Backhoe How do you dig a trench with a CUT backhoe?

grsthegreat · Jun 9, 2021

One thing I forgot to mention.... I only crossed trenches in commercial backhoes and mini and standard sized excavators. Never on a TLB System. I’m not too sure how sturdy the subframe mechanism is. Definately would not try this on a 3 point backhoe.

4570Man · Jun 9, 2021

boostmg said:
I have a Branson 3620h w a bh250 backhoe. Based off my estimate the machine weighs 7800lbs.

bh is subframe mounted.

im looking at the manual right now and the boom pin is 32x206mm and the swing frame pins are 45x107mm. I am just guessing that is where most of
The stress would be applied.

so far i managed to find a case backhoe boom pin and that is 2” in diameter and if that machine weighs 15000lbs they reverse math means potentially a 1” pin would be the equivalent for my weight.

doing my best trying to problem solve but i would hope my machine is also overbuilt as that’s what i like and usually buy.

it’s just the lack of material out there on this topic is tough.

A 2” pin is more like 4x the strength of a 1” pin and that’s ignoring the vastly different possibilities for the metal strength. But putting that aside as long as your machine is subframe mounted it should be capable of lifting the machine and swinging it sideways.

boostmg · Jun 9, 2021

Cool yea i completely understand even the engineering of a real backhoe is different.

hopefully mine is well within it’s limits when doing it. I just wish there was more info in the manual about it.

BlueBerryFarmer · Jun 9, 2021

I straddle my 99' JD 410E Backhoe (weighs about 17K with thumb, other stuff) over the path to cut, drive fwd, makes ditches, even cuts thru hard pack in relatively no time flat.

Machine will likely outlive most of us (like my 66 JD 2510)

rScotty · Jun 9, 2021

boostmg said:
Cool yea i completely understand even the engineering of a real backhoe is different.

hopefully mine is well within it’s limits when doing it. I just wish there was more info in the manual about it.

As 4570 says, pin strength goes up by the increase in area instead of diameter. So that same pin with twice the diameter is 4 times as strong... But basically other things probably matter more than pin size. Pin size is just one thing to look at. But it's a good place to start.

I doubt you will find the information you are looking for as a specification. Even on big commercial machines where operators do move that all day, I don't think I've ever seen a spec for lifting and side-swinging. Too many variables.
I agree that with a subframe mount You can try to lift the back with the hoe. See how it goes. Frankly, most hoes have the strength to lift the tractor easily. Please use the other precautions I mentioned earlier about bucket positions before you try to lift and swing it very far.

And if yours has fluid in the rear tires, then I would NOT use the backhoe to lift the tractor clear of the ground at all. The reason for that has to do with the strength of the rear axles, bearings, and housing....not with the strength of the bh or the bh mounting.
Good on you for checking this stuff out first.
rScotty

ning · Jun 9, 2021

rScotty said:
And if yours has fluid in the rear tires, then I would NOT use the backhoe to lift the tractor clear of the ground at all. The reason for that has to do with the strength of the rear axles, bearings, and housing....not with the strength of the bh or the bh mounting.

I'm interested to learn the logic of this position.
From what I can tell, during normal operation, the "rear axle, bearings, and housing" have thousands of pounds on them (ie, the weight of the tractor, minus the weight of the rear tires/wheels/fluids). If you lift the rear of the tractor off of the ground, they instead have only the weight of the wheels/tires/fluid (pulling down, but the bearings don't care which direction the force is applied), which is considerably less.
I can see the bolts that attach the axle to the frame being stressed in an opposite direction than typical, but these forces are probably considerably less than they handle on a day to day basis when the tractor is being used as a traction device.

Midniteoyl · Jun 9, 2021

I'd be more worried about popping the bead off the rim.

rScotty · Jun 9, 2021

ning said:
I'm interested to learn the logic of this position.
From what I can tell, during normal operation, the "rear axle, bearings, and housing" have thousands of pounds on them (ie, the weight of the tractor, minus the weight of the rear tires/wheels/fluids). If you lift the rear of the tractor off of the ground, they instead have only the weight of the wheels/tires/fluid (pulling down, but the bearings don't care which direction the force is applied), which is considerably less.
I can see the bolts that attach the axle to the frame being stressed in an opposite direction than typical, but these forces are probably considerably less than they handle on a day to day basis when the tractor is being used as a traction device.

Two reasons.
One you answered it yourself when you said that the direction of the force is different. The bearings will not care, but the bearing support structure may. I don't know if it will but then there is the other reason....

The other reason is that if you've ever made that move, you know that it swinging that much mass on such a long lever and keeping it balanced without any side restraint or braking is tricky. On a short wheelbase 8 ton TBL it's not too hard if you are careful. But in a smaller, lighter, & longer Ag tractor the fluid in the tires becomes a much larger percentage of the total weight being swung. Those filled tires become a largish chunk of weight sitting out there on their own levers.

So the OP is a bh novice asking for advice. Everyone has a point where they say to themselves there are just too many things against doing this project this way.....and there comes a time to look for a different approach.

And sure enough, there is an approach that works fine. Someone else along with the OP already mentioned it back on page one. Just complete digging the ends of a dead-ended ditch from the side. Sure, you end making the ends wider than the rest, but it's easy enough to backfill and arguably easier to make the necessary connections - which is usually why we made the trench in the first place.

And keep in mind there is really no absolute necessity to make that swing move anyway. You can always either reposition or dig from the side. Back before we had our present machines we had a little 8 foot depth 3pt PTO-driven backhoe - damn dangerous little thing, but still way better than digging by hand. We used it for 20 years and only had a couple of dangerous moments. Like once when the auto draft control actuated and folded the BH seat up flat up against the rear of the tractor.

be careful out there,
rScotty

ayelvington · Jun 11, 2021

Had to put in several hundred feet of poly line for an irrigation manifold. I rented a trencher. Sooo much easier and got the job done in a day. I only used the tractor to close the narrow trench, and the scar was minimal. So, the question really is "Why?"