Have you seen this?

http://www.compudraulic.com/index_files/page0019.htm


What is the “Hydraulic Component Sizing Calculator”?

- It is an interactive tool designed to help you estimate the proper size of a hydraulic component based on static calculations.

- It is extremely helpful in predicting the hydraulic component performance when it is subjected to specific operating conditions.

- It is the most quick, easy and cost efficient hydraulic calculator.

- It helps the non-technical to respond quickly with a professional answer

quote:

Originally posted by CompuDraulic:
What is the “Hydraulic Component Sizing Calculator”?

- It is an interactive tool designed to help you estimate the proper size of a hydraulic component based on static calculations.

Hmmm, static calculations. I thought the goal is to move something? Then what? That requires dynamic calculations.

But Peter, the Price is surely low enough.
However, there are at least 4 freebies I have come across in my browsing.

Do a Google search for "Formula+Fluid Power+Calculator" to see how many there are.

This message has been edited. Last edited by: Bud T,

quote:

Originally posted by Bud T:
But Peter, the Price is surely low enough.

What is the cost of redesigning the system so it works under dynamic conditions?

Peter asked:

quote:

What is the cost of redesigning the system so it works under dynamic conditions?

Didn't you know, That's the way it's done by the UNTRAINED in a discipline like Fluid Power!

I sure did enough of that in my early days in the College of Hard Knocks util I finally learned there were persons who knew what to do and I started getting help and an education. That is one way to learn but it certainly not the best way.

Been that way for years and from the feedback I see NOTHINGS CHANGED or is going to CHANGE.

Oh well, Someday Maybe???????

quote:

Originally posted by Bud T:


Oh well, Someday Maybe???????

Bud, if you got t-shirts printed up with this on it, I'd be the first one to buy one!

Peter, nice to see you're still around. Just remember, us fluid power rookies need to walk before we can run, which is what static calculations are good for.

I can't open the links from here.

I see mental distinctions between
-'static' no motion, P = F/A type situations. Stall torque and force are about the only situations I can think of. Simple math, like the FPS certification tests.

-'dynamic' the first few milli/micro/fraction seconds of any change. F = ma, capacitance, resonance, natural frequency and spring rates, etc. analysis required, not just 'simulation'. This is Peter's natural habitat, and the area I am trying to find better software and more skills.

-but there is also 'steady state but not static'. Velocity and force is reached, the dynamics has settled out, and pressure drops = inlet pressure. Even servovalve circuits reach this at slewing speeds and loads. Jack Johnson's VCCM equations describe.

Agreed, too much fluid power design is static only, by someone with 30 hours of training 10 years ago, and the circuit needs rebuilding to be even passable. Then it bangs and shocks and overheats until it is replaced by electric servos.

Many circuits need full analysis. I would not want to fly on a Boeing deisgned by excel spreadsheets.

But most bang for the buck I think is to get so many of the absolute novices (who think they are trained) to at least understand the concepts of dynamics and use simple 'steady state' calculations instead of static equations. That would at least be a great step forward, at least in the company I work for.....


kcj

Kevin wrote:
"But most bang for the buck I think is to get so many of the absolute novices (who think they are trained) to at least understand the concepts of dynamics and use simple 'steady state' calculations instead of static equations. That would at least be a great step forward, at least in the company I work for....."

I especially like the Magic Word TRAINED Kevin.

However, if you've been following the Post's on the subject of TRAINING of DEDICATED FLUID POWER PERSONS I'm sure you realize That Ain't Gonna Happen in the near future, probably not ever if it is up to the feedback I see.

Kevin also wrote:
"Agreed, too much fluid power design is static only, by someone with 30 hours of training 10 years ago, and the circuit needs rebuilding to be even passable. Then it bangs and shocks and overheats until it is replaced by electric servos."

My sentiments exactly Kevin. What if Mechanical and Electrical persons received the same type and amount of training? where would thos two fields of endeavor be????? Bangs and Shocks would be the least of the wories of all the deceased in that case.

Since my first article in the March 1988 Edition of Hydraulics & Pneumatics Magazine titled "Is there a Fluid Power Engineer in your future?" I have not been aware of any real effort to change the situation, In fact I see MUCH RESISTANCE to change.

Should not be in my opinion, notice I did not say HUMBLE opinion.

Oh well, Someday, Maybe!!!!!!
(I'm glad you like that one Josh and the rest of the discussion. You appear to be in that College of Hard Knocks classroom all Fluid Power persons have attended. Too bad it SORTA WORKS. However, it has kept Fluid Power from being the force it could be in my opinion.)

So the Post's on this and the other Fluid Power Forums will continue to be plagued by Log Splitter circuits and other such undertakings and not on a level anywhere close to those on Electrical or Mechanical Forums. Those forums see more post's per day than Fluid Power forums see in a month or more.

quote:

Originally posted by kevin j:
This is Peter's natural habitat, and the area I am trying to find better software and more skills.

Kevin, there isn't much information on how hydraulics really work. Jack Johnson doesn't cover it in his books. I still regard the VCCM as a static calculation because it doesn't take into account the effects of the bulk modulus of oil.

A dynamic equation would look like this

dp/dt=BulkModulusOfOil*(Flow0()-Area0*Vel)/(mv0+Area0*Pos)

The above equation is for computing the rate of change in pressure, dp/dt. Flow0() is the flow into side0 ( cap side ). If Flow0 is negative then oil is flowing out. Area0*Vel takes into account how the piston is compressing or decompressing the oil on the cap side. When Vel is > 0 the cylinder is extending and the pressure will drop on the cap side. The rate of change is also dependent on the volume that is being compressed. The smaller the volume the faster the rate of change. mv0 is the minimum volume of the cap side which is the volume of oil between the piston and the valve when the piston is fully retracted and position = 0.

What is tricky is that every micro second the velocity, position and pressure will change so the values used to calculate the rate of change for the next micro second are different. The Flow0() will be difference because the pressure drop across the valve will change.

This is a non-linear differential equation. I don't care how many people Bud trains. Until there are engineers that understand equations like these the progress in hydraulic technology will be slow.

There aren't many engineers that can solve equations like this because they forgot all the math and numerical analysis they ever learned if they learned it at all.

Bud, you are talking about people trained to get oil from point a to point b and keeping it off the ground. I am talking about a higher level of training that isn't just hydraulics related.

quote:

-but there is also 'steady state but not static'. Velocity and force is reached, the dynamics has settled out, and pressure drops = inlet pressure. Even servovalve circuits reach this at slewing speeds and loads. Jack Johnson's VCCM equations describe.

Yes, this is the first step. To derive the VCCM equation you must believe that objects will accelerate until the net force is zero. Therefore it is force that makes things go. Not flow.

Those that use the flow makes it go equation V=Q/A get into all sorts of trouble.

quote:

Agreed, too much fluid power design is static only, by someone with 30 hours of training 10 years ago, and the circuit needs rebuilding to be even passable. Then it bangs and shocks and overheats until it is replaced by electric servos.

Yes!!!

quote:

But most bang for the buck I think is to get so many of the absolute novices (who think they are trained) to at least understand the concepts of dynamics and use simple 'steady state' calculations instead of static equations. That would at least be a great step forward, at least in the company I work for.....


kcj

Yes, if you want to get them to the understanding the VCCM level. I doubt many can solve systems of non-linear differential equations.

BTW, am making pretty good progress on my hydraulic simulator.

Peter wrote:

quote:

Bud, you are talking about people trained to get oil from point a to point b and keeping it off the ground. I am talking about a higher level of training that isn't just hydraulics related.

Getting oil from point A to point B and keeping it off the ground would be a lot better than much of the present situation. Going to the level you desire is the ultimate and I for one am all for it. Isn't that the way Mechanical and Electrical persons are trained? Then, of couse, thes TRAINED/DEDICATED persons must work in the discipline or they will forget what they learned as you stated.

At last I think I'm seeing your replies leaning to having TRAINED/DEDICATED FLUID POWER PERSONS not leaving the situation as it is. Correct me if I'm reading you wrong.

quote:

Originally posted by Peter Nachtwey:

This is a non-linear differential equation. I don't care how many people Bud trains. Until there are engineers that understand equations like these the progress in hydraulic technology will be slow.

Yeah, and that's part of the problem too, Peter. Not all engineers are at your level. I had to explain to one engineer who was designing a seatbelt testing device that his six cylinders would not extend at the same time as he had hoped, because he had them all Teed off of one control valve. I also had to explain to another engineer that his cylinder wouldn't pull with the same force that it pushed. He actually argued with me as I explained he was only working with the annular end of the piston.

I think there's a place for all levels of hydraulic education, from the 3 hour session I spent with the team leaders of my workplace (we sell more than hydraulics) to the top engineer at Eaton.

No Kidding Peter actually wrote this!!!!!

quote:

Kevin, there isn't much information on how hydraulics really work.

Maybe we really do need TRAINED/DEDICATED FLUID POWER PERSONS after all.