Who wants to settle a dispute? Komatsu PC 220

I have posted before regarding a problem with a PC 220-5 Komatsu having a slow tack. By slow track, one side does not pull as well as the other, especially under load or on an uphill. It is fine on flat ground. No problems, it walks fine.

After following a number of suggestions and replacing seals the problem persisted. We noted that the front rollers seemed to have to much vertical play so we took them off and found that the guide plate were worn out. That is the guide in which the front roller moves backward and forward under the spring preload.

There was a 20 mm gap on one side and a 10 mm gap on the other

The solution was to weld on plates to the roller supports and take up the slack which worked fine, except it made sense to build up both sides of one and one side of the other and then swap them. Left one on right side and right one on left side.

The result was a snug fitting roller on both sides, except the rollers were now on opposite sides.

Guess what, the slow track has swapped sides.

So the current dispute is regarding the roller, one party suggests that get the roller rebuilt and the problem will go away and the other party suggests that there is still some other problem

Anyone want to throw in their two cents worth?

cheers

You been drinking?? Seriously, not to be Captain Obvious here, but if it switched with the idler swap, you must have a bad bushing.

I honestly don't see what effect swapping the idler would have on travel power unless the idler was partly seized which you would probably notice with the head it would generate. If the bushing was worn to the extent that it affects travel then it must be totally collapsed. Is the track tension the exact same on both sides?

Points to note, neither party disputes the roller needs rebuilding
The machine walks perfectly on flat ground
The collapsed roller is not visually noticeable
Both tracks are correctly tensioned and tensioned the same

The argument goes that if the roller is badly seized why does it walk ok on flat ground , why does the problem only occur when turning it on a slope.

So one argument is there is something else wrong .

We will get the roller rebut and find out soon enough

Yair . . . . d4dozer

A couple of issues.

First off it is industry standard to refer to the rotating assemblies that carry the weight of the machine as "rollers" the rotating assemblies that carry the weight of the tracks as "carrier" or "support rollers" and the rotating assembly that slides on the track frame is properly referred to as an "idler".

If you stick to this nomenclature it saves confusion.

Now, when you say your idler needs "rebuilding" do you mean the bearings/bushings are seized or collapsed or do you mean the shell is worn and requires building up with weld?

I am not being smart azz, I'm just pointing out that there are folks on here who can really help and save you money and headaches. . .you need to speak their language though and, as always, pictures always help.

All the best with it.

Cheers.

Not seized yet, just dry as a bone and probably the thrust flanges are grabbing in the turn..... the combination of the slope and added drag probably exceeds the avalable drive torque. Just keep running it, the idler wheel will start clanging soon!

Sorry about terminology,

The idler looks ok, so it must be the idler bearing or bushing that needs replacing.

I don't know what you have done to the machine outside of what you describe in this thread, but when it is working properly and the pumps are balanced right, no one would be able to tell if an idler was dragging except by the noise it makes. The engine and pump combination is simply powerful enough to drive the chain over the idler without it turning at all. It would make a heck of a racket though.

On those machines a drift on one track frame under load, say traveling up a hill, in both directions indicates a weak travel motor or a pump slightly behind the other in output. A drift that changes sides, say from the right side track to the left side when traveling up a hill the other way, indicates a swivel leaking. A Dash 5 machine is likely well over twenty year old and unless the unit has been rebuilt, and even because it was rebuilt, you are very likely to find lots of worn internal components that will makes lots of odd and maybe even exciting things happen.

John C. said:

I don't know what you have done to the machine outside of what you describe in this thread, but when it is working properly and the pumps are balanced right, no one would be able to tell if an idler was dragging except by the noise it makes. The engine and pump combination is simply powerful enough to drive the chain over the idler without it turning at all. It would make a heck of a racket though.

On those machines a drift on one track frame under load, say traveling up a hill, in both directions indicates a weak travel motor or a pump slightly behind the other in output. A drift that changes sides, say from the right side track to the left side when traveling up a hill the other way, indicates a swivel leaking. A Dash 5 machine is likely well over twenty year old and unless the unit has been rebuilt, and even because it was rebuilt, you are very likely to find lots of worn internal components that will makes lots of odd and maybe even exciting things happen.

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Not looking to disagree, but I'm going to assume D4 knows the difference between the right and left track. He mentioned changing seals did not fix the problem. So, D4, first things first. What seals were you referring to? My thoughts are if you really want to get to the bottom of this, you are going to have to verify that you are getting proper pressure and flow to the drive motors. If the problem switched sides, however, my guess is it's not a hydraulic issue. Unless BOTH your pumps and/or drive motors are shot. If they are (also, I bet your rails are in awesome condition, too LOL) it wouldn't be too surprised if a little bit of tough going along with a dry idler could cause it to pull. JMO.


Edit: Tracks can be funny. The old 1080B I used to run was really weird. The first couple moves of the day, one track would have almost no power. Until you went the opposite way. Then, rock on. Sometimes the left, sometimes the right. Never knew which until you moved.

I want to put test gauges on and measure the pressure at the pump, (we were about to do this but the fittings had the wrong thread) The argument that is put to me is fix the idler and all will be OK, I say lets check the pressure, I cant see any physical problem with the roller but also cant explain why the problem has swapped sides......I would have thought that if the idler was binding, it would also bind on the flat as well as on a slope - plus I can imagine that the hydraulics should have the power to overcome the intermittent binding - even if it grunts and groans

We went over the machine an replaced all seals that were weeping at all. The swivel seals were not replaced.

The drive motors were also inspected, all looked ok BUT NO pressure tests. (Not that I know how you would do that - plus I was not there when they were taken apart, but told they were all good)

But I think the pressure test at the pump is the first thing,

So why did I post this? Because I think to go out and buy a new idler or have it pulled down and rebuilt will not fully solve the problem, but it is hard to tell other people what to do when they are helping you. I would like to get it right once and for all and I will fix the idler, but I need to be convinced that it is seized or worn out because it is ok on flat ground and does not move up and down now the guides are fixed.

If you could have turned the bearing shafts by hand when you had them out, there was nothing wrong with them.

Case drain tests need to be run to check the efficiency of a motor. Just taking them apart and putting them back together usually doesn't tell you anything. The swivel or rotary union in the center of the machine is the usual problem that you are describing. The seals deteriorate over time and use and will present many oddball issues like what you are describing.

It takes four gauges in total or two per pump to check system pressures. You have to do specific things with the machine and read the pressures at those times and then interpret what you are seeing. One gauge on the outlet of each pump will be helpful to a point but will not tell the whole story of the condition of the systems.

Excuse my ignorance, but what is a case drain test?

d4dozer said:

Excuse my ignorance, but what is a case drain test?

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If you check out the hydraulic lines to the travel motors you will find that there are 4 of them if your machine has single speed travel or 5 if it has 2-speed. The 2 largest ones will be the same size and are the ones that supply & return oil from the motor in forward and reverse, the 3rd is a small line that is pressurized to release the parking brake, the 4th is the line that is pressurized to activate the 2-speed travel, and the last one is the motor case drain line which goes directly back to the hydraulic tank. All piston-type hydraulic motors (or pumps for that matter) leak internally into the pump/motor casing, therefore they need a "case drain line" in order to get the leaked oil back to the tank. The amount of oil flowing from that line is an indication of the condition of the internal parts of the travel motor in your case.

If there are any specs for it the case drain flow can be measured, otherwise the only way is to compare the quantity of oil that runs out of the case drain line in (say) 1 minute while the motor is on full load in a given speed, doesn't matter if it's low or high so long as both motors are tested the same way.

My 2c. On a machine this old I would recommend resealing the swivel as a first step, especially if you have no knowledge whether it's been resealed recently if ever. If gives you a chance to evaluate the "iron" parts in the swivel while it is disassembled because sometimes over the course of years weird things happen to the housing and/or the spindle that cause all sorts of strange travel motor issues. It's a relatively simple process and enables you to remove the swivel from the list of possible root causes of your travel problem. Remember that every one of the lines I mentioned above has to pass through the swivel to get from the upper frame to the travel motors. In total for both sides there should be 7 different oil paths through the swivel - 4 for the main motor propulsion lines on both sides plus 3 common lines for brake, 2-speed, & case drain.

Thanks Nige

That makes a lot of sense. I will get the swivel gone over as the next step. I climbed under and it is not the easiest thing to get to...... I will hold of the case drain test until after the swivel has been serviced.

Could be as simple as a hose that is partially collapsed on the inside limiting flow to one track.

Not sure if this is relevant or not, but I worked on a PC200-5 that was traveling very poorly and was pulling to one side. Turned out to be the cables from the levers to the travel valves were out of adjustment and were not pulling or pushing the valve spool fully. The owner thought his hydraulics were shot, so it was a cheap fix and it worked like a charm afterwards.

From all the suggestions that have come out so far it's obvious that there is a world of possibilities that could be causing this problem, but they have to be gone through in a logical way.

Thanks thebaz - yes checked that one through, spent a bit of time getting it adjusted perfectly, but it made no difference. I will try again next weekend, I gotta fix it!

Now that is a different thing than I've seen in that model of machine. All the Dash 5 machines from PC200 on up that I've worked on had pilot controls for the travel functions. Does this machine have chicken leg control levers on pedestals and not the short levers on the arm rests?

John C. said:

Now that is a different thing than I've seen in that model of machine. All the Dash 5 machines from PC200 on up that I've worked on had pilot controls for the travel functions. Does this machine have chicken leg control levers on pedestals and not the short levers on the arm rests?

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There are two foot pedals with levers so you can use your hands or feet, want a photo?