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  1. #1
    Join Date
    Nov 2006
    Location
    NW PA
    Posts
    27

    Default Kubota backhoe dipperstick repair

    I bought a year 2000 L35 used late last fall. I drew up the parts for a mechanical thumb, and they are being cut out on a CNC plasma. Then I will weld up the thumb and install it.
    The problem is that the inside (operator-facing) flat surface on the dipperstick where the thumb base will mount has a bulge in it. The bulge is in the area between the the pins for the bucket linkage. Apparently the previous owner really stressed this thing at some point, but it was likely the only time because the whole machine is in great shape.

    L35 DipperstickBulge 012sm.jpg

    I talked to the dealer and what they would do is cut out the bulged area and replace with a new piece of plate. Which is what I thought they would say. They have never done this repair before. They did not know if the steel was an alloy steel or just mild steel.

    I definately will not spend the $1,000 bucks for a new dipperstick.

    What do you guys think?

    Thanks,
    Nick

  2. #2
    Join Date
    Aug 2006
    Location
    Browns Valley, California
    Posts
    1,713

    Default

    Assuming your thumb base is going to just be a piece of plate welded at right angle to the dipper, what I think I'd do is profile the base of the thumb for the bulge with a plasma cutter or an O/A torch and just weld it up. The worst thing that can happen is the thumb weld will fail, I'm thinkin.

    A thumb really doesn't take much pressure in use; it just holds wired shaped stuff in the hoe bucket.

    That certainly is an unusual failure. My baby tractor's (B7800) hydraulics would not be able to put that kind of a hurt on the dipper!

    Hank
    ...from the Gadget Garage
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  3. #3
    Join Date
    May 2008
    Location
    San Diego
    Posts
    180

    Default Thumb options

    Why don't you make the thumb mount as wide as the stick? That way you can weld it to the sides, which is the strongest part.
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  4. #4
    Join Date
    Nov 2006
    Location
    NW PA
    Posts
    27

    Default

    Hank & Lance;
    Thanks for the replies. From all I've read at thumb mfr's websites, they all seem to concur that the base plate of the thumb should set on the flat inside surface between the welds. Then it is essentially welded to the existing welds/sides of the stick. But only welded the 2 sides parallel to the length of the stick and never across the short width of the stick.

    I was shocked that the hoe had that muck force. But the L35's are very strong for their size. So they tell me.

    The gouge depth to fit over the bulge would have to be around 3/8" at the max, but it is right where the main pin of the thumb will be.

    I think it will work to cut the bulge out w/ a wheel (minimize the heat), weld in the patch. Any suggestions for the patch material?

    Thanks,
    Nick

  5. #5
    Join Date
    Feb 2005
    Location
    N.E. SD
    Posts
    1,378

    Default

    I would cut it out and replace it with mild steel.
    Jeff

  6. #6
    Join Date
    Nov 2006
    Location
    NW PA
    Posts
    27

    Default

    Thanks Jeff & Ironhead.
    That's what I was thinking and hoping to hear. I will likely Tig it and grind the welds flush. Then proceed to attach the thumb base plate.

    Will keep you all posted as this progresses.

    I apologize for the spelling in my posts. Not much for typing.

    Nick

  7. #7
    Join Date
    Aug 2006
    Location
    N.C.
    Posts
    362

    Default

    I'd check for cracks as it could have been water got into it and froze.... I have seen ice do lots of damage to steel even down here were 30deg. is cold
    George W. Bush was saving your butt whether you liked it or not!
    Fear is temporary, regret is forever
    HH210 with SG

  8. #8

    Default

    I have inspected many of these. Typically it is CJP welded ( open root or ceramic backing ), back gouge root, welded out, ground flush, and then ultrasonically tested.

  9. #9
    Join Date
    Nov 2006
    Location
    NW PA
    Posts
    27

    Default Update

    Well I chose to try to contour the baseplate that mounts to the dipperstick over the bulge. You can see the contour templates I made in Contouring pic 008. Transverse templates every inch for six inches and one longitudinal template along the centerline. Same technique as what one would do for carving an arch for a violin plate or archtop guitar. Once close to the templates I would spray some paint on the bulge, set the plate on it and whittle the high spots down until the contact all over.
    Once the baseplate is welded solid to the diperstick, them I'll finish welding the baseplate assembly itself. Now it is just tacked to minimize distortion...
    Attached Images Attached Images

  10. #10
    Join Date
    Nov 2007
    Location
    Saskatoon, Sask, Canada
    Posts
    1,270

    Default

    Looks good, almost to good to use!!!
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