how to build your own custom backhoe subframe

[dfkrug]

Do you know what part/kit# there is to add that subframe support to the tractor?

The JD document I took the snip from is titled "Product services Information"
and has part # LVU17203 at the bottom. That part # does not come up on
JDParts when I enter it there.....maybe it is "whole goods", and not "parts".

I think I first heard of this doc on TBN....maybe someone else has tracked
this down?

Anyway, I will next show how Woods and Bradco make subframes for the
JD 4x00/4x10 tractor, and my own solution.

 

[Baby Grand]

Keep it coming - this is good stuff!

 

[dfkrug]

Here is a factory subframe from Woods for the JD4310. The photo shows
it mounted to another Prairie Dog, and it is of the ladder style. You can
see the enhanced toplink if you look closely.

Woods provides subframes for both the 4x00 and the 4x10 tractors, and
they have different part #s, but the installation manuals show identical
drawings (2nd photo). You can see that they utilize the 3PH lower arm
pivots as the only attachment at the rear. I think this is not a good idea
because the 3PH pivots are part of an all-aluminum axle housing. Followers
of my 4300 rebuild project have seen that that aluminum casting is not very
strong (3rd photo). BTW, Woods does not list subframes for the JD 3x20s,
which use even more aluminum back there. Woods manuals for all their
subframes can be viewed in PDF on their website.

 

[arrabil]

What do you think about a Woods-type subframe that ties the lower 3pt mounts to above the drawbar? The drawbar is capable of supporting 1000lbs on the 42/43/44x0 and so it would distribute the strain on the lower 3pt mounts and prevent the subframe from twisting them off too. [This is what I was considering as a starting point.]

 

[dfkrug]

Bradco produces a subframe for the JD4300/4400/4310/4410 that is a bit of
a hybrid of the two types. It has four mounting points, but it does not
wrap around the top of the axle housings. They avoided hanging anything
off the axle housing (good!), and instead uses the ROPS bracket for rear
support. The ROPS brackets are 1/2" plate steel, secured with four 19mm
grade 10.9 (similar to SAE grade 8) bolts. Bradco replaces the bracket with
their own, with added weldments. This is superior to what Woods has done,
and I will do it this way, too. The pix are drawings from the Bradco
installation manual.

The subframe does not fully wrap around the axle because there is simply
no room! This was a challenge for me, since I wanted to make a 4-pt
style subframe that wrapped around the axle and did not depend on a
toplink. Bradco eschewed the toplink, but I don't feel comfortable with
the potential flex in the area I marked on the drawing. I am going with
an enhanced toplink. See the first drawing yellow arrow annotation. To
give Bradco credit, they probably build that part of the subframe very
stout to avoid this problem. I think the toplink will brace against these
forces successfully without the additional strengthening necessary.

Because the front mount for the subframe is much narrower than the
ROPS brackets, Bradco put some Z-bends in the frame rails (#3 in the
2nd drawing). I used this approach for one of my 955 subframes. It is easy
to fabricate, but you will need to add a brace (#5) if you do it this way.
Bending forces on a frame element with these bends will cause twisting
if no brace is used.

To reduce the wiggle you get with pins, Bradco uses wedges (#1) to secure
the top 2 attachment points. This is an interesting approach that I find
intriguing, and I have a lot of respect for Bradco engineering. I have no
personal experience with this wedge approach and how it works to limit
wiggle in the field. I do think wedges with rectangular cross-sections and
the holes for them will be more laborious to fabricate. If others have
experiences with the wedge approach, I hope they comment here.

 

[Johndeere3720]

Keep it coming - this is good stuff!

This is really good stuff!

 

[dfkrug]

What do you think about a Woods-type subframe that ties the lower 3pt mounts to above the drawbar? The drawbar is capable of supporting 1000lbs on the 42/43/44x0 and so it would distribute the strain on the lower 3pt mounts and prevent the subframe from twisting them off too. [This is what I was considering as a starting point.]

There are 4 bolt holes in the bottom of the gearcase steel casting...these
are used for the drawbar brackets. You could take the drawbar off and
use the holes to reinforce the subframe, but you will lose the Woods
quick-attach capability. The QA capability is too often used with the
sacrifice of structural integrity.

Note that it is better to support the hoe with connections that are as
far outboard as possible. This will reduce bending stresses on the axle
housing, and those long bolts that attach them to the center gearbox.

I will be posting some underside pix of my completed subframe shortly.

 

[jdmar]

Thanks for all the info. I am now only digging 6" deep in loose sand!
Peter

 

[dfkrug]

Woods makes hundreds of different subframes for many many tractors.
This is one of the reasons that the makers of the Prairie Dog hoe copied
the structure of the Woods 7500. The earlier subframes sold by Woods
were of the ladder type, and they often required you to mount brackets
to the tractor carcass that blocked off the 3-pt hitch lower lift arms. This
made it very tough to use the 3PH when the hoe was dismounted. The
ladder frames also extended very far to the rear; I suspect that was to
provide clearance for the seat. Woods did not optimize their subframes
for the closest possible hoe mount. Some of Woods' subframes for
different tractors are so similar that I suspect that they also tried to
minimize how different each one was to limit manufacturing costs. Kind
of like a "least common denominator" approach to design. A custom subframe
can improve that by optimizing for a particular tractor.

As a point of reference, an integrated TLB will have a departure angle of
as much as 20 degrees; an attachment subframe is rarely better than 15
degrees.

I have purchased and installed only one Woods factory subframe (on the
L2550 above), and I found the price to be reasonable (about $500), but
the wait was very long. Their newer 4-pt subframes are over $1000.

The pix show Woods 4-pt subframes for Kubota L-series and B-series. In
the latter case, you can see that the subframe does not have a structural
member that wraps around the rear axles. Lack of clearance is the likely
reason. I like how robust these units are, and their use of existing threaded
holes in the Kubota castings where possible. (Note that Kubota and
Kioti have many unused threaded holes available on their tractors, while JD
has few. I don't know about other tractor brands.)

It is also interesting how Woods' design strategies have evolved. Newer
subframes no longer block the 3PH, and earlier pinned connections are
often replaced with secured bolts. They even provide a wrench to help
speed up the mount/dismount process (3rd photo). These last 2 photos
and the first one show Kubota Grand L 4-pt subrames.

Pin attachments are quick to install or remove, but they wiggle. Bolts are
more secure, but they can loosen up and they take longer to attach
and remove. Any slop in rigid mounts will allow wear in the holes. Bradco
attempts to find the best of both worlds, with pins and wedges.

 

[magicheater]

Here is what I have done so far to modify a sub-frame not made for my tractor.Not a lot to do but did have to work within some limiting factors. Had to drill an extra hole in the forward brackets. Had to widen the the rear portion of the framework to match up to my tractors dimensions. Couldn't go too wide or I would have to modify the hoe mounts also. The forward to aft dimensions were spot on, otherwise I would not have purchased it.