Announcement

Collapse
No announcement yet.

Spring tension

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Spring tension

    I was kind of looking for a spring that pullled a certain amount of weight, like 50# with no stretch till that amount is applied,, is there a spring site somewhere?
    http://www.facebook.com/cary.urka.urkafarms

  • #2
    I believe the laws of physics would make this impossible. Spring rates are fairly linear (excluding progressive springs) What are you trying to do?

    Comment


    • #3
      Sberry27

      I have learned a lot from your posts. I did a search on the net and found a mega spring site.
      www.springsmanufactures.com

      Hope it is of some help to you.

      This worked in my search engine but not in the reply try the post below for companies in your state!
      Last edited by NoDak; 01-20-2004, 01:35 AM.
      Electricity provided by Miller Bobcat, Flames by Smith Equipment.
      Member, Secret Society of Carbon Arc Torch enthusiasts.

      Comment


      • #4
        Mabe a better one Zycon Industrial Directory springs.
        www.zycon.com/Results/Springs.asp
        Electricity provided by Miller Bobcat, Flames by Smith Equipment.
        Member, Secret Society of Carbon Arc Torch enthusiasts.

        Comment


        • #5
          Re: Spring tension

          Originally posted by Sberry27
          I was kind of looking for a spring that pullled a certain amount of weight, like 50# with no stretch till that amount is applied,, is there a spring site somewhere?
          S,

          Tension springs can be wound with an initial tension like you want. The spring will not start to extend until the tensile load exceeds the built-in initial tension, then the spring behaves linearly as you would expect. I think it will be a fairly big spring to get a 50 pound initial tension value. I have purchased springs like that from Century Spring.

          http://www.centuryspring.com/home.htm

          Good Luck!
          Bill C
          "The more I learn about welding the more I find there is to learn..."

          Comment


          • #6
            Then I stand corrected, though I'm still confused as how this could be possible. Could someone explain?

            To have a spring that doesnt move until 50lbs is applied, would require an infinite k when 0-49 lbs is applied, then change to some other k when it hits 50 lbs, which is impossible for a hunk of metal to know.

            I mean say you get a 1000lbs/in spring and put 50 lbs on it, it's still going to move a little (1/20th of an inch). The downside is it's only going to move another 1/20th of an inch when you put an additional 50 lbs on it.

            You can get a progressive rate spring which has two (or more) spring rates built into it, but by nature the lower spring rate will "comply" with the load first meaning it will be the opposite of what you want.

            What am I missing? I went to those sites, but could not find anything on a spring like Bill said.

            Thanks,
            Mike

            Comment


            • #7
              turbo2ltr,

              Extension springs are twisted to form their shape with no gap between coils. If you overtwist them then they will have a pre-stressed condition where a residual force tries to pull the coils closer together. You can't see the additional residual force, because the gap between coils is already closed, but the residual force pulls them tighter together. You can measure it, because the initial tension is the force required to start opening a gap between coils. You can play with a paper clip and see a similar phenomena depending on how much you overbend the clip before putting it onto paper.

              Try this link for more info...

              http://www.centuryspring.com/cscpdf/...%20SPRINGS.pdf
              Bill C
              "The more I learn about welding the more I find there is to learn..."

              Comment


              • #8
                Ahh! Thank You. I get it now...

                I never really think about springs in extention. Too used to dealing with car springs...

                Good info!
                -Mike

                Comment


                • #9
                  Originally posted by turbo2ltr
                  Ahh! Thank You. I get it now...

                  I never really think about springs in extention. Too used to dealing with car springs...

                  Good info!
                  -Mike
                  You are welcome, Mike. From what I understand, the initial tension is a characteristic of the manufacturing process, but is not usually a controllable variable. I guess if you wanted to pay a huge amount of money you could get a custom initial tension, but normally you get what they give you. I'm not sure that was what Sberry had in mind, but was all that I could think of...
                  Bill C
                  "The more I learn about welding the more I find there is to learn..."

                  Comment


                  • #10
                    That threw me for a loop too, until you explained about the closed coil design with "preload". Now for the mind boggling (for me at least) question, Would the preload change if you cut the spring shorter? (Ie, buy a softer spring then tune it by shortening it?)

                    Comment


                    • #11
                      Yes Bill, I havnt looked at the sites yet and was going to look around and see if I had something in stock. I will look tonight at sites. I am running a simple control with a hyd cyl and I was wanting a saftey valve type of thing. If someone should muck up the adjustment during install I wanted some kind of stress relief instead of them bending all the brackets up. Under normal use the load is minor but if someone would set the initial length adjustment without enough relief in it there might be a disaster. The would be kind of,,, well,, idiot proofing.
                      http://www.facebook.com/cary.urka.urkafarms

                      Comment


                      • #12
                        Originally posted by Timinmb
                        That threw me for a loop too, until you explained about the closed coil design with "preload". Now for the mind boggling (for me at least) question, Would the preload change if you cut the spring shorter? (Ie, buy a softer spring then tune it by shortening it?)
                        I think the spring preload would decrease proprtionate to the amount of preloaded length that was removed.

                        Comment


                        • #13
                          Originally posted by bomberz1qr20
                          I think the spring preload would decrease proprtionate to the amount of preloaded length that was removed.
                          Wow, this is mind boggling.

                          According to the page that Bill posted, the rate would [edit]increase[/edit] (I need a math lesson) if you removed coils with everything else being the same.

                          Last edited by turbo2ltr; 01-20-2004, 01:46 PM.

                          Comment


                          • #14
                            If you take it to the extreme, and remove all the coils...how springy is a solid peice of wire?

                            According to that page, the rate is inversely proportional to the number of coils with everything else being the same.

                            Each coil "gives" or moves a little for a particualr force (F). This distance is cumulative and you get how much the spring is displaced by adding all these little movements when F is apllied. If there are less coils, each coil still moves the same amount for the same F, but there aren't as many of the coils to move, so when you add all the movement up, it's less. Less movement, with the same load would be an increase in rate.

                            Ehh, right?

                            Comment


                            • #15
                              Watch, clock, motion picture camera springs are sort of constant pressure springs. They are pretensioned wound and C holder is placed over spring then the spring is installed into camera was what I worked with mostly and the C holder removed. The pressure was fairly constant but increased some as spring was wound untill it bound coils togeather.

                              Even better constant pressure spring was used in the recent wind up radios. That spring was wound up lets say clockwise and unwound onto another roll in opisit direction like it was laminated or something.

                              Comment

                              Working...
                              X