cyl with built in counter balance valves

[muddstopper]

I have a bunch of small cyl off a old boom truck. I am trying to use these cyl's to build a small, (2000lb) crane for my dump trailer. The cyl I want to use for the boom has a built in counterbalance valve. I need the cyl to gravity feed down. I am just wondering if I remove the valve cartridge and plug the hole, will the cyl work as a normal double acting cyl, or will oil bypass internally where the cartridge valve was. This is the only cyl I plan to use with this type of valving and I could use as is, but it requires pressure to allow oil to flow back to tank. Using this cyl as is would mean I would have to power down to get the cyl to lower. For a boom, this is normally a safety feature to prevent the boom from falling in the event of a broken hose, but is unnecessary for my use and could foul me up if my electric hyd pump fails.

 

[4570Man]

I think the only way to bypass those would be drilling a hole in the cylinder and welding in a new port.

 

[muddstopper]

they make different cartridges to make the counter balance work in different ways, but it would cost more than just buying a new cyl. Cyl only has a 7in stroke. I am thinking about just taking the cyl apart and chucking in the lathe and removing the base and replacing with a normal base. I would also have to remove the tube to the rod end and install a port. Thats my cheapest route. I think there is something else also going on with this cyl. Its awful long just to have a 7in stroke, It could have a extend limiter inside to prevent it from over extending and possibly buckling under load. I wont know until I take it apart.

 

[oldnslo]

Mudd,
for reference you can usually dismantle a counterbalance valve and use pieces of it to to block the cavity.

On the assumption you have a sun counterbalance you can dismantle it in the following manner. NOTE: Do NOT damage the hex portion of this assembly or the O-rings on the hex portion you will need these.
1) turn the adjustment to remove all of the spring pressure. For Sun this is typically clockwise. Tighten the jam nut on the adjustment.
2) look at the bottom of the threaded portion of the valve which i will call the retainer. There should be a slot that is partially crimped shut approx 1/8 - 3/32 from the end of the retainer. Pry this slot open.
3) hold one end in a vice or a Collett with the slot where you can see it easily. this makes the next step easier.
4) Now slowly turn the part not in the vice while looking at the slot. You should see a wire ring in this slot, one end is bent at 90 degrees and locks into the round portion of the valve that I will call the cage. keep turning the part until you see the cut end of the wire ring. Use a dental pick to pry up the end of the wire ring and then turn the part to unwind the ring out through the slot.
5) remove the wire ring and pull the two pieces apart. This might require a slight twisting and rocking action. A spring will be loose in the retainer so remove this also.
6) Valve dismantling is complete.

Now comes the harder part. There is a small drilled hole in the retainer From memory it goes in at an angle close to one of the O-ring grooves. This is the pilot hole that connects the rod end port and pilots the C'balance valve open. You must some how block this connection. You might be able to tap the hole in the cylinder that connects to the valve cavity or else you will have to plug the hole in the retainer. This will see the pressure on the blind end of the cylinder.

Once this connection is blocked, screw the retainer back into the cavity and you have successfully removed the C'Balance valve and can use the existing ports on the cylinder.

 

[muddstopper]

Mudd,
for reference you can usually dismantle a counterbalance valve and use pieces of it to to block the cavity.

On the assumption you have a sun counterbalance you can dismantle it in the following manner. NOTE: Do NOT damage the hex portion of this assembly or the O-rings on the hex portion you will need these.
1) turn the adjustment to remove all of the spring pressure. For Sun this is typically clockwise. Tighten the jam nut on the adjustment.
2) look at the bottom of the threaded portion of the valve which i will call the retainer. There should be a slot that is partially crimped shut approx 1/8 - 3/32 from the end of the retainer. Pry this slot open.
3) hold one end in a vice or a Collett with the slot where you can see it easily. this makes the next step easier.
4) Now slowly turn the part not in the vice while looking at the slot. You should see a wire ring in this slot, one end is bent at 90 degrees and locks into the round portion of the valve that I will call the cage. keep turning the part until you see the cut end of the wire ring. Use a dental pick to pry up the end of the wire ring and then turn the part to unwind the ring out through the slot.
5) remove the wire ring and pull the two pieces apart. This might require a slight twisting and rocking action. A spring will be loose in the retainer so remove this also.
6) Valve dismantling is complete.

Now comes the harder part. There is a small drilled hole in the retainer From memory it goes in at an angle close to one of the O-ring grooves. This is the pilot hole that connects the rod end port and pilots the C'balance valve open. You must some how block this connection. You might be able to tap the hole in the cylinder that connects to the valve cavity or else you will have to plug the hole in the retainer. This will see the pressure on the blind end of the cylinder.

Once this connection is blocked, screw the retainer back into the cavity and you have successfully removed the C'Balance valve and can use the existing ports on the cylinder.

Thanks, I did not know this. I also was trying to screw the adjustment counter clockwise to reduce pressure, My goal was to try to lower the pilot pressure setting enough that the valve would actually bypass. Never had one apart so I dont know if what I was attempting will even work. I'll fool around with it this week and either screw it up or make it work as you suggested.