Hydraulic Press with Adjustable Force Setting for Testing Linear Actuators

[Joel79]

I am looking to validate the force output of a custom actuator that has the capability to push and pull at a 37,000 lb linear force, 4 inch stroke. We are looking at practical ways to quickly test this dynamic force output before moving on to the next phase of the project. One idea is to use a standard hydraulic shop press. This would allow us to maintain 37,000 lbs of pressure on the end of the power screw driven actuator as it is moving up/down. We don't currently have an automatic shop press and I wanted to know if typical shop presses can do the following:

-set to a certain force/pressure (perhaps with a 3 way valve on the hydraulic pump output)
-can be back-driven
-provides constant pressure while moving

We are looking into adding a custom circuit on a standard hydraulic press but I'm not convinced that a product like this isn't already out there.

Let me know your thoughts.

Much appreciated!

 

[handleman]

How fast do you want to move? If you're going pretty slow, gravity does a good job of maintaining constant force. If you're going fast, you'll probably need special hydraulics to keep up.

 

[Joel79]

Fairly slow - 2"/minute. As for using weights, I want to be able to scale up the system for larger actuator testing, so using large weights seemed impractical but I'm open to all ideas. I appreciate your quick response.

 

[hydtools]

It would seem that you would need a double ended cylinder to be able to load both push and pull tests. The shop press may be able to offer only push loading.

Ted

 

[IRstuff]

Couldn't you just push against a load cell, which you'd need anyway to measure the actual load?

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[handleman]

He needs something that can supply force during moving. Pushing against a stationary load cell would be static only.

I assume you're gonna need two of these things at some point. How about just pointing them toward one another with a load cell between?

 

[Joel79]

Yes - we would ideally use a double ended cylinder where we could control forces in both directions. I can't seem so find an OTS product that does anything like this. Perhaps we can modify the piping on the press to regulate pressure on both sides of the cylinder. See attached high-level P&ID.

 

[MintJulep]

I'm with handleman. Gravity is cheap and reliable.

Class 3 lever with your actuator being the "effort".

The engineering reduces to selecting a beam size and length.

 

[CWB1]

I seriously doubt you will find what you need off the shelf in one package, however I dont see anything that couldn't be easily procured. Each of those features arent uncommon on presses in various industries.

 

[BrianE22]

If you want to spend some money you could make it closed loop servo controlled. If you have a frame, hydraulic actuator and pump then you would need a servovalve, controller and load cell. You'd input the desired load and the actuator would move as required (in or out) to maintain that load.

I've found decent stuff on ebay. For controllers I like the MTS 458 console with a DC card for the load cell. They're available every once in awhile. If you keep it MTS, they also sell load cells and servovalves.

 

[btrueblood]

You really don't need the pump in your P&ID, just the regulators to supply the resistance. Your actuator is doing all the pumping.

You do need an oil cooler.

As Mint said, gravity loads would work too...but you need 18-some tons of stuff, and a linkage supporting it that won't bend and bind.

 

[Joel79]

After some internal discussion, we are mostly set on the modified hydraulic press. We found one that has built in pressure reliefs on both the push and pull side to allow us to test both actions of the actuator. We are planning on swapping the relief valves based on the required force test. We will use a load cell to verify load. We explored the lever/weight idea but the size became impractical for testing 35,000 lbs.

Here is the product that we are considering:

https://www.gregsmithequipment.com/75-Ton-Electric-Shop-Press

BrianE22 - Using a servo controlled valve would be a good option if we had constant flow, but our travel is so slow that a pressure controlled approach seems more practical.

btrueblood - you're right about not needing a pump - but it will likely come in handy for resetting positions. Additionally, it will allow us to test the actuator when the force is in the same direction as the travel.

Really appreciate all of the input - keep it coming!