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  1. #1
    Elite Member dfkrug's Avatar
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    Feb 2004
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    4,595
    Location
    NorCal
    Tractor
    05 Kioti CK30HST w/ Prairie Dog backhoe

    Default how to build your own custom backhoe subframe

    Not many tractor owners are willing to go thru the process of making a
    custom subframe to mount a backhoe attachment securely to their tractor.
    I want to encourage anyonewho is reasonably handy to consider doing
    this....it is very rewarding, and you can endup with a TLB setup that
    comes close to what you would get if you had a factory-integrated
    Tractor-Loader-Backhoe. A custom subframe can be built BETTER than an
    add-on subframe from a maker of hoe attachments. More on that later.

    I get asked to build a subframe for someone else's tractor now and then. I
    never take them up on the offer, but I am happy to show them how I do it.
    I have helped some folks long distance, but that is difficult. I want to use
    this thread as a go-to place for those considering the fabrication of their
    own subframe. In my approach to design and fabrication, I always want to
    have both the hoe and the tractor here: measure 3 or 5 times, and cut only
    once, hopefully. I have learned a lot about backhoe attachments and
    subframes by owning and making them, and by analyzing the many samples
    I have seen. I have a large database of hoe attachment specs, but I
    am always looking for more data and new ideas.

    In this thread, I will show the process I went through to design and fabricate
    a subframe to attach a Prairie Dog 7.5 backhoe attachment to a John Deere
    4300 tractor. I will use this and other examples of subframes to illustrate
    different design approaches. Comments and questions are welcome.

    But first, I want to discuss the basics.

    What is a subframe? It is a structural member(s) that is rigidly tied
    with welds, bolts, or pins to the main structure of the tractor. The
    subframe rigidly transmits the forces from the implement to multiple parts
    of the tractor's structure. By distributing the forces caused by the
    implement, the tractor is protected from excessive concentrated forces, including excessive tension as well as destructive bending moments.

    Subframes are used as a superior way to mount a backhoe, instead of
    using the Three Point Hitch (TPH). There are many cases where a
    Category 1 TPH has been used to successfully mount a backhoe.
    There are also numerous documented cases where TPH-mounted hoes
    have broken the toplink mounts, or cracked tractors in half. That is
    no news to TBN members. Subframe-mounted hoes can also provide a
    better integrated tractor with the hoe mounted much closer in to the
    rear of the machine. A closer-mounted hoe will increase the minimum
    departure angle, which is a fancy way of saying it won't hit the
    ground as often when driving through a depression, or onto a trailer. Some
    off-the-shelf subframes do not mount the hoe any closer than a TPH mount,
    however. A closer-in hoe mount will also improve a tractor's drivability.
    If a large weight it mounted far from the center of gravity of a tractor,
    it will have what is called a high polar moment of inertia. This inertia
    will resist changes in steering input.

    In the first photo, I show the parts that comprise a 3PH hoe attachment
    mechanism. On the left are the parts that are permanently bolted to the hoe.
    The other parts comprise a much stiffer toplink, and brackets to keep the
    lower 3PH arms (not shown) from rising. The second and third photos show
    the same tractor on the 3PH, and on a Woods subframe, respectively. This
    early Woods subframe does not mount the hoe any closer to the tractor
    than the 3PH mount does.

    Next: subframe types
    Attached Thumbnails Attached Thumbnails -three_pt_hitch-jpg   -l2550_3pt-jpg   -l2550-woods_sub_a-jpg  
    Last edited by Muhammad; 06-21-2010 at 07:18 PM.

  2. #2
    Bronze Member
    Join Date
    Sep 2004
    Posts
    60
    Location
    MN
    Tractor
    Kubota BX1500

    Default Re: how to build your own custom backhoe subframe

    Very interesting.. I look forward to the next chapter..

    I would really like a small backhoe for my kubota BX and have been giving much thought to building or modifying pieces of a purchased stand alone system.

    Thanks,
    Robert

  3. #3
    Veteran Member
    Join Date
    Dec 2009
    Posts
    1,001

    Default Re: how to build your own custom backhoe subframe

    I am going to watch with great interest. I have been thinking of ways to set up for my 416 Allis G.T... My first part will probably be a one arm loader, and then maybe a backhoe.

  4. #4
    New Member
    Join Date
    Apr 2009
    Posts
    6
    Location
    North Alabama
    Tractor
    Yanmar YM1500

    Default Re: how to build your own custom backhoe subframe

    Very good info. I look forward to the next post.

    Later
    D.james

  5. #5
    Veteran Member magicheater's Avatar
    Join Date
    Jul 2009
    Posts
    1,668
    Location
    central Wisconsin
    Tractor
    Kubota B7800, B26 TLB

    Default Re: how to build your own custom backhoe subframe

    I had the very same Prairie Dog Digger. A very quick and capable hoe with the pump unit they have. Sold it in pursuit of a larger unit.
    Working to increase the scope of the small tractor experience, one quick attach at a time.

  6. #6
    Platinum Member
    Join Date
    Nov 2008
    Posts
    690
    Location
    Brampton, On\lot Powassan, ON Canada
    Tractor
    Kubota B4200\MF 135\Kubota B3200

    Default Re: how to build your own custom backhoe subframe

    I plan to add a subframe for my backhoe as well. I don't so much have a problem when digging as when I want to use the hoe to move the tractor around a bit. Thats when things get iffy and I wish I had a sub frame. thanks.
    Unimogdave

  7. #7
    Elite Member dfkrug's Avatar
    Join Date
    Feb 2004
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    4,595
    Location
    NorCal
    Tractor
    05 Kioti CK30HST w/ Prairie Dog backhoe

    Default Re: how to build your own custom backhoe subframe

    There are two major types of subframe used to mount backhoes to tractors:
    The first I will call a ladder frame because it usually has two long beams
    that go underneath the tractor (first drawing), connecting at the rear axles
    or differential housing, and somewhere forward of the tractor's center. Some
    form of toplink is usually required, too. My crude drawing is a side-view
    schematic. Sometimes there are "rungs" on this type of subframe for more
    structural stability.

    The second major type of subframe avoids the use of the tractor's 3-pt
    toplink in favor of four pinned or bolted attachment points. This requires
    that the subframe wrap around the rear axle housings, so it must be
    detachable in that area. These "Four Point" subframes are what you
    will find on most modern CUTs and purpose-built TLBs. As a bonus, this
    type of subframe is often very quick mounted/dismounted. This leaves half
    or more of the subframe mounted to the tractor, even when the hoe is
    removed. See the second drawing.

    These 2 types could just as easily be distinguished at the "undermount"
    type, and the "axle-surrounding" type. Some subframes are the latter
    style, but don't use four detachable points. The point is the two categories
    are not perfect.
    Attached Thumbnails Attached Thumbnails -subframe_ladder_b-jpg   -subframe_4pt_b-jpg  

  8. #8
    Elite Member dfkrug's Avatar
    Join Date
    Feb 2004
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    4,595
    Location
    NorCal
    Tractor
    05 Kioti CK30HST w/ Prairie Dog backhoe

    Default Re: how to build your own custom backhoe subframe

    There are some rather odd subframes that don't fit either of these
    categories. I have seen subframes from Deere for both the 955
    and the 4300/4310 that are little more than small brackets that bolt
    to the sides of the rear axle housings (photo). This approach has not
    worked well, however, as JD later required users of their hoes to buy a
    separate reinforcement subframe to add to that. I have posted a page
    from JD's Subframe Installation Manual, which is dated 2005. That could
    mean that this reinforcement was developed in response to failures
    in the field. Like the one in the below photo. Here is a TBN thread
    I posted about one of these broken JDs:
    http://www.tractorbynet.com/forums/j...oken-half.html

    The two small brackets are mounted using the same bolts that hold the
    aluminum axle housings to the cast steel center gearcase. This has also
    been a reported problem area. JD strongly advises users of backhoe
    attachments on the JD4300/4310 to use the additional reinforcement.

    This has not been much of an issue with the 955, since that tractor comes
    with a full external frame, unlike most CUTs.
    Attached Thumbnails Attached Thumbnails -jd47_jd4400_subframe-jpg   -jd_4x00_subframe-jpg   -ebay_broken_4300_b-jpg  

  9. #9
    Gold Member
    Join Date
    Oct 2003
    Posts
    487
    Location
    Ohio
    Tractor
    JD 5425 & 4300, Yanmar 1500

    Default Re: how to build your own custom backhoe subframe

    I trust your knowledge and skills from your other posts...now you are scarring me! I have a 4300 with the 47 hoe on it. My tractor is not currently cracked in half and I would not like that situation to change. Do you know what part/kit# there is to add that subframe support to the tractor? Looks like it is smart insurance to me. I plan on keeping my tractor a long time. One thing I liked about this Deere was the integral backhoe support that seemed to me (oops) to be stranger than many of the 3PTH models out there. I liked that you lifted with the 3PTH but then the actual weight was carried by the steel plates bolted to the tractor. Looks like this is why I am not a licensed engineer!

    Peter

  10. #10
    Veteran Member
    Join Date
    Jul 2008
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    1,019
    Location
    Winterstown, PA
    Tractor
    JD 4200 & X475

    Default Re: how to build your own custom backhoe subframe

    Thanks dfkrug.
    JD 4200 w/ 420 Loader, 8B Backhoe, 59" Snow Blower
    JD X475 w/ 54C Deck & 3-Bag Power Flow

    Looking for an engine out of a JD 4300/4310/4400/4410. Send a PM if you have one (or a parts tractor).

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