Hello, Gumboot here, (a Newbie). Have just moved over to a Mini Ex. (Bobcat 430), after 30 odd years on a JD tracked loader. Have a problem with the house slowly rotating out of alignment. If left with bucket off ground, will eventually rotate to point of most gravity, obviously exaggerated by being on a slope. M/C will do this with engine on or off, hydraulics active or not. The problem is both clockwise and counterclockwise, so my first thought, a stuck relief valve, doesn't seem likely. Can't seem to find anyone else on the forum, (at least in recent years) with the same problem. No pressure checks yet. Any advice would be most welcome, Thanks.
Machine off should have swing brake applied (takes oil pressure to release). With that said, the swing motor contains the brake assembly. Perhaps a Bobcat familiar tech will advise if just the top needs to come off, or if the whole swing motor needs removed. Either way, the apply springs and/or wet friction lining need replaced. If it didn't swing drift with the engine off, the problem would likely be hydraulic. In your case, it sounds like a mechanical fault.
Yes, thank you, that makes sense. presumably, if the brake assembly is worn, then even having pilot pressure applied and released on the brake piston, (machine running), would show the same symptoms; which is the case.
Swing brakes have no wear. They only get applied when the house is stationary. If you machine has one, then you have something wrong. Solenoid valve stuck open, maybe someone changed the plumbing to the wrong place, possibly something broke in the motor. You didn't say how the swing works when you are using it?
I've seen broken Belleville washers on swing brakes in minis before. And, damaged lining in there before, too.
OK, both good points. First, swing motor parts breakdown, doesn't appear to show a brake pack, so worn components, belleville washer etc, seems less likely. To answer John C's question, swing seems to operate fine when running the machine, stops when joystick released, (although immediately starts to creep), can be inched slowly, no jerks ,shudders, or mechanical noises. So, looking at the suggestions so far, if a solenoid valve was stuck/bypassing, would that only occur in one direction? this problem is Bi-directional, so presumably something common to left and right swing. Would pressure readings give any clues? Not sure where to measure, or what the readings should be.
A solenoid would be for the swing brake which you apparently don't have. Does the swing drift either way depending on gravity or only one way each time?
Either way
Kind of sounds like either a loose motor or just a quirk of the machine. Do you have a hydraulic schematic for the machine?
Get a break down of the swing gear box that the swing motor sets into.
here's the Hydraulic schematic. Don't like the sound of a machine quirk! Surely other Bobcat operators don't have to cope with this? Noticed that there is a case drain filter on the return line; if this is constricted, could it have an affect on the swing motor?
Coming up; not a lot in there, what's you're thinking? Will lift the floor panels today and take a look
Check items 21 and make sure they don't have any debris in them that's hanging the seat up.
If you have a legend for that schematic, can you look up what number 46 is. It appears to be some kind of throttling valve. The system is closed center so shouldn't drift either way. There are two check balls in the motor itself. You can see them close to item 44 in the slew motor representation. Some debris holding one of those open might let the motor drift. Can you put the boom on the ground against something so the house can't swing and then try to listen for bypassing oil in the motor when you operate the swing. You might have someone in the cab that you trust and then you can listen with a stethoscope or a big screwdriver for a distinct hiss. You can do the same thing by listening with the engine off and the house drifting to one side. My guess in either instance is that the problem is in the motor.
OK, as good a place to look as any. Not today, 104degrees here right now! Thanks for the input. item 46 is listed as a compensator. I don't know what that is, but have a gut feeling that it's in with the spool valve blocks, if that's the right term. So far, since the problem seems to be in either direction, I am having a hard time pointing fingers at closed centre devices; however, my ignorance of hydraulic systems is legendary. If it was "debris" holding open a check valve, or anything else for that matter, I would expect a single ,directional problem, not bi. i am going to have to delve in, and check the port reliefs on the motor, Hyd. oil for contaminants etc. Am now awaiting new filters, pressure gauge test kit, and caps and plugs for the Hyd. lines. Since the machine is still operating, it's not stopping me working, but is more of a nuisance value, so will keep plugging away, and keep you all informed. Thank you all so far.
Either a check valve or a port relief can allow the drift in either direction but the check is more likely. The other possibility is damage inside the motor itself. The parts diagram isn't clear enough but it doesn't look like the motor is an axle piston type.
Well, I'll start with the simpler paths, and check the port relief valve readings, when I get the pressure kit; will keep you all posted, thanks to all, so far.
Good day folks According to the schematic this machine is devoid of a slew-swing brake I guess that Bobcat have a wide specification for slew creep maybe Gumboot has the spec. Kind regards Uffex