Restraining 31day clock springs

Discussion in 'General Clock Discussions' started by chrisuk, Sep 5, 2017.

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  1. chrisuk

    chrisuk Registered User

    Sep 4, 2010
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    I had a situation where 'C' clips could not be used, even with the spring fully wound there was insufficient space between movement pillars/arbors to fit them. I know I could have used wire to wrap the springs but then had a 'I wonder if' moment. I have a lot of those plastic cable ties (1.3mm thick 4.7mm wide) so decided to test them. I made a tie into a loop and and passed it over a horizontal bar fixed to the table of the pillar drill. The top of the loop fitted over the hook of a digital luggage scale. The top loop of the scale went over a hook fixed in the drill chuck. I wound the table down which drew the quill after it. I then used the quill lever to exert force on the tie. I tested five ties to destruction and the lowest reading I obtained before the ratchet on the tie failed was 70lbs, so I used them to hold the springs. If you want to try this make sure that you test some samples of your cable ties first.
    View attachment 355681
     
  2. harold bain

    harold bain Forums Administrator
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    I hope your health insurance is paid up. These springs are hard enough to work on with wire, and tend to want to wander out sideways when you are not looking. Add in the possible failure of a cable tie, and it is a recipe for disaster.
     
  3. gleber

    gleber Registered User

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    I have used cable ties, but never just one by itself. I usually use 3 with the outside ones going in one direction and the middle one the other way and offset a little. I still get a little queasy when working on it.

    View attachment 355724

    Tom
     
  4. lpbp

    lpbp Registered User
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    No on cable ties, there are two places where it can fail, the plastic itself and the ratchet, there are some clamps that are thinner rather than round are flat, these usually work, if not go with the wire.
     
  5. David S

    David S Registered User
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    Chris this topic has come up a few times as you can imagine. You have done due diligence and have tested your cable ties and they far exceed the separation force required according to experiments that I have done.

    Most cable ties are made of Nylon 6/6 or similar and nylon can dry out if stored in very dry locations and hence loose its strength, hence the concern of some.

    I started out using the round section C clamps but found that they often interfered with internal components. So I switched to wire. There are various types of wire. Some use soft annealed wire used for things like suspended ceilings, or electrical contracting. I use 20 awg wire but some prefer 18 awg.

    ONce the restrained spring is transferred to the mainspring winder and released, I keep the wire intact so that I can be sure it will keep the spring in the correct diameter when I reassemble the movement, only after final assembly and test, do I cut the wire off.

    Others have used some sort of cord with a knot that they trust.

    David
     
  6. bangster

    bangster Super Moderator
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    I've used 70-lb test cable ties for tasks far beyond clock mainsprings. But don't use the cheap little ones: use the big 'uns
     
  7. BLKBEARD

    BLKBEARD Registered User
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  8. chrisuk

    chrisuk Registered User

    Sep 4, 2010
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    Back home now, thanks for all your comments, the idea of using more than one tie is good. The springs I was working with were left restrained for several days without the ties moving. I'll have to come up with some sort of jig to measure the pull that a wound up spring exterts on the tie.
     
  9. David S

    David S Registered User
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    Chris I made a fixture to try and measure the hoop stress a while ago. I will be interested in what you come up with.

    David
     
  10. bangster

    bangster Super Moderator
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    Fact worth noting: When you buy a new wire-restrained mainspring,you can hold it in a gloved hand when you cut the wire, and keep it restrained with your hand, until you release it.
     
  11. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    The Korean 31 day springs com with an additional retaining piece that sits both between the outer two turns of the spring and across the plate and pillar and must be removed from the restrained spring so that the plates can be separated.
     
  12. harold bain

    harold bain Forums Administrator
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    You should remove these with the spring let down, and no restraint, then wind them up, put your restraint on, and let them down again. These are to force the spring to unwind away from the movement. If they are not properly put back, the springs will foul against the next wheel up in about a week.
    .
     
  13. kinsler33

    kinsler33 Registered User

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    Another thin alternative to cable ties or round-section C clips is a worm-gear hose clamp. These are thinner than nylon cable ties and of unquestionable strength. I've used them when C clips proved too clumsy.

    I'd also recommend a pair of flat-section C-clips from Timesavers. They're too expensive, but in general they're worth it.

    M Kinsler
     
  14. James McDermaid

    James McDermaid Registered User
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    I am in the electronics business and I don trust zip ties to hold cables let alone a spring.

    I have used brand new fresh ties and broken them with my hands..

    The white one are worst.

    Jim
     
  15. kinsler33

    kinsler33 Registered User

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    I didn't know that, and thank you.

    I have found that there are several configurations of these strange 31-day spring restrainers/retainers, and t's a good idea to take a picture of them before disassembly, for they can be rather counterintuitive to re-assemble. (It's _always_ a good idea to take too many pictures of every movement, for that matter: you never know when something strange will happen.)

    And yes, white nylon zip ties tend to be a bit less reliable than, say, the black ones. I think it's because they're more sensitive to zapping by sunlight or other ultra-violet sources, and then they get brittle. But I've had surprises with black zip ties as well, and I've learned to test each one by giving it a sharp crease prior to installation. Even then, it's a good idea to be suspicious of their strength.

    Mark Kinsler

    on the other hand, you can construct just about anything with zip ties and half-inch steel electrical conduit.
     
  16. Willie X

    Willie X Registered User

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    I would recommend that you stick with soft iron tie wire. The kind used to hold rebar together in reinforced concrete. It's cheap and sold at nearly all hardware stores.

    Some people don't seem to understand that a restrained spring is not always a static unit. It can unexpectedly jump, when the coils slip, and if this happens you better have something strong to stop it. Now, if the spring coils never did this trick, it actually takes very little strength to hold a spring at the '8-Day run down' point. This is where the springs should be restrained, at about 1/4" to 3/8" smaller than the great wheel.

    Willie X
     
  17. roughbarked

    roughbarked Registered User

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    I use wire as suggested above. Have a set of C rings but usually use the wire instead.
     
  18. R. Croswell

    R. Croswell Registered User
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    #18 R. Croswell, Sep 10, 2017
    Last edited: Sep 10, 2017
    I sometimes use cable ties on very narrow and light springs as found in some 30-hour clocks and alarm clocks. It can be hard to keep wire from slipping off these narrow springs. The flat cable ties I use for this are nearly as wide as the spring and these springs have limited strength so a failure will be only a small 'disaster'. I do have the various flat and round C clamps but they never seem to be the right size. So I use #18 soft steel wire for almost everything. I would be afraid of #20 steel, or copper wire. (The smaller the No. the heavier the wire).

    I think multiple cable ties (or wires) may provide less protection than one may assume. Most of the load will be held by the tightest tie. If that one should bust there could be a chain of failures. For really brutal springs I'll use two wraps of wire, not two pieces.

    With 30 day springs the the main difference is in the length of the spring, not so much in the strength. But if the restraint does fail, all that long spring flying is sure to cause a bigger mess

    With cable ties in this application it isn't that the rated strength of the tie will be exceeded so much as defects and variations in the ratchet lock from tie to tie and maker to maker. All ties are not created equal. When testing ties, put a drop of mainspring oil on the clasp first. I had previously used ties occasionally until I experienced failures. I believe tie had gotten a drop of oil on it accidentally and it let go on me. Restraining springs is a "mission critical" operation where failure is not an option.

    RC
     
  19. Willie X

    Willie X Registered User

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    I have always recommended using 16 guage tie wire but after RC's post I thought I would measure the wire I have. It measures .063", which is 14 guage, soft iron tie wire.

    Maybe a previous roll was 16 guage?

    Anyway, I like the 14 guage and would recommend it over anything thinner. No way on the 20 guage! Except on maybe a little baby spring.

    Willie X
     
  20. R. Croswell

    R. Croswell Registered User
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    Lowe's sells the 16 gauge wire https://www.lowes.com/pd/Blue-Hawk-Steel-Rebar-Ties/4007055 which I think is a good choice. I've never had a failure with 18 gauge but as I stated earlier, I use two wraps on real heavy springs. I think 16 gauge would be a better choice.

    RC
     
  21. David S

    David S Registered User
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    I goofed in my previous post. Somehow I had 20 awg on my mind for another thing I was working on. I do indeed 16 awg rebar wire as others have mentioned. I remember trying to get 18 awg but the hardware store was out.

    It is fairly soft and doesn't have much memory so it is easy to shape in a curve and get it around the mainspring without fouling an adjacent arbor. I think it has a breaking strength of around 100 pounds depending on which tensile strength you use. From my experiments trying to determine the hoop stress in a fully wound spring I came up with range of 6 to 10 lbf. The weak part is probably the area where you twist it, and especially if you over twist. The black surface is not all that slippery so stays in place fairly well while twisting.

    I am working on a Sessions T&S now and here are pics of the restrained springs.

    View attachment 356274

    David
     
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