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Why does Caterpillar use high tracks?

Jim D

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Nov 11, 2012
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408
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equipment operator
I wondered if a high track has better leverage over the track its trying to move verses an oval track design ?

A long time ago, Cat had an explanation that went like that. They said that the articulation geometry of the high drive tracks gave better/more tractive effort pushing, compared to oval track articulation. (To me, if that is true, it means they give less pulling a ripper.) I don't actually know if the tracks pivot differently on a high drive.

They also said that the rubber suspended, rocking, track rollers improved traction. I have no real knowledge about that, someone else will have to say if it is true.
 
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nicky 68a

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Apr 14, 2013
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england
I run both,and John C has valid points that I side with.
Any extra costs with tracks or purchase of initial tractor are recouped over time with much lower costs on repairing them.Removing components and time spent on repairing them is massively quicker than conventional tracked machines,therefore,labour and downtime are reduced . Of course,you still have to buy spare parts for them,but with Cat,availability is second to absolutely nobody.They're also an abundance of other manufacturers making spares for them which helps keep the cost down if you don't ,or can't, use Cat all the time.
As I can't afford to replace my dozers every few years,there is only one option for me and that's Cat.
I do alot of final trim on batters etc,and I have no issues with hi drive tractors in the d4,5 and 6 range.
Only used 7,8,9 and 10 tractors for dozing,pushloading and ripping.I have never had a big hi drive on a batter,so can't comment.
As for ripping.......A hi drive is a no brainer
 
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alco

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here
Liebherr couldn't have timed it worse. They spent lord knows how many years developing this new model and then released it right at the point the open pit mining industry has literally taken the biggest sh1t in recent history.......

And there's the key Nige......they haven't actually released it yet. They've only built a few prototypes at this stage. The brochure is all still very preliminary. Who's to say when they will actually officially announce and release it.
 

Oxbow

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Nov 22, 2012
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Idaho
I noticed that on a sidehill application the C.G. of the whole machine is higher up, curious to get some
real world operator feed back if they are less stable.

I believe that despite the looks, the center of gravity is actually lower in the high drives vs. ovals. I know I am more comfortable on a sidehill with one. I like the visibility better as well, although Komatsu has redesigned their machines to move the cab forward which makes it comparable.

Regarding undercarriage cost I cannot speak from personal experience, but I suspect that the majority of big applications such as mines would use something else if the cost per hour, or perhaps cost per cubic yard was higher overall with a Cat than the competition. I also believe that sprocket segments on the mid sized dozers will last through two sets of rails, which I don't believe ovals usually do. I have not had to pay for these components myself though so I may be speaking out of my posterior and will submit to the opinions of those who have actually been involved in the purchase and repair of undercarriage.

Also, in my experience a D8R is much better balanced than a comparable oval machine and can back as steep or steeper than an oval machine if equipped with a ripper.
 

alco

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Trouble is Clete track had a hi drive LONG time ago before Cat.

If you want to do some digging, look up CL Best. They actually had a high drive around a decade before Cletrac, and CL Best was one of the founding partners that formed Caterpillar, so................
 

Dickjr.

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I believe that despite the looks, the center of gravity is actually lower in the high drives vs. ovals. I know I am more comfortable on a sidehill with one. I like the visibility better as well, although Komatsu has redesigned their machines to move the cab forward which makes it comparable.

Regarding undercarriage cost I cannot speak from personal experience, but I suspect that the majority of big applications such as mines would use something else if the cost per hour, or perhaps cost per cubic yard was higher overall with a Cat than the competition. I also believe that sprocket segments on the mid sized dozers will last through two sets of rails, which I don't believe ovals usually do. I have not had to pay for these components myself though so I may be speaking out of my posterior and will submit to the opinions of those who have actually been involved in the purchase and repair of undercarriage.

Also, in my experience a D8R is much better balanced than a comparable oval machine and can back as steep or steeper than an oval machine if equipped with a ripper.


I think it normally wears out two sets of segments to one set of rails. If the 8R doesn't have a ripper , then the oval track machine is better balanced and will back up a steeper bank?
 

Scrub Puller

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Mar 29, 2009
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Gladstone Queensland Australia
Yair . . .

A bit off topic but this issue of tractor "balance" I think is a little misunderstood.

Sure, a tractor can work and be productive with out some weight on the back but what a joy it is to have a properly set up machine.

Now, going O/T even further. On You-tube I see these large new fangled dollyless scrapers hitched straight to the back of (say) a D8.

In order to keep a bit of balance they leave the blade on and even then at times I see the thing is struggling to turn . . . what a bloody wank.

If they dropped blade off and got a dolly on that scraper the thing would come to life.

I believe bladeless direct drive tractor with the idlers set high, hooked to the right sized dollied scraper with a good operator would lose some of these doughy modern rigs in it's dust.

To take this a little further I watched a clip (can't find it now) of a tractor running on a bloody haul road . . . they seem to have forgotten you fall off the pile or bank as soon as the scoop has dumped and scramble out of the cut anywhere you can.

Cheers.
 

Oxbow

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Nov 22, 2012
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Idaho
I think it normally wears out two sets of segments to one set of rails. If the 8R doesn't have a ripper , then the oval track machine is better balanced and will back up a steeper bank?

I see your point, and I obviously worded that poorly. I have never run a D6 or larger tractor of any kind without a ripper, at least since the era of 9U, 3T, 17A, 2U, and 19A dozers that I have run; no, the 19A did have a ripper on it I think (tekoa maybe?)

Come to think of it, with the high drives having the dozer closer to the front of the tractor, I believe that they have felt better balanced to me than say a D7G or D8H, which have always felt nose heavy, and would certainly climb steeper going forward than reverse. In my opinion the high drives were a little more equal as far as how steep they would climb forward vs. reverse. I have not had the opportunity run them next to comparable sized oval tractors to compare though, so I may be completely wrong (as has happened many times before).
 

Oxbow

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Nov 22, 2012
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Yair . . .

A bit off topic but this issue of tractor "balance" I think is a little misunderstood.

Sure, a tractor can work and be productive with out some weight on the back but what a joy it is to have a properly set up machine.

Now, going O/T even further. On You-tube I see these large new fangled dollyless scrapers hitched straight to the back of (say) a D8.

In order to keep a bit of balance they leave the blade on and even then at times I see the thing is struggling to turn . . . what a bloody wank.

If they dropped blade off and got a dolly on that scraper the thing would come to life.

I believe bladeless direct drive tractor with the idlers set high, hooked to the right sized dollied scraper with a good operator would lose some of these doughy modern rigs in it's dust.

To take this a little further I watched a clip (can't find it now) of a tractor running on a bloody haul road . . . they seem to have forgotten you fall off the pile or bank as soon as the scoop has dumped and scramble out of the cut anywhere you can.

Cheers.

Scrub, in 1976 I was running a little JD 450 cutting curb and sidewalk grade in on a subdivision in Bellingham, WA. The contractor that had done the bulk of the earthwork was finishing up and had one cat and can left on site. It was a direct drive D8, perhaps a 2U, and the operator and I would visit during lunch. I was young and trying to learn all I could, and he was near retirement age and enjoyed sharing his knowledge and good tales.

There was one moderately steep side hill that he would come across after leaving the cut in route to the fill, and for some reason at about 3:00 every afternoon he would manage to lay the scraper over on it's side, at which time the spool of cable on the rear of the scraper, which did not have the big wing nut to hold it in place on the rod, would cascade down the rest of the slope. He would then recruit me to help him get the scraper back on it's wheels, and to gather up and rewind the cable back on the spool, and get it hoisted back onto the scraper. Fortunately there was no more than about five or six wraps left on the spool, so it wasn't a big chore.

He did this almost every day that last week he was there, at about the same time, and I have always wondered if it was purely accidental. The older I get, the less I think so!

Sorry to hi-jack the thread folks.
 

catsparky

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Jan 26, 2008
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1
Location
all cal
I know this is an old thread but speaking of high track how do you think the new Liebherr high track will do . I know in the US they don't have a big dealer network but this could maybe be a game changer ? I ran a 721 about 8 years ago and not a bad machine but a high drive hystat ?
Just like to hear what you might think how it will be .
 

RonG

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Dec 2, 2003
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Meriden ct
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heavy equipment operator
You know,for an old fart that spent so many years on a dozer it is a joy to read the input from others about the different views they have on the different concepts encountered over the years,and yes,I can still learn something.Don't forget,I started in the army as a teenager at heavy equipment school at Fort Leonard Wood in Missouri and then on a TD-18 for my three years in Germany which I have documented here with many pictures over the years.I have been involved in most aspects of earth moving ever since my army days and now since I got sick and can't do it any more but I can still learn.Keep it up guys.Thanks,Ron G
 
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Willie B

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Jan 2, 2016
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Mount Tabor VT
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Electrician
I'm guessing here.

In reverse with oval drive design worn chain tends to lift off the rear driving sprocket so the primary driving tooth carries the track chain bushing at its tip. The discrepancy between chain bushing spacing, and sprocket spacing won't transfer any work to the next tooth until the first bushing is well up the first tooth. As the next tooth approaches, it'll touch the tip to the bushing until the preceding bushing slides down into the gullet between teeth. There's a lot of steel on steel sliding with only tangential contact, lots of pressure on a tiny area of contact.

With high drive, the angle of approach changes somewhat to take some of this wear in reverse, and convert it to forward wear. Also some of the abrasive material falls away before reaching the sprocket.

Shaft seals & bearings must last longer if isolated from some of the mud and snot.

Pitch, or spacing is always different between sprocket, and chain, might having fewer gullets engaged at one time reduce wear caused by this discrepancy?

Sticky snow or mud pack into the gullets of a sprocket effectively enlarging the diameter of the sprocket, and fouling the shape of the gullet. With high drive the chain gets some opportunity to lose some snot before engaging the sprocket. the bottom of the sprocket has an opportunity to dump the snow before it engages again with chain.

A 100 ton crawler exerts considerable shock load dropping off a shelf. If the drive axle bearings, and shafts must carry this shock, that can't be good. Undercarriage replacement is considered an operating expense. Crawlers cost a lot to operate. Final drive failure is a bigger thing.

It'd be tough to compare wear. It seems really big crawlers are placed in more abusive conditions than smaller ones less likely to have high drive.

There's the old story of a doctor, lawyer, and engineer out hunting. They get lost, a storm comes up, and they take shelter in a cabin. The wood stove they find is 3' off the floor. They theorize why the obviously brilliant owner did this. One thought health advantages, one thought safety improvements, the third thought efficiency.

The owner arrived in time to clear the matter up; "I didn't have enough stove pipe."

Willie
 
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D11RCD

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Aug 20, 2008
Messages
163
Location
Australia
Occupation
Diesel Mechanic
Heya folks,
I've been curious about this for quite a few years now so I've spoken to many people about as well as having read up on the issue. Incidentally we are doing transmissions systems at TAFE and so I have access to quite some literature regarding this exact topic. Here's my 2c.

The main reason is that a high track machine's final drives are isolated from impacts and shock loadings, improving final drive life. Additionally the final drive unit is not rolling around literally "in" the dirt/mud/dust. Because majority of our contaminates in earthmoving enter through seals etc it makes very good sense to lift this component up and have it out of the dirt. Again, less wear is the goal here.

Secondly, when we consider the machine's balance (ignoring blade and ripper, and only taking into account the tractor) the main machine weight is over the tracks, not on the rear. This gives significantly better traction (allegedly, I'm a fitter not an operator). Obviously if it had a giant blade and no ripper it would be forward heavy, or a giant ripper and small blade would be rear heavy. Common sense prevails- balance the weight of your blade with something on the back. Furthermore the track frame can then be extended forward of the machine, rearward or both depending on the configuration. XL configuration has the front idler more forward than standard, XR has the rear idler extended rearwards and LGP has the idler in the same position as XR, while extending the front idler further than even the XL configuration. Because you can't shift around the final drive of an oval track machine this gives greater "from factory" customisation.

From a serviceability standpoint being able to remove the transmission through the rear is certainly an advantage worth noting. Any way to improve serviceability is always going to save money in the long run over a machine's lifetime. Does this outweigh the additional undercarriage wear from having two idlers? That's for the bean-counters to figure out but we must keep in mind that a high track machine has more track plates to spread the wear around. Personally I cannot understand seeing any high track without a carrier roller but they are around... All that does is increase the track wear as it whips over the large space, especially at higher tractor speeds.

From a physics standpoint we would lose some power because an oval track is pulling the track over itself in the same plane as the track is driving the ground. A high track is pulling it around and idler and then to the ground on a different plane so it's impossible that some energy isn't lost.


I hope you all find this interesting, I've always wanted to be able to contribute to this sort of discussion :) If you want me to post pictures of some of the diagrams and paragraphs in my texts then I'm more than happy to oblige :) Peace!
 

steve smit

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Nov 23, 2017
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australia
just b difrent there all show haha na supose to keep the final drives outa the mud and rock ther alright but hard riping tuff going komatsu out do a cat any day
 

Randy88

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Feb 2, 2009
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D6's are the norm in my area for size, when the high drives came out, most old timers then refused to run them, the complaint list was so long, if anyone actually wrote them all down, it would be a very large book to say the least. Mainly those young enough to change got used to them and after the old timers all faded into memory, the sales picked up and since CAT offered nothing else, you could say take it or leave it sort of philosophy, you could say sales of high drives rose steadily?? verses what, selling nothing at all??

I've ran both high drives and oval's, never saw firsthand all the benefits CAT has shoveled all these years, even after telling me how much better they are so many times I could retire several times over if they'd have paid me a dollar for every reminder of the benefits.

If your running the machines daily, year in and year out, thousands of hours per year, those benefits might work out, for me who own and run many machines with few hours per year on each in the overall scene of things, I'd do a transmission and finals maybe once per machine in my lifetime, the disadvantages outweigh the benefits ten to one.

As for other makers building high drives, first off the patents ran off years ago, as in decades ago by now, and yet only a handful of prototypes have been put out and not many went beyond that point, which speaks volumes to many us.

Next is, if all these benefits are note worthy, why isn't every machine Cat makes, high drives including hydstat's in the smaller dozers, don't those machines have finals and motors as well that deserve to up out of the mud, muck and filth?? Wouldn't changing finals on those machines much better if they were up top verses down in the crud as well?? Or in the bigger picture wouldn't they be able to compete in the price of dozers and lose sales??

But above all else, lets not forget the famous, bragged about, trend setting, setting new horizon's, leader of technology to set the norm for centuries to come, of the great, slow speed high torque diesel engines on dozers?? Which also never went over industry wide, only to flop and fizzle out and now ever CAT's people say to not buy a dozer with those in, the repair costs are too high and parts are getting scarce, etc, etc, etc and not one other makers ever got on board to mass produce those style of engines or dozers with them in, but at the time, it was all the rage and a CAT exclusive..............much like high drives.................question is, will they do a better job of keeping the high drives alive over the old slow speed, high torque engines of years ago. But then again if I recall, after all the bragging is done, CAT is no longer in the over the road engine market either, leaving all those die hard truckers to wonder what happened to the best maker to ever build engines only to refuse to sell them to those same folks who spend their entire life bragging about them, to buy and run something else and where is all the bragging now of the industry leader?? those trucks run just fine with cummins, detroit and now many others doing the leading.

But I guess when you quit making engines for the over the road market, that's the time to build a truck, powered with an engine that can meet emissions and bought from a competing company of CAT to power that truck.........but I know, I should just shut up and leave it alone, after all, CAT is the leader of the industry, and also the first the get out of those same self trend setting trends, did I hear and see CAT now makes an electric oval track machine?? where's the high drive on that, electric motor in the mud, much and filth, now that makes perfect sense..........to CAT, doesn't that machine have finals or do the tracks fasten directly to the motors, where are those bragging about all the track benefits of the high drives for the electric dozers?? But above all else, do the electric's start better in frigid weather than those famous slow speed high torque Cat exclusive engines of years gone by. And to think I can't order a brand new high torque low speed diesel in a new D6T, such a bummer, after all I was told of the benefits of those engines over the years, couple that to a high drive and I'd have thought, it would be an ideal dozer, the best of all worlds, both high torque low speed engine and high drive.

But to answer your question, I think it gets down to a company trying to sell machines with their designs built into it and its up the customer to decide if those benefits are worth it or not is about the jest of it.
 

Welder Dave

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Oct 11, 2014
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Canada
I think despite what anyone thinks sales numbers don't lie. Cat has the market share whether their machines are better or not. Another big reason why is Cat has the best parts back up and availability. It's not like their customers have bought a high drive, hated it and went to something else. There's a lot of repeat sales of high drives that are often more expensive than the competition. From my understanding Cat doesn't make the smaller dozers in high drive because they are more expensive to build/buy and aren't used in the same type of conditions as the high drives. You aren't going to be doing heavy ripping with a D4. Komatsu, JD and others have good machines too but Cat doesn't have the market share because users don't like their high drives. I was reading the history of the D10 and I think the 1st prototype was in 1970 so they didn't exactly rush it to the market.
 
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