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Question on gussets at weld joints

Discussion in 'The Hokey Ass Message Board' started by drw47, Jun 27, 2011.

  1. drw47
    Joined: Dec 8, 2010
    Posts: 81

    drw47
    Member

    Just finished welding my new rear frame rails. I want to weld Gussets on those joints. Is there any rule as to how far out from the origional weld the Gusset should be? I have a few paper models laid out on the rail. What do you think? [​IMG][​IMG][​IMG]
     
  2. randydupree
    Joined: May 19, 2005
    Posts: 658

    randydupree
    Member
    from archer fl

    i like number 1
     
  3. Old Buzzard
    Joined: Sep 29, 2007
    Posts: 14

    Old Buzzard
    Member

    I did #1 on the S&W junk I welded up....
    A suggestion... Don't make any sharp corner welds. #1 w/ the corners rounded will reduce stress points.
     
  4. There actually are some rules to follow if you are a structural engineer. I would have to dig some books out to get them for you. Bear in mind that you are not building a bridge or a metal structured building and some of those rules are overkill to alleviate liability.

    A quick reference book to help you would be Structural Steel Drafting or a Good Mechanical Handbook (like a machinists hand book).
     

  5. Rex Schimmer
    Joined: Nov 17, 2006
    Posts: 743

    Rex Schimmer
    Member
    from Fulton, CA

    dw47,
    Adding a gusset in the place you are showing has a pretty minimal affect on the strength of the frame rail. The very best place to increase the strength of the rail in bending, which is the biggest loading it will see, is to add a strap along the bottom of the joint, make it extend 3-4 inches on each side of the joint, radius or taper the ends. In bending the top flange is in compression load, the lower flange is in tension and the sides are in shear. With the bottom flange in tension this makes your weld at the joint on the bottom in tension and adding the strap to the bottom reinforces that weld.

    Rex
     
  6. 51 MERC-CT
    Joined: Apr 5, 2005
    Posts: 1,594

    51 MERC-CT
    Member

    I prefer fishmouth plates (no welds straight across main rail) sorta like this:)
     

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  7. 48 Chubby
    Joined: Apr 29, 2008
    Posts: 1,014

    48 Chubby
    Member Emeritus

    What you have laid out are not gussets, those are fish plates. The frame looks to fabbed from 2X3 or 2X4 tubing? A box section is by definition all ready gusseted. Seems to me that you are trying to reinforce the welds, properly done the joints are as strong as as the materiel.
    I vote for none at all. If you keep adding welded on patches you will only create stress. A plate welded to the side of the rail contributes nothing.
     
  8. 51 MERC-CT
    Joined: Apr 5, 2005
    Posts: 1,594

    51 MERC-CT
    Member

    I agree with Chubby, if it is indeed tubing, if wanted the plates should have been rosette welded on the inside of the tube.:)
     
  9. R Frederick
    Joined: Mar 30, 2009
    Posts: 2,658

    R Frederick
    Member
    from illinois

    But now that you are where you are now, I'd drill some 1/2" holes in the plates you plan to use. Weld them around the edges, and rosette weld the holes full.
     
  10. Listen to Chubby.
     
  11. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,226

    Da Tinman
    Member

    you need fishplates. #1 with rounded corners would be fine. I make my fishplates oval shaped so the stress is never square with the weld.

    the load stresses on the frame rails are such that it stresses the welds in the weakest direction. The fishplates add more welded area and with rounded corners will eliminate any stress risers making your frame a lot stronger at the bend than it it is at the straight sections.
     
  12. 73RR
    Joined: Jan 29, 2007
    Posts: 6,545

    73RR
    Member


    Where, exactly, did you study engineering?

    Yes, there are better ways to strenghten the joint, all depending on the need, the intended goal and the available space, but plating the side(s) is also helpful.

    .
     
  13. drw47
    Joined: Dec 8, 2010
    Posts: 81

    drw47
    Member

    One thing that may hepl is that I cut out pie pieces rather than doing full cuts, so I have uncut metal on both outside bends. This is all great info and I appreciate all comments. Gives me alot to consider. [​IMG]
     
  14. I like those myself and have used something similar on past jobs where I felt it needed some reinforcement. Welding across the frame rail, I was always told to avoid where possible.

    Bob
     
  15. kkustomz
    Joined: Jul 4, 2007
    Posts: 342

    kkustomz
    Member
    from Texas

    Number one is ok, where the welds terrible that you ground off? If you beveled the tubing and ran a nice weld there is no reason other than decoration if you are building this for the rear of a old ford or chevy, they are very light weight. Gussets inside the bend side of the tubing really do the job when trying to eliminate flex. I assume your worried about your weld joints cracking or tearing, just do number 1 plates and do not use any more heat or weld bead than nessesary.
     
  16. Roger Walling
    Joined: Sep 26, 2010
    Posts: 1,146

    Roger Walling
    Member

    If you are concerned about the welds, I would use the fish mouth plates recomemed by "51 Merc" but I would make them a little longer (1 to 2 " longer) and plug weld them with 6, 3/8" holes onto the inside of the tube.

    Leave about a 3/32" gap and then butt weld at a higher heat than you would use if there were no back up plates.
    Then grind all you wish, you will still have a 100% weld.
     
  17. I do as Jay does. Have someone lazer cut a dozen or so plates so you have some for future use
     
  18. PinHead
    Joined: Jun 3, 2005
    Posts: 243

    PinHead
    Member

    What others have said, I've never heard of them called fishplates before, but if you're using flat plate on the outside then that is what you want - no sharp corners, and a plug weld or rosette on each side of the joint you're covering. We use patches like these for reinforcing butt welds on rail car repairs where I work, albeit a bit bigger in scale.

    If you do it again, the better solution would be to leave a gap in your butt joint, about the same size as your material thickness, and put a solid backing strip behind it, even better if you bevel the edges of your butt joint about 45 degrees or so. I'm not exactly sure of the strength difference but it would look a little cleaner anyway. But using a fishplate in this case is fine too.
     
  19. Francisco Plumbero
    Joined: May 6, 2010
    Posts: 2,531

    Francisco Plumbero
    Member
    from il.

    My opinion ( Which may be worth less) is that cutting the square tube in this way actually leaves that uncut part weaker due to the bending of it to shape.
    A weld most likely would be stronger, due to the weakening caused by the bending.

    If I did a plate, no matter what type, I would leave the fillets of the weld, they add strength and are perfectly acceptable to look at. The act of removing the weld fillets for visual appeal would render them a lot less effective.

    I am tending towards the fish mouth because it changes the stress pattern on the tube. Had you left the dimes, I would have maybe said none required, but now you cut some strength off, and we can't see by looking at the dimes how good you are or not at welding, so now I would fish mouth them per Chubby and Jay.
     
  20. drw47
    Joined: Dec 8, 2010
    Posts: 81

    drw47
    Member

    I ground off the welds in anticipation of adding the FishMouths/Gussets. I figured it needed to be flat. Didnt really figure that there would be so many Pros and Cons. Live and Learn, Just love working on the car annd I want it to be safe !
     
  21. Pete1
    Joined: Aug 23, 2004
    Posts: 1,915

    Pete1
    Member
    from Wa.

    Are you building a destruction derby car??
    If not, forget all the add on stuff.
    If you can do certifiable welding, there is no reason for it.
    Don't grind off the welds.
    For what it is worth, ground off welds will not pass tech in most racing venues.
    In some cases on cages, open corner gussets are required.
     
  22. mysteryman
    Joined: Apr 20, 2011
    Posts: 253

    mysteryman
    Member
    from atlanta

    just curious what kinda of welder / rods you using
     
  23. 71buickfreak
    Joined: Sep 26, 2006
    Posts: 609

    71buickfreak
    Member
    from Oklahoma

    I recently stretched the frame on an S10 chassis to fit a 48 Chevy truck. I made L-shaped cuts , so I had an nice weld surface and some built-in strength. Then I added fish plates on the inside. Very strong.
     
  24. drw47
    Joined: Dec 8, 2010
    Posts: 81

    drw47
    Member

    I used my old stickwelder, at about 130 amps with 6011 rod.
     
  25. Francisco Plumbero
    Joined: May 6, 2010
    Posts: 2,531

    Francisco Plumbero
    Member
    from il.

    Must be pretty thick stock for 130 on 6011, if you root passed it, it's a shame you ground it. Was most likely very strong. I'd fish plate it if it was mine and leave the welds showing, just buff them to remove the slag. That's my opinion. See what Jay and Chubby think.
     
  26. HellsHotRods
    Joined: Jul 24, 2009
    Posts: 1,350

    HellsHotRods
    Member

    In the aircraft industry, most often than not, the welds are stronger than the material being welded (after being tested). You should be able to accomplish the same thing if you are doing a proper weld, set up, etc. Then, as Chubby said, no additional plates will be required.
     
  27. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,226

    Da Tinman
    Member

    I say fishplate em, then you dont have to worry about if you should fishplate it or not.

    they arent going to hurt anything and if your not sure 100% in your welder or welding skills, it may save your ass.
     
  28. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,130

    Relic Stew
    Member
    from Wisconsin

    You want the fishplates to be diamond (or fish) shaped. A sudden transition with a vertical weld creates a stress point. The reinforced part bends less, making the unreinforced part next to it flex more. A gradual taper transfers the bending stress more smoothly.
     
    Last edited: Jun 27, 2011
  29. That's an acceptable setting and rod, 6013 would also be a great rod and produce less spatter. Just my preference.

    Bob
     
  30. Yes, don't grind those welds at all. I chip and brush them, that's it.

    Bob
     

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