Why Triangular Tracks?

in-too-deep · Dec 5, 2012

Why are they better than plain old parallel
tracks like they used to be? Same amount of
track on the ground but more moving parts.
I'm missing something.

Old Roy · Dec 5, 2012

My guestimation is keeping the drive sprockets out of muddy areas less wear, and easier to clean.. almost self cleaning. Don't know for sure just my 2¢

NEBeef · Dec 5, 2012

(quoted from post at 19:41:19 12/05/12) Why are they better than plain old parallel
tracks like they used to be? Same amount of
track on the ground but more moving parts.
I'm missing something.

Yup, as said - keeps the finals out of the dirt some...

Bob M · Dec 5, 2012

Primary reason is the elevated drive sprocket ("high drive") is it permits the use of planetary gear reduction at the track drive sprocket. This results in a stronger the final drive. It also makes it easier to maintain. And since the finals don't help support the weight of the of the machine it lessens wear and tear on the finals.

The disadvantage is tracks can wear faster as they must move over a 3rd sprocket. Also track replacement is more costly because the tracks are longer.

Billy NY · Dec 5, 2012

You'll open a can of worms on some forums with that one.

I'm going to say that the older design, certainly well proven and in use, must have had a lot to be desired, (dead axle/final drive)

On the older caterpillar tractors, it required special tooling, high tonnage pullers etc. + a lot of labor to take apart, the newer design, I believe is more "modular", easier to take apart, trans is supposed to roll out. Also the weight of the tractor on the sprockets, shock loads and or similar, I believe was another motivating factor. Large mining operations and similar, putting thousands of hours on these, overhauling them etc. easier to work on, more service time, likely had some influence. In short, there was reason for the design, with benefit. They do have a production model, D7E that looks like the old design, I saw one on a lowboy a few weeks back, but I have no idea if its the same or similar final drive arrangement of the past.

I can only believe that the changes in design, back in the 70's was motivated by many factors as mentioned above in addition to a design that is easier to service, repair and overhaul.

There is a real old Cletrac crawler model with an elevated sprocket/triangle tracks, must have been ahead of their design.

Larry NEIL · Dec 5, 2012

Much easier to service and as Bob said a stronger final drive.
Mud , as long as the sand content is low is actuall a lubricant for the tracks. In my area our norm was 8K to 9K hrs on a set of tracks and due to proper maintanance and good clay MUD!
Did some projects northwest of us where all the gravel pits are and I wore out a set of tracks on a 955K in 2800 hrs.
3 things that absolutly kill undercarrige life are: Operatin g in abrasive soils, excessive travel speed and improper track adjustment.

Anonymous-0 · Dec 5, 2012

(quoted from post at 21:23:02 12/05/12) Much easier to service and as Bob said a stronger final drive.
Mud , as long as the sand content is low is actuall a lubricant for the tracks. In my area our norm was 8K to 9K hrs on a set of tracks and due to proper maintanance and good clay MUD!
Did some projects northwest of us where all the gravel pits are and I wore out a set of tracks on a 955K in 2800 hrs.
3 things that absolutly kill undercarrige life are: Operatin g in abrasive soils, excessive travel speed and improper track adjustment.

p, what Larry said

BIG RUH · Dec 5, 2012

According to Cat, it's easier on the transmission

Anonymous-0 · Dec 5, 2012

Travelling in reverse wears tracks faster and high speed reverse is the worst. Elevated sprockets on the larger machines allows for modular components that can be changed individually without having to tear the whole machine apart. There's also less shock load on the final drives with elevated sprockets. I think I read somewhere that track wear is about the same. There's always been a debate over elevated sprockets and if they are better.

RodinNS · Dec 5, 2012

The primary reason for Cat High drives was to get the sprocket up out of the danger zone where it could be impacted by rock, etc on the end of the track frame. A busted idler is cheaper to fix than a busted final drive...
Secondary concerns... high drive allows for an easier component layout in the transmission case. Those machines have a modular, planetary transmission that is easily serviced by pulling the sun shafts from the final drives and unhooking the input shaft... then undo the bolt ring on the back and the whole works slides out on a tray. So the machine is far, far easier to do major service on. IIRC, a Cat tech told me years ago that they'd have a 4H transmission on the truck in about 2 hours. You won't even hope to do that on any competitors machine...
Beyond that... probably not too many advantages. I find the machine to be nose heavy with a high center of gravity. However... it does also have considerably more ground clearance. That can be an advantage.... Personally I like high drive dozers. You're also seated up high and have good visibility.

Rod

RodinNS · Dec 5, 2012

The 7E is also a diesel electric machine... so that may require a drive layout that is not favorable to a highdrive design.

Rod

in-too-deep · Dec 5, 2012

All cleared up!

in-too-deep · Dec 5, 2012

Thank you!

MarkB_MI · Dec 5, 2012

Not too hard to figure out: In the old-style setup, each final drive had to support about one-quarter of the weight of the tractor. By moving the final drive above the axles, it only has to support a portion of the track weight. Everything in the final drive can be much smaller, and it can be engineered to handle very high torque loads without making compromises in order to handle radial loads. It solves a lot of engineering problems, it's easy to service and it's probably cheaper to make.

casecollectorsc · Dec 5, 2012

Also thought the hy drive kept the front of the crawler on the ground when pullin. Not as likely to rotate over backwards.

gbs · Dec 5, 2012

Bob M has the correct answer cheaper to build more expensive to maintain,one factor they try to explain away is how the rails&sprockets last longer using 1/3 the surface area to pull the same load

Offandgone · Dec 5, 2012

More ground clearance.

Winchester1 · Dec 5, 2012

I was told track life is extended as it does not have to make a 180 degree turn. Also if/when a final drive fails/needs rebuilt R&I is a matter hours vs days. Large operators overseas and dealers normally have rebuilt final drives on hand.
It has beed 20 years since it was explained to me but in an overseas environment with hand tools only a final drive failure was a nightmare.

Komatsu was coming on strong as a competitor then (have since faded) and Cat needed something to make their dozers different and better. Imagine marketing had some say in it too.

Billy NY · Dec 5, 2012

I saw the preview, and that one I just saw was the first one I've seen, the diesel electric & single blade cylinder were features that stood out, nice size tractor up close.

Anonymous-0 · Dec 6, 2012

The sprocket does not support the weight of the machine as it is higher than the bottom rollers on a conventional undercarriage. I doubt the high drive is cheaper to build or they'd still be making D4 high tracks.

RodinNS · Dec 6, 2012

The biggest problem with D4 high drives was their weight... You get a 12 ton dozer with a 9 ton engine... and the machine is capable of doing more work than the engine can push. It was more or less a crossover type machine in it's size.... in that it's too big for landscape work because it's weight tears the place to hell... but it's too underpowered to be be a serious production dozer for it's tonnage.
A lot of people, when they look at mine.... mistake it for a 6. Truly, a 6H was double this machine in power and tonnage... but this machine does about match a 5C/D for power and tonnage....
I think the main reason for discontinuing the 4H was that that crossover model has now become the 6m...

Rod

Billy NY · Dec 6, 2012

Obviously the load changes, per terrain. I can't say why the smaller D4 tractors did not retain that design, I've run several of both types. I do believe that depending on the use, type of work, terrain, the sprocket can take/transfer an increasingly heavier load, more impact and shock loads, one can only speculate as to what high use, high hour heavy mining and industrial applications does to shorten service life of the old design, compared to the newer designs. I do know what a a job it is to take one of these down to the bevel gear compartment, sprockets, finals disassembled, I can see why any change to make it easier to work on would be beneficial.

I think the real answer would have to be provided by CAT, this is an old change.

They had D5's in the mid 90's that were not high track design, and as of late or somewhat late the D3G, D4G, and D5G were not high track, each of those performed well.

One thing is for sure, sit in the seat of one of these and get a rock, something projecting, steep slope with same, whatever clearance the sprocket has from bearing significant weight can and will change constantly, especially in soils around here, unless you are taking clean level cuts each time.

oldtanker · Dec 6, 2012

I have a book on the history of Cat. The high track design was as started to make them more competitive. Cat started playing with high track sometime in the 60's to over come the flat tire peoblem on wheel loaders in the mines. It does make it easier to maintain and reduces wear on the sprocket/protects the finals from damage. The D4 didn't get it because of cost and weight issues.

Rick

RodinNS · Dec 6, 2012

The D4 certainly did get the high drive... they just discontinued it mabey 10 years ago or so.

Rod

scotc · Dec 6, 2012

Only if it makes it nose-heavy.

Anonymous-0 · Dec 7, 2012

They still make the D5 high track which replaced the 4H. The 3208 turbo wasn't the best engine. A non turbo at lower HP is OK because it's not pushing the limits of the engine. I know the early 953's with the 3208 turbo required engine rebuilds a lot more then the newer versions with improved engines. I think the 4H had the same HP rating as the 953.

Billy NY · Dec 7, 2012

I remember the first 4H I ran, had spent a lot of time on D3's before that, the latter was much more nimble, and the 4H was the limit for the tag trailer behind the single axle, + height, seemed like it was up there. One place we had a 4H or whatever model it was by then, not bad, grading and so on, but for topsoiling around new houses, was always a D3, or equivalent size JD, we had a nice new 550 JD was about '94 or so. I ran many D6D's, reliable, well built, but old school, I demo'd a new D6H LGP or whatever the letter was in '94, new from the lot, what a difference between it and the old D6D, we had 2 of those, brand new U/C's, totally rebuilt, could not compare it to that new D6. I also demo'd a D65 PX LGP Komatsu, against the D6, nice machine, first joystick control dozer I ever ran, company went with the Komatsu, D6 LGP would turn with a full blade in soft material, Komatsu would not, D6 LGP, could get through areas that the Komatsu could not, I put these side by side on that huge wet stockpile, I can remember being in it up to the fender on that new D6, and getting out, and waving down an excavator to free up the Komatsu on the same pile, both were excellent machines, I preferred the CAT, but ran that D65 after it went back. Komatsu took literature photos of me on it, I have a few random shots too, somewhere.

I can't say why the hi track would get out of the soft stuff a little easier, the whole pile was like running on a waterbed, would heave up on the outer edges, I always feared sinking in it, LGP's had 36" pads, unreal the flotation difference.

RodinNS · Dec 7, 2012

The 4H had a 3204T. It's been a good engine here.... Rating was 90 at the flywheel.

Rod

RodinNS · Dec 7, 2012

Most people either forget or just plain don't know.... but when those H series tractors came out their power and tonnage would replace 1 class above in the D series tractors. If you ran a 5D... the 4H was roughly the same tractor. The 6H would outwork the last flat 7 and so on.
That little 3D is mabey 16000#. Our 4H as it sits with rock guards and full sweep package is 25-26000 plus whatever mud it can carry on it's track frames... and that alone is substantial. I think for comparison a later 6C is only about 33K... but 130+ horse.
I'd have to go back and look at the performance book but IIRC, the 4H outweighs the 5D and certainly the 5C.

Rod

Why Triangular Tracks?

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