Question for a hydraulic guru

[sunsation288]

Hello all , i am in the process to built a table lift for motorcycle , and i have bought 2 used cylinder ( the seller have not be able to say to me where they come from ), i have be able to retrac and extent the ram fearly easy with my hydrolic unit , but when i have reach the limit of fully extend .... i have not be able to retract it ? ( they look to be lock ) , i have two port for the bottom ? one is for extend , but the other one i have no idea ? maybe it's a port i have to pressurise to unlock ?
hope my question made sense ? , if not feel free to ask
and sorry for my bad english
Regards
Christian

 

[nehog]

Re: Question for a hydrolic guru

Post a few pictures of the cylinders, that may help with answers--otherwise people will just be guessing.

 

[sunsation288]

Re: Question for a hydrolic guru

Thanks Nehog , i am at work right now , i will post picture for sure , since i have not 2 hydrolic unit , i will try to pressurise the unknow purpose port with a grease gun ? (using the gun with hydrolic fluide)
that made sense ?
thanks again for helping

 

[scott37300]

Re: Question for a hydrolic guru

If you have a port close to the top of the cylinder and another port towards the bottom of the cylinder this would be to push the ram back and forth. You pressurize the bottom port will push the ram out, you pressurize the top port it will push the ram back in. You will need a switch/valve that will send you fluid to either port to make it move. I'm not so much a hydrualic guy, more pnuematic. I've used these switches with air on projects before and it "dumps" the air out. For hydrualic you will need a switch that will return the air to your resovior.

 

[akdiesel]

Re: Question for a hydrolic guru

Does your hydraulic pump have a pump switch and a relief switch?
It should not matter too much if the ram has a port for pressure in and pressure out as long as you have a place for the fluid to go.
Some pumps have a three way valve and others have a simple bleed valve and the weight on the ram will retract it.

 

[sunsation288]

Re: Question for a hydrolic guru

Thans guy for helping , yes i have a simple bleed valve on my hydrolic unit , and the weight of the ram and the table will lower my cylinder , but right now my ram are fully extract , and i supply hydrolic pressure on the upper port and the pressure rise in my unit and the ram don't lower

When i start to play with yesterday, i have be able to travel up and down (i don't reach the fully extend position ) , but as soon i have go fully extend one time he go in lock mode ?

sorry guy for my bad english
Regards
Christian

 

[galute]

Re: Question for a hydrolic guru

I wouldnt think that it's going into any type of lock mode. Sounds more like it's pushing the piston past the down port or the piston seals are sticking in place when fully extended. If applying pressure to the down port doesn't move it then you most likely have an internal problem with the seals. You can take it apart and have a look inside. They are pretty simple.

 

[sunsation288]

Re: Question for a hydrolic guru

I wouldnt think that it's going into any type of lock mode. Sounds more like it's pushing the piston past the down port or the piston seals are sticking in place when fully extended. If applying pressure to the down port doesn't move it then you most likely have an internal problem with the seals. You can take it apart and have a look inside. They are pretty simple.

thanks galute , any idea of the purpose of the third port ? , i am at work right now , but tomorow i will try to pressurise the third one and see if i can do something (like applying force to push back the ram with a small pump jack)
thanks to all for trying to help
Christian

 

[sunsation288]

Re: Question for a hydrolic guru

Ok update guy ....what i have found so far on the internet , the third port it's maybe a transfert spool , and allow the oil under the piston to evacuate ? when the piston retract ... this is why my piston can't retract since oil is trapped under , fail safe ?
that made sense guy ?

 

[galute]

Re: Question for a hydrolic guru

That really don't make sense to me. If it was an oil return it would just pump the pressure thru the return and the piston would not go out. My guess is it's probably a port for some type of pressure regulator to keep the cylinder from destroying whatever work it's intended to do. As you said, a fail safe pop off valve kind of thing.

I still think if it works properly partially extended then locks up fully extended then the piston is going past the port at the top for some reason. That would create a vacuum at the end that would be very difficult to push back in without some way to relieve the vacuum. My guess is either something is missing on the inside of the cylinder or it's designed to have what ever it was installed on limit it's outward travel so the piston don't pass the port. Of course this is all speculation on my part without actually seeing the unit. Like I said before, they are simple. If you have the tools take it apart and inspect it. Shouldn't be hard to see the problem. Just be careful putting it back together and not cut the seals up.

 

[Spareparts]

Re: Question for a hydrolic guru

That is what is called a "Pilot Activated Safety" keeps the cylinder from dropping until it gets pilot pressure on the retract mode. To get the pilot pressure you have to install a "T" on the retract port with a small line to the pilot port (second port on the extend end of your cylinder). When you activate the retract mode you pressureize the pilot valve and the cylinder will lower the table. The cylinders you have are 2 way and need pressure to operate them both directions, what you need is a cylinder without the pilot system, also a adjustable flow control valve to control the fall of the table

 

[sunsation288]

Re: Question for a hydrolic guru

That is what is called a "Pilot Activated Safety" keeps the cylinder from dropping until it gets pilot pressure on the retract mode. To get the pilot pressure you have to install a "T" on the retract port with a small line to the pilot port (second port on the extend end of your cylinder). When you activate the retract mode you pressureize the pilot valve and the cylinder will lower the table. The cylinders you have are 2 way and need pressure to operate them both directions, what you need is a cylinder without the pilot system, also a adjustable flow control valve to control the fall of the table

Wow many thanks Spareparts , your comment made lot of sense to me , but since i lift a working table of 1/2 thick by 30 inches wide and 93 inches long (around 300 pound) , do you think i going to have enought weight to lower it if i pressurise only the pilot port ? ,
i will keep you posted for sure


right now i am in the process to build my garage (28x36) and the cylinder have to be under the slab , every thing have to work right , the work are supposed to begin this coming week

 

[sunsation288]

Re: Question for a hydrolic guru

 

[RobSmith]

Re: Question for a hydrolic guru

Before you put that cylinder under the slab. Put a large diameter concrete pipe in there for the ram to sit inside. If something does go wrong you can remove the ram to work on it.

 

[sunsation288]

Re: Question for a hydrolic guru

Before you put that cylinder under the slab. Put a large diameter concrete pipe in there for the ram to sit inside. If something does go wrong you can remove the ram to work on it.

yes you are right , i have bought a 14 inches diameter pipe ...for if someting go wrong , thanks for the advise
Christian

 

[dtt454]

Re: Question for a hydrolic guru

an actual photo would make it easy to tell if your cyl has an internal counterbalance valve.

 

[sunsation288]

Many thanks to all to trying to help , and sparparts have it right , i be able today to retrac all the ram with little pressure to the second port in the bottom

 

[sunsation288]

 

[sunsation288]

 

[sunsation288]

Now i have two cylinder for the price of one !!! , since we always thinking the first cylinder was bad , the seller giving me the second one no charge ....

 

[sunsation288]

with a small 3 phase drive , i can power my hydro unit on the 240 single phase i have at home

 

[sunsation288]

 

[sunsation288]

i take moment to thanks you all for trying to helping me , it's realy appreciated
Christian

if i can begin my garage dream ....i hope for the end of the week , or next week for sure
what i have bought so far
-door cutouts to insulate under the slab
-all my light 16 x (4 tube par unit T5) it's going to be sunny !!
-Chromalox 10 kw heater
-Modine 55 BTU LPG
-Lincoln Squarewave 175 TIG/MIG
- my working table with cylinder
-8 full size cabinet (24x36x84)
- all my electric stuff

 

[the lone]

nice slow down valve lol

 

[sunsation288]

ok , the instalation is done

 

[sunsation288]

and every thing working very well !!!