You know what STEPHEN, you are absolutely correct!

Well I don't know how to do it correctly I guess, but I think the top design is not good because: 1) How is the hydra fluid in the dead end circuit going to stay topped off also consider fluid expansion due to temp change, 2) you now have three stress points all working against each other.

Maybe the best way is to plumb it as two one way cylinders as someone above suggested.

Thanks STEPHEN for staying in there making me understand.

Sure has been a lot of over thinking on this thread. It is as simple as teeing the lines to top of one and bottom of the other sides cylinder. The other lines will do the reverse. All types of equipment use this arraignment. Every rack and pinion swing on log loaders are plumbed like this and have been doing it for years.

"cojhl2" wrote:

You know what STEPHEN, you are absolutely correct!

Well I don't know how to do it correctly I guess, but I think the top design is not good because: 1) How is the hydra fluid in the dead end circuit going to stay topped off also consider fluid expansion due to temp change, 2) you now have three stress points all working against each other.

Maybe the best way is to plumb it as two one way cylinders as someone above suggested.

Thanks STEPHEN for staying in there making me understand.

What the top circuit needs is a way for fluid to bypass the piston seals to sync the travels and flush out the air. Something along the way re-phasing wheel lift cylinders work on a JD disc harrow. JD uses a pair of short small grooves in the barrel ID at the end of travel to allow fluid to short circuit the piston seal. I put one together backwards once, now I make sure to mark all parts BEFORE disassembly. The JD way really works well on the disc, you can remove and replace cylinders and to get the air out just hold the control all the way until the cylinders are both equal, no air problems. One other method I have seen is for two small holes drilled through the barrel, one on each side of the piston at the correct stroke. The holes are connected via a passage welded on the outside of the barrel. With a bit of machine work, a needle valve could be made into the exterior passage to block it once the system is synced.

Well I'm back also,, the more I think about this STEPHEN, it won't freewheel. All valves closed, cyls are isolated. left cyl retracts, vol of oil from head side = AreaL x LenL. That vol needs to go to other cyl rod end where AreaR x LenR. Since AreaL > AreaR, LenR must be > LenL.

So in a parallel arrangement the system is locked.

I am getting dizzy.

I must go back and study your last post and understand that JD design.

STEPHEN and all I hope I am not beating this thing to death(well I am I guess) but I just gotta understand!!

"cojhl2" wrote:

Well I'm back also,, the more I think about this STEPHEN, it won't freewheel. All valves closed, cyls are isolated. left cyl retracts, vol of oil from head side = AreaL x LenL. That vol needs to go to other cyl rod end where AreaR x LenR. Since AreaL > AreaR, LenR must be > LenL.

So in a parallel arrangement the system is locked.

I am getting dizzy.

I must go back and study your last post and understand that JD design.

STEPHEN and all I hope I am not beating this thing to death(well I am I guess) but I just gotta understand!!

This is what the system needs to isolate the cylinders at the cross over when control pressure is released. I have used them before and they are THE magic bullet for leaky spool valves. ph.parker.com/us/en/dual-pilot-operated-check-valves I had a 1950's 6000 lb Clark lift with a drifty mast tilt control. Experts said the only fix was to send the spool out to be chromed and the body lapped. One $60 part and a few hoses worked purfectly until I junked the lift.

I have to agree with o i h, I think you guys are over thinking this. Either way will work. One cylinder will work too. I just prefer the way I have done it as I feel it puts less stress on the centre pivot of the blade.

The first diagram will not work, it is trying to tip the blade backwards and forwards and will only tear out the pivot pin, the second is the normal way to plumb tilt cylinders with no timing, phasing or bleeding to do, to link the rod ends together and supply pressure and return to the head ends will and, as set up and tested does work, but is difficult to charge the rod ends with oil and does not have as much force available, I don't reckon we need any more theory.