Lifting capacity

[J_J]

Does anybody know if the lifting capacity includes the bucket, or is it the bucket plus what you can safely lift. If you put the forks on, does the lifting capacity remain the same?

 

[MrJimi]

J_J, why does this sound familiar?? I know it's a great question because I don't have an accurate answer for you. I think its without anything. But if you have nothing? How can we pick-up anything.
I am watching for the answers also
By the way, I had a great this weekend, Thanks
Jim

 

[Bob999]

Does anybody know if the lifting capacity includes the bucket, or is it the bucket plus what you can safely lift. If you put the forks on, does the lifting capacity remain the same?

For equipment like skid steers the lifting capacity is done according to accepted standards and it is my understanding that it includes any attachment, including either a bucket or forks.

However, as has bee discussed in other threads, PT apparently does not determine their lift capacity according to any recognized standard. For that reason I think the only way to get an authoritative answer would be to ask PT for explanation of how they determine the lift capacity of their machines.

 

[BobRip]

I picked up a stone that was weighed when purchase as 813 pounds. The 422 (rated at 800 pounds) would just lift it using the forks. I had a person standing on the back bumper so this was over 200 pounds of counter weight. The stone was about 24 to 30 inches in diameter and six inches thick so its center of graviity was at least 1/3 of the way out onto the forks. These seems like a pretty honest weight rating if you don't mind adding a counter weight.

 

[J_J]

I believe that PT rates their lifting capacity very low due to safety concerns. Although the hydraulics can probably lift a good bit more, PT is using a conservative figure to help keep the user within a safe envelope. As someone said, if you add more weight to the rear end, you can surpass PT's ratings. If you go beyond PT's rating, you must take into account the extra load being placed on the wheels, rims and wheel motor's shaft. If those wheel motors start leaking, it is probably because you have exceeded the safety margin, or you have dropped one of your wheels in a hole or deep rut. Reversing the rims, is a positive in a more stable platform situation, and a negative in a loading situation. The front wheel motor shafts, take most of the abuse, simply because we always want to move a little bit more. The more weight we put up front, the weight on the back wheels will be less.

 

[MossRoad]

My 425 is rated at 800 pounds. I don't think it will lift 800 pounds in the bucket. I've had over 600 in the bucket with me on the seat and it was tippy. Therefore, I believe it is probably rated at the quick attach point, so it probably doesn't include the weight of the bucket.

Some day I'll do a pictorial weight experiment with patio blocks and show everyone. We'll weigh a block, stick it on, then another, another, etc... until it tips.

A couple years ago I did this with the small bucket, loading it over my trailer when I brought blocks home. As I set two of many blocks in the bucket, which was a few inches over the bed of the trailer, the bucket came down on my foot. I took them out, and the unit came off my foot. So I put my hand on the bucket and rocked it back and forth with only a few pounds of force at that tipping point. I should have counted the blocks and weighed one right then, but I was in a hurry.

 

[J_J]

Does anyone think that there is a safety factor when one adds, say 200 lbs to the rear of the PT in order to increase the lifting capacity. Do you think the relief valves will activate when you raise a load greater that your rated lift? Do you think the relief valves should be reset?

 

[Bob999]

Does anyone think that there is a safety factor when one adds, say 200 lbs to the rear of the PT in order to increase the lifting capacity. Do you think the relief valves will activate when you raise a load greater that your rated lift? Do you think the relief valves should be reset?

What kind of safety factor are you referring to? safety from tipping from lifting a heavy load? Safety from breaking a component or bending a component from overstressing it? safety from bursting a hydraulic component from causing the pressure in the system to exceed design specifications?

With respect to the relief valves, I would expect that they are designed to open at the rated operating pressure of the components in the system and I have no idea how those pressures might relate to the lifting capacity.

My understanding is that with skid steers rated by standard rating systems that the lift capacity is a percent of the tipping load. Clearly tipping load is influenced by the addition of weights.

 

[MossRoad]

Does anyone think that there is a safety factor when one adds, say 200 lbs to the rear of the PT in order to increase the lifting capacity. Do you think the relief valves will activate when you raise a load greater that your rated lift? Do you think the relief valves should be reset?

Well, I have thought about that a few times, myself. Since I have never had the reliefs activate and have had the unit up on its nose many times, I would be reluctant to add more weight to the rear of the unit for fear of breaking something.

 

[J_J]

Bob, Yes to all those safety factors.
Relief valves are design to protect components in the hydraulic circuit, by limiting system pressure from exceeding other component limitations. Say you have a pump that can put out 3000 psi, but your cylinders have a rating of 2500 psi. You would then want to limit the pressure to something less than 2500 Psi for longevity. I don't know if you know this or not, but the force required to raise an empty bucket is very low, probably not more than 400 psi. The actual working pressure at around 2750 psi is only achieved when your lifting weight approaches the maximum lift capacity.
Yes, you can cheat the system as designed, but will the steel, joints, bearings, etc tolerate the excess. You might see components with a test pressure on it. That means that product, or one out of a batch of 1000 was tested at a much higher pressure to account for safety reasons. A stamped hydraulic hose at 3000 psi, might stand a test pressure of 4500 psi.
The whole point is that you have to be aware of your system and what you are trying to do with it. You can use it as is, or customize the system for your particular purpose. Most people like to get a little more out of a system if possible. That's my story and I am sticking to it.