Hydraulic assist

[bwhirry]

OK can anyone explain to me exactly how this works, mechanically. I understand the basic linkage and function but how does the cylinder match the movement of the pitman arm. Basically what i want to know is how or what regulates the ram from running away from the pitman arm. What keeps them from binding or fighting each other? And yes I realize the fluid for the ram comes from the gearbox and they share pressure from the steering pump.

[Super Steve]

when you turn the wheel one way fluid in the box is directed that way (lets say to the right) when doing hydro assist you drill a hole into the passage where the fluid goes while turning the wheel right. turning left is the same concept except the hole is in a different passage (the left turn passage) this causes them to work together,


http://www.pirate4x4.com/tech/billavista/HydroAssistTap/index.html


5th picture

[Mechanos]

It's voodoo magic!

[dahoyle]

And yes I realize the fluid for the ram comes from the gearbox and they share pressure from the steering pump.



So what is your question, then?

[Badburn]

OK can anyone explain to me exactly how this works, mechanically. I understand the basic linkage and function but how does the cylinder match the movement of the pitman arm. Basically what i want to know is how or what regulates the ram from running away from the pitman arm. What keeps them from binding or fighting each other? And yes I realize the fluid for the ram comes from the gearbox and they share pressure from the steering pump.

This is actually a really good question, in my opinion.

Hydraulic fluid does not compress of stretch. Lets say that you turn the pitman arm 2" to the right, how do you know if the steering ram has moved 2" inches to the right, what if it only got enough fluid to extend the ram 1.75" and is binding the crap out of the mechanical linkage?

Anyone ???

[Rustyrunner]

This is why ram diameter and pump selection are so important in a hydraulic assist steering system. To small a ram or too big a pump and your ram will be too fast. To big a ram or small a pump and it will be too slow and ineffective.

The principle of hydraulic assist is solid. You see it on heavy trucks(cement trucks, gravel haul ect) all the time.

[82FB]

The draglink keeps them from fighting each other. It takes more pressure and less volume to move the pitman as compared to the ram, so since fluid follows the path of least resistance, it moves the ram, which in turn, turns the steering arms. This takes much of the load off the draglink and the pitman arm.

[Rustyrunner]

The draglink keeps them from fighting each other. It takes more pressure and less volume to move the pitman as compared to the ram, so since fluid follows the path of least resistance, it moves the ram, which in turn, turns the steering arms. This takes much of the load off the draglink and the pitman arm.

I am a bit confused by what you are saying. The pitman arm is mechanically connected to the steering wheel. Steering wheel-steering shaft-worm shaft-power piston-sector shaft-pitman arm. No volume of fluid is moving the arm. The steering fluid is only assisting by pushing on the power piston. Yes the surface area of the power piston is larger then that of the piston in the ram. So if they were both fully hydraulic you would be right. The power pistion would be more powerful but slower. But like i said its not fully hydraulic. The power piston will move as fast as you can spin that worm shaft and no faster.

The thing saving your ram from running away is the rotary control valve which directs fluid to build pressure on either side of the power piston and ram or dump back to the res when assist is no longer needed. The valve wont save your ram from being too slow though and becoming a drag on the system because the ram is either too big or the pump is too small. Like i said originally, matching the pump size and ram size is key.