Friartuck

Constant Force Spring

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The attached pics are of what I believe is a constant force spring. Its coiled up and is wound tight by the shaft. This is not automotive, but the questions still are valid for a automotive/metallurgy perspective. The diagnoses is that the inner part of the spring broke and someone lost it. While I can regrind a small hole for the hook on the shaft to catch the end of the spring, the laxed state of the spring pops it off the hook. I think what is needed is to unanneal the first few inches of the spring to bend it into a tighter radius and make constant contact with the hook. Could this be as simple as heating those first few inches and letting them cool gradually before bending? Should this be unannealed while in the tight condition? There is a lot of meat left on this spring and was hoping to salvage it. Even a repalcement might have the same condition. FYI, the spring is 7/8 wide X 0.015 X about 30 inches.

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This looks similar to an Edison Phonograph spring.  Outside case different of course.  I just took the spring out of mine and filed a new taper and notch on the inside end. No tempering or annealing.  Had a difficult time rewinding the spring to get it back in its case but it has lasted 60 more years.  Not played often but three or four times a week.

 

iu1PB385IL.jpg

Edited by Tinindian
blurry picture (see edit history)

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Annealing and bending will likely work. Ideally the heated to dull red first few inches should be cooled at a rate slower than they will cool in open air. The answer is to immediately bury the heated portion in an insulating medium to slow down the cooling rate. The old school medium was wood ashes. They still are excellent and readily available . Any attempt at re-harding to a spring temper will likely cause future failure. 

Once annealed drilling and filing will be possible.

Have fun. Looks like a fun project................Bob

 

Edited by Bhigdog (see edit history)

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Looks like a clockwork spring in a barrel, e.g. phonograph, clock, music box and so on. By shortening it, you will reduce the running time of the item by a small amount. Is that OK?

 

BTW, it is not really a constant force spring but is pretty close. English clocks tended to have a barrel and American clocks did not, once they showed the world how to factory-build clocks by the thousand. If the length of spring is getting a bit short, the (clock?) will also slow towards the end of a wind. That spring is still in reasonable shape with most of it at the outside of the barrel.

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Thanks for the responses. This is a phonograph spring. If I were to anneal it, could I accomplish using a torch till dull red and back off the heat gradually, say over a 10 minute period? How long is enough?

Tinidian, where did you acquire the spring for your project? It looks new.

 

What is the difference between blue spring steel and stainless?

Edited by Friartuck (see edit history)

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 Have you tried victroladoctor.com and other suppliers of parts for old phonographs?

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The picture was from a Google search.  My Edison Amberola Cylinder phonograph was bought in April 1916 for Sylvia Reid's (my Grandmother) 25 birthday. It cost $60.00 and came with four cylinders. Cylinders were added and in the 20's a Winnipeg manufactured stand/cabinet was bought to hold the cylinders. It was used regularly until WWII. I first remember it being played in 1947. In 1957 I started playing it regularly. In 1973 the spring broke and I took it apart and shortened the spring by two inches, re-notched it and reassembled it. The mechanism is in excellent working order and the stand is in original shape.

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Yes, it could be repaired. I would buy that machine a new spring. Retire the old spring. A new spring will come oiled to prevent rusting. It isn't lubricated for use. There is a tool called a "spring winder" used to install the spring safely in the barrel. Otherwise you could well get hurt or ruin the new spring. Clock repair folks have the tool. I have heard of spring suppliers loading a spring for you if you send them the barrel. sometimes........... Be careful. 

'

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You have a spring winding tool: your lathe. If you want some details I should be able to find them for you. As said, be very careful, there is a lot of power in that spring even "unwound" in the barrel. If you anneal the end, you should get it out of the barrel and make sure you just do the end. Also clean the spring and oil it but minimum oil coz it will dry and make the spring sticky, so it won't unwind evenly as the phonograph runs.

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Yes, get a spring winder.  I didn't have one.  Just clamped one end in my vice and wound the spring.  Had to stop twice and just stand.  I couldn't let go and needed a rest so badly.  Even if I had a chair that I could have sat on it would have been better.  Some of us have to learn the hard way.

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I did forget to mention......WEAR LEATHER GLOVES ! It will slash your hand faster than a blink.

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11 hours ago, Friartuck said:

Thanks for the responses. This is a phonograph spring. If I were to anneal it, could I accomplish using a torch till dull red and back off the heat gradually, say over a 10 minute period? How long is enough?

Tinidian, where did you acquire the spring for your project? It looks new.

 

What is the difference between blue spring steel and stainless?

 

That could work but is a bit more hit or miss because the thin spring changes temp so fast. If you wish to do that, wire two pieces of 1/4" or thicker steel, sandwich style, to the spring section you wish to anneal. Heat the sandwich with a torch until dull red and cool slowly by using insulation or repeated heating. The sandwich is a heat sink to even the cooling rate out.

Blue spring steel is carbon steel. Stainless spring steel is stainless steel, likely 400 series if it's heat treated.

Not sure of the suitability of them for different applications...........Bob

Edited by Bhigdog (see edit history)

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