Synchronizing two cylinders

[scrappy isb67]

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.

but every example you mention above are mechanically syncronized! In th OP's case there is no easy way to mechanically syncronize them.

OP, what exactly are you trying to steer? I have a couple ideas but I need to know what exactly you are working with.

on a conventional vehicle steering setup the Master/Slave setup I mentioned in my previous post might work OK if the inside(of the turn) cylinder is the master(AND that cylinder extends to make that turn), it would simulate ackerman angle.
ackerman angle is there to compensate for the different turning arcs for a vehicle in a turn where the inside wheel has to turn more than the outside wheel.

the other option is a pair of balanced cylinders. with flow dividers you are still going to have issues with one turning faster one way and slower the other way with unbalanced cylinders.

 

[ParkerFly]

If you're familiar with a tractor pulling sled, these tires are on the front of it. They lift the front of the pan as the sled goes back down the track to the start line. This picture isn't the best but will give you an idea. Part of the catch here is that the tires fold all the way up going when it's being pulled. A tie rod could be made to work but would be a little tricky and one more thing to trip over.
Lots of other sleds use a setup basically identical to this, that's why I feel sure it will work as I get the details figured out. It's almost always on level, relatively smooth ground and speeds are 10 mph tops. Most of the steering will be minor corrective steering just to keep the sled straight.

 

[wdchyd]

I would guess that either a mechanical flow divider or two cylinders plumbed (and sized properly) in series could work

a mechanical flow divider has a set of gears to allow equal flow regardless of pressure plumbed in to cyls like Wilcokubota's post

the two cylinders in series (exhaust from one goes to the next) would have to be sized so that the stroke would be the same

 

[wdchyd]

Flow divider..... FD Flow Divider [950 Series] : White Drive Products, Inc.

 

[Leejohn]

You ever play around with jetting? I have a inline fitting that has a jet in it that a guy can change. It's to bad I only have one, if I had 2 I would send them to you. I also have a joystick control valve that has jets in it. If you could find the fitting you could jet the base end of each cyl. and get them to match. Might take a little time but, I think it could be done with very little $$.

 

[wdchyd]

You ever play around with jetting? I have a inline fitting that has a jet in it that a guy can change. It's to bad I only have one, if I had 2 I would send them to you. I also have a joystick control valve that has jets in it. If you could find the fitting you could jet the base end of each cyl. and get them to match. Might take a little time but, I think it could be done with very little $$.

??...are you referring to restrictor fittings..??...though it may work, it brings on another set of problems.....ie: pumps blowing over max pressure relief, pressure intensification on cyls, slow reponse, heat........

 

[Leejohn]

Yes I was and you are right about the other problems. That control valve I have I bet it is a low psi pilot valve. When I posted that all the problems went over my head, now you make me feel like a ---.:ashamed:

 

[wdchyd]

Leejohn, didn't mean to rain on your parade.....Sorry, wasn't my intentions

Free advice always welcome here.......Yours and Mine....It's hard sometimes figuring out other peoples dilemas when you can't see it for yourself

 

[scrappy isb67]

If you're familiar with a tractor pulling sled, these tires are on the front of it. They lift the front of the pan as the sled goes back down the track to the start line. This picture isn't the best but will give you an idea. Part of the catch here is that the tires fold all the way up going when it's being pulled. A tie rod could be made to work but would be a little tricky and one more thing to trip over.
Lots of other sleds use a setup basically identical to this, that's why I feel sure it will work as I get the details figured out. It's almost always on level, relatively smooth ground and speeds are 10 mph tops. Most of the steering will be minor corrective steering just to keep the sled straight.

thanks for the picture, now I understand what you are trying to do!
Unfortunately with that setup a master/slave won't work at all unless you move both cylinders to the same side of the pivot point (I.E. in front of or behind).
Flow dividers should work with it set up as is since both cylinders retract for left and extend for right. it will just turn faster to the left and to the right with more force. which isn't a cancern, alot of tractors have the same turn characteristics.

my question now is do flow dividers work in reverse too? as in to combine equally 2 input flows? if not will they allow flow in the opposite direction at all?

 

[wdchyd]

mechanical flow dividers work on a principle similar to two pumps connected together at the shafts......

one port in splits the flow through both gear (or geroler) sections equally to two output ports......

the internals reverse for return.....

this link explains.. FD Flow Divider [950 Series] : White Drive Products, Inc.

 

[wdchyd]

Great thing about these puppies is you can intensify hyd pressure if needed from a low pressure system

Just run output from hyd pump through flow divider, then run one output to tank, the other output in to the hyd system and VOILA, twice the pressure (although half the flow)

 

[techman]

Be careful with a flow divider. Due to tolerances and differences in leakage, they WILL slowly get out of sync. In a well designed circuit, one or more additional valves are needed to re-sync the cylinders. Additionally in many cases with some small error, a flow divider can generate excessively high pressures, so additional relief valves are also generally recommended. Bottom line is that it can get complicated quickly with a flow divider.

Paul

 

[olde man]

tech man is correct you're complicating your circuit and not solving your problem

 

[ParkerFly]

my question now is do flow dividers work in reverse too? as in to combine equally 2 input flows? if not will they allow flow in the opposite direction at all?

You can get ones that do and ones that don't. Mine were supposed to be in today but were a day late shipping, I'll know by tomorrow afternoon how things are working.

 

[scrappy isb67]

You can get ones that do and ones that don't. Mine were supposed to be in today but were a day late shipping, I'll know by tomorrow afternoon how things are working.

the reason I was asking was that if they do then you would only need one.

 

[olde man]

all of the ones i know about require two for this function however sun hydraulics makes a valve to do this with eliminating the need for the the two gerotor flow dividers. if you go with the gerotor you can still "t" in the inlets and use the outlets to cross connect the cylinders keeping the steering turns even

 

[bcp]

It's almost always on level, relatively smooth ground and speeds are 10 mph tops. Most of the steering will be minor corrective steering just to keep the sled straight.

Keep it simple and just use two valves. Two handles close together, plumbed so forward on both, with one hand, is left turn, for example. If the wheels don't look quite right, then adjust one of the valves.

Bruce

 

[ParkerFly]

Well everything is working like it should after the flow dividers were installed today. The cylinders work together so my steering appears to be up and running. Thanks to everyone who helped with this.

Justin

 

[gengine]

Well everything is working like it should after the flow dividers were installed today. The cylinders work together so my steering appears to be up and running. Thanks to everyone who helped with this.

Justin

When I posted earlier, I had a completely different idea of what you were trying to do. I think i got it now, but would you mind posting some pictures? It sounds like something that I may be doing to my Case 930.

 

[ParkerFly]

I'll try to remember to snap some pictures tomorrow. I would have today but I need to get the hoses tied back up and the gallons of fluid laying everywhere cleaned up.