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  1. #1
    Platinum Member RedNeckGeek's Avatar
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    Butte County, California
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    Kubota L3240D HST, RTV900

    Default Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    I'd played around enough with the little Nardi backhoe to know that the way it mounted to the tractor wasn't rigid or rugged enough for the trenching job that was planned for next week. Way too much side to side flex along with groaning noises that just didn't sound healthy for the tractor. I'd seen mounts made by others here, and while it didn't look impossible, it did look time consuming. I'd talked at length with Rob Liefveld, and even visited him once to see his Nardi setup, and that was a tremendous help. But instead of worrying about how it might go, I decided to dive in and get'er done.

    Work started with a few measurements to get an idea of what links would be needed and how much material it would take. A shop called All Metals just south of Oroville proved to be a treasure trove of remainders and new stuff, and soon I had 10' lengths of 5/8" x 2 1/2" bar and 1/4" x 2" x 3" heavy wall tube laying on the garage floor. Next I blocked up the backhoe in back of the tractor and shoved it around and shimmed it so it was level and centered behind the tractor's 3 point mount.



    More detailed measurements showed that a pair of brackets under the axel would line up almost perfectly with the lower 3 point mounts on the backhoe, with just enough space for the 2" width of the rectangular tube.



    The top 3 point mount on the backhoe was pretty solid, but it was located far to the rear of the 'hoe. That would mean a long length of bar going forward, then angling out to meet up with a new bracket I'd weld to the Roll Over Protection System (ROPS). I figured if the ROPS was strong enough to keep the tractor from turning turtle, it would be strong enough to keep the backhoe in line. I made top and side view sketches with rough dimensions that would be adjusted to fit as fabrication progressed.





    The bottom links were the first to be made. I turned up some 2" diameter spacers to fit inside the tube to keep the walls from collapsing where the bolts would go through. Since I couldn't reach far enough into the tube with a band sander to flatten the back side of the tube seam weld, I also cut a groove across the face of one end of each of the spacers. Then I welded the spacers into place inside of the tube. At that point I could drill through both the tube and spacer and have a nice smooth walled hole. The digital read out on the mill made accurate positioning of the holes possible, good to just a couple thousandths of an inch.

    Next I removed the lower brackets from the tractor to which the links would mount and drilled two holes in each of them to match the holes at the back of the links. Even though I took extra care in measuring the hole locations, when I tried to mount the links to the brackets the bolts wouldn't line up. That's when I noticed that one of the long bolts that attached the bracket to the tractor was sticking out a little too far, keeping the link from moving high enough to align with the hole. Every thing lined up just fine after the bolt was shortened, but mounting and dismounting the brackets and drilling all those holes still took a couple of long days. At 3/4" each in diameter, that's a lot of steel to turn into chips. The bolts holding the brackets to the tractor were very hard to reach, another time consuming detour. Thank goodness for impact wrenches, as there was just no room to swing a conventional wrench or socket!

    With the lower links bolted in position it was time to start on the upper links. My first sketches showed the links running parallel to the ground from the backhoe mount and then angling out and up to the ROPS. I found some pine the same size as the steel bar and decided to mock up the first bar, as cutting pine is a lot faster than cutting steel, and it was a lot cheaper if I screwed up. I quickly found out that I wasn't smart enough to calculate the correct compound angle to make the second part of the link bend both out and up, so settled on just making it bend out. I figured that if the arrangement wasn't strong enough, I could add another set of links that connected higher on the backhoe and hit the ROPS higher too. So I finished up the pine mockup and used the dimensions to duplicate the parts in steel, tack welding the pieces together and tweaking them to fit as I went along. When i had the link all tacked together I bolted the ROPS mounting bracket to it, held the assembly up to the ROPS, and tacked the mounting eye in place. Then everything got disassembled and finish welded. I started off using the stick welder, but quickly learned that I was long out of practice for the out of position welds that would be needed for the ROPS eyes. So I switched over to the wire feed welder, turned the dials all the way up, and made a series of overlapping spots, letting each one freeze before moving to the next spot in the joint. Not real professional, but I ended up with strong welds with a minimum of metal in my boots. With both links completed a trial fit showed that only a little bit of misalignment existed and tightening the mounting bolts brought everything together perfectly. To finish the top links I turned two spacers that fit between the bars in the section where they paralleled each other. Bolts through the spacers would add lateral stiffness to the setup.

    With all four links in place it was time for a smoke check, so I fired up the tractor and deployed the outriggers on the 'hoe. The first thing I noticed is that the hoe moved a up a little bit as the pads on the outriggers touched down, then the back of the tractor started coming up. At that point the old 3 point mount would have been moaning and groaning and the backhoe seat would have been hitting the ROPS bar as the backhoe pivoted back into the tractor. I also noticed that the outriggers wouldn't deploy far enough to lift the tractor tires all the way off the ground, and I remembered the extensions that Rob had fabricated for the outrigger pads. That might be another job for the future, but I'm hoping I won't need it. Next I used the backhoe arm to push the bucket down into the ground. This time both the 'hoe and the tractor moved up, enough so that the wheels were off the ground. No weird noises resulted, and everything seemed nice and solid. The last test was to raise the backhoe and quickly slew the bucket from side to side. Very little slop was present, a major improvement from the old 3 point mount. I felt like I had gotten away with something, and that the extra set of links wouldn't be needed after all.

    To make the backhoe easier to mount and dismount I'd need to cut the lower links short enough so that the pieces that stayed bolted to the tractor wouldn't interfere with the lower arms of the 3 point hitch when they droped low enough to engage other implements. Then I'd have to come up with some sort of joint to connect them back together. Again Rob had already figured out how to do that, so I just copied his idea. It involved a plug in the end of each tube that would engage the open end of the mating link, and a cross drilled hole through which a pin would pass to keep the two together. I didn't have a steel bar thick enough for the plug, but two pieces of the 5/8" bar stacked with a 1/4" piece would do the trick. Once stacked I welded them together, then cut 1 1/8" diameter holes in the side of the tube ends to weld the plugs in place.



    I'd already been using the mill to drill the holes, and I took advantage of the setup to just mill off the extra weld metal above the face of the tube. Much easier than grinding it off; I spend way too much time grinding my welds as it is!



    The plugs were finished up by milling facets onto the end that would guide the tubes into alignment as the tractor moved back to the 'hoe. I used those little angle magnets sold at Harbor Freight for gauges, and just clamped the plugs into the milling vise with one plug at each end to keep from springing he jaws. It turned out to be a pretty solid setup and I was able to take 0.075" cuts pretty easily.

    The last step was to assemble the tubes and match drill the hole for the connecting pin. Instead of just drilling the hole, I used a boring head to keep the diameter very close to the pin size. It worked out very well, with the first couple of times putting the pin through needing a mallet to drift the pin home. To finish I had to cut the pin length down and redrill the hole for the keeper, two simple tasks for the lathe and mill.

    Much to my relief, on reassembly everything still fit together and provided the same degree of rigidity and strength. I found that Rustoleum gray was a pretty good match for the Kubota paint at a fraction of the cost, and that Tractor Supply sells orange paint that matches the Kubota and Nardi color almost perfectly. Good thing, too, as I had to cut an access port into the side of the hackhoe leg guards so that a longer bolt could be installed at the rear of the top links. Thank Dog for plasma cutters!

    To prop the backhoe up when it's off the tractor I made a little stand from left over steel tube and scraps from my friend Louis' garage. Took about an hour to knock together and holds the 'hoe at just the right height to get the lower arms connected.



    So with the backhoe was ready to go I thought I'd try a little trench to see how it worked. I was hoping to follow a shallow drainage ditch that already runs parallel to the driveway, but after just two scoops I hit solid rock less than a foot below the surface. Oops: I'd need at least eighteen inches for the trench. Looks like I'll end up a few feet from the edge of the driveway where there's more soil, but it'll be a little tougher getting the tractor in there, especially up in the narrower sections of the easement onto my neighbor's property. We're already planning to clear that section with a bull dozer, so the extra work shouldn't be a problem.

    Here's a hearty Thanks! to Rob and the others here that have made their own mounts! I'd have never tried it without your insights and encouragement!

  2. #2
    Super Star Member J_J's Avatar
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    JACKSONVILLE, FL
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    And no pictures what-so-ever.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  3. #3
    Platinum Member RedNeckGeek's Avatar
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    Kubota L3240D HST, RTV900

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Quote Originally Posted by J_J View Post
    And no pictures what-so-ever.
    Thanks for the heads up, J.J.

    The images were working fine when I originally posted the note, but had somehow been deleted from my server. I've uploaded them again and they appear to be working.

    Oddly, I can't edit the text of the original article, as there is no "Edit" button next to the "Quote" button at the bottom. Any idea what's up with that?

    Sorry for the inconvenience. This Internet stuff is great when it works, but I guess Al Gore isn't keeping close enough watch on his brain child...

  4. #4
    Veteran Member
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    Mid. Coast Maine
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    7610 hst

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Worked great for me,, Nice looking job

  5. #5
    Veteran Member Luremaker's Avatar
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    Kubota L3130HST & NH TC18

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Hi Sjmarbu,

    Do you have any pictures of the parts which stay attached to your backhoe and what stays attached to your tractor. I want to build my subframe soon for my L3130 which is similar to your kubota L3240.

    I have been looking at as many sub-frames as possible and I like your setup. Would there be any benefit to extending the lower portion so that it bolts onto the loader subframe?

  6. #6
    Elite Member teg's Avatar
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    Raleigh, NC Hillsville, VA
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    L2800 - HST

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Quote Originally Posted by sjmarbu View Post
    ...Oddly, I can't edit the text of the original article, as there is no "Edit" button next to the "Quote" button at the bottom. Any idea what's up with that?...
    You only have 24 hours to edit the post... then it's locked. Not sure why...

    TBN upgraded the software for the forum a while back and they had forgot to do the edit "lockout", so I went back to several old posts and corrected "things"

  7. #7
    Veteran Member Luremaker's Avatar
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    Kubota L3130HST & NH TC18

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Quote Originally Posted by Luremaker View Post
    Hi Sjmarbu,

    Do you have any pictures of the parts which stay attached to your backhoe and what stays attached to your tractor. I want to build my subframe soon for my L3130 which is similar to your kubota L3240.
    After rereading your post it is all clear now. Thanks for posting.

  8. #8
    Platinum Member RedNeckGeek's Avatar
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    Butte County, California
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    Kubota L3240D HST, RTV900

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    The backhoe's been working great for the last month, and the mount's been getting a real workout in the rocky soil here. Only two problems have surfaced: A loose hydraulic line (easily fixed) and an issue with dismounting the 'hoe. There's not much level, much less paved, ground around here, and I had the Devil's own time getting the 'hoe off the tractor. What worked fine on the level concrete floor of the shop/garage didn't fare so well in the off camber graveled lot where the 'hoe lives when it's not on the tractor. I ended up removing the two bolts that hold the lower links to the 'hoe, then the rearward pieces of the lower links could be disengaged. Otherwise there was just too much twisting to let the coupling disengage. Not really a big deal as the two bolts are easily accessed.

    A bigger problem surfaced when I tried to hook up my box grader. It turns out that the two links that control side-to-side sway on the three point mount hit the short mounting link for the 'hoe that stays bolted to the tractor.



    It took a couple of iterations, but the solution was to flip the sway bar over so it came out, then down, to the rest of the three point hitch.



    The only permanent change to the Kubota configuration was a small modification to the brackets that attach the sway bar to the three point hitch. The brackets have a finger that keeps the bracket from rotating, and that finger had to be amputated.



    The upper mount for the sway bar was also relocated inboard and a spacer fabricated to keep the two ears of the upper mounting bracket from bending in (see second photo above). The resulting configuration lets the box grader drop all the way down where it needs to work, and come up all the way as well.

    I just wish I'd spent a little more time measuring the location for the cut on the lower backhoe mounting link, as an inch shorter would have eliminated this problem. Live and learn...

  9. #9
    Veteran Member Luremaker's Avatar
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    Ontario
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    Kubota L3130HST & NH TC18

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    sjmarbu, Thanks for the update. I'll take the required measurements this coming weekend and hopefully have my frame finished before the end of next week.

  10. #10
    Platinum Member RedNeckGeek's Avatar
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    Kubota L3240D HST, RTV900

    Default Re: Home Brew Nardi Backhoe/Kubota 3240 4 Point Mount

    Just a quick update and a correction, the correction first:

    The trick of flipping the sway bar over only worked because the sway bars on my tractor had become bent while using the box grader. When my lot was graded last year the bulldozer operator left quite a few stumps in the ground, sheared off level with the surface. Every time I hit one with the tractor pulling, and especially pushing, the box grader, it really stresses those sway bars, even to the point of bending like pretzels. They should be straight, not bent at a right angle as is shown in the photo above. I hadn't realized what was going on when I designed the 4 point mount. The sway bars have since been replaced, and back in the original position they now fowl the lower legs of the four point mount unless the 3PH lifting arms are level or higher. I've also found that clearances between the front and rear sections of the lower links of the 4 point mount are so tight that they are very difficult to get apart once they become dirty. That could probably be remedied by taking a few thousandths off the male spud, but for now I'm finding it easier to just remove the two bolts that connect the lower links to the frame. It doesn't take long, and I think it actually makes mounting the backhoe a bit easier because I don't have to hit the spuds with the open ends of the links while seated on the tractor. Instead I've been installing the mounting bolts loosely, then using the hydraulics on the backhoe to move it up and down, in and out until the rear hole in the links aligns with the mounting holes on the 'hoe.

    By way of an update, the mount is still goin' strong, as is the 'hoe, and I've since put a fair amount of trenching in this rocky ground. It's not always and easy job, certainly no where near as powerful as the neighbor's JD 440 monster construction backhoe, but for smaller landscaping and trenching jobs it's hard to beat the Nardi and kubota for maneuverability. It's strong enough to let me break into a septic line, and I'm embarassed to say that the Google satellite even caught me in the act (I can actually see the white dot of my t-shirt on the back of the tractor in the satellite photo).

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