Clock Runs For Hours/Days Without Bob/Pendulum But Not With Bob/Pendulum

[Rob Martinez]

Looking at some old threads this issue has come up before but the responses seem to veer off into diagnostics for a clock that runs then stops. I can see where these 2 issues are in the end identical, but I cant help but think that as a troubleshooting indicator, the fact that it runs great without the presentation of the load a bob adds to the train, would drive a different set of possible assumptions.

Rational: Leveling (beat) and the absence/presence of power are non issues since in my experience an unlevel/out of beat clock runs even less without a pendulum/bob than with, and if there is enough power to keep a crutch without a pendulum/bob moving for hours then clearly it is getting power. However, is it possible there is not "enough" power? I am not sure that is even a possibility....

An issue that 1 of the 2 clocks in question (American time and strike and a French time piece) also have is that the French one intermittently will work with a shorter/smaller pendulum and bob but a slightly longer/correct length of pendulum and bob consistently stops.... Both are very fickle clocks and will only run if perfectly level/in beat. What might that indicate about the French clock?

Bottom Line - Are there some additional things I can assume or that I should consider since these clocks have the unique ability to run only without a pendulum and/or bob? Or should I just treat a clock that works without a pendulum and/or bob, but stops with a pendulum and/or bob, the same as any other clock that stops?

 

[Randy Beckett]

Both of the clocks you mention might have(usually are) recoil escapements. If these escapements are adjusted so that the anchor is too shallow in the escape wheel, they will run readily without a pendulum, but will barely run, if at all, with a pendulum. If they do run, the pendulum swing will be very small. This is because the deeper in the escape wheel the anchor is, the longer the power stroke, and there for stronger impulse, to the pendulum will be.

This is just one thing that will cause this, other than the things you mention.


Edit- Now that I think about it, a deadbeat escapement will do basically the same thing if adjusted too shallow.

 

[Tinker Dwight]

Running without the pendulum only indicates that the
clock has enough power to run without the pendulum.
Little else is gained from this knowledge.
Tinker Dwight

 

[Willie X]

Have the mainsprings been stretched out and given a good rub-down lately? I'm assuming the rest of the train is in good condition.
Willie X

 

[Ralph]

You aren't explicit enough. Without the bob, does that mean the crutch is till driving the suspension spring/rod.

Pictures, specifics, etc would help. The French clock, how thick is the suspension spring?

Ralph

 

[Rob Martinez]

TD - The following is more of an academic question than one on the clocks in question -- I agree, running without pendulum/bob does indicate that a minimum amount of power is available. However, doesn't running without a pendulum and or bob also indicate the clock is in beat or very near in beat? Actually, doesn't running (with or without a pendulum/bob) for hours/days indicate there is no acute problems with the power train? I wouldn't go so far as to call it a mid-speed test (eg. more than slow but less than a fast-speed test) but it seemed to me in the past that if I have one on the bench that worked without the pendulum and or bob I figured my job was pretty much done.... until I ran across these two...

Speaking on my problem specifically I am leaning towards Randy Becket's theory about the shallow contact between the pallet faces and the escape wheel's teeth since one of my symptoms is that one of the clocks will intermittently run with an undersized pendulum and bob....

 

[bangster]

Running without a pendulum tells nothing about beat, because it's driven strictly by the power to the EW, without anything to provide the rhythmic discipline we call "beat". A free-running crutch has no beat center: tilt the clock any way you like, and it will still clatter along. The regularity of its ticks and tocks aren't governed by anything except whatever resistance the escapement provides against the power of the spring.

You may or may not have a beat problem, but you can't rule it out by the behavior of an uncontrolled escapement.

 

[Tinker Dwight]

Bang is right on, absolutely zero about the beat.
A recoil given only the crutch to drive will swing it with the
clock at all kinds of angles.
Beat must be set with the pendulum attached.
The only thing you determine is that the wheels all turn.
If it is a dead beat clock, it may not run at all without the
pendulum.
A recoil will just about always run.
Tinker Dwight

 

[Rob Martinez]

Thanks for the clarification -- with a pendulum but no bob I still find that these clocks will not run if not level but clearly I need to look at them again.

Thanks again!

Rob

 

[Tinker Dwight]

Thanks for the clarification -- with a pendulum but no bob I still find that these clocks will not run if not level but clearly I need to look at them again.

Thanks again!

Rob

The case and the movement are two different parts. Beat setting and case levelness
are also two different thing.
For looks, it is desired to have the case level when setting the beat but it is
not absolutely necessary.
Beat setting is a movement parameter that can be set for reasonable slightly
off level setting of the case ( things like the floor not being level ).
It must be done with the full pendulum rod and bob.
See the "Beat setting 101"
https://mb.nawcc.org/showwiki.php?title=Beat_Setting_101
Tinker Dwight

 

[bangster]

Thanks for the clarification -- with a pendulum but no bob I still find that these clocks will not run if not level but clearly I need to look at them again.

Thanks again!

Rob

The pendulum rod with no bob is still a pendulum...acts like one and is one. Just a very light one.

 

[shutterbug]

It sure sounds like a power problem. Some video of the clocks running would help. Especially the escapement.

 

[Tinker Dwight]

The pendulum rod with no bob is still a pendulum...acts like one and is one. Just a very light one.

So, technically a crutch is as well.
The rod may not be heavy enough in weight to pull
a slightly bent suspension spring straight. This will give a false beat location.
It will run faster than with the bob as well.
Tinker Dwight

 

[bangster]

So, technically a crutch is as well.
The rod may not be heavy enough in weight to pull
a slightly bent suspension spring straight. This will give a false beat location.
It will run faster than with the bob as well.
Tinker Dwight

No, the crutch is part of the escapement. It needs a pendulum to regulate it. It can't serve as its own pendulum. If you hang a pendulum on the crutch, you don't get a long pendulum. You don't get a pendulum at all. You get a long crutch.

..............

I'm re-thinking that, in the light of tic-tac movements. A "crutch" straightened out could serve as a pendulum, but not with a recoil escapement.

 

[Tinker Dwight]

No, the crutch is part of the escapement. It needs a pendulum to regulate it. It can't serve as its own pendulum. If you hang a pendulum on the crutch, you don't get a long pendulum. You don't get a pendulum at all. You get a long crutch.

..............

I'm re-thinking that, in the light of tic-tac movements. A "crutch" straightened out could serve as a pendulum, but not with a recoil escapement.

You are right that it is part of the escapement but it is still technically a pendulum.
It is a mass, though small, waving back and forth from the power of the escapement.
It runs faster than you might think because it is being pushed by the recoil escapement.
It is still slower than a massless rod. Gravity and its mass have some effect.
To be meaningful as a time keeping element, it would have to have a sufficient mass, near
the end, to counter the constant pushing from the escapement.
Many old verge clocks had no crutch. They had just a rod with a weight.
They make lousy time keepers but what we used today as a pendulum
clock has been refined over the years.
Tinker Dwight

 

[Ralph]

I think it is a stretch to call an escapement appendage a pendulum when any restorative gravity effect on it is swamped by power from the escapement.

IMHO... Ralph