hydraulics Help

[Charley Davidson]

have a 4' brake press I bought at the scrap yard a while back, it was originally equipped with air cylinders but someone tried to replace with wrong size hydraulic ones. I have fitted it with the right stroke cylinders but now need help with the powering of them. I bought this http://www.harborfreight.com/10000-...ferralID=d69f32c1-5aa4-11e1-a6d5-001b2166c62d but I do not believe I can use it cause it's not 2 way power. Is there a way to use it or do I need to go another route?

Here's a pic of the brake press

 

[Tom Griffin]

Charley,

Your "two way power" comes from either the type of cylinder you select or a return spring. It looks like you have two way cylinders on there already, all you need is a valve to route the fluid to one side of the cylinder or the other.

Tom

 

[Charley Davidson]

Those are the wrong cylinders but the new ones are 2 way. Am I getting this right? I need a valve for up then switch to go back down? I have a DC powered self contained unit off some kind of tailgate or wheelchair lift, don't know working condition yet.

 

[pdentrem]

You will something like a " single spool directional control valve " this may not be exactly but gives you the idea.

http://www.princessauto.com/pal/pro...v/BM20-Single-Spool-Directional-Control-Valve

 

[arvidj]

pdentrem is correct about the type of valve you will need. It will have two lines that go to the opposite ends of the cylinder plus one line that will go to the pump and one that will go to the tank.

If the valve is 'open center' then when the lever is in the neutral position fluid will flow from the pump to the valve and then back to the tank. When you move the valve to a non-neutral position it will direct the pump pressure to on end of the cylinder an the fluid that must come out of the other end back to the tank. When you move the valve to the other position the same thing happens except the pressure goes to the other end of the cylinder.

 

[Tony Wells]

That's typical of the control valve found on log splitters. Northern Hydraulics is one source. That pump has the pressure, but I don't see a volume rating. Depending on the cylinder diameter, it might not be all that speedy.

 

[Charley Davidson]

Not too concerned about speed as it's not important on a brake press (to a certain extent) more concerned about control. I would really like for it to completely cycle by just holding the pedal down continuously.

 

[Tony Wells]

For that you wold need some adjustable limit switches and some electric solenoid valves. Can be done without too much trouble. You could get repeatable bends that way, I would agree.

 

[OlCatBob]

Hey Charley,
I'll bring you a single spool, double acting, control valve and leave it with Woody, unless there is a better place. I'm off tomorrow (President's Day) so it'll be Tuesday probably.
Bob

 

[Tom Griffin]

Charley,

A simple way to accomplish what you are trying to do is to make your own foot pedal around a double acting valve and spring load it in the up direction. That way you would step on it to close the press and when you let up, it will reverse the valve and open the press. For safety reasons, it would not be a good idea to automate a full cycle because you would always want to have the ability to stop the press if something goes awry. :yikes:

Tom