Calculating FEL Lift Capacity

[Fallon]

I keep thinking about permanent mounting a pressure gauge on my loader lift circuit where I could see it well from the seat. Would probably need to come up with a pressure to weight chart, but it would be able to tell you data on the fly for everything.

Might only be accurate at a particular height though. Not to mention different implements & how close the load is to the pins would affect observed pressure vs. actual weight.

 

[gladehound]

I predict that you will wish you had ordered a higher capacity scale.

It was only $50. I have a lot of pulleys so can easily weigh anything I can lift by putting it on the leveraged side of the blocks.

 

[davedj1]

If that is the lowest pressure relief setting in the system than yes. You also have a main relief for the tractor. If the main relief is set to a lower pressure, that will limit the max pressure to the loader and your loader relief will never go into relief. If the main relief for the tractor is set higher than 2000 psi, than you will have 2000 psi to the loader limited by the loader relief valve.

I am using an auxiliary pump that will be added to the front of my tractor. Should I put a pressure relief before the valve? I hate to keep cluttering up this thread but it has so much good info and such great advice. I will start another one if you all think I should.

 

[npalen]

I have no objection as the original poster but can't speak for everyone.

 

[LD1]

LD-1 - would still appreciate if you could post the roll back force graph that you have for your Kubota!

Sorry for the delay. Been a busy last few days

Here is what a typical loader force curve looks like. 1 KN = 225#

I have a project coming up where I'm going to use a boom pole. So I really want to understand the forces involved and what the tractor can handle before using the boom pole. Since some of the things I need to lift with the boom pole are of unknown weight, I've ordered a 1,100 pound hanging scale with hooks top and bottom so that I have an idea what I'm getting into before I get into it.

Don't worry, have a separate spread sheet to figure out ballast needs. In addition to the 1000 pounds of fill in the tires, the cage and me, all of which = about 1,500 extra pounds on the rear. I plan to put 1,700 pounds on the 3pt and most of that weight will be inches from the ground.

Most modern loaders have a stronger curl force than lift force at/around the bucket edge.

But as the load is moved forward.....the curl strength drops off much quicker than lift force. Usually to the point that they are about equal at the tip of 48" forks.

A boom pole, say 8 or 10' long on the loader......you are gonna find that your curl force is weaker than the loader lift cylinders.

 

[gladehound]

.....the curl strength drops off much quicker than lift force. Usually to the point that they are about equal at the tip of 48" forks.

A boom pole, say 8 or 10' long on the loader......you are gonna find that your curl force is weaker than the loader lift cylinders.

Thus the scale. at 10ft past the pins, my lift cylinders will lift more than twice what my curl cylinders will lift. Don't want to pop a cylinder!:shocked:

 

[LD1]

You really should bet a gauge, attach it to a tee, and a pair of QD fittings. Insert it inline with the curl cylinders so you can monitor the pressure those cylinders are seeing while lifting with the lift cylinders.

I have a gauge that I can move to any port on my loader. IT normally spends its time on the lift circuit.....with a little math on the fly, I can get a pretty rough estimation of how heavy something is I am lifting. But with the QD's and Tee, its easy to put it on any of the 4 circuits.

When I had my L3400, I attached a make-shift 15' boom to the loader bucket to lift, and set trusses on the shop I built at my old house. The trusses were only ~200#, and I couldnt curl them at all. But lift was no problem.

 

[gladehound]

I am using an auxiliary pump that will be added to the front of my tractor. Should I put a pressure relief before the valve? I hate to keep cluttering up this thread but it has so much good info and such great advice. I will start another one if you all think I should.

I've give my 2 cents but I hope someone who is more qualified answers your question. I've never set up a hydraulic system.

That being said, as long as you have an appropriately set relief in the system you should be fine. Lots of hydraulic systems have only one relief. Typically a tractor has a relief for the main system and when you add a loader it has it's own relief on the valve. My only concern with relying on a loader valve relief for a PTO pump is that it might not be sized large enough to handle the flow. If it's not, pressure could still increase even if it's open. So check that out. Makes sure the relief can flow the full output of the pump.

 

[davedj1]

I've give my 2 cents but I hope someone who is more qualified answers your question. I've never set up a hydraulic system.

That being said, as long as you have an appropriately set relief in the system you should be fine. Lots of hydraulic systems have only one relief. Typically a tractor has a relief for the main system and when you add a loader it has it's own relief on the valve. My only concern with relying on a loader valve relief for a PTO pump is that it might not be sized large enough to handle the flow. If it's not, pressure could still increase even if it's open. So check that out. Makes sure the relief can flow the full output of the pump.

Very good info, thank you

 

[Fallon]

All these calculations are missing one thing... The loader might not be the weak spot. There is a good chance your maximum loader lift capacity is actually based on your front axle or front tires. Personally I'd much rather go into relief, or blow a hose than bust my front axle. Blowing a tire with a heavy load could easily result in rolling the whole machine in many circumstances too.