rapid hydraulic actuation 2

[engrnick]

How can one rapidly actuate a hydraulic piston?

probably about 4500lbs,(2000kg) with a 4-6" (100-150mm) stroke distance, in .2 seconds?

I don't know if this is possible, that's why I'm asking you guys,
TIA.

 

[pob786]

Hi, you don't mention the diameter of the cylinder (volume/area to work out pressure required to lift 2000KG) or whether double/single acting, but you'd probably get away with an accumulator large enough for the volume required for the speed, in the supply to system, prior to direction control valve if cylinder is double acting!!!!!.
Regards,
John P.

 

[hydtools]

You need to stop it, also. So part of the stroke will be needed for that.

Ted

 

[hydtools]

In a hydraulic handheld paving breaker we could accelerate the piston to 35ft/sec in a distance of .75in. in about .01sec.

Ted

 

[engrnick]

Thanks guys, good to see it's possible. Right now piston diameter hasn't been determined, but an accumulator sounds like it would do the trick..

What's a good way to stop it? I was thinking an elastomer damper since it only does it once, but if you have a more elegant method, please share.
Nick

 

[hydtools]

I would suggest a choke built into the cylinder.

An elastomer will absorb energy and then return it to the piston, bounce with little dissipation.

Ted

 

[engrnick]

Do you know where I can see an image of how the choke works?

 

[hydtools]

Research hydraulic piston cushion

Ted

 

[EdDanzer]

What is the application?

We experimented with a casing hammer and used a pilot operated check valve to uncrease the flow for the high speed movement so the control valve did not have to be so large. We had to vibration isolate the valves and use thread locker on the fitings. The acceleration was almost 1G so the housing had to weigh as much as the moving weight to keep it from jumping off the pipe.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[PNachtwey]

I am still waiting for someone to ask the obvious question. Is the cylinder rod up, down or horizontal?
Once that is known it is easy to calculated the required cylinder diameter.




Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[hydtools]

I think also important questions are 'How rapidly?', 'To what speed?', 'In what distance?'. Although they are related parameters.
The simplistic answer to how one can rapidly actuate a piston is to push it hard.

Ted

 

[byrdj]

I did not see a desired cyclic rate.
instead of pushing it open, how about spring force dumping it closed?

 

[PNachtwey]

I did not see a desired cyclic rate.

This isn't required to tell if it is possible. It is required to determine the pump and accumulator size.

instead of pushing it open, how about spring force dumping it closed?

Then the net FORCE required must not only accelerate the load but it must compress the spring.

The answer is that engrnick's application is possible depending on how much money engrnick wants to spend.


Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[byrdj]

the simple calcs would be
Force (4500) = area X pressure
volume = area X stroke (5)
time (0.2) = volume / flow

 

[engrnick]

Hey all,
good questions:
Cyclic: used once, then retracted at a slower rate than the opening. it will be inspected/serviced after that.
orientation: upwards.
how rapidly: to actuate within .2 seconds, and to 4-6" extension.

This is for a proposal. If we can get this concept to work, I'll get an expert to design this hydraulic circuit.

Thanks everyone!

 

[PNachtwey]

This quote is from another thread.

If you like PNachtwey's debates, have a read of the "flow makes things go" and the whole pressure is resistance to flow threads on the fluid power forum.

Below is an example of why I challenge all the "flow makes it go" people. They design systems that don't work and in general give hydraulics a bad name.

the simple calcs would be
Force (4500) = area X pressure
volume = area X stroke (5)
time (0.2) = volume / flow

Wrong! Very Wrong. Even if the orientation was horizontal.

Perhaps, this thread should be in the mechanical area. If one used a heavy spring that exerted 4500 lbs at 6 inches or full stroke and would exert enough force to accelerate the load from 0 to 6 inches when compress in 0.2 seconds then all one would need to do is use the hydraulic to push down the springs and the load to 'cock' the system and release the oil to let the spring push the load up. This would require calculating the right spring constant and that wouldn't be too hard. I have know idea if springs of a specific spring constant and size are available though. It would be simple.







Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com