Cylinders in parallel

[JDHornet]

Long story short, I have a New Holland 850 baler that I've been fighting hydraulic cylinder leakage. Rebuilding it hasn't fixed, replacing the cylinder is expensive. I'm looking for input on my plan to fabricate a mechanical locking system instead of the factory way of using hydraulic pressure. With out getting into a CAD program I'm hoping you can see what I'm thinking.

Ok so think of a pin and latch system in which the latch is spring returned onto the pin welded to the tail gate. I'm thinking of actuating the latch with a small hydraulic cylinder that is run in parallel with the main lift gate cylinder. My thinking is even though the two cylinders would appear to fight each other, one trying to open the tail gate while the other simultaneously is trying to release the latch, that the latch cylinder will have less resistance and so will activate before the lift cylinders begin applying real pressure against the latch. On the closing of the tail gate the latch would bump up out of the way of the pin and spring back down into the locking position. As long as I don't apply pressure the retraction process the faulty cylinder won't back feed into my latch cylinder. Clear as mud yet?

While you may suspect that adding cylinders and hoses would cost more then replacing the one troublesome cylinder you'd be wrong. Replacement cylinder is $412 and I've figured up supplies from Surplus Center would cost around $150, and I'll never question the tail gate creeping open while baling again.

Do you think my assumption is correct that the two cylinders will cooperate operating in parallel?

 

[MJPetersen]

If I understand it correctly your problem is that the cylinder has, what appears to be, internal leakage. it simply does not hold its positon through time. Since you have suggested that you rebuilt the cylinder and the problem has not changed I would suggest that the problem is not in the cylinder at all, but rather the valve that operates the cylinder. In my opinion you have a couple of options that are better than your lock mechanism. 1) try operating the cylinder with a different valve and 2) install a positive check valve. This prohibits the cylinder from moving without input pressure from the main operating valve. Such as this from Surplus Center. I do not know your hyd requirements and this is only an example of what is available. The cost would be less than what you have proposed and it would be simpler to boot. My opinion only and the results may vary.

Mike

 

[RickB]

Have you tried using a different remote valve or a different tractor to power the gate? Perhaps the valve is the source of the leak, not the gate cylinder(s). Find a NH belt style round baler and check out how they incorporate mechanical locks into a two cylinder gate lift system. It may be adaptable to your machine.

 

[JDHornet]

The NH850 has valve lock which is what they use to lock the hydraulic cylinders. I've rebuilt that and tried the other remotes on the tractor, no fix. Here's why I'm convinced of the cylinder, I can remove the return lines of both cylinders while retracting and only the left cylinder will pass oil out of the cylinder hose. The strange thing is the cylinder won't leak down with the tail gate open, I've been told by someone on yesterday's tractor site that my age of baler was known to have a defective cylinder wall that would cause my symptom. Hence the reason I'm thinking of building a mechanical locking system. I can't justify the cost of a newer baler or I'd just replace the dang thing.

Rick, I have looked other balers, most I've seen so far use a cam system in which the cylinder pushes over a cam lock before it begins lifting the gate. Unfortunately I haven't been able to invision how that would work on my baler.