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proper way to shorten a frame?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by laketex, Nov 19, 2001.

  1. laketex

    laketex 3/4 ton status

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    I need to know the proper way to do it since I'm going to look at a truck tommorrow afternoon that's been shortened. I know what do look for in the welds, but does it need to have plates that cap it off on the inner and outer rail or what?

    Sherman, Tx
    <font color=red>The blazer's almost on the road....anyone got tree fiddy?</font color=red>
     
  2. 55Willy

    55Willy 3/4 ton status

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    My friend took a 73 long bed and cut 26" out of it. It is now an 1" shorter then a Blazer. He welded the frame up right behind the cab and added another crossmember and braced the inside of the frame with probably the thickest angle iron I have seen with like 6 or so grade 8 bolts on each side.

    <font color=red>Life is like a mud hole:</font color=red><font color=blue>
    When the S#!T gets deep, you have to keep moving and friends can always pull you out</font color=blue>
    55 Willy's
     
  3. RGF

    RGF 1/2 ton status

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    I took 22" out of a 1ton frame and welded the outside of the rail, added 1/4" plate on the inside that extended around 8" on both sides of the cut. I put a couple beveled slots in the middle of the plates so that it wasnt only welded along the edges. I dont think you need to go nuts with big thick plates, the frame is only 3/16 to begin with.

    RGF
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I ran a frame machine (among other things) for several years in a body shop that I was part owner in. I have repaired, shortened, and lengthened frames on pickups and heavy trucks. If you know what to look for in a good weld, that is obviously a good start. Make sure the welds are strong and even with good penetration. It does not have to look like a role of dimes has been laid down side ways to be a good weld but it is a good indication of the skill of the welder. If it looks like wads of bubble gum, *walk away* without hesitation.

    As far as plates, I don't like them, I don't use them, and I think they cause more harm than good. No offense to anyone who may choose to use them but, I think of them as a crutch for someone who does not trust their work. "Fish plating" causes a rigid area of the frame where they are welded in. Truck frames are *designed* to flex. Removing the ability of the frame to flex along it's length will create stress points along side the rigid areas. Just like the area around the steering box, when you localize flex (stress), you get cracks. I have seen pieced frames done by expert welders (better welders than me, but not frame men) weld up frames and it would break right beside the welded "reinforcing" plates. Now, but welding (end to end and weld the meeting) is also to be avoided. Generally what I did was cut a 1/2 to 1" wide strip (sectioned to fit inside the frame) from the scrap frame pieces (same exact alloy) and tack them behind one piece so that it forms a pretty much solid wall inside the frame. Then, slide tab A inside frame section B until the 2 pieces of frame are lined up (with beveled edges). Then, you can weld the butted edges with a hot arc, get good penetration, and not worry (as much) about the puddle dropping out or "blowing through". This results in a repair that will still flex with the rest of the frame and will be pretty much as strong as the original frame before the cut. I have seen frames that I welded that were subsequently wrecked to the point of being completely mangled and I have never (after I learned the described procedure) had a frame weld break.

    There is one thing that is hard to tell after the fact (you can only guess based on the quality of the weld) is whether the frame has been hardened by improper welding. Usually from improper pre-heating and welding multiple passes without properly watching the metal temp between passes. Many other factors can also lead to a brittle area around the weld which is likely to crack.

    I guess the short answer is be careful and skeptical. Try to find out as much as you can about who did the work and what their qualifications are. If any of it looks less than professional, better to err on the side of caution. I'm not a formally trained welder and most of what I know I taught myself or learned at the Kansas Jack frame machine 2 week course. However, I do have "real world" experience and this description is based upon that. Take it "for what it's worth"...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  5. LKJR

    LKJR 1/2 ton status

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    Don't know how to reply after a descriptive novel like his, very good job, I know the "chop shop'?? I think anyway, in Cali, does a lot of this and they do a Z cut on both sides on the trucks they shorten. to keep the stressed area from welding or whatever over a broader area and don't have a butt seam, I would avoid any kind of butt joint in a frame if it were me.......

    Like em big and topless
    Excuse me...Would you mind removing your import from under my chevy?
     
  6. chevyracing

    chevyracing 1/2 ton status

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    <blockquote><font class="small">In reply to:</font><hr>

    As far as plates, I don't like them, I don't use them, and I think they cause more harm than good. No offense to anyone who may choose to use them but, I think of them as a crutch for someone who does not trust their work. "Fish plating" causes a rigid area of the frame where they are welded in. Truck frames are *designed* to flex. Removing the ability of the frame to flex along it's length will create stress points along side the rigid areas. Just like the area around the steering box, when you localize flex (stress), you get cracks. I have seen pieced frames done by expert welders (better welders than me, but not frame men) weld up frames and it would break right beside the welded "reinforcing" plates. Now, but welding (end to end and weld the meeting) is also to be avoided. Generally what I did was cut a 1/2 to 1" wide strip (sectioned to fit inside the frame) from the scrap frame pieces (same exact alloy) and tack them behind one piece so that it forms a pretty much solid wall inside the frame. Then, slide tab A inside frame section B until the 2 pieces of frame are lined up (with beveled edges). Then, you can weld the butted edges with a hot arc, get good penetration, and not worry (as much) about the puddle dropping out or "blowing through". This results in a repair that will still flex with the rest of the frame and will be pretty much as strong as the original frame before the cut. I have seen frames that I welded that were subsequently wrecked to the point of being completely mangled and I have never (after I learned the described procedure) had a frame weld break.

    There is one thing that is hard to tell after the fact (you can only guess based on the quality of the weld) is whether the frame has been hardened by improper welding. Usually from improper pre-heating and welding multiple passes without properly watching the metal temp between passes. Many other factors can also lead to a brittle area around the weld which is likely to crack

    <hr></blockquote>

    That's what I was going to say!!!!!!! [​IMG]

    Like to go sloppin' 'round in da mud in a rapid fashion....=)

    <a target="_blank" href=http://coloradok5.com/gallery/albun31?&page=1>See my pics here</a>
     
  7. laketex

    laketex 3/4 ton status

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    man what a bunch of good ideas of what to look for. I appreciate it greatly. Always like to know what i'm buying first hand instead of trusting the seller. Thanks again.

    Bryan

    Sherman, Tx
    <font color=red>The blazer's almost on the road....anyone got tree fiddy?</font color=red>
     
  8. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    A "Z" cut is one of the best ways I have "heard" of when lengthening/shortening a frame. It is harder to do than a straight cut, but it does ellimate the "butt" seam. No matter what kind of cut it is, the joint is only as good as the weld so inspect that carefully. I also agree that you can overbrace the frame, as stated above, it was designed to flex (which for most of the people on this board is a good thing).

    See my rig at <a target="_blank" href=http://coloradok5.com/gallery/Leadfoot> click here </a>
     

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