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(Metalshapers): Re: Choosing a steel for seat belt anchors?

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  • msaforum@metalshapers.org
    Kevin C. Kelly ( kkelly ) has posted a new message titled Re: Choosing a steel for seat belt anchors? . Posted: Wed, Dec 1st, 2004 - 10:47AM kkelly I thought
    Message 1 of 7 , Dec 1, 2004
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      Kevin C. Kelly (kkelly) has posted a new message titled "Re: Choosing a steel for seat belt anchors?".


      Posted: Wed, Dec 1st, 2004 - 10:47AM



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      kkelly


      I thought the heat treating was more for toughening up the threads. Since most racing organizations specify Grade 8 hardware (7/16" typically), I thought 1/2" would add an increased safety facter.
      Reply View Thread




    • msaforum@metalshapers.org
      Gene Newcomb ( geneatcdm ) has posted a new message titled Re: Choosing a steel for seat belt anchors? . Posted: Wed, Dec 1st, 2004 - 10:55AM geneatcdm We ve
      Message 2 of 7 , Dec 1, 2004
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        Gene Newcomb (geneatcdm) has posted a new message titled "Re: Choosing a steel for seat belt anchors?".


        Posted: Wed, Dec 1st, 2004 - 10:55AM



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        geneatcdm


        We've made a million seat belt parts for Beams Industries. The tongues are hardened the retractor bases are generally not and we make an extension that is 3/16 x 1 1/2" cold roll. It is for the retractor base on school busses and elevated type seats.
        4130 can be heat treated at that thickness and any other if you have a big enough oven. 50ish Rc. Tempered back at 500' or so for a number of hours but that is academic. Point is you don't need to.
        If you think MS 1/2" is not strong go with 3/4" MS or 1".
        Gene
        Reply View Thread




      • msaforum@metalshapers.org
        Roger VanHoozer ( rog02 ) has posted a new message titled Re: Choosing a steel for seat belt anchors? . Posted: Wed, Dec 1st, 2004 - 11:10AM rog02 Hi Kevin:
        Message 3 of 7 , Dec 1, 2004
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          Roger VanHoozer (rog02) has posted a new message titled "Re: Choosing a steel for seat belt anchors?".


          Posted: Wed, Dec 1st, 2004 - 11:10AM



          *


          rog02


          Hi Kevin:
          Are these custom mounts to be the anchor points for the seat belt hardware or are you going to loop the belt webbing around the mounts?
          As Richard has already responded, heat treating tends to make the part more brittle without raising the ultimate tensile strength. The "Grade" of a bolt has more to do with the shear loading (side loading) capability than the tensile (straight line pull). The limiting factor of this type of mount would still be the threaded area of the attachment.
          If the belt mounts are intended to have the webbing looped around them and secured with a slip adapter then there will be some other design factors to be considered. Poynter's Parachute Riggers Manual states that webbing loses approximately 50% of its tensile strength when it is turned about a bolt (looped back around hardware)given a perpendicular pull to the hardware. For angles of load other than perpendicular, further decrease the effective tensile of the the webbing will be exhibited (I.E. Belt Dumping).
          A proper seat belt installation requires quite a bit of fore thought to make it safe under a wide range of scenerios. I would suggest referring to the belt manufacturer for technical assistance.
          Roger VanHoozer
          FAA Certified Parachute Rigger (NPD)
          Reply View Thread




        • hemirambler
          Hey Fellas, I think there s some confusion going on here: If a material such as steel is hardened it becomes stornger in BOTH Tension and Shear. A quick look
          Message 4 of 7 , Dec 1, 2004
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            Hey Fellas, I think there's some confusion going on here:

            If a material such as steel is hardened it becomes stornger in BOTH
            Tension and Shear. A quick look at a stress strain curve can
            illustrate that if you'd like.

            As for "loading" of a bolt - technically speaking they are NOT meant
            to be used in SHEAR - they are TENSION fasteners. And YES I know I'm
            gonn acatch soem "flack" for this comment, but read on and I will
            try to make the case in point. If a bolt "sees" shear it is usually
            just a matter of time before it fails. Dowel pins are often used to
            carry shear loads. They are of course typically hardened to
            increase their ability to carry the load amoung other things. Dowel
            pins are also fit TIGHT to prevent the "working" of a joint -
            without that they can sometimes "beat" themselves to death - leading
            to of course failure. But getting back the bolts again, a preperly
            designed joint (using fasteners) will be designed such that the
            clamping load induced by the tensioning of the fastener will "carry"
            the shear loads as such the bolt never "sees" the shear load - just
            the tension load - if critical a pin or step or some other means of
            carying shear loads will be designed into the mix. AS far as bolts
            grades go - the higher the grade -typically the harder the bolt and
            as a result the stronger the fastener. As stronger fastener will
            stretch the same (at least in the beginning) as a weaker one
            (young's modulus) at least until the weaker one starts to yield or
            plastically deform. So the stronger bolt will take MORE tension
            (torque) before yielding thus providing MORE clampling force. Most
            bolts are typically tensioned (tightened, torqued) to induce 75% of
            yield. meaning that there is a fair margin (25%) before you could
            DEFORM your bolt. As economics enter the equation we now
            see "torque to yield" bolts. These bolts as the name implpies are
            toqued to 100% of yield thus providing additional clamping -
            thus "acting" like a LARGER bolt - at least economically speaking -
            the downside of course is that - you only use them once!


            If you don't believe any of this - go look at the stress strain
            curve for a fastener tested to failure. As the test specimen starts
            to plastically deform the cross section is actually being reduced -
            however the tensile numbers continue to increase or even levels off,
            but, the part is actually getting stronger since it is now smaller -
            this can be a result of work hardening. This curve will basically
            continue until failure.

            Working loads are typically calculated on the 75% of yield whereas
            safety factors are calculated using the yield point.

            As far as a seat belt goes - I would first determine what the
            industry standard for the acceptable safety factor is and then go
            from there. I really don't think avoiding the "brittle" fasteners is
            a big concern since I don't see a cloth seat belt being able to
            apply much of a shock load, but that's just a guess.

            Every industry used different factor of safety - I once talked with
            an Indy car designer who used 1.1:1 as a safety factor. In the
            medical industry we typically use 4:1 safety factor - sometimes
            more! Of course determining what loads are involved is the
            challenge!


            Sorry to babble on for so long - I hope this helps make this subject
            a little more clear.



            Jacin in Ohio



            <snip>
            --- In metalshapers@yahoogroups.com, msaforum@m... wrote:
            > Hi Kevin:
            Are these custom mounts to be the anchor points for the seat belt
            hardware or are you going to loop the belt webbing around the
            mounts?
            As Richard has already responded, heat treating tends to make the
            part more brittle without raising the ultimate tensile strength.
            The "Grade" of a bolt has more to do with the shear loading (side
            loading) capability than the tensile (straight line pull). The
            limiting factor of this type of mount would still be the threaded
            area of the attachment.
            If the belt mounts are intended to have the webbing looped around
            them and secured with a slip adapter then there will be some other
            design factors to be considered. Poynter's Parachute Riggers Manual
            states that webbing loses approximately 50% of its tensile strength
            when it is turned about a bolt (looped back around hardware)given a
            perpendicular pull to the hardware. For angles of load other than
            perpendicular, further decrease the effective tensile of the the
            webbing will be exhibited (I.E. Belt Dumping).
            A proper seat belt installation requires quite a bit of fore thought
            to make it safe under a wide range of scenerios. I would suggest
            referring to the belt manufacturer for technical assistance.
            Roger VanHoozer
            FAA Certified Parachute Rigger (NPD)
          • Dick Raczuk
            Jacin of Ohio Right on. The one thing I missed, and maybe it was brought up, make sure wherever this bolt is being installed,whatever size it may be, have
            Message 5 of 7 , Dec 1, 2004
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              Jacin of Ohio
              Right on. The one thing I missed, and maybe it was brought up, " make sure
              wherever this bolt is being installed,whatever size it may be, have some
              method of spreading the load so it doesn't pull through the mounting
              surface". ( big heavy washer)
              Dick
              Jacin of Ohio sounds more Knightly
              ----- Original Message -----
              From: "hemirambler" <jbarnes8@...>
              To: <metalshapers@yahoogroups.com>
              Sent: Wednesday, December 01, 2004 10:34 AM
              Subject: [metalshapers] (Metalshapers): Re: Choosing a steel for seat belt
              anchors?




              Hey Fellas, I think there's some confusion going on here:

              If a material such as steel is hardened it becomes stornger in BOTH
              Tension and Shear. A quick look at a stress strain curve can
              illustrate that if you'd like.

              As for "loading" of a bolt - technically speaking they are NOT meant
              to be used in SHEAR - they are TENSION fasteners. And YES I know I'm
              gonn acatch soem "flack" for this comment, but read on and I will
              try to make the case in point. If a bolt "sees" shear it is usually
              just a matter of time before it fails. Dowel pins are often used to
              carry shear loads. They are of course typically hardened to
              increase their ability to carry the load amoung other things. Dowel
              pins are also fit TIGHT to prevent the "working" of a joint -
              without that they can sometimes "beat" themselves to death - leading
              to of course failure. But getting back the bolts again, a preperly
              designed joint (using fasteners) will be designed such that the
              clamping load induced by the tensioning of the fastener will "carry"
              the shear loads as such the bolt never "sees" the shear load - just
              the tension load - if critical a pin or step or some other means of
              carying shear loads will be designed into the mix. AS far as bolts
              grades go - the higher the grade -typically the harder the bolt and
              as a result the stronger the fastener. As stronger fastener will
              stretch the same (at least in the beginning) as a weaker one
              (young's modulus) at least until the weaker one starts to yield or
              plastically deform. So the stronger bolt will take MORE tension
              (torque) before yielding thus providing MORE clampling force. Most
              bolts are typically tensioned (tightened, torqued) to induce 75% of
              yield. meaning that there is a fair margin (25%) before you could
              DEFORM your bolt. As economics enter the equation we now
              see "torque to yield" bolts. These bolts as the name implpies are
              toqued to 100% of yield thus providing additional clamping -
              thus "acting" like a LARGER bolt - at least economically speaking -
              the downside of course is that - you only use them once!


              If you don't believe any of this - go look at the stress strain
              curve for a fastener tested to failure. As the test specimen starts
              to plastically deform the cross section is actually being reduced -
              however the tensile numbers continue to increase or even levels off,
              but, the part is actually getting stronger since it is now smaller -
              this can be a result of work hardening. This curve will basically
              continue until failure.

              Working loads are typically calculated on the 75% of yield whereas
              safety factors are calculated using the yield point.

              As far as a seat belt goes - I would first determine what the
              industry standard for the acceptable safety factor is and then go
              from there. I really don't think avoiding the "brittle" fasteners is
              a big concern since I don't see a cloth seat belt being able to
              apply much of a shock load, but that's just a guess.

              Every industry used different factor of safety - I once talked with
              an Indy car designer who used 1.1:1 as a safety factor. In the
              medical industry we typically use 4:1 safety factor - sometimes
              more! Of course determining what loads are involved is the
              challenge!


              Sorry to babble on for so long - I hope this helps make this subject
              a little more clear.



              Jacin in Ohio



              <snip>
              --- In metalshapers@yahoogroups.com, msaforum@m... wrote:
              > Hi Kevin:
              Are these custom mounts to be the anchor points for the seat belt
              hardware or are you going to loop the belt webbing around the
              mounts?
              As Richard has already responded, heat treating tends to make the
              part more brittle without raising the ultimate tensile strength.
              The "Grade" of a bolt has more to do with the shear loading (side
              loading) capability than the tensile (straight line pull). The
              limiting factor of this type of mount would still be the threaded
              area of the attachment.
              If the belt mounts are intended to have the webbing looped around
              them and secured with a slip adapter then there will be some other
              design factors to be considered. Poynter's Parachute Riggers Manual
              states that webbing loses approximately 50% of its tensile strength
              when it is turned about a bolt (looped back around hardware)given a
              perpendicular pull to the hardware. For angles of load other than
              perpendicular, further decrease the effective tensile of the the
              webbing will be exhibited (I.E. Belt Dumping).
              A proper seat belt installation requires quite a bit of fore thought
              to make it safe under a wide range of scenerios. I would suggest
              referring to the belt manufacturer for technical assistance.
              Roger VanHoozer
              FAA Certified Parachute Rigger (NPD)






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            • hemirambler
              Sir Dick, That is an EXCELLENT point! Unless the fastener has something good to attach to - everything else is pointless. Some EXCELLENT guidlines can be
              Message 6 of 7 , Dec 2, 2004
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                Sir Dick,

                That is an EXCELLENT point! Unless the fastener has
                something "good" to attach to - everything else is pointless.

                Some EXCELLENT guidlines can be found in the Drag Racing Rulebooks.
                They cover attaching to sheet metal (floor pans) as well as fastener
                sizes and grades. As I recall the seat belt manufacturer (at least
                the one I bought) kinda wimped out with some such words
                as "securely fasten" or something.

                Both IHRA and NHRA both have a CHEAP rule book that will steer you
                in the proper (safe) direction without getting into all the mumbo
                jumbo. I am sure ther are out racing organizations that publish
                specs as well -I'm just not familiar with them.



                Squire Jacin <grin>


                --- In metalshapers@yahoogroups.com, "Dick Raczuk" <stutz31@c...>
                wrote:
                > Jacin of Ohio
                > Right on. The one thing I missed, and maybe it was brought up, "
                make sure
                > wherever this bolt is being installed,whatever size it may be,
                have some
                > method of spreading the load so it doesn't pull through the
                mounting
                > surface". ( big heavy washer)
                > Dick
                > Jacin of Ohio sounds more Knightly
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