Ok. I know this is an OLD argument. But it has been forgotten for some time. I would like to debate for the sake of understanding. Please open your mind and try to understand what I will write here. I will write it as I think it the best I can...with all the errors in spelling and grammar. Here goes: The caterpillar high drive dozer design. Obviously, in comparison to old oval track designs...it has many advantages. These advantages would be most noticeable in steering clutch and diff-steer machines right? It might have advantages possibly in HEAVY hydrostatic dozers but not so much in compact light hydrostatic dozers right? IF we examine the advantages of hydrostatic dozers and the lack of transmissions...then we get into a loss of the rear tray removable transmission advantage, correct? (Most current hystat dozers are oval design) Why are most hystat dozers oval? Cost? DO HYDROSTATIC DRIVE DOZER SYSTEMS LAST AS LONG AS TRANSMISSION/STEERING CLUTCH SYSTEMS? OR LESS? DO THEY LACK BRUTE? BUT GAIN AGILITY AND SMOOTHNESS? I can see the if a large company has a fleet of dozers out on a huge highway project. It is VERY handy to be able to pull up next to a high drive dozer with a service truck and inspect final drives....slide out a transmission from the rear without removing the cab and slide in a reman unit..... etc.... And also...is the extra track links....extra pads, extra idler, all really worth it? does this depend on whether or not you use your dozer for extreme conditions? Owner operator versus fleet? The downtime of tearing a final drive down and cost of loss of time on job? And, how many years and hours you want a dozer to last and be rebuilt over and over? Obviously a small time owner operator can't afford a new d6t at 400 grand versus an older oval track dozer. I mean...if the average d6 gets $150 per hour..how in the hell could anyone afford to buy that sucker and work it by the hour and pay the payment. An old d6h or d6d or whatever in good shape would be most profitable right? But if you run the holy hell out of a d6t on a huge project that has a time objective(production goal) larger than the concept of an houry rate...get the d6t cause it has more balls and speed than the old d6d..... Is it kinda like the idea of a rebuildable engine versus a throw-away motor? One has liners and the other has no liners and has cavitation thus ruining the block? Is the high drive sorta like the rebuildable engine with liners? etc? Well...the rebuildable motor might weight more...and throw away may be lighter and cheaper with its obvious advantages too.... If we think about how each track may be powered by a hydraulic motor...wouldnt the rear (imagine no trans) access design advantage make it beneficial in accessing the hydraulic drive motors as well? The benefit might be hydo motor service without removing the cab(or tilting). And, main pump access beyond that where a transmission might normally reside. And all the usual advantages such as keeping the final drives out of the dirt and shock load. But then....wouldnt there be less GEAR whip-like pressure on a final drive with a hydrostatic powered final drive than a steering clutch or diff-steer dozer? We could take this one step closer and imagine a high drive design ELECTRIC drive dozer similar to the new d7E. Why didn't CAT combine the high drive with the Electric drive? Cost? Or, will they do that in the future once the prototype testing with customers stage is on down the road? If we back up in the time machine of these systems...and compare two dozers. Let's say.....a CAT d5g and a CAT d5m. Obviously the d5m is a little bigger, heavier and will push more in a straight line. But let's imagine they were the same weight, size, and horsepower. Lets just imagine that they are doing the same job...all things the same except the track drive system. I would personally imagine that the d5g would seem to do finer slow finish work in tight precise areas with the hydro system. The d5m would have an advantage in lasting longer in rough material....but being a little more fidgety with the controls in that it was a steering clutch design right? So, one trade off for the other? Is the d5m the better deal or the d5g? Will the d5g last as long if we imagined these dozers to be the same weight and horsepower in the same job setting for 20 years? I would compare a komatsu or deere whatever....but I want to not focus on brand name...but rather the high drive versus oval track design in relation to current drive systems....versus what the future holds. If we go by what we see in the D7E.....is CAT saying that a new d11 with electric drive will not need a high track design? It just seems to me that the lighter the dozer...the less necessary it is to have a high track design. Right? I mean....super huge dozers are for quarries and mega-shift hour crunching work. Smaller dozers are lasting way less hours than a d11 that is rebuilt over and over in a quarry. The weight of the heavy dozer demands more extreme final drive and track design than that of a small finish dozer. Right? The small dozer generally pushes lighter material over its lifetime and yet the same hardness of steel is used in a d5g than that of a d11...... Is the defining variable that we are looking at; the weight/density/of soil and rock, gravity pressure(weight of machine) on tracks, factored by time? Think about it this way and this is hard to convey in writing.... The strength of steel that Cat uses in undercarriage and sprockets and rollers and bearing etc.....is it the same for a small dozer as it is for the biggest? If this is true....the more power you add...and weight....yet the soil and rock will always weigh the same(imagine that the job for the small dozer is the same as the big dozer)....the more stress steel has to endure. If this is true....then undercarriage and track design matter MOST in heavy dozers. It is not as important in small dozers. I know that small dozers cost less...because they are smaller. Large dozers cost more because they are larger. But also....Large dozers are exponentially stressing the steel more then the smaller dozer if we imagine that the same hardness of steel is used for small and large dozers. Even if you have a grouser on a track that is 4 inches thick for a d11 and 1 inch thick for a d3......the steel may be the same hardness. Thicker doesnt mean harder when considering abrasion. It only means that there is more material to be sanded away over time. The thickness only buys time (at the loss of money)against the increased horsepower and weight. If Caterpillar says in the future that in a d11 with electric drive that the electric motors provide smoother shock free propulsion of a final drive....then the high drive was only beneficial against the ground shock load. Not the driveline shockload. Yet, a big question remains at the present time....why does it seem as though cat D11 dozers seem to last twice as long and hold twice as much value over something such as Komatsu d475? I mean...is it only because CAT designed a better over all dozer and komatsu has crappy quality control over-all? Or was it MOSTLY because of superior design with emphasis in the high drive system? This is where brand name might come into play here....the typical argument will ensue about CAT versus Komatsu. But hey.....Let's imagine Komatsu was on equal quality level with CAT yet the Komatsu chooses oval track and Cat chooses high drive. What wins? And considering all of this....Do we want and need high drive electric and hydrostatic dozers or is it superior to really use the old oval design?
G'day Mountainmover! Seems to be that this is a great conversation that gets ruined far too often. If you consider the undercarriage alone then I don't think that it is a very clear decision either way. The oval track has some advantages, and the high track different ones. I know by this point that both of these setups work very well. Having worked on some of the Cat high track dozers I did notice that the steering pump, implement pump, and a ton of hoses all live right under the cab above and behind the engine. I haven't had the chance to work on an oval track and get a good view of how it all fits together but I wonder if the way Cat's differential steering works regarding the location of said steering pump (correct me if I am wrong but I have been led to believe that it's different to the other brands) necessitates a little more space. That said, everything being in that layout may be because of the high track arrangement so I might be backwards. As Cat is the only company selling high track dozers I am using them as an example, although worth noting, I see a lot more Cat dozers than anything else out here. This is a D6K with hydrostatic drive and you can see that if it was diff steer then the pump I mentioned would be above and behind the engine- and inside the cab. I don't have an image the same with a high track diff steer machine that shows the location of the transmission and steering pumps, if anyone has one please post it! Above is the D7e and the electric drive clearly doesn't need heaps of space to work which is one of the advantages of it I've been told. It looks to me like it is significantly more compact (and therefore road transportable) than a high track machine like the D7Rs. As for the shocks to the final drives debate goes I believe that high track is far superior. That part makes the most sense out of everything but I don't think it is the only reason behind the decision to go high track. I have heard that oval tracks push harder, but I can't think of a solid reason why. Possibly because there are more teeth of the final drive in contact with the track at a given time, or maybe because the drive is in the same plane as the track in contact with the ground. I'm still getting my head around how all the machines fit together so correct me if I'm wrong anywhere, but that's my 2c for now :tong
Thanks for the reply D11RCD! I get what you are saying! One basic advantage that I failed to mention in my initial post was the shedding of mud. It is great to be able to shed mud in the big center open area above the roller frame of a high track design. I hate the "packing up" of mud on an oval design dozer. It seems to really wedge in there on oval track dozers. Also, the fall of mud and debris from the high sprocket and upper track angles gives the clods of dirt more velocity to split and fall off of the triangle shape roller frame covers. The win on this goes to the high track design. And, it is very easy to shovel out the mud on a high track dozer which becomes important on a daily basis. I would think that a high track d7E design would be superior in some ways? Maybe it was initial cost when bringing a production prototype to the market. Cat might have not wanted to drive the cost up on the first electric model. They may have assumed that most d7 sized dozers were less likely to run in swamp and LGP conditions anyway right? That market is usually d6 size and smaller? I also prefer a high track design when back up a slope. I love how the rear idler seems to protrude past the rear of the machine. Or so...it seems this way.....giving a longer footprint. This feels as though it assists in giving more track against a rear slope than rear fueltank sheetmetal. It would kinda like be having a jeep that the rear tire protrudes out further than the rear bumper. Perfect for backing up steep embankments without hitting the rear bumper first. I would think that the higher cab placement in a high track that sits slightly over the engine gives a more centered position that takes out many of the bumps that hammers an operator right? And gives better visibility. It seems that the new komatsu dozers that copy the old euclid rear radiator design is taking advantage of more visibility in the front and more forward placement of the cab(near center). I would think that Cat would optimize the high track design by using it with the electric drive. Or, the hydrostatic designs. But......do hydrostatic dozers last longer than steering clutch or diff steer dozers? Which one can last more hours? Do the drive motors go out quicker than the steering clutch systems? I would think that the repair cost of clutches versus a hystat drive motor would be lower. And then the pump...but then go back and figure the cost of a transmission and well....where are we now? It seems that smaller equipment benefits from hydrostatic systems and larger equipment benefits from steering clutch design. But somewhere in the middle diff steer fits in how? I would imagine that electric drive motors still have to have outer support near the sprocket that would be called a final drive. Wouldnt the advantage to accessing this be in favor of a high track design? I have always heard that final drive repair can be made without even breaking a track but i am not sure. I have never repaired a final drive on a high drive dozer that i can think of.......And electric drive dozers are tooooo new to know. I would think that pulling the electric drive motors out the rear on trays with a high track design just as you would a high drive dozer transmission would be advantageous. Tilt the cab back to remove the generator. Right?
Why don't you direct your question direct to CAT ? I am sure they will have an answer
Thanks for the suggestion Garrie. I have tried contacting CAT with ideas, questions, and such...with not answer. I can ask a CAT dealer and mechanic and they have no idea. That would be nice though......
MM, I own a old shuttle shift oval track loader, have worked on many older oval track machines and a few of the new hystat tractors, I am not certain as to what you are asking or what purpose. Mud still packs in on the lower rollers of the hi-tracks, they do shed it better as to the rails themselves but the carriage assembly still requires cleaning regularly to remove the compacted materials. Hystat has advantages over shuttle which have advantage over direct drives but each has a viability to its own, hystat is constant variable speed where a shuttle may have only two or three hard speeds and a torque converter to apply force in varied amounts. A direct drive will climb until the rails slip, the engine dies from oil supply loss or the tractor rolls over as it just won't give up but will only have those speeds of the trans and the slippage of a clutch or a clutch/torque combination as a few tried early on. Longevity of the hystat units has not played out yet, those machines are just now reaching an age of repurposing to smaller end users as the old machines of the 20th century have already done. Deere hydrostatics are heavy in the market but are buyer beware in many cases as the parts are highly expensive, some hard to find and used not much better than the work slick components many are trying to repair, there is a reason to so many of the old machines being in bone yards. A gear fails in a direct or a clutch in a shuttle is usually not too bad a piece out repair, a hydrostat on the other hand may require the full rebuild of a transmission to accomplish any form of lasting repair. One of the primary purposes of oval track design was dropping Center Of Gravity on the early tractors, hystat units can still set the engine low(cats' D6 hitrack engine sits 3 feet below the hood) while the driving force can sit high keeping COG low while affording better visibility, much of it is garnered visual appearances. It is faster and simpler to build a hydro than a direct or even a shuttle drive, electric drives I am not too well acquainted but as they are being built they must have a cost variable to make them viable possibly from lack of oil quantity for the driving mechanism, hystats do require considerable cooling electrics would not need.
Yair . . . Interesting discussion. The thing is of course the hi-track concept is not a recent development, there are examples of other manufacturers producing elevated sprocket machines way back to the 'thirties. Nowadays of course they are available from Chinese and Russian manufacturers . . . even Cat played around in the early days, here is a hi-track version of the "Caterpillar fifteen" . . . and it's even got a support roller. (big grin) Cheers.
I'll take the bait and stir the stinkpot. Ground clearance? Scrub's Cat 15 is an Agricultural tractor. It is less top drive than a dropped track frame to give crop clearance. Examine the development of rubber track agricultural tractors. Look at Case quad track. I think transmission type has more to do with the market than engineering. Skidsteer and mini replaced a backhoe and small dozer....
Yair . . . FarmWrench is exactly right, that Fifteen is an agricultural tractor. I would like to see a shot underneath to see how they braced the track frames to maintain crop clearance. . . interesting though that the geometry looks remarkably similar to a modern hi-drive. Obviously ground clearance and stability on side slopes will always be a trade off. There never seemed to be enough clearance when ripping or working in timber . . . how much clearance under the belly plates/lowest point of a present day D10? I was surprised to see (in the cutaway posted above) that the electric D7 appears to have a combination of spur gear end planetary reduction on the final drives. FarmWrench . How are those Quadtracks working out in the real world, there looks to be a lot to go wrong. Cheers.
I still remember when Case came out with those, now Deere has their own. Were work horses but short on track and drive hardware life when you used them for what they ended up doing pulling multiple small belly pans. Side thrust on turns do them in faster than anything.
I can honestly say i love my hightrack dozers!!!!! Owner operator here.Had D6c's D7E(old one) D6D,and in 1988 bought my first D6H and still have it.It has paid for it's self several times.Lots of plus that you have already talked about. Easiers dozer to clean mud out of tracks of any.Big plus here because of muddy conditions.You can have trans out in less then 2 hours.Don't have to mess with the A frames like the old flat track machine.Better hard bar setup,rides easier.Dozer blade lifts close to twice as high.Hydraulic has lots more break out power then the old gear pumps,when prying out tree stumps. Dozer hinge points last thousnds of hour longer then the old machines.Semi U blade a big improvment.More room between push arm and track pads compared to the old machine,that when they got wore would cacth on the pad when tilting the blade taking out trees. Engine,trans has been about a tossup for hours.Finals no comparsion high track has lasted far longer with very little repairs. Hours on my D6H since new and repairs(again this owner operator)15,500 hours until engine overhaul.Trans 18,000 and all that was needed was bands, bearings, seals orginal gears was still like new,bearings was still good shape ,but replaced them.There was only one metal band that showed wear where it had slipped and turned the band dark. Finals has 18,000 nours and both has oringal gears,just has had bearings seals replaced.Did redo the right side plantery gear where the park brake is.There was a updated cage and gear.Along with bearing.No work on diff steer and oringal hydraulic pump.So do the math and machine has been and is still paying it way. Still a nice machine to run for it's age. Weak part has been equlizer bar bearing will be the fisrt thing to go.Mine didn't have grease zits when new,but has them now.Front idlers wear fast because of the size around of the idler and weight of the 7 yard semi U blade carring it around. starter and battery,Machine still has the oringal alternator. Could say more ,but enough for me to say i love my high track.Good luck
Picture of it when i repainted it severals years ago now. Sorry one of my D6R that we did at the same time.
Construct'o...............wow....thanks for the info! You hit some great points. I never thought about the blade rising twice as high. That makes so much sense! I hate how some dozers wont allow me to walk up to a slope and raise up the blade and then climb without digging in. This seems to be a great advantage even with electric drive! Do all dozers have equalizer bar grease fittings? If so...I need to grease mine!!! I have had the same thing happen when the c-frame hits the track and snags a pad. I have run a dozer with one pad missing and had the blade frame snag another pad...and another..and another! Running a dozer with a missing pad is also dangerous as it will pick up a tree and carry it around the sprocket and slap your brains out! A trans out in 2 hours? Unreal! It would be nice to reach from the rear under the cab and pull electric motors out for service! Right? Your diff steer has been that reliable? Even the early models?
The trans is setting on a set of rails when you go to remove it,so it slides out on the rails.Take off drawbar,pull the outside axiles,take the driveshafts loose drain oil.Take the shift cables off,if R remove the electric shift harness.Basic remove,simple and easy! As for the finals easy also,split track,don't have to remove,pull the axiles,take out the bolts which usely do the inside set and take every thing out togather,but can split the final from the inside plantery gear and park brake.Just easiler to remove in one piece,plus can check the park brake. No messing with the old track A frame like on the old low track machine what a pain then pressing off the sprocket hub to get to the inside cone seal that was a joke.Seal might be good ,but the rubber o'ring was broke or weak and always was seeping final oil.Don't miss the that atall. Diff steer side of final have to take loose the diff steer motor under the cab,not sure you can get the final out without removing the motor? Since i have never had to remove it.When we did that side of the finals we split the final from the diff steer plantery part and just did the final. As far as a few updates over the years like the one for the park brake cage and gear, the diff steer system is still the same as todays machines.My 1988 machine was the first year that you could get diff steer ad semi U blade.The first high track D6H was build in 1986,clucth steer and straight blade. Equalizer bar on the D6R had grease zit, the early H had plugs where the zits went.Probably thought you would over grease don't know there thought.Zit are on the outside edge of the bar where the ouside bearing seals go.There is also one on the right side of the machine in the engine compartment for the main pin in the middle of the bar.My early H didn't have it.So when we rebuilt it we ran a grease hose down in it so we could grease it.It had the plug thing also.Not sure Cat was thinking there. Has been good since then.When they quit taking grease it's time to pull the bar and replace the bearing and seal,before the bar gets the ends and middle bearing bores beat out.Bearing cost not that bad,welding up bores and reboring high dollar fix then. High track worse thing is compacting type dirt,heavy clay the track tend to want to slip a sprocket teeth every now and then,with a big bang,just when you don't suspect it.A lot of the problem is because if you look the clay builds up on the final drive inside housing where the rail part of the track runs between the sprocket and the final housing. The clay gets hard and keeps building up until it tends to push up on the rail,then you loose the depth of you teeth on the sprocket and then the bushing will roll over the tip of the tooth and make the track bang or pop. On my D6H i actually made a scrapper out of a curved grade blade edge.About two or three inches wide.Welded a bracket to the frame and made the scrapper part so it would slide up and down and mounted it between the track frame and the groove on the final where the clay builds up on the final drive housing.Keeps the clay cleaned out and really helped on the bang and poping of the track. Used the curved blade edge which fit the curve of the inside of the final so it wouldn't dig into the housing of the final drive.It has to be slotted to slide up and down so you can get it adjusted to not rub on the final ,but clean out the clay or mud.The track frame pivets which ie the reason you need some clearance for the cleaner .Has worked good for all these years since new.Don't know why Cat hasn't come up with something.Did this on my own. Sorry about the long post.Good luck
Yair . . . Real good informative posts Construct'O . I have never been around Hi-tracks much and I find it difficult to envisage your mud/clay scraper . . . any chance of pictures some time? Cheers
Surely the blade lifting twice as high, and the pads hitting not the c frame has nothing to do with being high track or standard track? It seems more about just being a better designed blade arrangement, regardless of the undercarriage type?
Yair . . . Plant Fitter . There are a couple of things in Mountainmover's quote I don't quite understand. I don't see how proper "C" frame could ever snag a track pad . . . that's why I like them, they are one piece and don't sway around like the old style bull blade/push beam set up. To assist with the problem our early Allis twenty-ones had slide/guide plates like this machine . . . not all units had them and I could never see the point when running "C" frames. Secondly, I have never been on a dozer that digs its blade in before climbing . . . it would have to be something wrong with the system and it wasn't lifting to normal height or a very steep hill . . . you reckon? Cheers.
Even if he is talking about a blade like on the Allis 21 in the picture, surely it is more to do with the blade frame being badly designed than what type of tracks it has? Sometimes with a PAT blade, I have found it will dig in a little bit even when lifted right up, at the base of a steep hill or trying to get through a narrow ditch. But it is generally a hill that it won't climb up anyway. Maybe PAT blades don't lift as high as normal blades due to the pivot of the arms not being as far back. But again, it's more to do with the blade and frame design, and nothing to do with what type of tracks it has.
Yair . . . Gotcha Plant Fitter . As far as I can see neither problem would be contributed to by the style of tracks . . . and thanks for the heads-up on the PAT blade, they obviously don't lift as high and being a dinosaur and all (and not being around machines any more) I forget that they exist. Cheers.
I was talking about a c frame on certain older dozers snagging a pad when it sways. Yes. I had a cat d4d once....a straight blade. I actually shouldnt use the word c-frame...umm...what word should i use? Push arms? Braces? Blade frame? It would sway in certain places and rub the pads and eventually a pad would pop off...and then snag the open spot and catch the next pad...and the next pad. Domino-affect. I have had many dozer rub the pads. Mostly older units. My Cat d6d....it will climb slopes steeper than the blade will rise up. It has the angle blade 12,6 blade with twin tilts. When flat footed...at the toe of the slope..the blade will sometimes catch the slope when taking off up the slope. Happens often when walking slopes. Also occurs when i need to do that little back drag action on the slope where it meets the toe..... I end up having to take the edge of the dozer and draw lines in parrallel with the slope like little stair steps...then take my track and get parallel with the slope and walk it sideways resulting in a botched but mostly uniform slope. Does this make sense? Anyone ever use this technique? It is hard to explain. Anyway.....In my imagination...I would think that a high track dozer usually has a higher hood..and higher hardnose where the cylinders mount thus resulting in higher lift height. Right? A trackloader has a high hinge point....so it will obviously have high reach. But a more leveraged pushing action when trying to fine grade and doze...as apposed to a dozer which mounts the c frame in line with the roller frame. I have noticed that light finish dozers usually have high lift action to work extreme angles....which is less needed in straight strong pushers like mid size machines and up.....
So back to the concept of a high drive in conjunction with electric or hydrostatic drive.... Do the electric motors have complex final drive and planetary gears leading up to the sprockets? Would the CAT high drive ease of maintenance be an advantage here? Would the high blade lift action help? Well..the d7e seems to have the euclid type single blade cylinder which is mounted at the upper portion of the hard nose. That must eliminate the limitations of the two size cylinders...well..wait..no? They can just reposition that on any type of dozer right? But the higher up..the more leverage the blade will press on the hardnose. So, that requires a more beefy hardnose around the radiator. Would it help the electric motor output shafts to have less pressure in a high drive design? It seems as though the high drive isolates the finals from shockload that is amplified by the weight of the machine on an oval track design. the high drive seems to only have the weight of the track and the forward and reverse action through the track chains... I had no idea that DIFF STEER was soooo reliable. What is different about CAT diff steer versus the old case two speed design...or the interntional dozer systems of steer? anyone have a good explanation? I kinda have my own explanations but i am not confident in explaining. thanks
Yair . . . Mountainmover . A discussion here on differential steering . . . What I know as a "C" frame is exactly that, a solid frame from trunnion to trunnion. They cannot sway apart from slop from worn trunnion balls. They apparently have gone out of fashion. Chears
That was my thinking. The only way a C frame could hit track pads would be if something hadn't been maintained right. In that case don't criticize the desgin, criticize the person who didn't take care of the iron ..........
Re PAT blades, I've had them snag while transitioning onto a hill, but I think it's more to do with the blade sticking further forward, rather than how high they lift. Another thing mentioned, about high tracks being top heavy on slopes, for me is a non-argument. I've had high track 5's and 6's on 40 degree (measured 40, not YouTube 40) side slopes, and they were rock solid. That's as steep as I go nowadays in any machine, as I try to judge slopes with my head, not my cojones. There was a press release from Cat in the '80's addressing this, showing how a high track 6 was as stable as a D6D or E. I think any difference is a non-event for most normal operations.
On the same tack as the PAT Blade sticking further forward one thing which hasn't been mentioned so far is the redesign of the blade and linkage that went with the change to high-drive. The introduction of the almost vertical blade lift cylinders mounted on the front of the hardnose and the stabilizer link means the blade is much closer to the front of the tractor than before. Therefore even if the blade lifts to the same height the clearance at the front of the tractor when transitioning from level ground to an upslope is going to give the appearance of being more, whether it actually is or not. Also it's interesting that the cylinders on a high drive have a longer stroke - if you compare an 8K (45") to an 8N (56") it's an 11" difference. This would suggest that the high drive tractors do lift the blade higher.
Here is a coupler pictures not very good one.New camera.One of the scrapper and another one of the top of the final drive groove where the clay builds up and pushes up on the rail.Sorrry for the bad picture.
As far as the cylinders they have longer stroke was said above so lifts higher.I was comparing the lift height to a D6C. As far as the pads hiting dozer it is the pad hiting the dozer arm when you have the blade tilted cutting roots on a tree ball.The old D6C and others had a bumper block in the center of dozer frame with diagonal arms coming off it to the outside of the dozer blade(not C frame dozer)the pins get wore at the end of the bracket that connects to the dozer arm and when you get side pressure on the blade and tilted, the arm will move in enough for the pad to catch on the dozer arm. There are also shim that you can add at the bumber block to help the side play.(D6C) The hightrack dozer doesn't have the diagonal cross arms, the dozer arm is one piece that connect to the bottom of the blade and is curved in a C then extends over to the center of the dozer from both sides.Where it meets it has a bearing in the left arm and a short stub on the right arm that fits in the bearing.That is where it hinges when the blade is tilted. The dozer arms on the high tracks set out farther from the track frame giving it a lot moe room between track pad an the dozer arm un like the distance on a low track machine D6C.Hope that help explain a little .Good luck
Yair . . . Thanks for pics of the mud scrapers Construct'O , I can see where you are at. Re the blade sway carry on, I was just going through the archives and there is a good view of those anti-sway guides here . . . . (Big grin) Cheers.
Scrub, I honestly believe that guy has a more immediate problem than blade sway...
That must have been some root ball, Scrub...
Yair . . . It didn't happen often but erosion gullies like that were a constant hazard when pulling at night or in heavy dust . . . the drill was to pull the shut-off when you felt her going, hang on and hope for the best. Mostly it looked worse than it was and there was seldom any major damage although I did put one completely on its side. Apologies to the original poster for the hi-jack, I will start a new thread a few old pictures that have turned up in the archives. Cheers.
double post
So in my experienced with high track dozers....i notice the blade lifts higher. The machine runs free-er with less binding in stick gumball situations. Backs up a slope better because the rear idlers are protruding further out the rear and keep the balance point more neutral. Easier to work on. The blade raises higher when walking up to a slope toe and then running up the slope. Although the cab seems higher....which enhances visibility....the weight actually seems to be tucked underneath in center better when running sideways on slopes. Not saying I am the expert on high tracks...but I have run my fair share. Of course..i started this thread to learn others opinions.... I think there could be advantages to an electric drive system in a high track dozer setup. And...why are compact track loaders using a high track design???
The size of the drive motors on CTL's and once the guarding and mounting was in place, wouldn't give the machine any ground clearance.
An old time Finning (Cat Dealer) mechanic told me the reason Cat went to the High drive was the high rate of final drive failures on D8H's and K's. He said it was a big problem here in B.C. building logging road with an angle blade, when you are cutting into a side hill with lots of rock. The extra leverage of the wider angle blade was a big factor. But having the pivot shaft and final drive the same meant the final drive took a beating. Apparently they had a lot of Warranty claims, some with less than 1000 Hours. much of it could be blamed on operator abuse. if you have ever cut side hill in the mountains you know it can wear on you constantly steering out of the cut. The goal was to separate the final drive from the pivot shaft. When the High drives came out everyone said the undercarriage would wear out faster because you are turning the track under tension twice instead of once. I think this is why Cat went to low drive on the new D7E electric. but notice they have a separate pivot shaft! Doug
I understand what you are saying. I work in the mountains. We have to do constant turns while cutting dirt from one side of the blade and filling on the opposite side. We call this benching with a dozer. Before excavators became so popular in all grading applications...we would use the dozer for everything and do small stump digging and initial starts with something small like a rubber tired backhoe. The back hoe was handy to get the flat place started to get the dozer started off in the bench. This was also super handy before tilt blades became super popular on the average small earthmovers dozers. Anyways....we had a d5b dozer with 12 foot angle blade. 3306 engine with no turbo. Dry steering clutches. The blade was wide and the engine was decently powerful....ANd when doing constant pressure turns in hard material or soil...the dead axle in the final drive would give way. Over and over. Might have been the dozer design...but I knew of other contractors having the same problems with other dozers in the mountains. All brands of machines were having problems. Something slick would come out in a brand like case..or international..or komatsu...but whatever feature they had...it didnt equal out overall any better than the standard Cat or Deere dozer at the time. A good operator that knows the limits of the machine sure did help. The owner operator seems to be best at this skill because of personal interest...obviously. I can see why Compact track loaders have the elevated sprocket design. But that obviously falls in line with an advantage on larger dozers. Even though it may not always seem to be worth the money....it would depend on soil conditions and etc...on a larger dozer. Back to what I brought up earlier about the blade on dozer digging into the hill before climbing..... I know that many people have commented that they havent had this happen and it must be a mechanical failure on the machine. Maybe I am not explaining this clearly because I have had this happen on all brands of dozers. If you are operating a dozer on the road bed. You cross the road and reach the slope. If it is a pretty steep slope....and you go from road bed to aiming right at the toe of the slope and you want to start walking up and down the slope(creating track marks for seeding) or grading the slope...many dozers DO dig in the slope before allowing the tracks to climb. The finish tractors seem to have a high blade rise. High track Cat dozers also seem to have a higher than usual blade rise. I am talking about nothing mechanically wrong..I am saying that the rise of the blade isn't as high as what you need for the slope angle. The engineered blade rise from the manufacturer. As far as a c frame wiggling...it is pretty common on some older tractors when the trunnion wears...and other joint. I have seen the c frame bump the track pads in small unnoticeable increments until you have to weld up the c frame with beads... Maybe the d7e is sooo expensive to begin with that the advantage of an elevate sprocket isnt affordable? Since the dozer is sooooo new.....we shall see what the undercarriage and final drive life will be? But also..maybe the shockload from an electric motor may be different? Also..maybe the balance point of the machine is different than with a large motor...and the roller frame is designed to alter shock load and is a new idea that steps away from what advantage the old high drive had? thanks
I've no experience with high drive/diff steer, but here's a video showing how diff steer works. https://www.youtube.com/watch?v=A5_iNL9q18Y If I understand correctly the IH system was a planetary setup that allowed you to slow one track relative to the other so that you could turn with power to both tracks (unlike Cat oval track machines). IH didn't have capability to counter-rotate tracks like diff steer high-track Cats.
Diff steer It would be nice to have a better explanation of diff steer. Also a good idea of reliability. Does Komatsu copy the concept in any if their dozers? Reliability of Komatsu ? This must be a stronger , better, longer lasting setup than a hystat design ?
The Cat diff steer tractors I've worked on (larger models) couldn't couter-rotate tracks. Maybe the smaller ones can, not sure about that. Basically the diff steer is a hydraulic motor connected to the drive that increases or decreases the speed of the LH track in order to turn the machine. The direction of rotation of the steering motor relative to the direction of travel of the machine determines the direction of the turn. The speed of the steering motor determines the tightness of the turn. So if the machine is moving forward and you want to turn left the diff steer motor has to run in reverse to slow the LH track down with respect to the RH track. If you want to turn right it has to run forward to speed up the LH track with respect to the RH track. If the machine moving in reverse it does the opposite. See illustration below.
I might be mistaken about counter-rotating the tracks....I was under the impression some would. But as I said, I've never run a high-track.
The diff steer machine will counter rotate ,but it has to be in netural then move the diff steer lever.Might have to increase the rpms,to make it more responsive,but will do it. Always seemed hard on the tracks to do it ,so i only do it sometimes when i neeed to make a slight turn in a tight spot.Not something i do all the time.
My experience high vs. low is D7H vs. D68P. Fairly comparable machines.....7 has more power and weight, 68 has more track on ground. The 7 will out cut the 68 all day long but if your pushin piles the 68 will run circles around the Cat. Climbing slopes edge goes to Komatsu. Don't know why exactly but forward or backward the 68 will dig a deeper hole wet or dry. Just takes twice as long if it's hard. Maintenance obviously goes to the high track. Everything and I mean EVERYTHING is easier, simpler to work on or service. Except putting fuel in.
I have, somewhere around here a book on Cat. The book states the reasons for going with the high drive were far less stress on the finals as they are not bearing the weight/subject to hitting rocks ect with the higher mount points and reduced sprocket wear with the sprockets up out of the dirt. Don't know if that's fact but the author claimed to have worked closely with Cat to write the book. Rick
I remember reading a Cat article on the D8L when they first came out in which they said the use of bogie undercarriage and going to hi drive reduced the vertical shock loads by up to 50% on track components which when u are working in rocky conditions must give u a smoother ride as well as being easier on the machine. They also said that in relation to less sprocket teeth in contact with the chain, its only the first 3 teeth that make contact with the bushes that take all the load, the first one has the highest load the other 2 to a lesser degree after that the chain is there for the ride around the sprocket which when u think of it, once there is a few thou wear in the pins& bushes they won't be taking load any way it will be the first 3.
it seems like a lot of poster have forgotten one important thing. Ask an operator whether he would prefer to run an 8K or an 8T as regards how his back feels at the end of the day........
Nige You hit on a great point. I started out on oval track machines, mostly D-8H and K, and D-9H tractors. They would do a lot of work, but had many drawbacks. When I first experienced a high track machine, I had skipped forward to a D-8R, and was only on it for a short time. I was very impressed at the things it did better than the K model I was using. Though taller visually, I am convinced the center of gravity was actually lower than the oval track. It would ride on side slopes that the K would not. Part of that was the bogie undercarriage that keeps more track in contact with the ground. Keep in mind, I am out West, and most of the ground I have worked is rocky. When the oval track would hit even a small rock on a slope, it lifts the whole track frame on that side, while the high track allows each idler and roller to rise independently to keep the rest on the ground. The next think I noticed is how much more it would push. With the oval track machine, going over a rock while pushing may cause you to loose a good deal of your pushing power, and you have to leave part of your load there in order to crawl over the offending rock. The high track machine rolls over the rocks much better. You still loose, but it is much less. Then, as Nige says, the ride quality is vastly improved. I think of what has been told to me over many years, and I pass it on to the newer operators when I can. "If it hurts you, it is hurting the machine" Running the oval tracks in a big rockpile, it was definitely a case of "it hurts". I know we had a much higher rate of track roller bearing failure on the older machines than on the high tracks. Better materials may be a factor, but I am convinced that the reduced impact plays a huge roll as well. The high track tractors are better balanced and show it with how they cut, push, climb, etc. I have pioneered roads in in some of the toughest ground to be found in the Mojave Desert, and have climbed slopes with D-8R and T dozers in hours that would have taken days with the old H and K series. I have heard that undercarriage was more costly on the high track, but in my experience that is not the case. When tracking the costs versus the hours, the D-8T and D-8R are running at nearly half of the hourly cost for undercarriage that I had with the D-8 H and K. Not everyone will have the same experience, but in my normal working conditions, it has been for my operation. As for the diff steer, it has been reliable. I have had to do the steering pump and motor on them, but the last one went somewhere around 13,000 hrs. I have seen a D-6T with weak steering and under 7,000 hrs, but I do not know how it was used. It is a LGP, and they turn harder than a standard one, so maybe it shortens the life of the steering set up. I will not say the older tractors were bad, but I will say that the high tracks have them beat by a long shot, in my opinion.