I could get an 8 day cuckoo to run in 1/2 of the prescribed weight.

I can't either, that's why I said it depends on the clock. But if you have good overswing with the factory weight you are good to go.

RC

 

[Willie X]

Power,
Check about 10 or 15 clocks that are in good shape (or new) and report back. A solid minimum weight range would be an interesting number but only for test purposes.
Note, the clock factory's shiped 1260gm weights for many years then it gradually shifted to 1500. They didn't do this for no reason. Willie X

 

[POWERSTROKE]

I have a Herr 8 day with moving squirrels running on 850 right now after rebuild. The pendulum swing is not great though. But it's running. Ran for 5 hours and stopped in warning. Runs on 945 consistently.

 

[JimmyOz]

Note, the clock factory's shiped 1260gm weights for many years then it gradually shifted to 1500. They didn't do this for no reason. Willie X

The weight grew as the automation grew.
8 day, time and cuckoo and some with music and little automation still use 1260.
8 day, time, cuckoo, music and medium automation (lifting axe,sawing log, turning waterwheel and so on) 1500.
All of the above + man and women kissing, waitress bringing drinks and so on 1750 ( if I remember right they also have a different movement).
I don't think you gain anything by looking to see if it will run under powered, if the movement has an issue it will show up on full power, trying it will just add extra work for yourself?