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Thread: Welding sub frame to dump truck for pintle hitch

  1. #1
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    Hello Bill,from another newer member.I've a question about welding for you,if you don't mind?

    I just purchased a dump truck and I am going to weld up a sub-frame for the pintle hook/taillights.The sub-frame will have two vertical plates on top,that will be welded to the last 6" of the outside of the frame.
    I was told that I should weld it to the rear face of the frame,and as it is a double frame,both frames should be welded to it.I think this is not only overkill,but I don't care for the idea of both frames being welded too one piece of steel so close together.My thinking is the frames are held together by huck rivets and bolts which allow for some(albeit slight)movement,and the welding of both frames to one piece will be too rigid during twisting of the frame,possibly leading to stress cracks.What do you think?

    Also,The plates which I'll weld to the frame will be 1/2" thick,welded on three edges(forward,top,rear edge), approx 6" of weld/edge,18" of weld/plate.I was planning on welding it with DC/reverse polarity 6011 or 7014 rod,and approx 230amp.
    Do you think this is adaquate attachment to the frame,and does my choice of rod/heat/polarity sound ok?I've used this combo before when doing fabricating/repair,with less juice on the thinner stuff,and it seems to give good penatration/strength,but I've never welded on frames.I've seen many with"Do NOT weld or drill holes in frame" stickers,so I don't want to heat it up so much that it causes a problem with frame cracking.

    I'll mount the pintle as high as possible in order to keep the leverage on the sideplates to a minimum.

    Thanks for any advice.

  2. #2
    Member ADMSWELDING's Avatar
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    jeffd if possiable sink the rear plate into the frame rails cut 2 c shapes out of the plate allowing the frame too come thru the plate.if not possiable fine bevel your plates your reffering too and grind all mill scale and paint away i would reccomend using 7018 its a low hydrogen rod meant for this type of structural application.7014 is low hy but not all position this is a detterent in this application.or it could be migged with .035 70s6 solid core wire if avaliable good luck.let me know how you make out .

  3. #3
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    Thank you sir.I'll pick up some 7018 rod,and take another look at covering the outside perimeter of the frame fully,although I think the box pivots may cause some interference on the top portion.

    Thanks again Bill,I'll let you know how it turns out.

  4. #4
    Member ADMSWELDING's Avatar
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    correction still asleep at4am

    early in the morning made a mistake 7014 is all position just has i beleive iron powder flux this rod could be used but i would still recomend 7018 lo hydrogen rod .no 6011 rod

  5. #5
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    Alrighty,preferably 7018,but 7014 will work,ixnay the 6011.I'll still buy the 7018,might as well do it right.

    I made a mistake also on the amperage.I've been welding at about 180 amp DC,not the 230 amp I'd mentioned.I had looked at the wrong scale.

    The only reason I've been welding DC reverse polarity is because I had welded some stainless,and forgot to switch it back to AC when I went back to steel.I left it there because my welds SEEMED to come out better on the steel with the DC,with better penatration.I've no scientific evidence of that,but just my untrained observation.Is there any reason to switch back to AC for this job?
    I know 7014 will work on DC,but how about 7018?

    Thanks

  6. #6
    Member ADMSWELDING's Avatar
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    Use Dc Ac Is More Pentrating But Will Not Work With 7018 Unless It Is 7018/ Ac A Special Type Of 7018 Use Dc Anyway.i Always Run Dc Unless Doing Aluminum
    Last edited by ADMSWELDING; 01-12-2006 at 08:46 PM.

  7. #7
    Administrator Squizzy246B's Avatar
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    We used to use the 7016 or 11016 for the root runs and the 7018 or 11018 for the capping runs. The 16's are a little more bitey but it does produce a better job for all positional work that must have full peno.
    Regards from the Scrub somewhere near Karratha, Western Australia

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  8. #8
    Senior Member xkvator's Avatar
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    just adding my .02
    notch the plate and sink it inside the frame rails as ADMS said...much stronger than butt welding to the end of frame.
    i usually add gussets from the bottom of frame to the lowest point on plate.
    i usually mig with the e70-s6 wire, but 7018 is what i used in the "old days"
    cleaning the steel with a grinding wheel/knotted wire cup makes a better weld
    i flash over the steel in the welding area with a torch to get rid of any moisture in the steel right before welding
    watch your amperage...too high and you'll be undercutting, which weakens the steel. for 1/8" rod, you'll be around 125 amps/DC reverse polarity...lower on the verticals.
    6011 is ok for mild steels and has a forceful arc and fast freeze characteristic...some like it for rusty metals/vertical apps./pipe - it will crack on heat treated material like frames...and old angle iron bed rails/scaffold braces.

    ADMSWELDING...welcome to the forum...looking forward to some more pictures of your artwork.
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  9. #9
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    I'm having a hard time designing something stout enough for my comfort considering the way this truck was built.The box sits tight on the top of the frame when down,and both of the frame rails were notched out to accept the boxes pivot frame.

    A:an exploded view of how the truck was built.
    B:the rear frame area.Not much room to work with inside of frame,or to the rear of box pivots.When box is up,the area rearward of pivot pins is crowded with pivots attached to box,and rear of box.

    C,D & E are what I've come up with for a design.All steel would be 1/2",including the rear main plate.The top "L" shaped side plates would be welded to the frame sides(shaded area in B),and the top of main plate would be welded to bottom rear cross member of the boxes pivot frame.

    I'll check on running braces down from further up the frame to bottom rear of sub-frame,like you mentioned xkvator.That would beef it up real good,if I can do it.

    Any opinions on this are welcome.I don't want to build something that's gonna fall off and remodel someones basement with their living room,via my trailer.
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  10. #10
    Member ADMSWELDING's Avatar
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    jeff the area under the angle iron cut out those two little l shapes and recess the plate into the frame a 1/4" top of the plate will run along the bottom of the angle used in the boss assy. forget the side plates on the frame put your gussetts under the frame rail and to the back of the plate.By recessing the plate it transfers the load to the frame of the truck weld the top of the pintle plate across the angle iron 100% keep us informed. good luck

  11. #11
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    Do you mean like this Bill?(the shape with the dashes)

    I understand what you meant with the gussets directly to back of plate,and underside of frame.
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  12. #12
    Member ADMSWELDING's Avatar
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    YES EXACTLY,When you add your gussets bevel your plates for a multi pass weld good luck and also good sketch very helpful in understanding your design,

  13. #13
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    I've got a grip on it now!I have to get the plate cut on a burn table anyway,so it won't be a hard adjustment to make to the design.

    Thanks again Bill!

  14. #14
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    Well,I just now got around to tackling this job.Had the steel all cut,found a nice Holland 90k pintle(overkill),asembled/welded the sub-frame together in the garage.I used 5/32" 7014 rod(I had it on hand),ran 170 amp w/DC reverse.I chickened out when it finally came time to weld the whole assembly too the truck frame.

    A welding shop now has everything in their possesion,and THEY are going to weld it too the truck for me,so it doesn't have a chance of falling off.They commented that although my welds looked good enough,they thought they may have been a tad cold,and that I should've run more juice,or used 1/8" rod instead of 5/32" rod.They recommended notching out the bottom of the outside frame,and welding the gussets(4) too both the outside,and inner frame.Whatever it takes to do it right,I say!

    That welding overhead,on your back is past my level of ability.It's easy when you can position the piece perfectly,and weld it.It's a whole different story when you're at the mercy of the piece of equipment.Too important to have good welds on this thing to chance it.

    So I'll leave the rest to the pro's!!

  15. #15
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    Jeff,

    Just one thing that i would add.

    run a piece of 3/8 or 1/2 x 2 flat stock horizontially across the back side of the hitch plate (with the 3/8 or 1/2 against the plate) at what would be the centerline of the pintle hitch to help take any deflection out of the area of the pintle hitch.
    I would also weld D-rings to the plate for the saftey chains instead of cutting the plate.
    Last edited by crash935; 04-02-2006 at 01:05 AM.

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