CAT D7E Electric Drive Dozer

[Deas Plant]

Dc/ac

Hi, Trackfanatic.
I agree with most of what you say and, while not out and out disagreeing with any of the rest of your post due to lack of knowledge, I reserve the right to disagree if further information leads me that way.

As I understand it, the Cat D7E diesel/electric dozer is all AC with AC induction drive motors. The system in its current form appears to have double reduction gears on the output shafts of the electric motors. The power is then fed to planetary reduction hubs in the sprockets. That is still a fair gear train, although I grant you there is no powershift or direct drive transmission, torque converter or steering clutches and brakes.

Personally, I like the idea but I'm reserving judgement until more information and bums-on-seats experience is available - or until Cat or a Cat dealer offers me the chance to play with one in some serious dirt.

Just my 0.02.

 

[Deas Plant]

Murray-Darling river complex

Hi, Aussie Nick.
Pardon me if I'm perhaps a little ill-informed here as I do live some few hundred miles away from both those rivers but I thought that the main problem with the Murray-Darling system was the amount of water NOT allowed to flow through it due to all the various impoundments that had been constructed. Not the least of these would be the Snowy Mountains scheme in N.S.W. and Cubby Station here in good old QLD but there are many other smaller impoundments that have a cumulative effect in reducing the systm's flow to a trickle and even to non-existence.

JUst my 0.02.

 

[trackfanatic]

Fair enough Deas. I hadn't looked at the Cat system and just assumed that they'd have done it similar to what I've seen. I'm no expert but have some experience, and assumed wrongly.

 

[Aussie Nick]

The irrigation was always a strain on the Murray Darling system, but despite this the system was managing to cope. A believe two years ago the Darling stopped flowing altogether and the flow in the Murray has declined in spite of a flush out of lake Mulwala,which is partly associated with pestulent weed destruction.
Melbourne's water supply declined to 29% a few weeks ago (Despite drastic reductions in consumption over the last three years) and the State Government has commissioned the construction of a desalination plant. Lake Eildon is a skeleton of its former self and it is impossible, almost, to take a power boat through some sections without ripping out the keel and prop.
I believe that some of the dams in Brisbane were also under some considerable stress.

 

[grunk36]

here is a video from conexpo about the D7E http://www.constructionequipment.com/index.asp?layout=nocclamp&articleid=CA6551310

 

[counter]

diesel over electric

diesel over electric power is so well proven, im surprised its taken this long to see itself into th h.e. market! perhaps im wrong, maybe the dust dirt is going to play a factor! but someone had to get there feet wet with this proven source of power. the mine shovels have been using this electro source for ,what , 50 years? i hope weve advanced a little since then!even if the electro thing works for the best, you still get ur diesel noise, smell, and grunt!!!! if this does work out, my opion would be, komatsu is going to be on this like a teenage boy on a cute blonde girl! i wish cat the best on this effort! im sure all the other h.e. mans. are watching this very carefully!its all good! progress is progress! i see many posters here to claim the old stuff was better built! and maybe so,but we have to move ahead! any of you guys want to start a fire in the boiler of ur tractor before you work? if ur doin a little pokin around the farm, thats one thing! most of the guys in here are triyin to make a living pushing dirt! damn ive babbled too long, deas is gonna be pissed! lol

 

[oldirt]

I would say the old stuff was very well built, so much so that improvement via complete redesign of the powertrain will be hard to justify.

Performance is something that is measured in thousands of hours, not video clips.

Just my opinion..

 

[JDOFMEMI]

I would say the old stuff was very well built, so much so that improvement via complete redesign of the powertrain will be hard to justify.

Performance is something that is measured in thousands of hours, not video clips.

Just my opinion..

Olddirt

Red this thread for some reviews of the machine. https://www.heavyequipmentforums.com/Forum/showthread.php?t=12753

And NO, I do not work for Cat. Just a lowly contractor.

 

[oldirt]

I have already read those, I am not dissing this thing, all I am saying is what we have been used to worked real well and lasted a long time under the most trying of operators and rough conditions. To beat that is going to take some doing, although it is completely possible. I am not against this at all, just pointing out the hurdles cat must jump over without a mistake. I am also quite sure they know exactly what this all means. Like in pitch, you can't win crap if you don't get the bid.

As for this big change in drivetrain, you gotta start somewhere. Maybe this will be the new standard. I don't believe I would like to be the guinea pig, although it would be fun if someone else paid for it.

I am no different than you, just expressing my opinions. Hopefully not to po anyone too.

 

[Greg]

I do have to agree with Dozer575 about the quality and type of operators coming out of the pipeline. Had a kid showed up here looking for a job, not that I was looking for any help in these wonderful economic times, informed me he was a third year apprentice, and informed me that he refused to operate any equipment lacking air conditioned cab, stereo and GPS.

 

[watglen]

My thoughts:

The motors and converter had better be water cooled cuz a lot of you guys operate in some dirty dirty conditions.

As much as those black box electric controls will cost a ton to replace for certain, electronics have come a long way and they really make problem diagnosis faster and more accurate. I recall a 6H i was considering buying, except it had an overheat condition in the tranny. The dealer had spent countless hours tearing it apart, replaced nearly every seal, pump, cooler, valve body inside the tranny. They simple could not get it to stay cool. Sucked for them, cuz anytime someone was looking at buying it, it would overheat. Even in near freezing temps in Ontario. Anyway, all i can say is modern powershift trannys are so complicated ,sometimes you get problems that can't be diagnosed. With any luck, this new drive system will eliminate that.

They've been moving trains, ships, and cars for years now with electricity. Its the next big thing.

Personally, i really like the idea.

 

[counter]

drivetrain! so true dirt!!!!!

I have already read those, I am not dissing this thing, all I am saying is what we have been used to worked real well and lasted a long time under the most trying of operators and rough conditions. To beat that is going to take some doing, although it is completely possible. I am not against this at all, just pointing out the hurdles cat must jump over without a mistake. I am also quite sure they know exactly what this all means. Like in pitch, you can't win crap if you don't get the bid.

As for this big change in drivetrain, you gotta start somewhere. Maybe this will be the new standard. I don't believe I would like to be the guinea pig, although it would be fun if someone else paid for it.

I am no different than you, just expressing my opinions. Hopefully not to po anyone too.

we will, just have to see whaat they do!

 

[counter]

dirsel over elecetro

i guess we can only see where the the new d-7 is going to go!i believe cat will make this idea really come aliveeeee!time will tell! id love to hear some other coments on this drive system!!!!!

 

[Tracklayer]

Some place in this thread or the other one, there is a link to an article calling this new D7 a hybrid. Does Cat call it a hybrid?

Looking at the various sources that give the definition of hybrid vehicles, I cannot say that I clearly understand what the definition is. Generally, the definition seems to be a vehicle that is powered by more that one power source such as a gasoline engine and an electric motor. And specifically, this would mean that either the engine could propel the car directly through a transmission, or an electric motor could propel the car directly by taking power from batteries. So hybrid vehicles have massive battery banks.

But I don’t think that a vehicle such as a diesel-electric locomotive could be classified as a hybrid because they cannot shift back and forth, running on just the electric motors or just the diesel engine. The engine and motors must work together in a way that has the alternator (or generator) and the electric traction motors acting as a type of transmission in which voltage and amperage can be varied to modify drive torque and speed. The same would have been the case with LeTourneau motor scrapers and wheel dozers.

I assume that this is the basic system used on the new D7. But to really clarify this, I am wondering if the D7 has battery banks beyond what would be needed to just start the diesel engine, and if power is taken from the batteries to drive the traction motors under some circumstances.

 

[Greg]

Nope, no hybrid of any style here and Cat does not call it one. Strictly Diesel electric, no batteries other than for starting the Diesel. I also think that automotive has totally missed the boat by not doing the same thing that Cat has done here. As I understand it this is also an AC arrangement. That is going to make it tough to adjust voltage and current to modify torque and speed. Diesel electric locomotives are not thought of as hybrid either. They are strictly Diesel electric also.

 

[Nothinbetter]

Hybrid and AC

That is going to make it tough to adjust voltage and current to modify torque and speed. Diesel electric locomotives are not thought of as hybrid either. They are strictly Diesel electric also.

That is not true anymore, with inverters AC has as good if not better control than DC today. With AC you have full torque through a large RPM range of the motor by controlling the volt Hz relationship. AC motors can be more efficient and easier to maintain than DC.

This dozer could also be listed as a series hybrid. That is a vehicle that a motor powers an electrical gen. source and that either powers batteries and/or an electric motor. Most cars are a parrallel, that the combustion motor can either power the vehical and/or charges batteries, and the electric motor can power the vehicle. Below is a link to a Cat document that they are calling it a hybrid drivetrain. The newer trains are also calling themselves hybrids. GE released a train a few years ago they were calling a hybrid due to it had battery packs that on braking would be charged up for later use. The DOE worked with both Ford and UPS to develop a hydraulic hybrid. It uses a pump attached to the drive shaft that under braking pumps fluid into a nitrogen filled tank to store pressure and upon take off the flow is reversed and the pump is used as a motor. This boosts th vehicle on take off.
I think hybrid is just the new catch phrase of the day. These use to be called Diesel electric or gas electric.

http://www.cat.com/cda/files/1577483/7/179PR09 D7E - Press Release & Images.doc

 

[Tracklayer]

Thanks for that information Greg and Nothinbetter.

According to that link to Cat, they do call the new D7E a hybrid. I do agree that the term hybrid has become a catch phrase. The term has become fashionable as a component of the green movement. I don’t know if that is the intent with the new D7E, but the green movement has become very popular as a marketing objective. I am wary of products that are developed and marketed to be green because that objective has no clear definition and often forces the design to compromise other aspects of its performance in order to meet a green objective. Green housing would be an example. As I mentioned, I looked at several definitions of the term hybrid. According to one definition, a diesel-electric locomotive would be considered a hybrid even without the new feature of storing dynamic brake energy in batteries for reuse powering the traction motors. However, calling a straight diesel-electric drive a hybrid does seem like the furthest stretch of the definition, and seems motivated by the ability to use the term as a marketing tool.

I am not reaching any conclusions based on this issue as it pertains to the new D7E. I am sure that it will get a chance to clearly prove itself to completely objective users who will evaluate it in hard terms of first cost, operating cost, maintenance cost, and performance. What I really find interesting is that Cat suddenly makes this radical departure in drive train design. If this is truly the way to go, won’t everything go this way? If so, it seems amazing that drive train preference could just turn the corner overnight.

Diesel-electric drive has been around for a long time, but it has only been applied to certain classes of equipment. Locomotives generally have settled on diesel-electric, but even with them, there has been considerable application of diesel-hydraulic drives. Back when Letourneau was building diesel-electric Tournapulls and Tournadozers, he must have thought that was the way to go. A lot of people must have asked Cat why they were not jumping on the Letourneau bandwagon. What would Cat have told them?

 

[Nothinbetter]

Some of the reasons we may be seeing this now are cost and tech advancement. Even though inverters have been around for a while it's only been the last 10-15 years that in this application AC motors have surpassed DC motors. Cost have also come down on inverters by probably 5 or 600 %. I know drives that use to cost $2500.00 - $3000.00 now cost $500-$600.00 (I'm sure the drives on the D7E are much larger than what I'm refering to). Now these have come down in cost to the point that even houshold washer machines, clothes dryers, airconditioners, and larger air compressors have inverters. These newer drives are also much smaller, and can do in some cases 100 times the amount older ones did. As computer chips get more powerfull and cheaper, this has helped the drives come down in cost and size. I know in the past drives were expensive and so were repairs. Now in some cases a drive a few years old can be replaced with a much better unit cheaper than they can be repaired. So it may now pay on smaller machines to make this work where in the past it looks like only high HP machines (mining trucks, shovels, trains etc).

Even with that the D7E it sounds like is going to cost 20% more than a D7R. The payback on a Hybrid car from what I have read is about 8 years with $3.00+ a gallon gas. I also wonder why the parallel system is used in cars and not the series like the D7E and trains. Seems like a lot of extra weight and mechanical loss to add a transmission.

 

[counter]

cat d7e

in regards to all the responses about diesel over electric, i was wondering if anyone here knows if letourneau was still toying with this set up, seeing that they started the research! we gotta love that company!!! talk about r+d! they really should be the "cat" of today!!!!!!!

 

[JDOFMEMI]

Counter

As far as "toying" with it, no. If you mean are they still producing diesel-electric drive as they have been for over 50 years, yes.

Here is a bit of info. http://www.letourneau-inc.com/mining/features.htm

and here http://www.letourneau-inc.com/mining/pdf/50_Series_Brochure.pdf

Letourneau and Cat have been managed in different ways over the years, and that has led each of them to where they are today.
RG had many ideas that were ahead of the reliable technology to make them work. When the company was bought out in the 50's or early 60's by Westinghouse, the company had the potential to grow and rival Cat, but due to choices made that was not to happen. Once Letourneau got away from Westinghouse, they were far behind Cat in market share, and have never been able to recover that.
They have done a good job of sticking with the things they are good at, like the large loaders.