Novice lifting question (Kubota specs vs. reality)

[Leozepolusa]

I would like to know if the lifting specs Kubota publishing for loaders and backhoes are governed mainly by available ballast or hydraulic limits. For example, my B21 specs say the loader lifting capacity is 926 lbs while the ballast (backhoe) just happens to be 986 lbs. Conversely, the backhoe specs say the lifting capacity is a little lower at just under 800 lbs which considering ballast seems to makes sense if lifting out further from the center of gravity. If I have the backhoe attached plus 400 lbs of liquid ballast in my tires, does this significantly increase my loader's lifting capacity, or will the hydraulics stall just above the 926 lb specs regardless? In general, what have you guys experienced when you try to exceed specified lifting capacities (carefully of course)?

Thanks,

 

[dex3361]

I would like to know if the lifting specs Kubota publishing for loaders and backhoes are governed mainly by available ballast or hydraulic limits. For example, my B21 specs say the loader lifting capacity is 926 lbs while the ballast (backhoe) just happens to be 986 lbs. Conversely, the backhoe specs say the lifting capacity is a little lower at just under 800 lbs which considering ballast seems to makes sense if lifting out further from the center of gravity. If I have the backhoe attached plus 400 lbs of liquid ballast in my tires, does this significantly increase my loader's lifting capacity, or will the hydraulics stall just above the 926 lb specs regardless? In general, what have you guys experienced when you try to exceed specified lifting capacities (carefully of course)?

Thanks,

I would say you will open the relief valve when you exceed the 926 whether no matter the ballast on the rear. The ballast makes it more stable and can (if behind the rear axle)take weight off of the front axle.

 

[littlejohn2009]

All ballast does is keep your wheels on the ground (most times..)

My Kabota, lifted the rear wheels off when I was pulling fence posts. So I called the tire shop...Come and put some calcium in my tires....I am surprised that the dealer (used) didn't make sure it was 'topped up'

He came and "your tires HAVE fluid in them" Yippee I said..'no money blowing out the door'. But i still keep raising the back end up....So I use it to my advantage..to put on tire chains in the winter...I drive up to my dump truck and attempt to lift it up And when i do I get one wheel in the air. And by changing the side i lift, I can control which tire is in the air..

 

[Trigger]

As previously mentioned lift capacity is finally determined by the hydraulics (relief pressure, cylinder size etc). However ballast contributes to lifting something safely/comfortably to that limit.
There are ways to increase your relief pressure, and within a certain range this may be OK. It will put more stress on the other components. My feeling is if you want to exceed your rated capacities by alot or do it often then unfortunately a bigger tractor may be necessary.

I also have a B21 with loaded rears, even with the hoe on I tried to pick up a "substantial" stump, curled the bucket and lifted the rear slightly.

 

[jim442]

The lift is determined by the size of the cylinders and the pressure applied to them. When you try to lift weight that exceeds the capacity of the cylinders and mechanical advantage (if any) you stall. Some pumps are positive displacement which means the fluid has to go somewhere so it spills over the relief valve (which builds heat fast in the system so don't hold it there). With a variable displacement pump the flow is no longer required so the pump "shuts down" the flow. The two ratings on the FEL are because of the depth of the bucket-capability goes down as you get weight out to the end. Hold the head of a sledge hammer in your hand and lift-not too hard, now hold the end of the hammer and lift. The bucket curl is another story, the rating (breakout) goes way up because now you are using the length of the bucket as a lever. So why not just put larger hydraulic cylinders in? Now you risk bending the loader frame or turning over the tractor, which is why you should never adjust the relief valve to "turn up the power". If the pump is capable of 2700 psi and can't make any more pressure that's one thing, but sometimes they are cut out below their capability. Everything is there for a reason-be careful when you mess with the design.

 

[Leozepolusa]

Jim,

Thanks for the info. I guess I am mainly just trying to figure out whether or not Kubota owners have determined if the relief valve does in fact kick in at or very near the published lifting specs, or if they can exceed specs by say 10or 20 percent without issue.

 

[jim442]

Good question for the dealer or even Kubota, my hunch would be that weight limit is the max (regulated or not) that should be attempted given the weight of the tractor. I'm sure if it could do more safely they would advertise it.
I know I will not be completely happy with my B2920 loader because I use a neighbors Ford with a 1 ton bucket now. I moved some big rocks (we call them our town vegetable) with that machine, but mine is a compromise between small enough to mow with, groom the driveway and a little landscaping with the loader. I looked at the L3400 for the loader I wanted, but most of my heavy work is done now and I will get most of my use out of the mower and 3pt hitch. Don't forget you can weld on a couple chain hooks on top of the bucket and drop the chain behind the bucket for a heavy lift, you will be at the pivot point (950lbs). I always swore I would never buy a tractor without 4 wheel drive or a 1000lb bucket (so I lied for 50 lbs)

 

[dex3361]

I have checked the Relief pressures on my L4400 and it was about 200 PSI below spec. I adjusted the relief to the spec and it works much better.

 

[repete]

I learned a number of yours ago with my L2550DT that it is best to just stick with the manufacturers settings of pressures.

My bucket is capable of lifting more than the "rated" ability ability. I did it all of the time. After replacing the outside portion of the front axle drive housing at about $450 each I soon realized the limits may have nothing to do with the loader ability to lift but is very likely what the "weakest link" is rated for. In my case it was the axle I am assuming.

I use the tractor hard though. 75 acres, 27 of woods and hills and 50 of pasture. It is an incredible little machine but it really saves you money to recognize it's limits. I have around 5000 hours on it I think and the only issues I have really had have been with breaking front axle parts. I service the engine every 100 hours like clockwork. Never a hydraulic problem or engine problem. Oil and filters are really cheap insurance, beats buying parts and down time.

 

[jim442]

The days of equipment being overbuilt are gone. Design and material knowledge are so far advanced that obsolescence is not difficult to build in anymore. We see this now with increased hydraulic pressures and smaller components especially in heavy equipment. This all translates to cost and bottom line. You can no longer assume that a big "fudge" factor is built in to ratings because it is not. One reason I don't buy power equipment at stores like H.D. and Lowes is the life expectancy is built in to reflect the price. I learned this with a line trimmer, paid more for a Stihl but is now 10 years old and still like new (and I put some hours on it). Big reason I went with Kubota is the fact that they make everything in the tractor, everything is designed to achieve an end result, not a pile of parts from different manufacturers with a dozen different quality procedures (or lack of)