# Horolovar Springs-Hooks Law

Discussion in '400-Day & Atmos' started by RodWall, Jan 14, 2007.

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1. ### RodWall Guest

#1
Hi all,
Can someone tell me what happens to the K in HOOK's LAW (F=kx) for the HOROLOVAR 400 day suspension spring when the temperature increases. Will k decrease with a temperature increase, which means that the 400day clock will run faster? And is this the same as for most metals?

Thanks,

Roderick Wall.

2. ### John Nagle Guest

#2
The horolovar springs are supposed to be temperature compensating but are affected by temperature. If the temperature cools the spring will shorten and the clock will run faster and vice versa.
btw if you are interested There is a very good book about Hooke "The Curious Life of Robert Hooke- The man who measured London by Lisa Jardine

3. ### John Nagle Guest

#3
enter Hooke's Law in your search engine and you will get a load of info.

4. ### RodWall Guest

#4

That’s interesting, It looks as if there are two things that effect the pendulum timing (with regard to the suspension spring). The temperature effect on both the length and the spring constant (k) of the spring. I hadn't thought of the length changing but of course it would. I did a search and found a site that stated that for most springs (that are metal) would get weaker with an increase in temperature. Which means that the spring constant (k) must get less if x (distance) is to increase for the same Force, if the spring gets weaker (Hook’s Law, F=kx), think I have this correct? Does that mean that HOROLVAR use a metal where the spring’s constant (k) increases to compensate for the length increasing. In practice I found that when the temperature increases the 400 day clock runs faster and when I wind the clock up it runs slower. I would like some comments about this.

Thanks,

Roderick Wall.

5. ### John Hubby Principal Administrator NAWCC Star FellowNAWCC Life Member

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#5
To all:

For info, Horolovar NiSpan-C suspension springs ARE temperature compensating. So are the Elinvar springs used by Atmos, and the Nivarox springs available from German suppliers (Nivarox is a Swiss material).

The "k" for a Horolovar suspension spring is very nearly constant over a wide range of temperatures, from about -10 to 140 degrees F. Over that range the variance is 0.0023 percent per 5 degrees F. This equates to 0.0092 percent over the normal 20 deg. F change that might be encountered in a home or business under unusual circumstances (60 to 80 F). The timekeeping change for a standard 400-Day clock between those two extremes will be 8 seconds per day (4 minutes per month). In addition, the coefficient of expansion is constant over the same range. Thus, at ordinary ambient temperatures there are NO dimensional changes in a Horolovar spring (it won't increase or decrease in length), nor is there a material change in the modulus of elasticity (k).

The result is that the variance in rate of the pendulum in normal circumstances will not be noticeable. One could argue that the change in air density, as well as the expansion/contraction of the metal in the pendulum over that same range, can also cause a measurable rate change. Maybe, although one offsets the other. In normal service circumstances there is almost no measurable change as has been amply proven since 1949 following US Bureau of Standards tests that were made when Terwilliger was developing the original Horolovar suspension springs.

This kind of performance (or better) is characteristic of the three known commercial nickel alloys mentioned above, namely NiSpan-C (Horolovar since 1949), Elinvar (C. E. Guillaume 1918 patent, used commercially by Atmos since 1930), and Nivarox (currently produced by German clock suppliers). There are a number of other known alloys that exhibit the same characteristics but none are produced commercially for suspension spring or balance spring purposes.

Elinvar has less than 1/4 the change in "k" shown by NiSpan-C, thus the timekeeping performance of clocks using Elinvar for suspension springs will be better than using other alloys. In fact, the rate change over normal room temperature variations is hardly measurable, less than 2 seconds per day over a 20 degree F range of temperature. However, Elinvar is quite a bit more difficult to process into suspension springs and more brittle, thus more susceptible to breakage than NiSpan-C. J. L. Reutter and subsequently Jaeger-LeCoultre evidently decided that constant performance outweighed the manufacturing and possible breakage problems and have used that alloy since the first commercial production of the Atmos clock, now nearly 77 years and ongoing. Atmos clocks readily demonstrate rates to less than 1 minute per month (2 seconds per day).

Hope this will help shed some light on temperature compensating suspension spring materials and their performance.

John Hubby

6. ### John Nagle Guest

#6
Your mainspring is going to have a greater curve than the suspension spring. The energy of a mainspring is great then evens for a period and then tales off. This is often the reason for some timekeeping fluctuation over the course of the spring's power output.
Normally an increase in temperature will lengthen a suspension spring and/or pendulum resulting in a slowing of timekeeping.

7. ### John Nagle Guest

#7
ni span c on your search engine covers forms from spring to bar stock. also elasticity info etc. one thing to keep in mind is most clock springs are not produced of the quality (specs)to achieve the high end results of the materials used.

8. ### John Nagle Guest

#8
you have probably already seen this but I want to learn how to create a link! http://en.wikipedia.org/wiki/spring_(device)

9. ### John Nagle Guest

#9
this link doesn't work! what did I do wrong?

10. ### kirklox Registered User

Dec 17, 2002
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#10
Last edited by a moderator: Dec 7, 2017
11. ### John Nagle Guest

#11
thank you Sam!

12. ### RodWall Guest

#12
Hi all,

Thanks for your help. Well it looks as if the spring's time keeping ability should not change much with regard to temperature change affecting both the length and the spring constant (k) as they won't change much.

Interesting in that I also have an ATMOS clock that is next to the 400 day clock, a Badische Uhrenfabrik c 1902 Horolovar Plate number: 1015. The ATMOS keeps good time but the 400 day clock is not as good.

As John Hubby has indicated in his posting, this is because ATMOS use Elinvar that has less than 1/4 the change in "k" than the Horolovar which uses NiSpan-C in their suspension springs.

With regard to the main spring, the Horolovar 400 day book indicates that when the spring is wound up fully. The power to the clock is greater which causes the pendulum to swing around more, and the time for one cycle will be longer and is why the clock will run slower. Thanks everyone for you help, I have learnt a lot about suspension springs. The link for springs was also very interesting as it also contained an external link to a website to show you how to design and make springs, good if you need to make a replacement spring.

The temperature here in Melbourne Australia today is 40 deg C.

thanks everyone.

Roderick Wall.

13. ### John Hubby Principal Administrator NAWCC Star FellowNAWCC Life Member

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#13
Roderick, thanks for raising the question and also for noting the difference in performance between your Atmos and Badische clocks. One thing I might mention is that if your Badische has the 3-Ball style pendulum such as or similar to No. 28 in the Repair Guide, it will be difficult to regulate because that design unfortunately doesn't enable fine adjustment. If it has a disc pendulum, then be sure you make very small rate changes only from one direction as you approach the correct time and you will achieve better timekeeping.

With regard to the mainspring power question, you said:
This info from the Repair Guide is unfortunately not correct. If anything, the clock may run slightly faster when fully wound, since the impulse force available is proportionally greater than the frictional resistance of the time train and escapement mechanism than it will be as the mainspring winds down.

Further, greater or lesser rotation does NOT change the time of a rotation cycle for a given pendulum and suspension spring, within the elastic limits of the spring. This is because one of the physical principles of torsion pendulums is that they are fundamentally isochronous, meaning that the rate (period or time of rotation) will remain constant regardless of more or less rotation. For example, you will find that when a clock that operates at 8 beats per minute is first wound, the pendulum may be turning 290 degrees. As the mainspring winds down, the rotation will very gradually decrease over a period of several months to say 240 degrees, but the clock will continue to operate at 8 beats per minute, and the clock rate will NOT significantly slow down. This is simply the conservation of energy . . less impulse force producing less rotation. Noticeable slowing will only occur within the last month to six weeks of operation when let run for 400 days or more. That final slowdown is because the frictional resistance in the escapement mechanism begins to overcome the power available, to the point it will reduce the rate of the clock. For that reason, I recommend winding your 400-Day clocks at least every six months (do it at the spring and fall time change) to maintain the most accurate timekeeping.

Another example can be seen by comparing several 400-Day clocks side by side. A Schnekenburger operating at 6 beats per minute with a pendulum rotation of 680 degrees (1-3/4 turns per beat) will keep accurate time as will a Gustav Becker operating at 8 beats per minute with a pendulum rotation of 240 degrees. Similarly a miniature Schatz operating at 10 beats per minute with a pendulum rotation of 360 degrees. Perhaps an even better example is to compare two otherwise identical clocks with significantly different pendulum rotation. I have two Schatz 49 clocks, one runs at about 380 degrees rotation, while the other only produces 250 degrees. Both are operating at exactly 8 beats per minute and run within 2 to 3 minutes per month. The differences in rotation are a function of how much energy is transmitted to the pendulum at the escapement . . the one with high rotation has less frictional resistance (or a stronger mainspring or a better escape setup), yet the two clocks will run for the same period with very similar accuracy.

John Hubby

P.S.: 40 deg C just might slow down your Badische. Or the 0 deg C in Houston this morning would speed it up (at least a little bit)! :biggrin:

14. ### RodWall Guest

#14

My Badische 400 day clock has a disc pendulum. Thanks for the information on adjusting the pendulum rate "very small rate changes from one direction".

I have a system where I let the clock run for about a week for each of the following tests. I do three tests, one with the pendulum adjustment set to maximum another set to midway and another set to minimum. I then determine how many turns there are between the each setting then calculate the time (rate) change for each turn of the rate adjustment.

I then calculate the required number of turns required from the current setting (of the last test). I then turn the rate adjustment the required number of turns that should put the pendulum somewhere near the correct rate. I do another test. Then knowing how many turns was used for the last test and how fast or slow the clock is running, I again calculate the rate change for each turn.

With the new calculated rate per turn information, I repeat the test until I have the clock running on time. But this is where I should have made the rate changes in very small increments from the one direction as suggested. I found that when I over shot the correct rate setting and then went back the other way, my system didn't work because of the slack in turning the adjustment back. Thanks for your suggestion.

I have a good book packed away in storage that goes into pendulums escapements etc. When we move and unpack I will get it out again and relearn what I have forgotten. Yes Conservation of energy is all about converting energy into one form or another, energy is never lost. Your suggestion to wind a 400 day clock every six months is a good one, which I will do, thanks.

John (or anyone else), from your experience how accurate do you think I should be able to set the Badische clock to? I know this is a hard question but would like to know what you think is possible.

Thanks for your time and help,

Roderick Wall.

15. ### skclock Registered User

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#15
I’d like to ask a question to Mr.Hubby.
When I read that Horolovar Guide states that a wider rotation of the pendulum slows down a 400-day, I was very surprised and, trying to find the actual reason (in fact I was sure that a wider oscillation requires the same time, due to faster speed), I was wondering if a sort of circular error might occur in a torsion pendulum (as in a gravity pendulum) or any other sort of error.
Later, I read your post clarifying the Horolovar Guide’s statement is wrong.
Some observe that a gravity pendulum clock gains with the mainspring quite unwound, until it stops. I don’t know if it’s true, but this could be related to the circular error, that vanishes, as the oscillation amplitude decreases and this means that the pendulum period decreases as well(the clock gains).
So, it seems that a torsion pendulum is more reliable than a gravity one.
Is that correct?
Any comment? Thank you.

16. ### John Hubby Principal Administrator NAWCC Star FellowNAWCC Life Member

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#16
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Enrico said:
I know this will likely cause the gnashing of teeth from my friends who have precision gravity pendulum clocks, but IN FACT the average spring driven torsion pendulum clock fitted with a Horolovar suspension spring is more accurate than the very large majority of spring driven gravity pendulum clocks.

Here's why:

1) The torsion pendulum is inherently isochronous (keeps the same beat rate even with large changes in pendulum rotation) and not susceptible to the circular error problems that occur with gravity pendulums. In a gravity pendulum clock, the pendulum swing will change significantly between a fully wound mainspring and one nearly wound down, causing measurable rate changes in a week's time. In a torsion clock, there will be very little change in rate until the mainspring is almost completely wound down.

2) The torsion pendulum is hardly affected by normal ambient temperature variations; e.g. the change in length of the suspension spring is significantly less than will occur in the average gravity pendulum rod, and correspondingly has less rate variance with temperature. Similarly, the change in torsional modulus is minimal with changes in temperature and thus rate variance is quite low compared to a gravity pendulum.

Once regulated properly, an ordinary 400-Day clock will easily keep time within one minute per week, and many within one minute per month. How many spring driven gravity pendulum clocks can claim that accuracy?

Now, all will note I didn't compare a spring driven torsion clock with a weight driven gravity pendulum clock. The weight driven gravity pendulum clock has a big advantage over the spring driven versions because the circular error is constant and thus can be compensated. EVEN SO, there are many spring driven torsion clocks that will keep time better than the average weight driven gravity pendulum clock. Hands down, the Atmos clocks will do that and some of them even better than precision weight regulators.

Long story short: The long-maligned torsion pendulum is in fact more reliable than the average gravity pendulum.

John Hubby

17. ### RodWall Guest

#17
Thanks John for your help and information.

Roderick Wall.