Sus. Spring Material

[Jay Fortner]

Bronze vs steel alloy as it relates to thickness and oscillation rate.
I'm working on a Schumer disc pend. clock. I've been servicing this clock for the past ten years now and recently the lady brought the clock in and during transport if fell over and broke the sus. spring, The original spring is blued steel .0035 thick and 1.5mm wide. I replaced it with 1mm wide alloy steel of the same thickness and it ran seriously slow. I change it out with .004 thickness spring material and still it's running very slow. I'm sure the issue is the width of the spring material and haven't found anything wider than 1mm The only thicker spring material I've found is bronze.

 

[KurtinSA]

Not sure what a Schumer disk pendulum clock is...I can't seem to find any reference in the repair guide. That's the way to figure out what size, ie thickness, spring is needed. Haven't heard of blued steel springs...some of the earlier springs were bronzy in color. These might have been the springs produced before Terwilliger came up with the alloy NiSpan-C for making springs. Steel or bronze don't have the ability to hold a constant torsion constant over a range of temperatures...NiSpan-C does.

As for dimensions, the torsional response has to do with the cross-sectional area of the spring. I've always bought Horolovar suspension springs...they are the "correct" thickness and all I care about then is getting the proper thickness. I don't have the skill or brain power to measure the width of an Horolovar spring. Maybe someone has that tidbit of information written down somewhere! I believe all of Horolovar's springs are of a constant width.

If you have a variety of suspension springs, hopefully Horolovar made, find a way to mock up a suspension unit using the top and bottom blocks...no fork is needed. Find the proper length and without cutting the excess, slide the top block onto the spring and clamp it down. Then secure the top block on a test stand and hang the pendulum. Turn the pendulum and release. Begin timing how long to get 8 beats. Keep changing the suspension spring out in your test setup until you get close to 60 seconds. Then do a final cut and build the completed suspension unit. If you can't quite get there, but have a setup that gives say something under 60 seconds for 8 beats, you can thin the spring little by little with continued testing in the mock setup to hone in on 8 beats in 60 seconds.

Kurt

 

[roughbarked]

Yair to be fair, the width isn't the thickness. Basically get the closest and thin it. Because it is the thickness that matters more than the width.

 

[Bod]

Put up a clear photo of the back plate, and a couple of general shots, someone here might recognise the clock and know exactly which suspension spring you need.
If all else fails, then pick a mid range Horolvar spring, set the pendulum to its mid point of adjustment, and run the clock.
The speed of the clock, the amount of gain or loss, will tell you whether you need to go up or down the thickness, and by how much.
Non Horolvar springs, then you are in unknown territory, and can only go by trial and error.

Bod

 

[MartinM]

I assume the .004" spring you used in from Horolovar.
By how many seconds per minute or minutes per hour is it slow?
The thickest Horolovar spring is .0045".
The difference in rate by exchanging a .004" Horolovar spring with a .0045" spring is ~+20 minutes per hour or seconds per minute.

Alternatively, and assuming the break occurred at the pendulum end of the suspension, just remove the broken bit of spring from the bottom block and move the bottom block up on the suspension assembly a couple of millimeters. At worst, you'll need to thin the spring a bit to regulate the clock (Not knowing what kind of pendulum we're talking about, here.).

 

[Jay Fortner]

The clock ran for many years and kept decent time with the blued steel spring that was in it.
The dimensions are 130mm from bottom of top block to top of bottom block and 5.4mm from bottom of top block to top of fork.
The original spring is .0035" X 1.5mm wide.
There is a big difference in oscillation rate as it relates to sus. spring width. Think about it,a wider spring is going to resist twisting more than a narrower spring of the same thickness and length.
The original question was the difference in bronze versus steel.

 

[KurtinSA]

The original spring had a cross sectional area of 0.00021 mm^2. The setup with a 0.0035" and 1mm spring had an area of 0.00014 mm^2 while the 0.004" and (assumed) 1mm spring had an area of 0.00016 mm^2. So it's no wonder that just based upon the physical properties, the attempts to find a replacement spring haven't worked for the clock to keep decent time. I'm sure the properties of steel and/or bronze will have some effect but the area has to be strongly considered. Even going to 0.0045" spring is not going to get you to the original cross sectional area. But The Horolovar Store advertises bigger and longer springs from 0.005" and above. Use of an 0.005" thickness spring with a 1mm width (if that's what their springs are) will get you very near the original cross sectional area.

I'm new to some of this stuff, but it is my understanding that very few sources of suspension springs have the temperature compensation, or rather the lack of effect on properties due to temperature, than other sources. The blued steel spring you mention is something that I've not heard of before. The Horolovar springs sold are steel colored, certainly not bronze in tone.

If it were me, I'd try to acquire thicker springs from a reputable source and do some bench experiments to find the one thickness that will work in your clock. I still wonder what a "Schumer" disk pendulum clock looks like. Without a better idea of the manufacturer of the clock, the length of the suspension doesn't help us much. I checked the repair guide and the longest suspension unit distance between the top and bottom blocks is around 120mm. So, 130mm is a very long suspension spring.

Kurt

 

[Jay Fortner]

My bad!!!
The clock is a F. Zacher & Comp.
All the other info is correct.
Your cross sectional equations are very helpful and I'll keep that in mind if I ever run across something like this again.
Now I just have to acquire some heavier spring.

 

[KurtinSA]

Ah, that's interesting. I found this thread/post on F. Zacher:

Who is F. Zacher? | NAWCC Forums

From what John says, he was a retailer and seemed to carry Huber and JUF clocks.

Kurt

 

[shutterbug]

Just for reference, you get about 4 minutes per hour change for every .0001 thickness change. That's with Horolovar's springs. Thicker is faster, thinner is slower. Shortening the spring will also make it run faster.

 

[MartinM]

Kurt. Thanks for reminding me that Horolovar springs also come in .0050, .0055 and .0060 inch thicknesses. Brain fart on my part.

 

[Jay Fortner]

Ah, that's interesting. I found this thread/post on F. Zacher:

Who is F. Zacher? | NAWCC Forums

From what John says, he was a retailer and seemed to carry Huber and JUF clocks.

Kurt

That's the aminal! The one I'm working on appears to be the JUF with the less decorative pend.
I'll get into Terwillegers book and see what he has to say about it.

Thanks!!!!!!!

 

[etmb61]

That's the aminal! The one I'm working on appears to be the JUF with the less decorative pend.
I'll get into Terwillegers book and see what he has to say about it.

Thanks!!!!!!!

Terwilliger doesn't say much.

Many of the earlier disc pendulums had extra weight added in some form so the repair person could use the spring material they had on hand.

With enough extra weight you could use a pocket watch mainspring if you needed to.

Terwilliger assumes that all the old discs are equal to the sample he tested when he does give info. Reality is start thick and work thin.

Eric

 

[Jay Fortner]

Hadn't thought about taking weight out of the pend. I'll give that a try.