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Thread: Truck frame crack repair?

  1. #1
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    Truck frame crack repair?

    I've got an older Kenworth single axle cabover that spent nearly all of its life as a picker truck with an 8-ton crane mounted just behind the cab. The crane has been removed and I want to use it as a farm flatdeck/dump truck.

    The frame is cracked right around where the picker was bolted onto the frame. It isn't broken completely but needs repair.

    I've heard that some frames can be welded and some can't, due to heat treated frames and the like. I don't think this little KW frame is heat treated--at least I can't find any warnings on the frame about "no hot working"!!

    I am also confused about whether frame welding is allowed in my area--BC, Canada. I have heard that some jurisdictions don't allow frame welding, PERIOD but I hope this is just BS.

    Can anyone tell me what is required to do a repair that would be accepted at a vehicle inspection? Does it have to be documented that a ticketed welder did the job, at the correct phase of the moon and used the right brand of bubble gum welding rod, dipped in water just right, to seagull-shzt the crack together?

    Your comments and suggestions would be appreciated!

    Thanks,
    Jon.

  2. #2
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    are you sure its not an aluminum frame, i have seen really dumb people mount cranes on aluminum framed trucks with the same or worse results.

    I cant speak for your jurisdiction but having a properly qualified welder repair the crack usually isn't a problem, if it was my truck i would try and sleeve behind were the crack is a sufficient distance on either side.

  3. #3
    Senior Member heavylift's Avatar
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    any weld or truck shop should be able to fish plate the frame...

  4. #4
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    We have done many frame jobs- cracks, stretching, shortening mounting equipment ect. I would say on a older model, a heat treated frame is probably not so much of a concern. You could contact a dealer to be sure. Assuming a typical carbon steel frame- vee out the crack, drill the ends of the crack, run the root pass with 6010 or 6011 (depending on skill of welder- 6011 is a little easier), uphill or down hill progression- again depends on welder skill and preference, cover pass with 7018- uphill only. Grind weld smooth and fashion a "fish plate". Depending on exactly where the crack is in the frame you will gain maximum strength by plating the top and bottom rails along with the side of the frame. Boxing the frame is an option too, but depends on the severity of the crack, expected load, location, joint access and other truck components. Most cases don't require boxing. This type of repair is best left to an experienced welder. In the US a certified welder is required for any repair or alteration for on road service or where employees will be working with the equipment (liability issue).

  5. #5
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    Masterwelder is on target. Most KW or other frames are labled " DO NOT DRILL OR WELD TO FRAM FLANGES". I seen some dummies drill the flange to mount equipment and this is frowned by US DOT personal. What ever you do with the crack you need to fish plate the fram to stop it fron cracking again

  6. #6
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    Thanks, guys,

    All your comments give me a pretty good idea of what I have to do. It sounds like some common sense welding skills with a dash of checking with the local DOT boys to make sure that there aren't any "not so common sense" local rules that might rain on my parade!!

    Jon.

  7. #7
    Senior Member heavylift's Avatar
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  8. #8
    Senior Member Mike Mc's Avatar
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    Master Welder, what about using a wire feeder for frame repairs?

    Is it important that the fish plate be a similar frame metel too?

  9. #9
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    Hi Mike, Wire feed is ok in my opinion. For most, a 220v MIG with gas shielded wire (ER 70s-6, .035 dia min.) and a moderate skill level (able to pass plate test equivalent to thickness and progression [flat, uphill, overhead] required to make the repair) will make a fine repair. For advanced welders and heaver sections to be welded, gas shielded flux core wire provides excellent results. This process has higher deposition rates, uses higher current and works in all positions (wire diameter larger than 3/32" is limited to the flat position). A E70T1 electrode, .045 dia and CO2 shielding gas is typical for most applications.

    Using similar metals will simplify filler metal selection and will complement the base metal as far as strength and ductility, which may eliminate further cracking in the repaired section, welds and or fish plate(s).

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