Clamshell Bucket Speed

If the hinge pivot of the bucket has been well maintained and lubricated the problem is electrical. Could be the joy stick or the driver for the drum motor. I would look at joy stick first because of the mechanical operation of the pots in it. Switches usually control the function like open and close. A pot will vary a signal for speed. On a application which changes direction they usually use the same pot. The slowness of opening and closing indiactes this pot may have gone bad. There maybe be other fail safes in the crane that would limit the speed of the bucket opening and closing that may have failed. Upper limit switches for one.

How old is the joystick? Sometimes as these hydraulic systems age they need an additive like sildenafil citrate to keep working properly.

Sounds like maybe you got some schmootz in your proportional spool not allowing it to open completely. Need to know MUCH more information to give reliable diagnosis, but here are some things to check:

• Check the output signal coming from the joystick (4-20ma, 0-10V etc). Make sure it's outputing the full signal to the valve driver card.
• Check the signal from the driver card going to the valve coil. If it has full signal to the coil, check that the flow/pressure from the Prop valve are within manufacturer specs.
• Check your system pressure at the pump. Verify against Schematic.
• Check your system flow at the pump Verify against Schematic.
• If all of the above are OK, Check your case leakage at your rotary actuator. If it's below allowable in the manufacturer literature, it's ok.
• If all the above check out, you have narrowed the problem down considerably... Get back to us with results, for further troubleshooting.

This is all assuming that it's a hydraulic drive system.

I suspect strongly that you have a hydraulic system, if the closing speed of the grab is controlled....look for hydraulic pipes and pistons and check for oil leaks.

If no leaks found then you have a worn seal in the pump or circuit controls.

1. check the pump output hydraulic pressure (under load), as close to the pump as possible.

2. check that the circuit pressure relief valve is tight closed. When it leaks, the oil returns to the reservoir instead of increasing pressure to the grab operators.

3. If still no fault found, you need an experienced/ qualified person to check the seals and ports in the joystick assembly. It is not a good idea for ineperienced/ unqualified persons to do this, for many very good reasons !

Forgive this if the grab is actually electric ....

Can we go back to basics, is this an electrical drive or hydraulic? I can't see anything in the OP to say which. I'm quite used to the workings of electric two drum four rope systems. I'm not going to waste my time or yours if it's hydraulic.

this is an electrical system. not hydraulic. its driven by motors.

2 motors, 2 gear boxes with 4 wire rope drums.

now clamshell bucket open/close very slowly.

Well, then I'm not going to be of any help.

Hopefully someone comes around who knows more than I do about Electric drives.

Good Luck!

any way thanks for your help!!