Try to check the wear on the joints of the lever.
A lot of those levers wear on the joints and then it starts going down more slowly.
When it has wear on the joints replace it and calibrate the new lever.
no problem bbforks,
i actually do stand corrected
your right... the valve in the piston is a flow valve that controls fluid flow in the cylinder and aids in the sequencing of the cylinders. The velocity fuse valve is actually on most systems inside the fitting generally on the outside cylinder right hand side or the first cylinder for the inner channels.
I had to go back and read up on my hydraulics theory of operation on these systems.
Its what happens when you get old, brain goes first hehe ;o)
thanks
thanks for all the input.
just been working on site today and speaking to driver who told me that if you push lever realy hard mast goes down faster!
sure enough when i tried this - full speed
swapped over joysticks between sideshift and lift/lower.
Now lift/lower works perfect.
the joystick that was on lift works sideshift at acceptable speed, possibly starting to fail internally?
anyway I left the levers in swapped over position and all drivers are now happy!!
Just goes to show, sometimes dont think or look too hard at problems, try simple things first
No disrespect swoop-I'm just not sure we're talking about the same valve. There's a valve in the outlet port ( the velocity fuse ), the other valve in the bottom of the ram itself (inside the cylinder). You are correct that the velocity fuse is to limit downward travel of the carriage in case of a hyd line failure. The valve inside the cylinder is the differential valve- it's purpose is to equalize the pressures of the cyl below & above the lower packing assy ( this valve is only used in differential type cylinders).
it is a check valve designed to keep the fluid from exiting from the cylinder too quickly in the case of a line rupture. Some mfg's call it a velocity fuse, others call it a safety down valve, cat calls it a check valve.
It may serve a dual purpose as an equalizing valve but its original intent is to restrict flow in the case of a line break/rupture. (a safety check valve)
Unfortunately when this valve malfunctions it causes raise/lower issues and mast sequencing issues as well.
so whatever it is called by the mfg it has been an issue in many cases that I've seen such as this.
The valve in these newer displacement type hoist cyl's isn't technically a safety valve ( like the 10% limit valve in the inlet port). but rather a valve to keep both sides of the cyl (under ram & between ram & shell) under the same pressure- kinda like the lock valve in the tilt circuit- keeps both sides of the tilt cyl's pressure equal
sounds to me like a safety valve in your cylinder malfunctioning.
I've seen this symptom happen alot in different masts and it generally winds up being a safety valve either sticking or blown apart.
most cylinders in masts today are fluid displacement type and they install a safety valve in the piston at the base of the piston.
you already did the calibration mini levers
you can adjust the valves manually
Has someone shimmed the carriage rollers too tight. Also you can manually adjust the valve
Is the upright a triple stage? If so- how are do the secondary cyl's react to input ( up & down) once the primary cyl is fully extended? I assume the other hyd. functions are acting normally.
If the other functions & the secondary cyl's are acting normally, I'd suspect the valving inside the primary cyl. It seems when that valve goes bad it can have quite alot of different symptoms.