Bucket lifting capacity (math)

[apease]

One last calculation, then back to my day job! The sideways tipping calc looks very safe on level ground with the bucket at the same height as the center of mass of the tractor. Assume the tractor+loader+bucket are a point mass of W=2027lbs at X=22.5" (half the width of the tractor). Even with a very unbalanced load that has a center of gravity L=2' beyond the bucket edge, that gives you a massive F=1900lbs, which the loader would never lift. However, raise the bucket and tilt the tractor 10degrees to the same side as the load and L has just gotten bigger and X has gotten smaller and the calc get a lot less favorable quickly.

I hope this was fun for any other math/engineering geeks like me who might be reading.

 

[Grandad4]

Just using "seat of the pants" math, here's what's going on with laterally unbalanced loads in the FEL:
1. The heavier the load in the front, the lighter the weight on the rear wheels.
2. At some point, the weight on the rear wheels is 0, and the entire weight of the tractor is balanced on the front axle.
3. The front axle is on a single axis, lateral pivot to allow for uneven terrain, with stops that allow maybe + or - 15 deg. movement. (Unless you have a narrow-front tractor, which has essentially a 90 deg. stop - if you're lucky)
4. When there is 0 downforce on the laterally fixed rear axle, and all weight is on the front axle, which pivots, any lateral moment of force, such as an unbalanced load in the FEL, will tip the tractor to the off balance side.

In practice, you don't even have to be near 0 weight on the rear wheels to achieve instability when the tractor is actually moving. If the back end is light, a slight side slope, a pothole, a rock, or a slightly off-balance load can get things tipping in a very "sporting" manner. The further out in front of the front axle the weight is, the greater the force moment on the front axle pivot if it's off center.

 

[Raspy]

Mine will only lift about 850 lbs on a 3 foot square pallet on my bucket forks.

So all my lifting is done comparing whatever I am about to attempt to this limit. Further out on the forks equals less overall lift. Stuff set in the bucket equals more. My curl gives up before the lift, so I try to curl before lifting completely off the ground.

Also, I can hold more weight, by quite a bit, that I can lift. So as I was recently unloading pallets of tile from a trailer, I was able to take enough weight that I could drag them off the trailer and then carry them to the site. But once they were set down that was it.

While setting the H beam posts on my building with a A frame in the bucket, I could only curl them up by lowering the lift. Then lifting the load and carrying them to the foundation. Then, to set them on the foundation bolts I relied on the "creep" by lowering them to just over the bolts, getting off the tractor and aligning them by hand. As the hydraulics crept down they would ease down over the anchor bolts and I could start a couple of nuts.

 

[Raspy]

Grandad4,

I always have a box scraper or backhoe on mine for stability. Plus loads are carried low and slow. Mine won't lift hard enough to lift the rear wheels with this ballast. But sometimes a bucket full of gravel or dirt and a slope can get interesting. Especially if I'm just working the ground and not moving some object, I get into "efficiency" mode and start moving faster. Working with the A frame on the front definitely requires fairly level ground and smooth driving, especially with a 12 foot long H beam acting as a pendulum.

 

[LD1]

Also, I can hold more weight, by quite a bit, that I can lift. So as I was recently unloading pallets of tile from a trailer, I was able to take enough weight that I could drag them off the trailer and then carry them to the site. But once they were set down that was it.

This is the case with any loader.

Your tractor pump can only generate say 2500psi. This directly relates to how much it can lift.

But if the bucket is already raised and you are loading the bucket by hand, the only limiting factor on how much it can "hold" is how much pressure the cylinders/hoses can hold back before failing. There is NO check valve after the loader control valve. so with no where for the fluid to go, it will just build more and more pressure as you add to the load until a hose ruptures.

So if your tractor has 2500psi operating pressure, and you stack on more than you can lift, you are actually pressurizing the cylindres/hoses to BEYOND 2500psi.