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  • #16
    One of the more interesting threads I have seen on this site.

    TJ

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    • #17
      I should have had the angle, but alas not in the shop. A few other things got in the way, tis the dirt season. This tow bar will be hooked to a D9 cat to pull a 630 scraper. So there is just a straight pull. Two angles welded are allegedly cheaper than 8 x 8 3/4 square tube. Plan to bevel, tack with 2 in welds/foot and half both sides, then go for the gusto and weld. As the welds are opposing sides by the time I'm done it will still be straight by 1/4 in. 1/4 in in 10 feet you will not see and not affect the end goal. Not to pull disassembled but to pull the scraper loaded to move dirt. Sorry I forgot the camera these last two days. Will not tomorrow.

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      • #18
        Update : Got the angle in shop finally. Its cut in half and project was moved back in priority. Seems there is a scraper with the floor ripped out coming in monday.

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        • #19
          A continuous weld seems unnecessary. Seam welds create distortions, and as previously mentioned, the zipper effect. If I had to prepare and weld the joints described, I would first select Coreshield 8 Weld Wire - Diameter .072. This wire deposition allows a welder to finish with just two passes per stitch. The idea of positioning the angle pieces in a diamond orientation is right on and I would lay this out such that I tacked at the beginning of each stitch and at the end of every stitch to be welded. I would commit to 6" on 12" and start with the first stitch skip one and jump to the next until I got to the end, flip the weldment and repeat. Flip again and fill the first pass on each stitch skipped. Flip and repeat. Now it would be time to make all cover passes nice and pretty using the same system. My main question would be are we sure that two pieces of 10 foot angle welded together ends up being cheaper than one piece of tube only ten feet long?
          5 welding Rigs
          14 various shop weld machines
          150x80 shop full of metal working tools

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          • #20
            If most of the load is in the pull the weld is likely a moot issue anyway. Its built heavy, probably overkill anyway, probably not so closely engineered that it all makes a lot of difference. These issues would be different at absolute max high cyclical loading but if bending is an issue I would weld it all the way.

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            • #21
              I would think the zipper effect as mentioned above would not be an issue. I would look to ship building for an example.

              Also as sberry mentioned this weld is in longitudinal tension, so if the ends of the weld are wrapped around to the inside at the four corners, a crack has much less a chance of starting.

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              • #22
                FatFab,

                Are you an engineer. If not please explain how you guarantee the zipper effect hold no relevance.
                5 welding Rigs
                14 various shop weld machines
                150x80 shop full of metal working tools

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                • #23
                  Originally posted by MIKEDOGG View Post
                  FatFab,

                  Are you an engineer. If not please explain how you guarantee the zipper effect hold no relevance.
                  No I am not a licensed engineer.

                  I made no such assertion, please re-read my post. Allow me here it is, in red.


                  I would think the zipper effect as mentioned above would not be an issue. I would look to ship building for an example.

                  Also as sberry mentioned this weld is in longitudinal tension, so if the ends of the weld are wrapped around to the inside at the four corners, a crack has much less a chance of starting.


                  As you can see I said nothing about any guarantee.

                  Second I started the whole post with the phrase "I would think" this is a clue to you the reader that I am expressing an opinion, this is as apposed to a known or accepted fact.

                  In your post you asked for my qualifications, then went on with your question with the assumption that I had no such engineering qualification yet wanted clarification and explanation from someone you assumed had no relevant education. This is confusing to me. I would think you would have, at the point of deciding my level of education, disqualified me from further relevance in this discussion. You did not do so I will take this as an opportunity to expand my thoughts, as you show such great interest in them. Thank you by the way.



                  With the loading being applied to the long axis of the weldment, and the weld being nearly complete joint penetration, by virtue of the joint design. By wrapping the weld inside of the weldment i.e to the back side of the CJP one creates a smoother transition for the energy to rejoin the parent members. Also by the weldment being welded to near 100% penetration to the full length of the member once the load reaches the other end it is again transfered back safely into the parent member. Cool how it creates a circle for the energy to flow in with out hitting interruptions or abrupt edges, i.e. ends of welds as from skip welding or from the weld suddenly stopping at the end of the member.



                  If you have any other question for me please ask away I am all to happy to help.


                  remember I only speek to what I know and freely admit my errors and I avoid absolutes unless I am sure.


                  TJ
                  Last edited by FATFAB; 07-07-2008, 05:57 PM. Reason: added "do"

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                  • #24
                    Hey guys,
                    All of you sound like you have a great deal of experience with welds of this nature and the forces described (you guys lost me a few times). I have been keeping up with this thread and can't wait to see the photos. Please include a description of the pictures so those of us with less experience will understand.
                    Thanks,
                    Nick

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                    • #25
                      what about pull?

                      Iwould counter bow as much as possable and fully weld w/ duel shield

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                      • #26
                        I also doubt this is highly experimental.

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                        • #27
                          You could scale down the project and do some testing. Say get 2x2x1/8" angle about 4' long and skip weld one tube and continuously weld the other. Then do some load tests for bending. I bet the skip welded tube would fail sooner than the fully welded one. The tube legs between the welds will just "pucker" out during an applied bending force. I wouldn't worry about any "zipper" effect either. The ends of the tongue attachment points should be designed to not allow a zipper to get started. I'm not qualified in any way to make structural engineering decisions, but find myself engineering parts almost daily. I "practice" just like a doctor.
                          Russ

                          I did skip weld some tracks for a Bobcat loader trailer I built a long time ago. I used 5x5x 1/2" angle and welded 6" and skipped 12" to join the angles into channels. The welds were done with pretty large 7024 rod which made a pretty wide flat puddle. I flipped them and tagged the other side as well. Those channels stayed straight for over 20 years. They weren't holding a D9 to a scraper though!
                          BFM
                          Dynasty 200DX
                          Passport Plus

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                          • #28
                            Just got back from welding a floor in a scraper. Seems to have seperated front to rear on one side, completely. Have to go back in AM to finish. I can't wait to get pictures too. But alas dirt rules when the job is to move it. So tomorrow I take the camera to where these things are and do. I am not an engineer either, just a poor smuck stuck with these creatures from the black lagoon. Keep it friendly now, remember it is all good fun.

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                            • #29
                              The present design is working ok. So Boss not want to change. I did check the records and the last one was made of 8x8 1 inch angle. How the switch to 3/4 came about is... Any who its about 800 lbs of steel total.

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                              • #30
                                I hope they aren't replacing that 1" angle with 3/4" due to failure. This must be for a different scraper. Right?
                                Jim

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