Komat'su PC60-7 --Just Purchased Used--Some Questions

skyking1 said:

The rail is the steel chain that you bolt track pads onto. You can still have rubber surfaced pads if you really need them, or metal grousers.
Here is an example link
https://www.mclarenindustries.com/u.../rubber-tracks-and-steel-tracks/00971/009878/

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I submitted a quote request on that site.
Is that a complete set of treads and chain, or just a chain?
I wonder if the tracks on my machine are almost 20 years old. If I simply replace them, I'll probably get a long use out of them as my usage isn't commercial and only an hour a day.

I spent an hour today dredging out my pond. Was shocked to find buried "treasure" under that muck. Ordering a rolloff to get rid of that this week.

https://gearflow.com/itm/angled-pad-rubber-track-300x52-5x74
Everyone else is asking in the thousands.

"Burn it bury it or both?". Is that a saying?

Mark A Weiss said:

I submitted a quote request on that site.
Is that a complete set of treads and chain, or just a chain?
I wonder if the tracks on my machine are almost 20 years old. If I simply replace them, I'll probably get a long use out of them as my usage isn't commercial and only an hour a day.

I spent an hour today dredging out my pond. Was shocked to find buried "treasure" under that muck. Ordering a rolloff to get rid of that this week.

Click to expand...

Mark A Weiss said:

I submitted a quote request on that site.
Is that a complete set of treads and chain, or just a chain?
I wonder if the tracks on my machine are almost 20 years old. If I simply replace them, I'll probably get a long use out of them as my usage isn't commercial and only an hour a day.

I spent an hour today dredging out my pond. Was shocked to find buried "treasure" under that muck. Ordering a rolloff to get rid of that this week.

Click to expand...

Mark A Weiss said:

https://gearflow.com/itm/angled-pad-rubber-track-300x52-5x74
Everyone else is asking in the thousands.

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It sounds like one of those "if it sound too good to be true it probably is" and "you get what you pay for" I am always looking for a deal but have been burned a few times so I get not wanting to spent a lot on an older machine for your own use. I would try looking for a used track. the one in the link scares me unless there is a local dealer or someone you know that has had experience with them, How could they be so much cheaper?

The track in the link is a much smaller track going by the numbers. You need 450x83. 5kx74 and the one in the link is 300x52x74

Oh crap. I searched on the right numbers but the first thing Google returned was the wrong size track!
These things are dang expensive and heavy!
At this point i may have to bail out and try to get my money out by selling to a cash buyer. I can't afford these tracks unless I skip the July property tax payment.
Where would I get a used track that's not about to break?

UPDATE: one vendor called me back with a quote on the steel growsers... $4200. vs. $6500 for rubber.
Only other problem is they can't ship til Jul 30. Machine would be down for 5 weeks.

Kobelco ireland said:

Try searching by track size 450x83. 5kx74.

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By dimensions, I found this on ebay:
https://www.ebay.com/itm/1740747077...EkhMMq2KO%2B83zs%2BL|ampid:PL_CLK|clp:2047675

Although it says it's for a PC78.

cheapest i could find in the first two pages of results, maybe if you call them they'll sell you a single track.

https://rubbertracksamerica.com/pages/search-results?q=450X83.5X74

Both tracks look like they are badly cracked and missing large chunks. I suspect that as soon as I change one, the other will fail. Tracks must be over 20 years old.
I found a pair on ebay for about 3850. I can pay with PayPal credit. 169 a month for 24 months.
But the more I think about it, the more I'd prefer metal tracks. I've put in a question and am still waiting for sellers response.

What kind of grease gun is powerful enough to tighten these tracks? I tried adding some grease to the adjusters but the handle on the gun stops dead. I have to squeeze with both hands but this us both very difficult as well as it feels the the handle may bend or break.
Also, it was impossible to uncouple the fitting/hose from the grease fitting by hand afterwards. Had to use a pry bar and pliers to pull it off!
They have electric grease guns but my gut tells me I need some serious power, not a harbor freight class tool here.

Might need to change rollers or other components to switch to steel tracks. Need to check that out first. You are finding out where the term money pit comes from. Be glad it's not a bigger machine.

The person I talked to at McClaren Industries about the metal tracks didn't mention anything about needing to change anything on the excavator to use them, but that's a consideration that never occurred to me.
I think I prefer steel tracks because there are a lot of little rocks churned up in the fill I am driving over. That may be a contributing factor to the breakage of the old rubber track. Metal tracks don't care--they just crush any rocks that find their way into the sprockets.

When I bought this machine, I figured I'd get a hundred hours of use before something broke. Instead the first problem occurred less than 4 hours into operation, and it's been a continuous chain of problems since. I was naively thinking that I could so a few projects less than 50 hours total and then resell it in a year or two. The previous owner fortuitously sold it just hours before major problems erupted.

Now I've got the task of finding a way to get this machine operational again, so it's not down all summer. I finally got it to the point where it's not leaking hydraulic fluid anymore. I've yet to replace the ignition switch (the preheat position won't turn in that direction and it's tricky to start the machine because you must pull the key out just a smidge to find the right point at which it will turn. Tracks had better be it for a long while. I don't like the idea of going into debt this late in life.

It seems that the pitch is different if using a metal shoe. The number 74 came up in number of shoes in this one. The next page shows the rubber shoe and doesn't mention anything other than width and shoe pitch.

Mark A Weiss said:

The next page shows the rubber shoe and doesn't mention anything other than width and shoe pitch.

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That might be because rubber tracks are not inspected and measured to determine their wear rate in the same way as steel undercarriage. Steel U/C has specifications and wear limits for everything. I would surmise that rubber tracks are more of a subjective visual inspection for damage.

Mark A Weiss said:

What kind of grease gun is powerful enough to tighten these tracks? I tried adding some grease to the adjusters but the handle on the gun stops dead. I have to squeeze with both hands but this us both very difficult as well as it feels the the handle may bend or break.

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Can you post a photo or two of the area around the grease zerk for the tensioner.?

This thread may be of interest to you. The problem is still unresolved but I would say whatever the fix is for that machine will be the same for yours - https://www.heavyequipmentforums.com/threads/track-adjuster-wont-accept-grease.89804/

Rubber bands will always fail because of cuts. I've yet to see a band removed because it is stretched out beyond the adjustment of the front idler. Most track bands have a steel catch that locks on the sprocket and is held in place in the band by the rubber and steel strands that run the length of the track bands. The failure mode is a cut in the rubber that exposes one of the steel cables and allows water in and corrosion to occur. Once one band breaks, the track starts to separate at that point increasing the tear and exposing the next band in a cascading failure. I've seen literature showing some brands using Kevlar instead of steel to elevate the corrosion issue. The most common cuts seen on bands are caused by running the machine parallel to curbing in a housing development. Those cuts to the sides of the bands are for the most part cosmetic unless they are so far into the side of the band that they expose a cord. The bands put very little wear on the other components of the undercarriage. Track bands in general can last into the 2,000 hour time frame of use with a good operator. Most of the machines that I have inspected for the Cat dealer over twelve years of employment seldom go more than 1,000 hours, again because of the operator or the type of use employed by the owners.

Switching a machine from rubber track bands to steel chain is not necessarily doable either. I've inspected some machines where the dimensions of the bottom rollers were not the same as a machine set up for rubber bands. The drive lugs on the bands may be too narrow for the inside flanges used on many brands of mini excavators. More than a few times I've been called onto a job site where a new band did't fit right. The solution more than once was to call in the ignorant sales rep and rub his nose in the problem to solve the issue for my client. Steel track with rubber block pads, in my opinion is a more cost effective solution to minimize travel damage to pavement and concrete. The rubber coating on the pads will cut and pull off but you are dealing with individual pads instead of track bands as a whole. This set up cost a lot more than the rubber bands but lasts many times longer costing significantly less in cost per hour.

Nige said:

That might be because rubber tracks are not inspected and measured to determine their wear rate in the same way as steel undercarriage. Steel U/C has specifications and wear limits for everything. I would surmise that rubber tracks are more of a subjective visual inspection for damage.
Can you post a photo or two of the area around the grease zerk for the tensioner.?

This thread may be of interest to you. The problem is still unresolved but I would say whatever the fix is for that machine will be the same for yours - https://www.heavyequipmentforums.com/threads/track-adjuster-wont-accept-grease.89804/

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This is on the left side of the house:



and this is on the right side:


The manual shows this procedure.. "if the grease cannot be pumped in, move the machine back and forth." I wonder if they mean to have someone operate the track with the side of the machine lifted, while attempting to pump in grease?

I got a better look at my tracks while I was out snapping photos of the fittings.
The track on the right must have been replaced recently. It has no small cracks in it. It does have one 2" break on the outer edge in one spot.
The track that broke however has thousands of small cracks everywhere between the raised parts of the shoe. It's got maybe a dozen deeper gashes in the edge. But the cracking looks like UV light damage. I've seen these cracks on tires on abandoned vehicles that have sat for more than 20 years. That track is probably original with 6100 hours on it, is my guess.
The other track seems much newer and is in much better condition.

Try removing the two small bolts, the keeper plate and the block. That will allow you to remove the "double nut" (arrowed) as an assembly which likely has a check valve inside it. Try installing the zerk into the assembly with it off the machine and see if you can pump grease through it. If it won't take grease then the check valve would appear to be stuck. You might manage to free it with some form of penetrating oil or paraffin.

They don't last 6,000 hours in any type of use. It is common to only replace one track when they break.

Nige said:

Try removing the two small bolts, the keeper plate and the block. That will allow you to remove the "double nut" (arrowed) as an assembly which likely has a check valve inside it. Try installing the zerk into the assembly with it off the machine and see if you can pump grease through it. If it won't take grease then the check valve would appear to be stuck. You might manage to free it with some form of penetrating oil or paraffin.

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By "keeper plate", do you mean the L shaped bracket that's there to stop the bleeder from coming off if the nut is over loosened?
From what I've been reading about these, there's some 15,000 PSI of pressure behind these nuts. From what I can tell from reading the manual, it is only the outer (large) hex nut that is supposed to be loosened (maximum of one turn) to let the grease ooze out.

I assume that this procedure is done AFTER the pressure is released from this cylinder. Then the bracket, nut and grease fitting come off. Do I understand that correctly? Is the check valve in the grease fitting itself? I looked at a video of how a grease fitting works and it showed a ball bearing with a spring behind it. The spring keeps the bearing up against the opening in the tip of the fitting, sealing it shut. Effectively, a check valve.

It looks like the outer nut is the one the manual refers to, and is to be loosened no more than one turn, to relieve the grease from the cylinder. The L bracket and both nuts come off to remove the whole assembly for inspection? Can't the Zerk itself be removed without taking it all apart first? Or is that a safety issue?

This cylinder operates at extremely high pressures and I want to be sure I'm doing this safely. People apparently have been seriously injured or even killed because of removing parts that were still under pressure.

The important question (for safety) is how to be certain these nuts are not under pressure before removal.