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  • Welding 1/2" 4140 bar

    Ok, here goes. I have a drag boat. In that drag boat, there is a strut. This is the piece that holds the propshaft in place just in front of the prop. Meaning about .250" in front of the prop. It is LOADED!
    On a hydro, the lower half of the prop carries the weight of the back half of the boat. The boat runs 8.0 et @ 55 to 160 mph. About 900 hp into the propshaft.
    Best case scenario if the strut fails, it rips the bottom out of the boat, and the boat sinks. Worst..well, RIP.
    So, the strut is a tube welded to a vertical .500 plate to a horizontal .500 plate. Or a "t" with a tube on the bottom.
    1) Do I need to preheat? If so, how hot, and how critical is the preheat temp.
    2) Filler metal.
    3) Some flexing would be much better than cracking.
    4) What am I forgetting?
    Thanks
    As you can see, this is a critical piece. I know for a fact my buddies was welded without preheating. I read many threads and wonder if that was the right way to do it. (I did not do it)

    Wags

    PS, I only have a 180 amp mig welder. I have a Dynasty 300 tig.

  • #2
    You will need to post pictures and hopefully some good ones to get your best advise. There are many folks here who know things about metal that may or may not be familiar with your exact thing.
    They may have much better advice than what is currently being done by other racers.
    BTW what is the finish on the outside of this piece when it is installed?

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    • #3
      Is this a design that has been proven, and your just looking for how to fabricate it correctly? Or is this a new design as well? Yes welding 4140 in general requires pre and post heats. Pictures would help, prints are better, and any other engineering data you have would be very helpful in understanding the loads and cycles placed on the part. Beware the "shooting from the hip" answers.
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      • #4
        This is a proven design. I am not reinventing the wheel. Some guys make them out of I beam and cut one flange off. Some make them of mild steel. I am sure material is strong enough. Probably overkill for my class, but no reason to skimp here.
        I will try to post a picture tonight.
        Thanks
        Steve

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        • #5
          "4140"

          wag: visit www.interlloy.com.au for some of your answers.

          Dave
          "Bonne journe'e mes amis"

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          • #6
            Here is a picture old one on the right. Metal on the left. Ran out of coolant and steam.

            BTW, surface finish. I am open to suggestions. It must not be "coated". I must be able to see if cracks develop. I was thinking of parkarizing. It is in the water about 3 hours a weekend. 10 weeks a year for races.
            Thanks
            Wags
            Attached Files

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            • #7
              Myself, considering all the different beam sizes out there, would find going that route hard to resist.
              You would be hard pressed to find much advantage fabbing that part, IMO,
              out of 4140, and getting it both straight enough, and welded good enough, to exceed a heavy beam.
              You could even machine on the beam and make it very nice.
              Please don't take this wrong but the very fact that you present this question raises an eyebrow about whether or not this is a good idea for YOU to do.
              Billet would be the way to go. Esp. for a master machinist.
              Have you seen any made from aluminum?

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              Miller Dynasty 700...OH YEA BABY!!
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              Miller Dynasty 200 DX "Blue Lightning"

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              • #8
                Originally posted by FusionKing View Post
                Myself, considering all the different beam sizes out there, would find going that route hard to resist.
                You would be hard pressed to find much advantage fabbing that part, IMO,
                out of 4140, and getting it both straight enough, and welded good enough, to exceed a heavy beam.
                You could even machine on the beam and make it very nice.
                Please don't take this wrong but the very fact that you present this question raises an eyebrow about whether or not this is a good idea for YOU to do.
                Billet would be the way to go. Esp. for a master machinist.
                Have you seen any made from aluminum?
                I thought about the beam route. Some guys use beams. Struggled to find one locally. (Plus I only need 2', not 22') Open for sources.
                Straight--yep, no easy task, but doable.
                Me asking the question means beyond my capabilities. No offense taken Maybe right, probably right. Problem is, I don't know someone I trust more with my life than me. I could take it to the local weld shop, they do a half assed weld, I'd never know. That is my only reasoning. Never had to preheat any moly tube. It was all thinner stuff.
                My real preheat question is because my buddy had his done, no preheat. No cracks. That does not make it right, though.
                None out of aluminum that I know of.
                Thanks, really no offense taken.
                Wags

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                • #9
                  Many steel places have "drops"....They are easy to find. Houses only need what they need what they order. I have seen piles of drops scrapped.
                  Do you know exactly what the Big Boys are using here?
                  I have a friend who won a national meet but it was a blown hydro with a jet.
                  I know of another freind also,but would need a bit of time with the holiday going on. He runs at Havasou(sp) every year.
                  Gotta weld like crazy today and then intertain for 3 days.
                  I see virtually no advantage of using 4140 here. By the time you weld it as needed you will need to heat treat to gain strength back to where it is stronger and safer than mild and that is a weld that will be on both sides of the top and bottom. You will have a giant haz which for all I know might be a better thing if you are using the correct filler.
                  I would look much harder for a beam if you want this to be nice. Over half of your work would be done if you can find one thick enuff to suit the purpose.
                  I do understand your logic on doing it yourself. I was a racer for years and still fab a few things for friends. I made everything. Headers, pan, cage, rear end, seat, sheetmetal.
                  What size beam could you use if there was some? 8 inch maybe? Actually much bigger would be better, like 18" or something just to get a bunch more thickness I would think. You could even wing shape it.
                  What is the material of the bearing portion?
                  Where are you located? Just thinking about shipping.
                  Last edited by FusionKing; 09-04-2009, 06:25 AM.

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                  • #10
                    www.discountsteel.com has I-beam of all sizes, by their website, it looks like you could get just 2'. Offices in Ft. Worth and St. Paul, I doubt shipping would be outrageous.

                    Coating wise, maybe zinc or galvanized? The zinc plater I use would probably charge 5 bucks to plate it.

                    Hope this helps.

                    Don't be a tease, post some pics of this boat in action
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                    • #11
                      It is not ugly white anymore. I will see if I have any good pics.
                      Wags

                      I have to get a spectacular shot scanned in the computer. I will give it a whirl in the next few days.
                      Attached Files

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                      • #12
                        Omg

                        Holy chit mahn!! That's an engine! Couldn't you find a little bigger one to put in there? I like you logic - good luck in your solution.

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                        • #13
                          Actually 2 ft drops of beams are common in fab shops, scrap bins are full of them as there isn't much call for short drops. I personally wouldn't make it from an exotic alloy if mild would do.

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                          • #14
                            Well, just a final update.
                            I preheated the metal to 600F. Welded it in 2" sections alternating ends, etc to kep it from pulling all to ****, let it cool slowly and bolted her in. I could not have asked for it to work any better. Alignment was awesome. Weld seems to be excellent. It has about 50+ passes on it at 150 mph or so. (8) 6.0 runs at 1000' also. This takes 1200+ Hp ish to do. I have always and still do look at it every pass.
                            Preheat is my friend.
                            Thanks for the help.
                            Wags

                            BTW, I milled a slot in the top plate and pressed the vertical part in to the slot. I welded on the top then and around the bottom. (so this is about 30+ inches of weld total) The tube (that the propshaft goes through) I milled a slot for alignment and it had about .001 press to the vertical piece.

                            PS we won the last 4 out of 5 races after that. 1 for 10g.!!

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                            • #15
                              still wanna see pics of that beast in actions, please? i am glad that it worked out for ya. i didnt see this post until now. shoot me a pm next time you need a 2 or 3 foot drop of some heavy beam...... heck, i even have a 6 ft drop of 38 inch beam 390 pound per foot
                              welder_one

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