Ei guys,

I was planning to design an automatic parking and it has 4 hydraulic cylinders and I have this data given.

4 inches BORE
3 TONS
2 IN/SEC

and i need some reference to you guys on what will be the pump needed in GPM, electric motor HP needed and the PRESSURE needed.

Thanks.

Look in the Basic "Ebook" on the home page of this Forum and go to Page 5 of the Formula Section. The formula there will show you how to figure pump size and motor HP.

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

hi there Bud.

i just designed a circuit regarding automatic parking but still need to have some of suggestions and recommendation.. check drawing.

I want to include pressure switch aswell as oil cooler..

but still need a guide from you guys.

thanks.
koji

anyone please?

This is not meant to be demeaning Josh, But, I believe you need a lot more help than I or others on the Forum have the time or inclination to give.

Your present schematic is somewhat of a basic start. However, without knowing answers to a lot of questions I always ask when confronted with a customers request, there is no chance of designing a workable, efficient or reliable circuit.

You need to get more information from your instructor to even begin to make intelligent decisions on how to go about the circuit design.

In the Ebook I mentioned above, in the Formula Section on pages 14-15, is how I approach a hydraulic circuit design situation. This may not be all inclusive but will handle 95% of the circuits you might come across in your carreer, if you decide to make Fluid Power your life work.

Pages 16-17 covers what I ask for when designing a Pneumatic circuit.

Read these and you should be able to at least get an idea of what must be known before you can do any calculations or put lines on a schemattic.

The basic Ebook is not all inclusive when it comes to Fluid Power circuits but can get you well on your way in the Fluid Power field. However, you have to take the time to read it so you at least have a chance to move ahead in the world of Hydraulics and Pneumatics. The second Ebook covers basic circuits and has 3-4 simple, ractual machine circuits in the last section but still will only help with knowledge about basics. Assembling a complete circuit uses two or more of the basic circuits but even then component inteaction must be considered. Some of this can't be taught but must be learned from screwing up appliications and figuring out a fix.

At least that is the way I have found this fabulous world of Fluid Power.

quote:

Originally posted by Bud T:
This is not meant to be demeaning Josh, But, I believe you need a lot more help than I or others on the Forum have the time or inclination to give.

Since Jonah and Joshua were both biblical characters, I'll let this slide, Bud. LOL

Here are a few pointers on this circuit, since my level of hydraulic understanding is on par with the system you're designing. I'm assuming this is a parking lift, first of all.

First, you won't need 4" cylinders, which means you can use a pump/motor combination which is much smaller to get the same speed. I also don't see the need for an accumulator. A counterbalance valve is good, but I would put a counterbalance valve and pilot operated check valves on each cylinder. You'll also need flow dividers - 3 spool type dividers will be fine for this setup. The only trick, will be synchronizing them.

Bud, how's my analysis?

quote:

Since Jonah and Joshua were both biblical characters, I'll let this slide, Bud. LOL

Sorry about the name slip, I can blame it on Age and that gets me by with a lot of misteaks nowdays.

On your circuit design, I don't use P.O. Checks and Counter Balance valves since I found a Parker Gresen poppet design Counter Balance valve that does'nt leak or the Rexroth CheckQMeter, I believe it's called, that serves both functions in one valve. They operate smoothly and have leakage rates in the drops per minute which usually means No Bypass but just in case you get one that does dribble a bit we're covered. Even some P.O. Checks don't claim ZERO Bypass.

As far a Synchronization, I would have to know if the cylinders always made full strokes to a fixed stop,? Do they have to stop mid-stroke,? How level must the platform stay during the stroke,? What is the cycle frequency, How much out of level can the lift be while raising or lowering? to name a few. The answers to these questions, and possibly others, would determine how I would design a circuit to meet the needs of the Lift.

That is why I stay away from questions that, First appear to be Instructor assignments, and second don't have enough information to make it clear to me that the untrained person asking might take the information and use it to get into real trouble or cause injury to themselves or others.

I answered with the reference to my book since that is how I have sized circuits forever and if someone can't understand what I deem simple instructions, they need a lot more training by reading the rest of the book or taking classes from a competent instructor before messing with lifting $25-$50,000 vehicles.

Fluid Power is not as dangerous as Mechanical or Electrical systems but is not a no-brainer field of endeavor that anyone off the street can do. Someday that will become clear to the Industrial World and we will finally have Trained/Dedicated Fluid Power Engineers and maintenance persons.

At least, that is my thoughts on the subject.

Our controllers have been used to synchronize lifts like this. The last one was for RVs.

This design will not work. If the load isn't even the cars will be tilted off the stand.
The counter balance valve is on the rod instead of the cap side. I don' see what good that does. A two inch diameter cylinder at 3000 psi can lift 6000 psi slowly. The stroke is not provided. If the stroke is long the rod will need to be thick so perhaps a 4 inch diameter cylinder will be needed anyway just for mechanical strength. In this case the pressure can be reduced.

Unless there are just two levels the elevator will need to stop at a intermediate position and match the floor position pretty closely. I don't see any indication of how that will be done. There is no hint of how to synchronize the system. I would look at using some sort of rack and pinion system with hydraulic motors.

Bud, I couldn't find any information on that Gresen valve. What model series is it?

Josh;

It is the MHB valve. This page at the Parker web site is all i could find.

http://www.parker.com/portal/site/PARKER/menuitem.de7b2...xtcat=COUNTERBALANCE

It appears to be available but over the years I have found that company buyouts wind up with duplicate products being dropped. Sometime, suddenly and other times after a few years. The above page says the valve is still on the books but there does not appear to be a link.

Jonah, don't be discouraged. Learn everything you can about the circuit, the components involved and the mechanics and control of the system. Peter and Bud have well more than enough wisdom to make this project work, it's just a matter of getting it out of them!

quote:

Peter and Bud have well more than enough wisdom to make this project work, it's just a matter of getting it out of them!

The problem is that one must first know the rught questions to ask and what data is required to answer them. Jonah has flunked on both accounts.

Josh, doesn't it bother you that
1. The minimum power couldn't be computed given the data in the first post? Lifting 6000 lbs at 1/6 ft per second is 1000 ft-lb/sec. There are 550 ft-lbs/sec per HP so this will take at least 2 HP. One should be able to do that in their head.
2. The 2 HP is optimistic depending on the efficiency of the system but no data was provided so efficiency corrections can be made.
3 HP will do if the efficiency is only about 60%
3. The schmatic is screwed up as I pointed out above.
4. You are right about an accumulator not being need but that really depends on how synchronous the four actuators must be. No specifications are provided.
5. Can you imagine a 1/3/8 rod from a 2 in diameter cylinder extending up 24 ft? It isn't going to happen. How far can you extend a 2.5 inch rod? How would you mount a 24 ft cylinder? If there is a ground level and two higher levels?
6. You can't look at any problem as strictly a hydraulic, mechanical or electrical problem. One hydraulic motor can drive a series of chains and sprockets so that all four corners are lifted synchronously. Now the 4 inch bore is irrelevant. One must know figure out how big the sprockets must be and the torque required from the motor. Now this is a rotary application without an accumulator, why are we talking about a hydraulic motor instead of a VFD on the www.plcs.net forum?

Now I wonder why it has taken at week to figure this out. This isn't even funny.

Nah, it doesn't bother me. You wouldn't believe some of the machines I've seen people build whom have absolutely no background in hydraulics whatsoever. The guy who accidentally made a regeneration logsplitter that actually worked, because he plumbed it wrong. The guy that made an 8 cylinder house leveller with 8 solenoid valves to control the cylinders separately. The system was literally a gas powered powerpack, 8 valves and 8 cylinders, with reservoir and filtration. The guy made it work, and uses it every day.

These are the type of guys that think if you buy a bigger pump, it puts out more pressure. You be suprised at what a guy with an idea and the ability to fabricate can come up with. I know it's scary to you, but we're talking about guys that didn't even finish high school, and we expect them to know about load distances, static friction and the Bernoulli Effect. But trial and error and a MIG welder are all they need.

Josh wrote:

quote:

These are the type of guys that think if you buy a bigger pump, it puts out more pressure. You be suprised at what a guy with an idea and the ability to fabricate can come up with. I know it's scary to you, but we're talking about guys that didn't even finish high school, and we expect them to know about load distances, static friction and the Bernoulli Effect. But trial and error and a MIG welder are all they need.

Seeing is believing Josh.All you have to do is take a look at the hydraulic section of these two web sites.
http://www.hydraulicinnovations.com/forum/index.php

http://www.machinebuilders.net/forum/forum_topics.asp?FID=5&PN=1