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Is it safe and an acceptable pratice to weld a passenger truck frame?

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  • H80N
    replied
    Originally posted by Sberry View Post
    Weld, not weld etc there isn't a muffler changer got any business cutting on a truck frame period.
    Berry

    you have that right....

    wonder if Chuckduck ever got any satisfaction on that mayhem committed on his truck??

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  • Sberry
    replied
    Weld, not weld etc there isn't a muffler changer got any business cutting on a truck frame period.

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  • kevin
    replied
    there is one thing that no one is talking about, its called, the new steel, by gm. youve seen the chevy truck commercial, the truck is on the ice, then up comes a submarine, busting the ice all to heck, gm is trying to compare their truck frames to ice breaking subs. its more than marketing, its the real deal, body shops have had updates sent to them on, "not to weld" these steels, i have tried to get info from the mfg,s, with no luck. i suspect that this steel is used in suspension and front end steering components, sorta like what this post is about

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  • Helios
    replied
    Give a monkey a plasma cutter, and he'll turn a Lamborghini into scrap metal.

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  • old jupiter
    replied
    Okay, we're talking about the same thing, and if fish-plate is common terminology among welders, I'll keep using it. I looked it up before asking the question and learned that the term originated with the railroads a long time ago, meaning the two forged splice-plates that they bolted through each side of some butt-joints of two sections of rail (when they weren't making a thermite-weld, I guess). These plates had square ends. Ref. Wikipedia "fish-plate." I think I generally tend to use "doubler" when it's a plate that needs no tapered end, because of the application.

    FWIW, I first started learning about moving loadings and spreading loadings out with tapering structures in my long-lost youth when I was racing alky-burning outboard hydros. I later read a book by racing engineer Carrol Smith ("Build to Win," IIRC), who made the slightly tongue-in-cheek assertion that, "Machinists love to create stress-risers," by which he meant that they tend to turn shafts of all kinds with pointy-ended tooling that leaves square edges, unless you specify something else. Aircraft industry standard practices, which call for the very lightest weight possible in parts which still have acceptable fatigue-life, have been developed over its hundred-year history.

    Thanks for the info.

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  • Portable Welder
    replied
    Thanks H80N, Those are very good examples.

    About 6 months back I was doing some in-depth searching about frame repair and I cant remember the article but the engineer said the vee on a fish plate needs to be 2 to 2-1/2 times longer than the width of the plate.
    So at a minimum, if your fish plate is 12" tall or wide, you would want the taper to be 2' long.

    H80N's example also showed round plug welds which is common in wide fish plates.

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  • H80N
    replied
    Fishplate..

    Originally posted by Portable Welder View Post
    Old Jupiter, what you are calling a doubler, we call it a fish plate, the square cut fish plates are commonly found in a beam splice, in a house where two beams come together over a post.

    So I'm about 95% sure we are talking about the same thing.
    Fishplate is the term I was taught... have captured an image off the net and reposted here... NOT my work.. but representative of that type of repair..
    Attached Files

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  • Portable Welder
    replied
    Old Jupiter, what you are calling a doubler, we call it a fish plate, the square cut fish plates are commonly found in a beam splice, in a house where two beams come together over a post.

    So I'm about 95% sure we are talking about the same thing.

    Leave a comment:


  • old jupiter
    replied
    Maybe y'all can give me the correct terminology here.

    I've repaired broken booms/crowd-arms on smallish excavators, first prepping and welding the immediate break (often with backing plates), then grinding the new welds flush, and adding doublers all around, with long, tapered ends to spread out the loads and avoid hard-points and stress-concentrators, as some of you have described. I have been calling these doublers with tapered ends "fish-plates," but now in checking the definition I find that a fish-plate doesn't have to have the tapered ends. So is there an agreed-on term for a doubler that tapers out?

    (I believe that the welds used when replacing bent/broken sections of tubing in the structure of light aircraft are called "fish-mouth" welds, and the principle for making these welds is similar to what we're talking about, which is why I had thought "fish-plate" might be an okay term . . . ).

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  • USMCPOP
    replied
    That job was done by a third-world hack (or wannabe). Maybe you can get a third-world crackerjack welder who doesn't care about legal liability to fix it right.

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  • Portable Welder
    replied
    H80N, I just looked at the weld training and it looks like possibly advanced welding course that I-car will come in and train.

    There is still a difference between training and actually having a destructive plate test to become a AWS certified welder.

    However, If the class gets into engineering, Its more important to know how engineer the repair.

    I deal with structural engineers all the time because I have to weld on beams and bar joists, cell towers and several structural applications.
    Over the past 26 years I have learned a lot and don't even need a engineer a lot of the time.

    I run across a lot of architects that don't even know how to reinforce beams and bar joists and they can seal drawings ( That is scary )

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  • H80N
    replied
    Originally posted by Portable Welder View Post
    I certainly would'nt want a body shop to weld it, Its not so much about the welding as it is about how to shape the repair plate.

    A heavy equipment guy would know what I mean about a long diamond shape plate because we repair excavator booms, There should be no corners on this repair plate.

    If the depth of the frame is 6", each side of the diamond should extend 2 to 2-1/2 times farther than the depth.

    So a 6" tall frame should have a diamond shape patch that is 12" - 18" over all length.

    Your local high end welding shop would be your best bet especially if they work on a lot of heavy equipment.
    PW
    I was thinking an ICAR certified shop because they would understand what a manufacturer compliant spec repair entailed... while you and many of the rest of us here could perform a competent repair... maybe a portion of this involves the liability entailed in dealing with it... I sure would not want that liability following me home... justly or unjustly in today's litigious society...

    here is the link to ICAR

    https://i-car.com/

    Leave a comment:


  • Portable Welder
    replied
    I certainly would'nt want a body shop to weld it, Its not so much about the welding as it is about how to shape the repair plate.

    A heavy equipment guy would know what I mean about a long diamond shape plate because we repair excavator booms, There should be no corners on this repair plate.

    If the depth of the frame is 6", each side of the diamond should extend 2 to 2-1/2 times farther than the depth.

    So a 6" tall frame should have a diamond shape patch that is 12" - 18" over all length.

    Your local high end welding shop would be your best bet especially if they work on a lot of heavy equipment.

    Leave a comment:


  • old jupiter
    replied
    There are two separate issues here, the cuts, and the repair.

    Why the cuts were made at all is as baffling to me as to the rest here, and the fellow who did this work should get immediate scrutiny from the authorities.

    The repair work, which you tell us has since been "completed," is visibly a very poor job of it. Did you do it? I believe it is this is the reason the car companies as well as state departments of transportation tell us never to weld on frames. It's not that frames could not sometimes be welded safely, as Portable Welder explained, but not every amateur, however well-intentioned, who can (sort of) run a bead can do this correctly. The "repair" welding you photographed is all wrong. Possibly it could be saved by a professional who would prep the joint better, make good welds, and then add backing plates (maybe welded, maybe bolted) to spread the loading over a large area and away from the repair, where stresses will focus due to the disuniformity of the material in the heat-affected zone of the welds.

    If the photographed welds were yours, please, sign up for a two-night-a-week "Welding Brush-Up" class at your local technical college. You can enter any time during the quarter. Welding is a lot more satisfying (and safer) the more you know what you're doing. You won't learn how to judge this sort of problem, or how to weld it, by watching all those free YouTube welding videos, not even close.

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  • WillieB
    replied
    I once owned a 68 Jaguar E Type roadster. At very high speed it would go into a wobble. Investigating, I discovered someone had cut the transmission tunnel, lengthwise about two feet, then three cuts to floor level on each side. It took much needed strength from the car.

    There are idiots, and those who just don't care all around us!

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