Synchronizing two cylinders

[ParkerFly]

I'm trying to get two cylinders synchronized. The catch is that one is always extending and one is always retracting. They need to always operate at the same speed so that when one is extending it becomes extended at the same point the other becomes retracted, and vice versa. I haven't tried it yet but I'm guessing a proportional flow divider wouldn't work since it takes much more fluid to extend the one cylinder.
Is there a simple way of doing this? Thanks,

Justin

 

[J_J]

Could you reverse one cyl so they are both moving the same amount of fluid.

What is the application?

 

[scrappy isb67]

how precisely do they have to be syncronized? as in is there room so that one reaches full travel slightly before the other does won't cause damage?
Are they going to be interconnected mechanically? without a mechanical connection they cannot be timed perfectly for all situations.
with 2 double acting cylinders, you can get it close but there WILL be some variation without the mechanical link between them.

Like this:
hose from tractor->cylinder extend port-> cylinder retract port-> cylinder retract port-> cylinder extend port-> hose back to tractor.

set up this way the 1st cylinder(cylinder extends) will push fluid from its retract port into the retract port of the 2nd cylinder( cylinder retracts) and the second cylinder will push fluid out its extend port back to the tractor. The problem is getting the system bled between the 2 cylinders and any leakage in either cylinder and it will go out of sync.
with this the 1st cylinder is the master cylinder and the 2nd is a slave cylinder. I have seen this used to lift a winged wheel disk and they always ended up lifting the main frame 1st with a slight lag before the wings would come up.

 

[olde man]

are these cylinders operating from the same valve section, and what is the task they perform

 

[magicheater]

Could you reverse one cyl so they are both moving the same amount of fluid.

What is the application?

Elegant solution JJ.

 

[whodat526]

the easiest way i would think you could do it is run a hose from one port on one cylinder the a port on the other one (like take the line that extracts one cylinder and conect it the the line that retractracts the other cylinder and connect a single valve in the other to ports)

 

[Zebrafive]

A double rod cylinder if what you are connecting rods to are opposite each other.

Or two double rod cylinders, so each will have the same piston area in each direction. You will still need a flow divider if the loads are not the same on each cylinder, the lighter loade will always move first and the heavier load will not move until pressure is the same in each cylinder.

 

[jpm1]

If im reading and understanding properly, when you plumb in the two cylinders, run your feed and return lines from the valve to a centerpoint between the two cylinders then "TEE" off the feed and return lines with the same length of hose from the TEE to the rod and cap end of the cylinders now when the valve is actuated the cylinder move in sync with each other. Loader companies dont do it this way anymore because it costs more. Did it this way for years when i built equipment. . . .John

 

[ParkerFly]

the easiest way i would think you could do it is run a hose from one port on one cylinder the a port on the other one (like take the line that extracts one cylinder and conect it the the line that retractracts the other cylinder and connect a single valve in the other to ports)

This was set up as a hydraulic steering system on a piece of equipment. Two wheels on the front were steered by hydraulic cylinders. The above quote is what I tried, but it didn't work because whichever cylinder was extending was stronger than the one retracting and they didn't act at the same time. I figured out yesterday there probably wasn't a simple (cheap) way around this, so I redesigned the system and now they are always either both extending or both retracting. The reason I didn't do that before was I thought I'd need the strength of always having one pushing. Turns out I don't. I'll have two flow dividers on Monday that I'll use in the line and should have my cylinders synchronized after that.

Justin

 

[J_J]

Now that I think about the two cyl, our Power-Trac's steer the front section by using two equal cyl through a steering motor/valve like this. Both cyl mounted the same. We turn the steering wheel and the steering valve pushes the fluid where it needs to be. This system has worked successful for a good number of years, in mining and on the Power-Tracs.

Surplus Center - 5.9 CU IN STEERING VALVE (TORQUE GENERATOR)

No matter which way you steer, the fluid is gong into one chamber of both cyl, the base end on one of the cyl, and the rod end of the other cyl. The exit speed of the fluid does not matter.

Do you really need equal pressure, force and movement.

 

[ParkerFly]

On that loader those cylinders are in a way "attached" to each other. If one starts to move the other has to move because they're both attached to whats moving. Mine weren't, I had no tie rod between my tires, so the tire that was easiest to move (the one where the cylinder was extending) always moved first. Once that cylinder was extended the other would retract.

 

[J_J]

There is no tie rod on the PT. One cyl pushing one way and the other pushing the other way.

The fluid flow to each cyl is done in the $500 steering valve.

 

[ParkerFly]

Correct, but because those two cylinders are attached to what is moving they are forced to move at the same time and be synchronized. It has the same effect as a tie rod would have had on my system. My cylinders were controlled through a steering valve like you posted also.

 

[J_J]

A good way to avoid any conflict with two cyl is to use only one larger cyl to steer, if at all possible.

 

[WilcoKubota]

do you need something like this? The right-mid pic on the firsth page.

http://www.surpluscenter.com/adspecs/AS9-6845.pdf

 

[Zebrafive]

So you have NO way to connect the two steering knuckles?

 

[bcp]

How about a steering cylinder?

Surplus Center - 2.5x10x1.5 DA DOUBLE ROD HYD CYL

Bruce

 

[gengine]

Could you reverse one cyl so they are both moving the same amount of fluid?

the easiest way i would think you could do it is run a hose from one port on one cylinder the a port on the other one (like take the line that extracts one cylinder and conect it the the line that retractracts the other cylinder and connect a single valve in the other to ports)

Truck mounted plows are plumbed like this all the time. On my personal plow, my work plow, as well as the plow on the loader and three dump trucks with plows at work. All the articulated loaders that I have ever run do the same thing for steering. If your worried about it, how about two single acting cylinders? When one is extending, it is forcing the retraction of the other. The valve will take care of the flow of fluid.

 

[ParkerFly]

So you have NO way to connect the two steering knuckles?

I could have, but I think it took less time to move one cylinder than it would have to fab up a tie rod of some sort since the system wasn't designed with that in mind. It would have taken some work to get it done. I'll know by tomorrow afternoon how everything will work.

 

[Zebrafive]

I could have, but I think it took less time to move one cylinder than it would have to fab up a tie rod of some sort since the system wasn't designed with that in mind. It would have taken some work to get it done. I'll know by tomorrow afternoon how everything will work.

The bad thing about no connection between the two steering wheels is if one gets stuck (as in a rut) the other will move until the pressure needed to move the other one is less than that one. It could mean one wheel moving to the stop before the other moves.