1978 Lima 60 ton lattice boom truck was parked 3 years ago with boom up and now won’t boom down. Will lift up slightly as it’s almost all the way up but won’t go down. Hooked counter weight hoping the tension would help but no luck. Everything else is functioning as should. Any advice is greatly appreciated.
Most friction cranes have a ratcheting lock on the boom drum that will not allow the drum to spool cable off until released. I suspect that’s the issue. Another thought is the brake is stuck but if it comes up a little I’m thinking it’s the lock. It may release with a lever or pedal. Take a look at the drum and follow the linkage to the cab and see what you can do to release it. I’m not familiar enough with that model to tell you exactly where to look. Good luck!
Look at the dog on the side of the boom hoist drum ,a slight boom up with the dog button pulled it should release . If its boomed up really high the boom hoist cutout might be preventing it from moving enough to undog .Be careful not to pull against the boom stops . Its also possible while at a high angle and sitting its just stuck and may have to be pulled down . Just be sure the dog is clear of the ratchet on the side of the drum.
Any luck bringing the boom down?
We haven’t been back to work on it yet. Going this weekend.
I have seen boom stop tubes rusted on smaller old American cranes after setting with the boom held high for a few years. Some are turned over so the inner one is down to keep the rain out. Not sure if the Lima's are similar. If all else is loose a gentile tug will help.
I the boom dog is not set ,the boom brake is stuck. Lima booms down by engaging the boom power load lowering clutch then releasing the brake. It is accomplished by having a restricted fitting going to the brake wich delays it long enough so the boom does not drop. Check the dog and put it in boom down hook up a weight if you can, and beat on the brake band see if it frees up. There's a quick release valve on the brake circuit just like a truck that could be bad, either way if the brake band opens it will come down. Also it is a spring set brake , if you have a bad diaphragm in brake chamber, it wont work, you would here the air leak.