Good morning! I am new here and had an issue yesterday when operating my National 1400 Boom truck. I was setting trusses and when winching down, I would slow down to set them down gently. When I did that, it stopped winching down. I would start moving the lever and it would not move until I was almost full stroke and then it would shoot down. It was almost like the cable was "stuck" and then finally broke free, but it was not actually stuck on anything. I am going to look at it today but I figured I would ask first to get some ideas. Also, when I was doing multiple things like swinging and winching (up or down) or booming up/down and winching and I stopped the other movement while still winching, it would make the winching act funny for a split second. Almost like it had a surge of pressure to the winch controls for a split second and it would make the cable slap on the top of the boom. Normally if I was giving it a ton of throttle and stopped one motion, yes the engine would Rev up more because it was under less of a load and it would start to move faster, but it would never do this. Hoping that the issues are connected. Any ideas?
I'd probably start with pressure relief settings on the winch /brake, and if those are all correct, I'd start looking into the winch brake piston seals, and hyd pump output. In most of these winches, there is a spring applied- hydraulic released brake between the winch and the drum. When you push the lever to cable down, the hyd. must put enough pressure to the brake pack to get it to release and allow the drum to turn. There's usually test ports and a procedure in the service manual to check the pressures, and that's the easiest to do, so that's where I would start.
Awesome. I appreciate the info. I will keep you posted on what I find out!
If the winch brake piston seal is bad, most times you find hydraulic oil coming from the vent or drum seal. Do you see the same delay in hoist up as well?
Negative - only in winch down.
If the winch has been well maintained. I would pull the brake pack down. And inspect the usual components (piston seal, frictions, spacers, sprag, etc). Might be a good time to replace some wear items while your in there.
If your winch is set up like this one the valve on the back of the winch is where I would start. That valve releases the winch brake in hoist down. Basically it’s job is to make sure the winch motor has adequate pressure to hold the load before it releases the brake. We have a fleet of grove cranes and I keep a spare valve on my truck. I’ll admit that I’ve gotten lazy and if a crane won’t winch down but will winch up I just replace that valve. Not saying it can’t be the brake but out of all the cranes we have, I’ve replaced one piston because that valve over pressured it and broke the piston. Every other time that valve has been the issue.