Backhoe Bobcat Backhoe on a Grand L series

[design]

I am considering adding a backhoe to the L2900 that I own. It is a want, not a need. I saw an add for a "3 pt hitch backhoe". Upon investigation, the Backhoe is a Bobcat 907. (Similar to the 607 in the link below)

http://bobcat.com/products/att/pdf/backhoe.0306.pdf

Someone converted the bobcat system quick attach to a 3 pt. attachment.
My number one concern: is this backhoe to big for this size tractor?
All of the main cylinders are 3" and the digging forces are 2x the BH90 series.
If the tractor can handle that size hoe, is there a way to attach this hoe to the tractor so as not to break the tractor? How do you find/modify/build a suitable subframe.

I really like the specs of this hoe, but breaking the tractor is not an option.

Are there any Engineers out there who have thought about the loads generated from a hoe and considered where to reinforce the frame to handle them?

Design.

 

[john_bud]

That is a lot of hoe for your size tractor. Minimum would be a tractor in the 40hp range. You can make a subframe with a long weekend of skilled fab work. (A couple weeks for a guy like me!). Use 1/4" thick material and tie into the loader frame and the rear axle. Probably rectangular tube in the 2x4 range. I could post pictures of the 4pt attach for my Ford hoe if that would help.

It's up to you. You would need to use front wheel weights, rear wheel weights, load the tires, move them to full width and probably keep a full FEL bucket. It will work, but will overpower the tractor if you don't use care. Does it have a PTO pump? If not, your tractor is no where near the hydraulic capacity to run it over a crawl with the engine screaming. You probably want to be in the 12-14 gpm range at 1800 rpm.

jb

 

[dfkrug]

That's a substantial hoe, at 1300#. Your tractor(4x4) weighs 2800# naked;
maybe another 900# w/ loader. This hoe could work, but you should build
a subframe and not use the 3-pt hitch. The budget L-series tractors use
a less robust 3-pt hitch than the Grand Ls, too.

A subframe will distribute the huge bending forces the hoe exerts on your
tractor to the loader subframe.

 

[dfkrug]

That is a lot of hoe for your size tractor. Minimum would be a tractor in the 40hp range. You can make a subframe with a long weekend of skilled fab work. (A couple weeks for a guy like me!). Use 1/4" thick material and tie into the loader frame and the rear axle. Probably rectangular tube in the 2x4 range. I could post pictures of the 4pt attach for my Ford hoe if that would help.

It's up to you. You would need to use front wheel weights, rear wheel weights, load the tires, move them to full width and probably keep a full FEL bucket. It will work, but will overpower the tractor if you don't use care. Does it have a PTO pump? If not, your tractor is no where near the hydraulic capacity to run it over a crawl with the engine screaming. You probably want to be in the 12-14 gpm range at 1800 rpm.

jb

The L2900 has a 7GPM implement hyd pump. That will be plenty of flow
for a 3" cylinder.

Tractor hp has nothing to do with how well it handles a hoe. Weight is the
real issue. And at least 6GPM implement pump flow here.

My Deere weighs 800 lb less than an L2900 and the hoe on it weighs
1160#, and the custom subframe another 100# or so. Cylinder diameter
is 2.9". Works fine at only about 2000 RPM engine speed. Another 1000#
in weight and it would work even better. (I do not use weights or load
the loader bkt.)

I use mostly 1/2" plate and 1.5x3" channel for my subframes.

 

[design]

To all:
Two isues:
Hydraulic flow: A PTO pump could be purchased if I find the 7GPM insufficient.

Backhoe generated forces:
So I start thinking about the various loads going into the rear of the tractor: (By degree I am a metalurgical engineer, by profession, I am a mechanical engineer)

So: I want the load to go to the 4 wheels, (ideally the front wheels and the backhoe outriggers. Therefore the subframe would be in tension.

How do I ensure I have mounted to something strong enough in the rear of the tractor? Ideally I would want to make sure I can pick the rear end up to put the weight on the outrigger posts? Then what happens as I start digging? At some point I put enough moment through the frame that the front wheels get light. Do I worry about that? The hoe can generate 5000# of digging force with the dipperstick and bucket. The hoe will drag the tractor, hoe, any extra weight (including me, although my 200# does not add much) around like a toy. The hoe will also generate enough downward force at the rear of the tractor to potentially pick up the front end. Should I worry about this?

On several occasions I have had the entire tractor weight (incuding 600# of rear attachments) balanced on the front axle. (I am is the process of adding 900# to my balast box to solve that issue).

Is the rear end of the tractor tough enough to take the loads of the hoe? Where do I attach the subframe to (front and rear)? Are the ROPS mounting points fair game to mount to?

The L2900 was one of the first Grand L's. I do not know how the L2900 compares to the current Grand L's or to the 2800/3400 series. Any ideas?

Design

 

[dfkrug]

So: I want the load to go to the 4 wheels, (ideally the front wheels and the backhoe outriggers. Therefore the subframe would be in tension.

How do I ensure I have mounted to something strong enough in the rear of the tractor?

The subframe is in compression in some places, tension in others, depending
on what you are doing. My suggestion is you look at some Good Subframes,
like you see on an industrial tractor, or ones that try to emulate that
design on a CUT. I think the so-called 4-point mounting schemes used
by the newer Woods subframes work well. Also the integrated subframes
you see on the Kubotas B21, L39, and even the BX24 with the BT601 hoe.

Most tractors have many "extra" tapped holes in the rear castings. Take
a look under the rear axle and differential. These make good mounting
points. It is often OK to use the same connections that your ROPS uses.
The idea of a 4-pt subframe is it totally bypasses the use of the toplink
bracket in favor of 2 mounting points above the rear axle, on the left and
right hand sides. This requires extra links in this area.

BTW, I was wrong....the L2900 is the first of the "Grand Ls", arriving in
1998. After that, Grand Ls were designated Lxx10 or Lxx30 or now Lxx40
and the "standard Ls" were Lxx00. The Grands are more robust and heavier
than equivalent hp Standards. I have had both.

 

[design]

A woods 9000 3pt BH became available for a good price <$3K. Would I be better off using the smaller BH9000 instead of the larger Bobcat?
Who has plans for the woods subframe? I have some welding and fab experience and a new Ranger 8 waiting for a project to be tested on.
I welcome any input....


Thanks for all your help. I do not want to break my tractor.

Design

 

[dfkrug]

A woods 9000 3pt BH became available for a good price <$3K. Would I be better off using the smaller BH9000 instead of the larger Bobcat?
Who has plans for the woods subframe? I have some welding and fab experience and a new Ranger 8 waiting for a project to be tested on.
I welcome any input....


Thanks for all your help. I do not want to break my tractor.

Design

The Woods 9000 is a similar weight to the Bobcat you mentioned, I will
bet. You can buy the subframe from Woods, probably. Go to their
website and download the PDF file to get a look at it. Otherwise you
will have to custom build one that will fit your tractor.

A Woods 9000 hoe in decent shape for <3K is a deal. Grab it. I have
never found any used backhoe attachments that were any good. They
often sit outside for years.

 

[rtrent]

Woods site doesn't list a 9000 sub-frame for the L2900
Backhoe Sub-Frame Mounting Kits Operator's Manuals
Only for BH6500 and BH7500. Not even the newer BH70X or BH80X. Seems strange. You could call Woods at (800) 319-6637 .

 

[David_Kb7uns]

Have a Bradco 408 backhoe that came off a Bobcat and is now mounted on a L3130. The Bradco backhoes are set up so that either a skidsteer bracket or a subframe bracket bolt to the hoe. Would check with Bradco to see if they have a subframe assembly that you could rework and bolt or weld to the Bobcat hoe, probably would have to cut off the skidsteer bracket to make it work.

David