Backhoe mount - 3pt vs. subframe

[Jay4200]

I have always believed that the subframe mount on a backhoe is night and day vs. a 3pt mount, and probably wouldn't have even considered using or buying a 3pt mounted backhoe. However, at least with my subframe (and probably most others too), most of the weight is still born by the lower 3pt mounts, as they are used to mount the subframe rear bracket.

The front mount doesn't appear to do a whole lot, although one could probably argue that it helps to withstand lateral movement, although on mine the rear bracket is very tight, so I'm not so sure even a lateral twist is supported by the front mount. There is also a top link connected in the normal place, so (with the possible exception of certain lateral pressures, maybe) it seems that the strain on the 3pt mounts using the subframe would be similar, if not identical to a 3pt mount.

So, after reflection and examination of my Woods BH9000 subframe mount, and with the obvious exceptions of the 3pt lift arms and rock shaft, I am unconvinced that a 3pt mount is much different in regards to strain on the tractor compared to a subframe mount. Comments or explanations?

JayC

 

[RickB]

I have always believed that the subframe mount on a backhoe is night and day vs. a 3pt mount, and probably wouldn't have even considered using or buying a 3pt mounted backhoe. However, at least with my subframe (and probably most others too), most of the weight is still born by the lower 3pt mounts, as they are used to mount the subframe rear bracket.

The front mount doesn't appear to do a whole lot, although one could probably argue that it helps to withstand lateral movement, although on mine the rear bracket is very tight, so I'm not so sure even a lateral twist is supported by the front mount. There is also a top link connected in the normal place, so (with the possible exception of certain lateral pressures, maybe) it seems that the strain on the 3pt mounts using the subframe would be similar, if not identical to a 3pt mount.

So, after reflection and examination of my Woods BH9000 subframe mount, and with the obvious exceptions of the 3pt lift arms and rock shaft, I am unconvinced that a 3pt mount is much different in regards to strain on the tractor compared to a subframe mount. Comments or explanations?

JayC

Your discussion points have some validity for your specific machine, but other subframe mounts are totally independent of the three point elements and do a far better job of distributing forces across more of the tractor's structural chassis. Look at current production Woods 4 point subframes, Bradco 4 point subframes, or other machines to see different designs and construction.

 

[DK35vince]

My backhoe/subframe doesn't use the 3 point at all. I can leave the 3 point hitch on or completely remove it. Doesn't matter.
The subframe goes under the tractor and mounts to a drawbar bracket and a mounting bracket under the front of the transmission.

 

[dfkrug]

I have always believed that the subframe mount on a backhoe is night and day vs. a 3pt mount, and probably wouldn't have even considered using or buying a 3pt mounted backhoe. However, at least with my subframe (and probably most others too), most of the weight is still born by the lower 3pt mounts, as they are used to mount the subframe rear bracket.

The front mount doesn't appear to do a whole lot, although one could probably argue that it helps to withstand lateral movement, although on mine the rear bracket is very tight, so I'm not so sure even a lateral twist is supported by the front mount. There is also a top link connected in the normal place, so (with the possible exception of certain lateral pressures, maybe) it seems that the strain on the 3pt mounts using the subframe would be similar, if not identical to a 3pt mount.

So, after reflection and examination of my Woods BH9000 subframe mount, and with the obvious exceptions of the 3pt lift arms and rock shaft, I am unconvinced that a 3pt mount is much different in regards to strain on the tractor compared to a subframe mount. Comments or explanations?

Jay, here is a photo of the rear of a Kubota with a Woods old-style hoe
mount. I call this a "ladder-type" mount. Tho this is for the Woods 7500,
it sounds like this is the kind of subframe you have for the 9000.

You brought up several concerns. First, this subframe does indeed make
use of the 3-pt lower arm pivots, but the rear bracket is also bolted to
the existing holes in the rear axle housings. No way does all the weight
hang off those pivots and there is no rotation about those pivots. Straight
downward forces on those pivot holes is not the biggest problem with
3-pt hitch mounts anyway.

Second, the toplink adds stiffness to the whole mount, and the lower
part of the subframe and hoe connection is NOT free to pivot as with
a 3-pt mount. In the latter, huge tension forces are placed on the
toplink as the massive weight of the hoe tries to pivot about the axis
of the rear axles.

That force (torque about the rear axle axis) tries to lift up the front of the
tractor, placing huge bending forces about the center area (bell housing).
Adding a beam to offset this bending moment is what the long forward
part of the subframe does. The forward attachment of the subframe does
not have to be very big or strong since the moment arm is so long.

I also have a photo of your hoe (BH9000) on an L4830 that uses the later
Woods "4-point" subframe, a much better design, IMO. The old subframe
is still way, way, way superior to the 3-pt hitch connection, IMO. I
understand that Woods may only offer the older style subframe for your
L4200.

 

[Luremaker]

Here are the two different subframe styles in the above discussion. The ladder (older) style and 4pt (newer) style here are drawing taken from woods subframe manuals.