I have been looking at the cat D7E and i cant find any pictures or videos of them with hi drive tracks. Is this an indicator that the hi drives are going to be eliminated over the next few years, or is it just a D7 thing? Anybody hear anything about this or know what cats plan is?
just a D7E yoy wont see them replace the hi drives
Yair . . . I see you can buy flat track sixes and sevens in Australia (on the dealer website) is that a new carryon or was this always so? Cheers.
I don't know how long they have been available, but I have seen them on the Cat website for a couple of years at least. They look like the type of machine that you and I would like to have Scrub. They should also be much cheaper than the electronic hi-drive models. My only question is how much of them are the same as the older models. For example, is this new D7G series 2 similar enough to share parts with the old original D7G? If they are the same well and good, there should be plenty of parts around. But if they are not similar at all, parts supply could be an issue? I have never seen one in the wild so I don't know how many of them they have sold, if there are not many around parts may not be easy to get. However, with Cat backup I would still be confident to buy one.
Yair . . . Plant Fitter it would be interesting to know ratio of sales to hi-tracks . . . dunno, I suppose I'm a dinosaur but I just can't get my head around the hi-track concept. I understand it and it is proven . . . but it just doesn't look right. LOL Cheers.
Cat have stated that the hi-drive design is really only warranted in the larger sizes of crawlers. The complexity and cost of a hi-drive design apparently cannot be justified in the D7 and smaller size tractors. Remember that one of the features that Cat have always bragged about in hi-drive design, is the ease of removal of drivetrain components. This is a big selling feature when you're working on big-ticket items. With labour costs and downtime being so expensive on the big tractors, there's big savings to be had when you can have the guts of a D11 spread all over the floor of the shop in under 4 hrs, and back together and running the next day. Nearly everything in the hi-drives drivetrain is slip-fit, snap-ring retained components, and there's rarely any presses or adaptors involved - apart from rubber or steel bushings that are pressed in. As result, the maintenance costs on the high drives is lower, and their downtime is reduced. That's a BIG sales feature to companies who all want their plant with 100% availability.
I struggle with these confounded internal combustion engines - still can't figure where to shove the coal in.
Yair . . . OzDozer . I'm a bit confused mate. If this is the case it seems it would be logical to extend this design philosophy to all their tractors . . . why persist with "coal burning" flat track technology for some markets and, in the case of Australia (apparently) to offer both styles of drive on Sixes and Sevens ? Cheers.
they dont even use the acert motors in the G series, and cat does offer flat track 6's and 7's here in the US, the 7E and 6K
The 7E sold in the US is an electric drive unit and costs somewhere close to a D8T. If you don't like space age, then you will absolutely hate the 7E. As I recall the issue with the high drive on new machines has to do with the suspended bottom rollers. You only find them on D8 and larger machines. The high drive in the D6 and smaller machines ran up against competition that sold for a lot less. D7 size machines never really caught on heavy in my neck of the woods. They usually ended up in garbage operations from what I've seen.
But the common link to all the new low drives is they are not conventional p/t. Any new Cat dozer that has a transmission is a high drive. D6K is hydrostatic so it just has drive motors not a transmission, much like track loaders (963, 973, etc) have never been high drives and also are hydrostatic. The D7E is also basically a hydrostatic electric drive. D6T or D6N have transmissions and are high drive still. Cat says high drives help for ease of service and quick turn arounds on trans R&R and such - well no need when there is no transmission !
The reason is that the advantages of hi-drive over flat track are related to the overall cost of the machine - a large-size, much more expensive tractor has more margin in its construction costs to be able to install the hi-drive system. In the bigger tractors, the hi-drive advantages difference is larger and more noticeable. Then there's the "design improvements" that keep the hi-drive/flat track equation in a state of flux. New track chain design such as the System One by Cat makes the flat track system gain an increase in advantage over the hi-drive. The simple fact is that the flat track design was a proven design that worked, for over 60 or 70 years. Then came the vastly increased size of dozers, and this exacerbated the track/final drive problems that were inherent in the old flat tracks. The three major faults of the flat track design were: 1. Regular final drive/sprocket shaft/dead axle damage caused by operators bouncing the tractor over obstructions, and landing heavily on the finals, causing dead axle bending .. 2. The basic final drive design of spur gears under massive load, that created huge gear and shaft deflection, that resulted in shortened final drive life. The planetary gear drive system (for final drives) is superb, because all drive forces are evenly distributed. 3. The basic problem that a solid track frame cannot compensate adequately for uneveness in the ground which reduces traction and increases track slippage. The first two problems were virtually totally eliminated in the hi-drive design, and the suspended roller undercarriage went a long way to improving traction. However, in a smaller tractor, the % points of overall gain of the hi-drive are reduced, because the hi-drive undercarriage design is complex and consists of a lot more components in total. Thus the flat track design is adequate for all the smaller tractors. With a flat track design that includes a planetary final drive, there are some of the hi-drive gains, without the major cost of the hi-drive. The "snap-ring, slip fit" component design is part of the planetary final drive design, no matter whether its a flat track or a hi-drive, so there's some gain there. The drive train components are accessible enough in the smaller tractors, the hi-drive component accessibility doesn't have the same advantage there.
Yair . . . Gotcha OzDozer Thanks for the articulate and well thought out reply. . . it's a bloody marvelous recource we have here to set old dino's like me straight. Cheers.
one thing i have always wondered does a high drive have an advantage over a flat track when it comes to softground, i was running a 6T LGP in very soft conditions and a guy was running a 850J lgp deere right next to me and he was having a hardtime pushing the slop, he was lucky to be able to get a quarter blade full out without getting hungup, while i was able to push quite a bit more. I know there 2 different brands but both are about equal in comparison.
2 of the low drive dozers available in Australia, and maybe elsewhere, are not electric, not hydrostatic, just conventional transmission and final drives. They are the D6G and D7G Series 2. I am guessing that they are the same or similar to the original D7G, but I don't know. I am hoping somebody can tell us more about them. I realise the D6K is hydrostatic and the D7E is electric.
i remember my grandfather and a friend of his talking a little about these new d7e and they said some company did the whole electric drive thing years ago but it was a flop
I think the D7E would be a cool machine if they put vpat blade on it
The AC variable frequency drives are the new technology that is revolutionizing many industries. Factories and mills are putting AC drives on pumps which let them control the flow in their process without using control valves. Railroads are buying new large freight locomotives with AC motors and drives which are capable of pulling a good sized train by themselves, without the maintennance required by previous DC systems. Electric cranes are similarly being replaced or retrofitted with AC motors and drives replacing the old DC motors and controllers. I haven't had and opportunity to run a D7e myself but I think this system will become more common in the future. As for no hi-drive, despite it's advantages I wonder why no other manufacturer has copied Cat's design, I would have thought their patents on it would have expired by now.
Yair . . . norite I could be wrong but I doubt Cat. ever had any enforcable patents on the Hi-drive concept . There are several other examples of hi-drives if you do a search. They go back I think to 1929. Cheers.
Hi plant fitter; do you know where the D6G and D7G-2 are built ? Was told both were only built in china ? Dunno if they were built elsewhere or not, but am resonable sure neither are built in usa or japan. Both still use 3306 with DI. cheers merv
I'm guessing that has something to do with emissions specs.
Scrub Puller - Yes, Cat did have quite a number of patents on the high drive design. Yes, the basic principle has been around since the hi-drive Best 30 "humpback" tractor, of 1914 and 1915. And yes, those patents would have expired. However the effort involved in designing, manufacturing, and selling a hi-drive into the markets captured by the Cat hi-drives would be more than many manufacturers are willing to risk. I can recall discussing with a Senior Komatsu dealership manager, way back in the late 1980's, about Komatsu producing a hi-drive. He stated that he had seen plans and designs for a Komatsu hi-drive, and he was convinced that Komatsu would soon produce a hi-drive to match Cat. It's obvious the decision on hi-drives within Komatsu fell the opposite way to what he thought, because Komatsu have never produced a prototype, or even shown a planned design, for a hi-drive - and have continuously stated that the benefits of hi-drive are overstated. There's a very fine line between making an idea work, and making a success of selling it as well - as compared to having the idea fall flat on it's arse, and buyers turning their backs on you. Komatsu seem to be quite happy and reasonably successful at producing and selling flat-track designs. Best could never sell his hi-drive design, and he scrapped the design after two years of poor sales. http://www.steel-wheels.net/best.html
The 500th ED D7E has just been delivered so they are getting a few out the door. As to no high drive, Cat eventually worked out what they already knew in that the elevated drive sprocket needed the suspended bogie undercarriage so it would all work as a system so nowadays below a D8 will be flat track although there are also options for EDS machines if you so choose. Back in the day it was just good marketing of the concept that deemed it was the right choice on D7 and down machines but i suspect bean counters, other brands success (in flat track machines) have been a focus of marketing decisions and hence today why it is not as prevalent in the smaller classes. Absolutely no doubt in the world of the success in the larger classes, D11,s currently selling at around 5 to 1 against the 475 but it is great that Komatsu have such a good dozer to ensure the D11 keeps ahead it means Cat have to continue to invest in that model line which at the end of the day is good news for the end user.
D6T model dozer being sold currently are high drive.
Oliver also had a high drive with their little Model F (I think it was). That model also had that "string of pearls" track roller system. I think it was also called re-circulating rollers. The Cat high drive is part engineering and part marketing. Marketing is partly dependent on brand. Cat had enough engineering, marketing, and brand strength to pull it off. I think they were the only company that could have done so. There are pros and cons to the high drive. The biggest advantage is with the largest tractors. But once that proved successful, there would naturally be a marketing attraction to apply it to all sizes. I speculate that if I.H. or A.C. had come out with a high track dozer identical to Cat's first high track, before Cat came out with theirs, they would have been laughed out of the market. It would have been viewed as an Edsel.
Actually tracklayer, the model F was originally a Cletrac & Oliver bought them in the 40s, but you are right,they had a hi drive way back in the teens. Those model Fs were much more like the 1977 Cat D10 than the Best humpback. If you look at a humpback the drive sprocket is behind the rear idler whereas the F has the sprocket above & INFRONT of the rear idler . If you put the F & D10 side by each they look very much alike & neither one looks like a humpback... I must say, I do find it VERY revealing that Cats latest & greatest most technically advanced & up to date crawler is WITHOUT its beloved hi drive.I am amazed that IF & thats a big IF the hi drive is so wonderful not ONE company has tried to copy it! Not Komatsu not John Deere not Case not Liebherr etc,etc,etc, the list goes on & on. I do not count (& wont) the chinese copy cat thingys. The D4,D5,D6 & now D7s are now available WITHOUT the hi drive. ALL those models I see around are of the LOW sprocket design. All the new 6s I see are Ks & all the new 7s Ive seen have been Es. I wont even get into all the new 4s & 5s I see. So long Hidrive it was sort of nice to know ya!
Tracklayer , I'm always amused by the reams of Caterpillar "machine comparison" sales literature, that slammed IH's planetary final drives! Cat waxed long and lyrical about what a poor design it was! It was weak - because it had no support on the outside of the final drive - it was costly, because it contained so many parts compared to a Cat final drive - it was bound to twist and create rapid track wear by misalignment - the sales blurb went on and on. So what happens? Cat conveniently drop their old-style, spur gear final drives, after realising they were giving more trouble than any IH final drive - and adopt planetary final drives for the hi-tracks, and the new electric D7E! It's all about sales depts trying to get the wood over the opposition tractors, by pointing out features that may, or may not, have some element in truth. Many sales put-downs are merely debatable arguments, depending on the machines application. The hidden factors that affect machine reliability are rarely mentioned in sales literature - such as the companys QC, parts availability when you need them, and how much technical backup and support is available when you have a problem. 61BG - I don't think the hi-drive is going away any time soon. The system is in wide use, it has some advantages in the larger dozers - and the minimal downtime feature appeals to the large companies that buy $50M or $100M fleets in one hit, off Cat.
OZ Oh I agree, I think your right about the large tractors. Cat has proven that it can be a cost effective solution for maintenance turnarounds. Im thinking that its done in the small & mediums size crawlers. They will keep both options for a few years & as sales drop off for the Hi drives they will slowly drop them from the scene. The larger fleets that put on the 5000 hrs per year will see there finals being rebuilt every 3-4 years will see the benefit. The smaller operations that only put on 2000 hrs per year it will take them years to get into their finals so the Mtc turnaround wont be a big deal within the life expectancy of that machine. Even Cat can see all those small & medium size Deere & Komatsu crawlers that have given years of reliable & dependable service life of tracks & final drives that dont have any of the drawbacks of that of the Hi sprocket design.
In most mining operations in Australia, earthmoving equipment does a minimum of 5000 hrs a year, they don't sit around, I can tell you that much. The hi-drive undercarriage system has a very long life and surprisingly low hourly cost. I've seen undercarriage with 7000 hrs on it, on some of my nephews D9T's and D10T's, and it's only half worn, it's amazing - and these tractors of his, are nearly all out on mining work, on dry hire with a dozen different operators. There's been a lot of advances in undercarriage technology since the hi-drive first appeared. Better and better steels, improved hardening, improved undercarriage design, track alignment systems that perform far better than the old flat-track systems. Because the hi-drive track is longer, the wear is spread over a bigger number of links and bushings. The reduction of impact on the undercarriage by large amounts of rubber bushings also increases track life substantially.
Actually, the D7RII and D7E use the same track groups with HD undercarriage. Not sure if System 1 is available on D7E yet but that will be a different track group p/n. D7RII and D7E has the same track pitch links and even the exact same number of links. I think the track roller frame is longer and has an extra roller IIRC which reduces ground pressure even considering the 1000 lb weight difference between similarly equipped tractors. Look at the specalogs, the D7R has 114" between front and rear idler and the D7E has 119" between final drive and front idler (looking at STD configuration) resulting in ground pressure dropping from 10.9 psi on D7R to 9.9 psi on D7E.
Don't know about stateside, but over here there are three D6's available, the K, N, and T, and the last two are good sellers. Basically, they're a damned good machine, and it looks like they will continue in production for some time. and as the N is basically the same size as the old hi-drive 5 you could argue it's only the 4 & 7 hi drives that have been dropped. The 4 was too expensive for its size and the 7 was never a great seller anyway, which is why the 7E was a low-risk entry point for electric drive.
Most likely Brazil, or Indonesia. D6G and D7G were built in both places I believe.
Correct,thats what i said
The main thing there with EDS machines is the planetary final drive does not cop the loads of the machine pounding it as it backs over rough ground, Hard to deny Cat don,t promote those things
The thing is, that Cat have finally realised that a planetary final on a flat-track, despite their poo-poo-ing of IH's and Euclid/Terex's planetary final drives - despite its lack of outer support - works quite satisfactorily for the following reasons: 1. A planetary final spreads the load evenly across all gears and doesn't deflect gears like a spur-gear setup (i.e. - Cats old double-reduction final drive). 2. A planetary final drive can be provided with adequate support, by using a large inner diameter on the sprocket shaft. This gives a good "buttress" effect to any potential shaft deflection. 3. A planetary final is much easier to work on, and easy to dis-assemble and re-assemble. The only disadvantage with a planetary FD is the need to support the trackframe independently. Cat never found this a major problem on the D2 - the first Cat with a separate trackframe support shaft, and a sprocket with no outer support.
Hey Oz notice the whole track frame final drive design for the D7E is very similar to a mid 1960s IH TD20B !! Also the D2 final drive was probably the most robust final drive cat ever designed. 933G used the same final drive and Ive never known of any to break. Same pivot shaft design. And the final drive 'live shaft' was a similar design to AC. But didn,t have to cope with the blade loads, unlike AC. Although if you wanted to check and adjust the brg preloads it wasn,t as easy as the standard cat final drive. But planetary finals eliminates this anyway. Just my 10c worth.
tracks nice point the old green,&td machine's used planatary;s and that man from japan put suspenition on there track rollers so we back to ? witch way to go!
cat put the sprockett up in the air to eep it out of the the rocks and cheaper than a old 90v look at the hd41