How to find the spring characteristics of a single acting hydraulic cy

[luvjeethu]

I have a single acting hydraulic cylinder and i have its dimensions, stroke length and i can also measure the hydraulic pressure. Can anybody give some details which experiment will be suitable to determine the spring constant.


Thanks in advance..

 

[MikeHalloran]

The spring constant of what?


Mike Halloran
Pembroke Pines, FL, USA

 

[luvjeethu]

Spring constant of the 'Spring' which is for return stroke of single acting hydraulic cylinder

 

[hydtools]

What is the flow resistance to flow in the return line? This will tell you the pressure required to push the piston back. Knowing the pressure you can calculate the spring force required throughout the return stroke. Depends also on how fast you want to return the piston, this determines the return flow rate and the resulting return flow resistance to that flow. Seal drag needs to be added to that required force. Or the spring force minus the seal drag force is the force available to return the piston.

Ted

 

[micalbrch]

You can use Hook's law to determine the spring constant as long as the spring has a linear characteristic.

D=F/(L1-L2) where F is the force which is calculated with pressure and hydraulic cylinder piston and where L1-L2 is the change in length of the spring.

 

[kcj]

Do you mean the 'spring' or capacitance as used in Jack Johnsons VCCM equations for the compliance of a position control system?

That would be the volume of the oil being compressed, the changes in pressure, and the compression of oil and expansion of the hose and cylinder as pressure increases.

I have never worked with a single acting cylinder in that situation, but I would think the principles are the same.

Peter be the man to talk on that topic.

kcj

 

[kcj]

never mind, I see you were referring to a return spring.

how could I have edited a post rather than reply? k

 

[PNachtwey]

The spring constant of what?

The cylinder and load.

kcj, you need to look at what Jack Johnson wrote about capacitance. The VCCM equation doesn't apply here.


Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[kcj]

. The VCCM equation doesn't apply here.

correct, VCCM are at steady state conditions of speed and load, but his discussions of capacitance and oil volume are what I was referring to. I don't follow some of his applications from natural frequency to calculating gains, but that is my limited math.

I thought OP was asking about the spring rate of oil column, not calculating a mechanical return spring.

kcj

 

[PNachtwey]

How to compute a hydraulic spring constant

http://forum.deltamotion.com/viewtopic.php?f=18&t=126

Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com