New Caterpillar D7E - Opinions?

That's your one freebie yash, take a look at our rules page.

D7E and ripping

JDOFMEMI said:

DPete

Steering is by a tiller bar like any other diff steer machine, the only twist is a lack of twist. You no longer twist for directional control, it is a toggle very similar to a fingertip control type machine.

Speed has several ways of control.
One way is a proportional "dial" on the tiller that you roll with your thumb to speed up or slow down
There is also a series of selections on a dial that work similar to the autoshift feature in some machines. You can dial in 1.5 F, 2.5 R which is a pretty good working range, and several other settings, I do not remember all of them, but the one I liked is the user programmable, where you set your selection of forward and reverse speed, then a second forward speed, that you "shift" up to after you fill the blade.
With any of the pre selected speed ranges, the thumb wheel changes it when you desire, then at the next directional shift it goes back to the pre set setting.
You can also select full manual, and just use the thumb wheel.
The last way of controlling speed is with the foot operated speed modulator.
It is a lot of choices, but once you set it for your style and conditions, it is very easy to use.
The

Click to expand...

I realize that the D7 class is not intended for heavy ripping, but I still wonder if any of you has tried it in any sort of rock ripping. As the electric motors are capable of a very slow speed and still maintaining high torque I wonder if it can give the smoothness of a torque converter needed to avoid track slipping.

I for sure did some rock ripping on the old D7E, in the late 60's not many other machines were available for rock work in my place. They were of course no match for the D8 class and many of them got prematurely worn down being exposed to that kind of work. The old 4 cylinder was incredibly torquey though.

Hjolli

What I recall from operating it would lead me to believe it would be a strong ripper tractor. You can select any speed with the drive, and have full torque from stall right up to max speed. You can modulate speed without loosing torque. If you need less torque to control slip, you could dial down the engine speed as well which would reduce torque at a given speed, and do it with better control than a torque converter.
The speed control allows for very precise creep control, and I believe it would work well to control track slip.

JDOFMEMI said:

Hjolli

What I recall from operating it would lead me to believe it would be a strong ripper tractor. You can select any speed with the drive, and have full torque from stall right up to max speed. You can modulate speed without loosing torque. If you need less torque to control slip, you could dial down the engine speed as well which would reduce torque at a given speed, and do it with better control than a torque converter.
The speed control allows for very precise creep control, and I believe it would work well to control track slip.

Click to expand...

Can anyone explain how any of this is different from a hydrostatic machine??:beatsme

farm_boy said:

Can anyone explain how any of this is different from a hydrostatic machine??:beatsme

Click to expand...

With a hydrostatic you lose a lot of energy as heat through the system and from other loses, pumps motors etc. Electric drive has come a long way in the past few years and is more efficient now. With a dozer your not going to have it I don't think, but with other platforms you can recover some of the energy during braking. Down the road if this pans out it will probably be used in more machines.

Also would you have full torque at low speed with hydro?

I think one more thing that you can do and I think Cat is doing with the electric drive is load sensing. It will reduce speed to keep from stalling the tractor under heavy load, then as the load lightens pick up again.

Nothinbetter said:

With a hydrostatic you lose a lot of energy as heat through the system and from other loses, pumps motors etc. Electric drive has come a long way in the past few years and is more efficient now. With a dozer your not going to have it I don't think, but with other platforms you can recover some of the energy during braking. Down the road if this pans out it will probably be used in more machines.

Also would you have full torque at low speed with hydro?

Click to expand...

I would contest that this electric drive system would loose close to the same amount of efficiency as a hydrostatic system. This is why Cat has made a big deal out of the motors being water cooled. Electrical components this large will put off a ton of heat...heat = power lost. I'm not saying that a hydrostatic system is any more efficient. All I'm saying is that there isn't night and day difference between the two. With this tractor I will say that it will gain some overall efficiency due to driving the HVAC and water pump electrically, but I'm guessing this would only be a few percent.

With regard to full torque at low speed with a hydrostatic...the answer is yes because at low speed you're basically at a high pressure low flow situation...meaning high torque.

Nothinbetter said:

I think one more thing that you can do and I think Cat is doing with the electric drive is load sensing. It will reduce speed to keep from stalling the tractor under heavy load, then as the load lightens pick up again.

Click to expand...

Nothing new here either. Hydrostatic systems have been doing this since the beginning. I will say that with the addition of electronic controls, this has become light years better than back in the day with mechanical controls.

I guess what I'm having problems putting my arms around is all of the marketing hype about this machine when (that other than a couple of minor efficiencies that I mentioned above) it is no different in features than a hydrostatic tractor.

Low engine speed - check
Constant engine speed - check
Infinite speed control - check
Dynamic braking - check
Improved maneuverability - check
Full power to both tracks in a turn - check

All I'm saying is I don't think this machine is THAT revolutionary compared to what others (including Cat on smaller models) have been doing for years. No doubt it is a big improvement in fuel consumption, noise level & visibility over the D7RII and will more than likely be a pretty good tractor. I just think that it has been a little "over hyped" because of the greenies making the correlation with an electric drive anything saving the earth from evil carbon dioxide gas.

farm_boy said:

All I'm saying is I don't think this machine is THAT revolutionary compared to what others (including Cat on smaller models) have been doing for years. No doubt it is a big improvement in fuel consumption, noise level & visibility over the D7RII and will more than likely be a pretty good tractor. I just think that it has been a little "over hyped" because of the greenies making the correlation with an electric drive anything saving the earth from evil carbon dioxide gas.

Click to expand...

I'm really not familiar with how well this will work, but I'm going to disagree and perhaps make a fool of myself. First, I think the D7E will offer a lower operating cost than a comparable hydrostatic tractor (namely the 950J, given that everything else is torque converter at this point). This will be mostly driven by lower fuel consumption. Second, I disagree that the electric drive is similar to a hydrostatic.

The D7E operates in a pretty tight RPM band. If you listen to it when not under load and when under load, you won't hear a significant drop. I realize this is hardly scientific, but if we're just comparing a seat-of-the-pants feel, there is a difference in how much variation there is between a hydrostatic transmission under load and an electric drive under load. I think -- and this is hearsay at this point -- that the electric drive is far more removed from the engine than is a hydrostatic transmission. When there is a load on a hydrostatic motor, the physical hydraulic pressure increases, which means the powerplant will have to work harder to supply the increased pressure. While the same will happen with electric drive, I think that because the engine is powering a generator -- and not a mechanical pump -- there is added isolation between the engine and the motor. Just as hydrostatic allows for some additional protection from huge torque spikes, e-drive does the same (at the proverbial "next level"). As a result, e-drive can operate within a much finer RPM range than can a hydrostatic machine. (My conjecture.)

I'll give an example of how having an improved mechanical transmission is different from having a different transmission altogether. Cars can have, say, a conventional transmission with gears and the such, a CVT, or a hybrid propulsion system. I *realize* that Cat's D7E isn't a hybrid (in the sense that there is a battery pack and that energy is stored during some regeneration state) and that a CVT isn't a hydrostatic, but I'm just saying that having similar RPM characteristics isn't sufficient to have identical fuel economy. If I go from a Camry automatic transmission (roughly 21 city) to a Camry Hybrid (31 city), there's a pretty big jump. The Subaru Legacy (similar sized engine to the Camry I4, but with a CVT) improves only to 23 MPG city. (I realize that highway numbers are closer, but still different -- the Camry is 31; the Legacy, 31; the Camry hybrid, 34.) I'm just saying -- a CVT operates in a narrow RPM band; hybrids with CVTs do, too. However, it's the coupling of two different systems, one mechanical and one electrical, that right now offers the "best" results. (Note that this isn't a plug for hybrids -- I'd prefer if Americans just went to clean diesel -- but just a statement on different propulsion techniques.)

The ultimate question I'd pose to you is about Deere's own line. Hydrostatics will probably endure into the future for some time, but what will Deere be doing with its wheel loaders (if not dozers)? Is Deere *always* going to have a mechanical, TC with LUC transmission? Or will you begin to look at hybrids or hydrostatics? Do your engineers consider one propulsion technology to be superior to the other in that regard? (On a parallel, Volvo could have pursued hydrostatic technology in the L220, akin to what Liebherr has done... but instead decided to go with Hybrid. Was that truly just a marketing perspective? That "hybrid" is somehow better than "optimized mechanical?" I don't know the answer to these, btw... )

them1677 said:

I don't want to sound negative but the guys with all the Cat priase, have you operated any other new units lately? I know some Cat guys that would buy anything with a Cat sticker on it. Deere and Komatsu have hydrostatic units that have increased fuel savings as well as some of the other "new" innovations. I would like to see a side by side comparison by someone that doesn't have a picture of Cat under their name or come from the Great State of Obama.

Click to expand...

I was offered the chance to run the D7E a few days ago and I would like to give my two cents.:my2c First off let me say I only ran it for 30 min so I can't answer every question out there, but what I can tell you is that it could have used a few more days in the design dept.

I really liked the power train. There is not much I can say about it that hasn't already been said. I wanted to side load this machine to see how it compared to a diff steer machine and I found there was no comparison. When ever you wanted to turn a load or hard cut with a corner bit there was always track power to spare. The engine maintained a constant speed and never fluctuated. This machine could have used another 10,000 lbs for the amount of power it put on the ground.

Now the dislikes.
A single lift cylinder to lift the blade? When these machines get 10,000 plus hours and the wear points are sloppy my thoughts are controlling the blade may look like your playing on a teeter totter. :beatsme With twin cylinders some of that gets held to a minimum. I also think for those who clear big trees or need that max lift power it is going to be lost. Also does a dozer hand ever look over the hood for anything? Pushing scrapers or trees,maybe looking ahead to see changes in the ground so you can react, or even looking to see your laborer holding the grade rod. Now you have a cab post, air cleaner, exhaust pipe, and cylinder in direct line with you.

The brace arm on the blade looks to be beefy in pictures but after a closer look it will bend very easily where it connects to the push arms. tilt cylinder looks small and cheap as well.

Watch your head getting in or out you will hit your head on the mirror or backup monitor. Other than that the cab was typical, nothing to get real exited over. Although the visibility to the blade was second to none.

Cat should take a few lessons from other manufactures on there electric over hydraulic controls. Smooth only if you were at full stroke. Making small corrections the blade would jump and down and was very hard to make fractional corrections. M series graders T series tractors and most all of cat loaders are the same way. One manufacture has there controls perfected but I won't mention names that always starts a new battle.

My biggest complaint of all is the undercarriage. What were the reasons for going to a high drive system? Once again the finals are subject to impacts and high loads from rocks and stumps, and seals being cut buy foreign objects. Many of you talk about ripping rock ,I've never done so but that can't be good on a rearward final drive. I have owned 4 high drive machines and replaced 2 seals and rebuilt 1 final due to a bearing failure in 25,000+ hours. I have replaced countless final drives and seals on older flat track machines.
I live in an area where we spade out the undercarriage every night in the winter and there is nothing that spades any easier that a high drive machine. 30 min, one person and your on your way home, that looks like a good hour to me.

Overall it is going to be a good machine, but only time will tell.

Remember before I get slammed for my thoughts these are my opinions about this machine. Opinions are like a$$holes. Everyone has one.

A step backwards?

Without having ever tried or seen this machine in real life, I would agree with you Dirt Dogg on the subject of the low drives, and what also struck me when I first saw a picture of this machine was the "old fashioned" bracing on the blade. The D8 and up have the diagonal bracing bar, an ingenious and simple solution, and the D7H and D7R has this as well.

I would also think that one of the main advantages of the high drives is to keep final drives away from abuse.

It would be interesting to hear from users of the conventional drive machines (Komatsu and others) what their experience is with the low final drives, e.g. in ripping work.

I saw one of these monsters about a month ago but didn't get to run it.

As a mechanic there were some things I liked and some I hated. I liked the jack over cab and the serviceability of the machine. I'm kind of ambivalent about the electric drive attachments. Water pumps and air conditioning take a certain amount of horsepower to run them and don't care how that power is supplied. Belts are far cheaper and easier to fix. Wires get chaffed and shorted. I don't like my machine to light up literally when things go bad.

What I really didn't like was the fact that high voltage could be contained in the system with the engine shut off. There is an electronic function that is supposed to ground the system out when the engine is shut down. I don't like the idea of getting zapped when an indicator fails or the software gets a bug.

The drive system is really a red herring. I know from personal experience that low drives rip better. In smaller machines the extra cost of the high drive undercarriage doesn't break even with the oval tracks. Cat apparently has conceded this as all their small machines now are oval track. On the large machines Cat has increased the service life of their high drives and the component access really makes a difference in reduced down time and life cycle costs. The high drive works great on big machines and I would recommend it.

I know when I did run machines I never looked over the nose to see where I was going. I really liked the idea of being able to see under the corners of the blade. I wouldn't think I would have to run the machine for a hour or so before I got the feeling of exactly where the blade cutting edges were.

Time will tell how good of machine this turns out to be. I think this is a pretty good first production effort.

Hello all, first post here.

Lots of information and guessing in this thread. To confirm with what I know:

The D7 was chosen as the test mule for the electric drive platform because it is a low volume machine. It was changed to oval track for engineering reasons. As far as I know the plan is to expand the electric drive to other dozers if the 7E is well received.

Also, the first customer machine has been delivered so you can all get your hands on one now.

I have never operated one so I will not speculate about it however guys I have talked to say it is a great machine.

I'd sure like to take one for a test drive. They look pretty interesting. Quite a change for Cat.

My opinion

Just wanted to share some pros and cons from my experience so far:
My first impression after only one day of use was that I didn't like the dozer, but I figured I should give it a fair chance and wait until I was more comfortable with the controls. I have had the dozer for three months now and here's is my evaluation.

Pros: The line of sight in this machine are probably the best I have experienced. The hydraulic speed of the implements are adjustable and the blade is very fast. The engine is cleanly designed and has no belts.

Cons: The straight track design along with no decelerator make for an incredibly rough operating experience. I was sore after every day I ran this dozer. I would say it is comparable to a 155 komatsu it terms of ride. The toolbar and ripper controls need to be addressed, the round toolbar is so massive that you can't see what your ripping until you are 30 feet past it. The ripper controls are a little bit award as far as where they are located, if you have long arms you almost have to turn sideways to use them. As far as fuel economy....I understand that the machine is design to keep a constant rpm when in operation and in theory that should probably help fuel economy, but in reality I have actually used more fuel in a day than with the older D7r. I personally feel that having no decelerator may be the contributing factor.

In summary I'm really hoping I can find a lower hour d7r to replace this with. I hope caterpillar reconsiders this design before changing any other models. Newer isn't always better and don't even get me started on the J.U.N.K. Series H model scrapers.

Tigerotor77W said:

The ultimate question I'd pose to you is about Deere's own line. Hydrostatics will probably endure into the future for some time, but what will Deere be doing with its wheel loaders (if not dozers)? Is Deere *always* going to have a mechanical, TC with LUC transmission? Or will you begin to look at hybrids or hydrostatics? Do your engineers consider one propulsion technology to be superior to the other in that regard? (On a parallel, Volvo could have pursued hydrostatic technology in the L220, akin to what Liebherr has done... but instead decided to go with Hybrid. Was that truly just a marketing perspective? That "hybrid" is somehow better than "optimized mechanical?" I don't know the answer to these, btw... )

Click to expand...

Deere is developing two types of hybrid drive systems for loaders, one for large and the other for smaller machines (see 944K & 644K Diesel/Electric Hybrid Loaders). I thought they were being discussed here at HEF, but can't put my finger on where.

L

Dirt dogg? Why dont you like the quickness of the controls and the pressur it takes to control them, i love the T series dozers and M series graders just because of how sensitive the controls are

D7E bin there done that we have one at work i ran it for a week had a blast

vapor300 said:

Dirt dogg? Why dont you like the quickness of the controls and the pressur it takes to control them, i love the T series dozers and M series graders just because of how sensitive the controls are

Click to expand...

Usually with electronic controls the operator can adjust the sensitivity of the control response from the Monitor System.

Not on the D6 you can on the 8's and on up the 7E idk. And i dont think you can on the M's either