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  1. Jh0an1

    the amount of k in torsion spring

    According to SMI Handbook 1991: k = E d 4 / (10.8 Nt D) Where E = Modulus of elasticity (MPa | psi) d = Diameter of wire (mm | in.) Nt = Number of total coils D = Mean coil diameter (mm | in.) k = Rate (N·mm/rev. | lbf·in./rev.) You can handle the expression to get k per degrees of deflection...
  2. Jh0an1

    Loss of free length/force in a compression spring

    Thanks a lot for your valuable explanation, desertfox. It's very useful to know your experience with the spring for the valve.
  3. Jh0an1

    Loss of free length/force in a compression spring

    For this wire, is the maximum allowable torsional stress 40 % or 45 %? (I see different values in different handbooks).
  4. Jh0an1

    Loss of free length/force in a compression spring

    P.D. Lost length = 3.60 mm We can make a new spring 3.60 mm longer. However, I would like to know the root cause of the problem.
  5. Jh0an1

    Loss of free length/force in a compression spring

    Hi. I have this compression spring: d = 7.50 mm Nt = 5.5 REF. ID = 84 mm L0 = 130.60 mm REF. Material SAE 1070; Tensile strength Sut = 1410 MPa (reported by the wire supplier). L1 = 94 mm; F1 = 422 N +/- 10 %; corrected stress: 260 MPa (18.4 % Sut) L2 = 58 mm; F2 = 837 N +/- 10 %; corrected...
  6. Jh0an1

    Spring setting

    Dear Israelkk, you are OK. Rate and free length are not requirements, but reference information. The mandatory requirement is force at height of 26.50 mm: 362,4 N ± 10 %. The ends are closed and ground. Please, see attached sketch. I see your suggestion about unused deflection, and why it...
  7. Jh0an1

    Spring setting

    Hi, Israelkk. The spring requirements are: Material: ASTM A 227 class II Wire diameter: 2,50 mm Inner diameter: 9,20 mm Bore diameter: 8,40 mm Free length: 32,50 mm Max. deflection: 6 mm Total coils: 6 Rate: 60,4 N/mm Ground Use: in oil filters of cars Static Thanks by your help. Best...
  8. Jh0an1

    Spring setting

    Thank you for your replies. We are the spring maker. I need to answer to my boss if we must to suggest to the client to reduce the spring mass (no feasible by stress), to omit the presetting or to lookfor other cost reduction in manufacture line. We can't to buy a new fastest coiler machine...
  9. Jh0an1

    Spring setting

    Hello, Engineers. Presetting is a process by the spring manufacturer in order to increasing the ability of the wire to withstand higher stresses. The spring will be compressed to max deflection in the final device. So, is it allowable for the manufacturer omit this process? (Will lead the set...
  10. Jh0an1

    Allowable stresses of an extension spring, reply

    And about this issue, Carlson says: "SMI recommends a conservative and consistent use of the stress correction factor and advises the use of the Wahl formula" Jh0an1
  11. Jh0an1

    Allowable stresses of an extension spring, reply

    thread404-351326 Thank you very much to all by the help. I just talked to my friend. The springs are working fine today. I have gotten this information of Carlson, in Springs magazine, courtesy of Spring Manufacturers Institute, confirming your suggestions: "When to Use: The stress...
  12. Jh0an1

    Allowable stresses of an extension spring

    Hi, desertfox, The initial tension of 83,2 N was obtained after the first sample, by experimental measurement. I had to estimated initially this characteristic in 32.2 N (the value suggested by SMI 1991 divided by 2 to consider the stress relieving). The springs of this automatic coiler machine...
  13. Jh0an1

    Allowable stresses of an extension spring

    Hi, israelkk, Initial tension: force to begin the clearance between the coils. Force to 147 mm: 150 N minimum Force to 200 mm: 450 N around(according to equations of forces equilibrium applied by me) The two springs doesn't give the same forces at 147 and 200 mm length because the first...
  14. Jh0an1

    Allowable stresses of an extension spring

    MintJulep, you're OK. The analyzed spring it's not truly static. Thank you for your comment.
  15. Jh0an1

    Allowable stresses of an extension spring

    TVP, thank you by the help. I will use your information.
  16. Jh0an1

    Allowable stresses of an extension spring

    Hi, I'm a mechanical engineer from Venezuela. I'm helping to my friend with his seats factory. He need to improve an extension spring. The current spring has the following characteristics: - Material: EN 10270-1 Grade SM - Tensile Strength, Rm: 1690 N/mm² minimum. - Wire diameter, d: 2,50 mm...

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