making a subframe for my 01 John Deere 4300 and Prairie Dog backhoe attachment

[dfkrug]

Well, I recently finished another backhoe subframe. This may be my seventh or
eighth? I lost count.

This is for a 2001 John Deere 4300, and a new Prairie Dog 7.5, a Woods 7500 clone.
I recently rebuilt this former rental tractor; the thread is here:
http://www.tractorbynet.com/forums/parts-repairs/247806-2001-john-deere-4300-hst.html

Unlike the last subframe I wrote about, which was for the same model tractor
and hoe, this one is considerably different. Followers of my other subframe
threads can compare/contrast to my last 4300 effort here:
http://www.tractorbynet.com/forums/build-yourself/171760-how-build-your-own-custom.html

I did this subframe differently than the last for a couple of reasons: one was to keep
me interested. I don't really like to do repetitive stuff. The other reason is to show
that no single approach is better in every way. One way might be easier to make,
but harder to live with. Another might provide more durability, or one may be easier
to mount/dismount.

Anyway this one is sort of a "Five-point subframe". It will be made in two main
parts, a tractor-side ladder frame that stays mounted all the time. And a hoe-side
frame that is permanently mounted to the hoe. The tractor side will not interfere
with the 3-point hitch, and will provide some underbody protection to the exposed
hydraulic lines. Hoe mounting/dismounting will be much easier than the other 4300
subframe, which was one piece that always stayed mounted to the hoe. The
new subframe will mount/dismount using only 2 bolts and one pin.

First, I will post the DONE photo, showing how close-coupled the hoe is to the
tractor. This one has the best departure angle of any I have done, with minimum
tire-to-hoe clearance. Works great.

 

[Stimw]

That's a good looking Hoe! (can I say that here?)
The important thing with a subframe is that it protects the tractor center from the stresses.
I got a great deal on a new closeout Jinma Hoe on ebay ($2200.) and modified the subframe to fit my 3510 Branson.
I have a Welding/Fabrication Shop so it wasn't that bad of a project.
The Jinma Hoe does OK but I wouldn't want to make a living with it!!!! I do have fun with it and it beats a shovel! I also made a 6" bucket for it for trenching which works great.

 

[dfkrug]

OK, the plan is to use some 1.5x3.5x1/4" channel, which I have salvaged from
a now-defunct tractor dealer. (They were from Kubota shipping crates.)

These main rails will be welded to the lower ROPS bracket in the rear, and
hang from existing holes in the tranny tunnel up under the foward middle
of the tractor. I cut some 1/4" plate for the forward brackets and drilled them.

I plan to attach all the bolted elements to the tractor, position the welded
elements, then tack-weld them while mounted/positioned on the tractor.
Then I will remove all the bolts to do the final welding.

 

[akraven]

I will look forward to seeing how you design and build this. On the list of things I want to do to my tractor.

 

[dfkrug]

Here is the subframe after I tack-welded it, then unbolted it from the tractor.
I like to use a series of small automotive-type scissors jacks to fine-position the
channel steel before tack-welding. They are strong, secure, and are
hand-adjustable.

The forward section uses some shedule 80 pipe for transverse support. The
rear support uses some 1/2" plate welded to the frame channel, and the
ROPS lower bracket.

The 1/2" plate is the only steel I had to buy.....I never have too much 1/2"
plate lying around. I bought a 4' long chunk of 4"x10"x 1/2" angle steel
as the salvage yard for .35/lb, or about $35. Part of that is for the hoe-half
of the subframe, coming up.

 

[dfkrug]

Here is the tractor-side of the subframe all welded and painted.

On the forward supports, I boxed in the channel for strength.

On the rear, I added some 5/8" bar at 45-degrees to the channel. This will be
the only place where the subframe is bolted to the hoe-side subframe. I drilled
the 1" hole first, so I could use my drill press. These holes will have SAE
grade-8 1" bolts. (Sadly, hardware stores around here no longer carry one-inch
fasteners, so I had to go to Fastenal.)

Below the bolted element, I made a cradle in the channel to support a 1.125" guide
pin. The hoe-side pin will rest in this saddle, and the hoe will pivot upwards to align
the bolt holes. It will be clear in later photos.

 

[dfkrug]

Here the tractor-side subframe is mounted to the tractor.

The forward section uses existing holes in the tunnel casting (after
cleaning out the threads. Unfortunately, the undercarriage armor
in the rental service kit interfered, so I had to toss it. The frame
rails provide substantial protection themselves, however.

The rear attachment shows the ROPS bracket connection. Note
the new bolts; these are critical and the original ones were rusty.

 

[mjncad]

That looks to be a nice clean design.

 

[RoyJackson]

Great job, dfkrug!!
I wish I had your skills...and I wish I could still get near a welding machine.

 

[dfkrug]

Thanks, Matt and Roy....I knew I could count on you to read this thread.

Now for the hoe-side of the subframe.

I positioned the hoe at the operational height I want using the two 4x12
wood blocks. I also have my overhead crane supporting the boom for the
correct tilt. I connected up the tractor hydraulics so I could operate the
outriggers for the correct height. I want this to be pretty exact, so I
am not going to count on hydraulics to keep the hoe in position.

After that is all set, I will back the tractor up to exactly the place I want.

 

[Luremaker]

Your are doing a great job Dave. Thanks for posting a subframe that stays on the tractor. Looking forward to the hoe-side of your build.

 

[dfkrug]

This is how the lower part of the hoe-side of the subframe fits into
the saddle seen above.

I used some 1.125" rod, which fits just about perfectly inside some
schedule 40 steel pipe, size 1.5" I think. I cut some 2" pieces of this
pipe the long way to make the saddles. This is how I made the saddles
for my Kioti subframe, too:
http://www.tractorbynet.com/forums/build-yourself/95092-yet-another-custom-backhoe-subframe.html

This design is simpler, however. I will not use any bolts on the lower
part of the mount.

 

[RoyJackson]

How much ground clearance will you lose (if any) with the subframe?

 

[dfkrug]

Here's the long story on ground clearance, Roy.

The minimum ground clearance seems to be at the front diff, and that is
not affected by the subframe. The 2nd lowest hanging point is the center
of the rear gearbox, where the drawbar is attached. The rear part of the
subframe is a bit higher than that, so you lose nothing in the rear. (Note
that any JD owner can gain 2" of clearance back there by just removing the
drawbar bracket.)

Under the middle of the tractor, the ground clearance is about 3" less than
without the subframe mounted.

 

[dfkrug]

In this series of pix, I have completed the mockup and tack-welding of
the hoe-side elements. With the hoe unbolted and moved away, you
can see how everything goes together.

Next, I will do the finish-welding and paint everything before re-attaching
to the backhoe.

You can't see it, but I welded anti-turn tabs on one side of each side plate
next to the 1" nuts. This allows me to tighten the bolts with just one
wrench; getting 2 wrenches in there can be difficult. This is superior
to just welding the nut to the plate because it gives just a bit of play. The
holes are drilled to a tight tolerance.

 

[RoyJackson]

Keep 'em coming, df!!
This is a great thread!

 

[dfkrug]

The last thing I had to fabricate is a toplink. This is not absolutely necessary,
but it will add a bit of stiffness without overloading the toplink bracket. I made
an 11/16" pin to take up the slop in the toplink bracket holes so it fits pretty tightly.

Stiffness in the subframe is very important; flex leads to worn bolt or pin
holes, and eventual metal fatigue and cracking. But don't believe me; just
look at the subframes on serious, purpose-built backhoes. These subframes
feature no visible flex in the frames.

Careful observers will see the similarity of my toplink to a Woods 3-pt enhanced
toplink. I have a bunch of these, so I shortened one up and welded it solid. It
is over one foot shorter than the standard 3-point toplink. Sadly, I ran out of
gloss black paint, so it is flat-black. The show must go on.

 

[dfkrug]

And here is the final result.

I mounted the hoe as close as I could to the tractor. My tires are about 50% worn, so
I aimed for a 1" clearance to new tires. I trimmed the step a bit, and achieved
a slightly closer mount than the last 4300 subframe, due to the 3/4" additional
wheel spacing I got from reversing the rear wheels.

I made a mount for a new seat, and was off to the races.

 

[kairala]

a new member to this community.thinking of building a mini backhoe,for a power tiller of 12bhp.so i require some detailed free backhoe plans.please help with any valuable guidance and plans if any.thank you.
email kairala27@rediffmail.com.

 

[swick1]

a new member to this community.thinking of building a mini backhoe,for a power tiller of 12bhp.so i require some detailed free backhoe plans.please help with any valuable guidance and plans if any.thank you.
email kairala27@rediffmail.com.

Your biggest limitation will be weight. A backhoe needs at least 1000lbs of ballast to be at all useful. Otherwise the backhoe will move the tractor. I think you should create a new thread to discuss this machine