Electric drive Cat scrapers??

[9420pullpan]

i heard that by 2010, the Cat 657 will be running a 400hp engine in the front with a counterweight over the rear axle with electric drive motors in their scrapers. i heard this from a good source, that there is a prototype at the proving grounds in Arizona. i guess the only trouble they are having is with the gear ratios.

what do you think??

[Countryboy]

So essentially what you are saying is that it would be 4 wheel drive, mechanical drive in the front and electric in the rear?

Interesting concept. :yup

[farm_boy]

Mechanical drive or electric drive in front? I could see the engine turning a generator that drives front and rear motors. This is nothing new....LeTourneau had electric drive scrapers way back in the day.:yup

[9420pullpan]

i heard that it will be all electric motors all 4 wheels
they are getting 400hp at the flywheel but 800hp at the wheels. it is similar to a locamotive

[Countryboy]

Now I really like it. You could be an engineer and an operator at the same time. :thumbsup

[JDOFMEMI]

i heard that it will be all electric motors all 4 wheels
they are getting 400hp at the flywheel but 800hp at the wheels. it is similar to a locamotive

Maybe I was gone that day at school when they taught us how a 400 HP engine could provide 800HP at the wheels:spaz
Something don't sound right about this

[9420pullpan]

Maybe I was gone that day at school when they taught us how a 400 HP engine could provide 800HP at the wheels:spaz
Something don't sound right about this

locamotives do it everyday

[Countryboy]

Yup, the engine is making 400 hp to the generator and the generator makes the 800 hp to the wheels. :yup

[9420pullpan]

if your gonna be a conductor your gonna have to get rid of the air horn and get a train horn!!!!!!!

[dayexco]

if doubling horsepower is possible by going diesel over electric, why aren't they using that concept in our over the road trucks, cars, pickups? to get 500 hp on an over the road tractor, you could run a 250 hp, would be a substantial fuel savings!

[farm_boy]

I'm sorry guys.....but unless you regularly operate perpetual motion machines that generate anti-gravity fields, you will be hard pressed to get 200% effiency out of a powertrain like this.

If you were able to get more horsepower out of a powertrain system that you put into it you would have found a way to cheat the first law of thermodynamics.

This law states "The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings."

In other words, you can't get more energy out of a system than you put into it. :nono

Even with the best conductors, most efficient motors and generators you simply can not get more HP out of a system than you put in. You will always have losses, the most of which being radiant heat that can not be recaptured and entered back into the system.

With that being said, this is an interesting approach to a scraper. It would give the opportunity to operate the engine at the most fuel efficient RPM 100% of the time. It would also allow the machine to have infinitely variable traction control at each wheel.

[Jeff D.]

You could have a 400hp engine drive a generator and still get 800hp at the wheels with electric motors, if additional energy were introduced via battery packs(?) maybe. (similiar to the hybrid cars system)

It wouldn't be able to sustain that level indefinately, but the charge could be built back up during off peak power consumption times.

[farm_boy]

Theoretically.....yes. The issue you have is the size of such batteries would be so big that packaging becomes a problem. Where do you put them. The next issue is weight in that all of those batteries would get so heavy that I beleive you would start to hinder the performance of the machine and negate any advantage you get by going with electric drive in the first place.

These are a couple of reasons that hybrid cars don't have electric motors with equal to or more hp than the gas engine. Packaging and weight are the deal breakers.

[Jeff D.]

Theoretically.....yes. I agree, that's probobly where it would end too, at "theorhetically".

Someday though, it might could happen..............maybe.:wink2

I only mentioned it as a "possible" way to explain it.
But not very proboble.

[Countryboy]

Your theory makes sense farm boy. I don't know much about the thermowhatchamacallits so you win that one :thumbsup .

I do have to agree with Jeff too though......laws are broken everyday :cool2 .

So...if a locomotive engine is making 800hp then the output to the wheels through the generator would only be 800 electrical hp?

Is electrical and mechanical hp the same?:confused:

[farm_boy]

Good way to put it Jeff.

I agree 100%:thumbsup :thumbsup :thumbsup

[Jeff D.]

Your theory makes sense farm boy. I don't know much about the thermowhatchamacallits so you win that one :thumbsup .

I do have to agree with Jeff too though......laws are broken everyday :cool2 .

So...if a locomotive engine is making 800hp then the output to the wheels through the generator would only be 800 electrical hp?

Is electrical and mechanical hp the same?:confused:I didn't say any laws were broken, it's just getting power from somewhere else to subsidize the engines power.:wink2

1HP=lifting 33,000lbs 1ft up, in 1 minute. It makes no difference if it's electrical or mechanical.

That said, electrical motors often have more torque over a broader range, thus a 1hp electric motor will feel more powerful than a 1hp gas engine.

[Countryboy]

Originally Posted by Jeff D.
:yupAll this learning is making my brain hurt.:wink2

Ditto.:thumbsup

[Tigerotor77W]

I only mentioned it as a "possible" way to explain it.
But not very proboble.

Really?

http://www.volvo.com/trucks/global/en-gb/aboutus/environmental_care/The_Volvo_FM_Hybrid_Concept/Technology/Volvo_I-SAM_Hybrid_System.htm

(I'm not picking on you, Jeff, just using those specific words to illustrate... the marvels of engineering theory!)

[Jeff D.]

(I'm not picking on you, Jeff, just using those specific words to illustrate... the marvels of engineering theory!)But it still feels like I'm being picked on.:crying

:wink2 No........but that does show how fast technology is catching up to our "big ideas".

In regards to the scraper, is that how it works then? With a battery supplimenting the engine for the added power?

I'd still be suprised if it was. The additional 400hp would take alot of juice. But maybe?!

I've been wrong many times before, so...............:yup

I have heard the electric drive motors being compared too larger engines before, regarding torque, which might have been done for this scraper. Just for an example, it might've been said "The (4) 100hp electric drive motors can delivery torque comparable to an 800hp diesel engine." or something similiar.:beatsme


But Hp puts the element of time into the equation also, where as torque does not.

[Gavin84w]

Well, Cat electric drive trucks will be released for public consumption after MInexpo 08 and they will have a ways to go after that to gain market acceptance etc. I would think once Cat gets that right other lines may also get the electric drive as an option, wheel loaders and scrapers come to mind and all these years after some one else had these ideas!!

[Tegian]

I know Volvo in Sweden have a hybrid drive wheelloader testbed that are supposed to drink 30% less fuel (Theoretical savings could be up to 50%) also the forestry industry is looking into the diesel/electric drive concept driven by the huge fuel savings it offers. At the very least being able to have your diesel engine run at the most efficent rpm constantly saves you some fuel further savings can be found if you have a machine that does a lot of things that allow you to regain power somehow. Breaking, going down hill lowering the bucket etc

The next generation of military scout vehicles researched by BAE Hägglunds (That have built among other things the CV90 ifv exported to several NATO countries) are also moving in the direction of a hybrid drive train. Less moving parts and lower noise signature quoted as the main advantages.

[Deas Plant]

Hi, Folks.

I didn't say any laws were broken, it's just getting power from somewhere else to subsidize the engines power.:wink2

1HP=lifting 33,000lbs 1ft up, in 1 minute. It makes no difference if it's electrical or mechanical.

That said, electrical motors often have more torque over a broader range, thus a 1hp electric motor will feel more powerful than a 1hp gas engine.

I have always understood that an electric motor produced its greatest torque when it was stalled but I'm NOT Nikola Tesla so I'll stand to be corrected on this.

Debate away, boys. Who will be the last man standing? LOL.

[Squizzy246B]

Debate away, boys. Who will be the last man standing? LOL.

James Watt???:rolleyes:

[farm_boy]

Hi, Folks.



I have always understood that an electric motor produced its greatest torque when it was stalled but I'm NOT Nikola Tesla so I'll stand to be corrected on this.


DP:

I believe you are correct in this statement. Electric motors make a tremendous (for their size) amount of torque at 0 RPM. The problem is at the high current state that creates this high amount of torque it also creates a HUGE amount of heat. Components don't last long long when are exposed to this kind of heat for extended periods of time.

[hvy 1ton]

Electric motors are one of my specialties. The last three years i have been in Team 909. We design and build robots for FRIST competitions. Pretty cool stuff if you like fabrication and machining. :drinkup I would post the url to look around but i'm pretty sure the site is in pieces right now.

If you dynoed an electric motor you would get three important points;no-load, half-load and full-load. The load is the force counter acting the torque. For a fixed amperage the more torque needed the lower the speed.The graph of a electric motor is a function of torque and speed. Speed is X and torque is Y. The function has 2 endpoints (∞,0)No-load and (0,∞)Full-load and the peak HP is somewhere near the midpoint in the function. This function would resemble a bell curve and the peak would be the peak HP. ∞ -infinity- would technically be real numbers, but in a open ended situation it works. There is much more, but you need an real engineer to go beyond this.

So, an electric motor does produce the most torque at stall, but that is not quite the same as 0 rpm. It will produce more torque at low speed than at higher speeds though. I hope this wasn't to long, kinda my speech i give the newbies every year.:Pointhead

[surfer-joe]

Nothing new for Cat, they have played with electric drives before, mostly in haul trucks. But in the end they decided that the mechanical drives were more efficient. If they are now goofing around with a hybrid, it will be interesting to see how they handle the load demands of the drive-train. Could be they are on to something.

In mobile heavy mining and earth-moving equipment, it's going to be real hard to replace the diesel engine as a reliable, efficient, and cost effective power source.

Let's see now, a Titan 190 ton haul truck, with a Detroit 16V92 at 2000 horsepower, and a Marathon 800KW generator, could only handle two 150-175 horsepower electric wheel-motors, so that's a total of 300 horses coming from a 800KW gen-set. It did move the truck most impressively. But I seem to remember the L1400 Marathon loader running about the same setup and pulling four 125HP motors. Slower, but still plenty of traction.

[Tigerotor77W]

So, an electric motor does produce the most torque at stall, but that is not quite the same as 0 rpm. It will produce more torque at low speed than at higher speeds though.

Good points. I'm not an electrical engineer (and mechanicals, contrary to what appears to be popular belief, don't know EVERYTHING), but the fundamentals seem pretty correct.

The same is actually true if you plotted pump flow (x-axis) and pump pressure (y-axis). Being an engineer, it's neat for me to see such parallels between stuff I don't know as well (all things electrical) and stuff that relates to my coursework (introductory fluid dynamics). :o

[richardcatdaddy]

Seems to me,years ago a company had an pan that had electric motor.I think it was made by Westinghouse Luturnall.My dad run one when I was a kid and if your rpms dropped you couldnt do anytrhing.All the bowl,tailgait and ejector controls were electric with a diesel engine.If I remember right that is.Some of the older hands may remember these things.

[Tigerotor77W]

Westinghouse LeTourneau, perhaps?

[Deas Plant]

Hi, Hvy 1ton.
Welcome to the forum and thanks for the input about electric motor characteristics. Now perhaps you could clear up one point for me, if you would be so kind.

As I understand it, 'STALL' is stopped, no movement, nothing going anywhere. In an electric motor, would that not mean zero revs, stopped, no movement?

Richardcatdaddy, LeTourneau made electric-controlled scrapers for some years before he sold out to WABCO in 1953. WABCO continued the line for some years but eventually gave away the electric controls for the more reliable hydraulics.

As I understand it, LeTourneau could build anything he wanted in the 5 years after he sold his earthmoving line to WABCO so long as it didn't move earth. The 5 years were up in 1958 and by the 1960's he was producing 130 ton capacity electric-drive scrapers with multiple bowls and multiple engines driving generators. So it would seem that Cat may just be getting their act together, around 50 years after it was all first done - IF they do indeed produce an electric-drive scraper. And, if they make the 657 electric drive, they will still only have what Letourneau had in 1953 when he sold out to WABCO, a 50+ cu yard machine.

Buster Peterson of Peterson Engineering, a California Cat distributor, put 3 Cat 657's nose to tail with one operator in February,1965. This gave a capacity of 150 cu. yards and a combined total of 2,850 hp. At 186 feet long, it had an elevated operator station on the rear of the front scraper from which all 3 scrapers were operated. Only 1 was ever built.

[surfer-joe]

I saw a picture one time of that scraper assembly that Peterson put together. Can you just imagine hitting 8th gear loaded going down the haul road with that thing?

The big three bowl Letourneau was a monster, but a slow monster. Fully loaded in normal dirt or clay it practically crawled along. I watched one for several hours one day in Grand Rapids, Michigan. Played hooky from college for the day just so my buddy and I could drive down and see it. It traveled the same speed loading, traveling, and dumping. Never stopped, no push-cat. Just round and round he went.

[richardcatdaddy]

Yep,thats the one,the Westinghouse one I meant.Couldnt remember for sure but thats the one. Thanks.

[9420pullpan]

are you talking about these machines


5340

5337

5338

5339

[Deas Plant]

Hi, 9420Pullpan.
The top 2 photos are of Buster Peterson's triple 657 rig, which incidentally was sold to Peter Kiewit who also bought a tandem 657 rig from Peterson's. Kiewit late bought another 657, dismantled the triple rig and made 2 tandems out of it.

The second pair of photos are of a Euclid/Terex rig built along similar lines to the LeTourneau and Cat rigs and to fulfill a similar need.

Surfer Joe, Letourneau's FIRST self-propelled scraper used an old Locomobile engine driving electric motors in each of it 4 wheels. It did the grand speed of 1 mph, loading, hauling or dumping. He ended up pulling the wheels off it, installing tracks similar to a tracked logging arch, putting a drawbar on the front and pulling it with a Cat Sixty fitted with a generator to power the electricals. The 'adapted' model is still on display at some museum in, I think, California.

I do have some photos of the above machine somewhere but can't get my grubby mitts on them right now. Strange that, especially when you consider the 'spotless' condition of my desk.

[hvy 1ton]

An electric motor will produce the most torque at 0 rpm assuming that the full current is being provided and that the load is requiring a equal or greater amount of torque than the motor's torque output. As an electric motor is loaded it slows down and provides more torque which is just what about any other drivetrain will do. And just as any other drivetrain you need a transmission to keep the power source in its peak hp/torque range. Scrapers are an especially good match to electric drive b/c they don't need near as much torque on the haul road as they do in the cut.

[activeorpassive]

An electric motor will produce the most torque at 0 rpm assuming that the full current is being provided and that the load is requiring a equal or greater amount of torque than the motor's torque output. As an electric motor is loaded it slows down and provides more torque which is just what about any other drivetrain will do. And just as any other drivetrain you need a transmission to keep the power source in its peak hp/torque range. Scrapers are an especially good match to electric drive b/c they don't need near as much torque on the haul road as they do in the cut.

An electric motor produces the most torque when the motor is at full load at rated RPM. Unless a motor's rated RPM is near zero, loading a motor down to near zero increases a motor's slip (the difference between synchronous speed, or speed of the magnetic field, and actual speed). A motor's synchronous speed (speed of the magnetic field) does not change due to a constant frequency and voltage. So as you load the motor down you increase slip, thereby creating heat and shortening the life if not destroying the motor.

The only way to get a motor to produce full torque at near zero RPM is to use a Variable Frequency Drive (VFD) where the voltage and frequency can be varied, but the ratio of volts per Hz can be kept constant.

[randy448]

Did anyone say Cat would make the thing? Engineers try all kinds of ideas but few ever get very far.Books I have are full of one-of attempts at an idea.CAD is nice but still iron in the dirt gives you the real results.:usa

[John C.]

Horse power is horsepower and cannot be changed going through any kind of transmission device. As I recall the capacity of the electric motors in a locomotive are usually double the capacity of the drivers. In other words in order to ensure durability, the horsepower capacity of the electric motor is double the engine output horsepower. The motor could take producing 800 horsepower but the engine only put out 400 so the motor can take the high startup loads over a long period of time.

I ran and repaired Letorneau scrapers at one job I worked. They used diesel engines driving a generator with a clutch and five speed transmission behind the generator. These units did not use an electric drive system. The electrics worked the bowl lift, ejector and machine steering. Wire rope pulley systems driven by motors worked the bowl and ejector functions. They were very problematic in that limit switches were used to cut off power when a function reached the end of its travel. The limit switches often failed and the cables would be snapped like a piece of spaghetti. We were constantly replacing cables and switches as well as clutches.

Diesel electric haul trucks have been around for probably forty years or more. They work very well in dry conditions using good haul roads. Bring in copious amounts of rain and form deep mud and they develop the types of problems described earlier in this thread. They overheat and burn up.

Electric drives up until about 15 years used DC motors. I saw some large Haulpak trucks go into a coal mine here a few years ago that used AC drives. They haven't had the stall out issues that the DC drives did and I'm wondering why. Scrapers would be prone to stall outs all the time and in context of this disscusion perhaps the use of AC drives make sparkys possible for scraper use.

Does anyone have any input on this.

[Lashlander]

Welcome to the forum! Excellent information.:thumbsup

[Countryboy]

Welcome to HEF randy448! :drinkup

[activeorpassive]

Horse power is horsepower and cannot be changed going through any kind of transmission device. As I recall the capacity of the electric motors in a locomotive are usually double the capacity of the drivers. In other words in order to ensure durability, the horsepower capacity of the electric motor is double the engine output horsepower. The motor could take producing 800 horsepower but the engine only put out 400 so the motor can take the high startup loads over a long period of time.

I ran and repaired Letorneau scrapers at one job I worked. They used diesel engines driving a generator with a clutch and five speed transmission behind the generator. These units did not use an electric drive system. The electrics worked the bowl lift, ejector and machine steering. Wire rope pulley systems driven by motors worked the bowl and ejector functions. They were very problematic in that limit switches were used to cut off power when a function reached the end of its travel. The limit switches often failed and the cables would be snapped like a piece of spaghetti. We were constantly replacing cables and switches as well as clutches.

Diesel electric haul trucks have been around for probably forty years or more. They work very well in dry conditions using good haul roads. Bring in copious amounts of rain and form deep mud and they develop the types of problems described earlier in this thread. They overheat and burn up.

Electric drives up until about 15 years used DC motors. I saw some large Haulpak trucks go into a coal mine here a few years ago that used AC drives. They haven't had the stall out issues that the DC drives did and I'm wondering why. Scrapers would be prone to stall outs all the time and in context of this disscusion perhaps the use of AC drives make sparkys possible for scraper use.

Does anyone have any input on this.

Yes, horsepower is horsepower...but torque was the topic. And torque can be divided or multiplied through various means.
There are plenty of DC trucks floating around, but their numbers are fading. DC voltage is easier to control, but the proliferation of cheaper Variable Frequency Drives is making AC motors the technology of choice.
VFDs have come a long way, and although higher in cost at initial setup vs DC applications, the advantages are greater after even a short time period.

AC motors are cheaper to produce, and usually require less maintenance due to the removal of brushes and slip rings. This factor alone rules out DC for use in larger horsepower applications (4,000+) There are brushless DC motors, but even they have a higher maintenance cost in the long run, due to the addition of the excitation field winding for the DC rotor's armature, as well as the addition of the necessary rotating diode packs to control the field current going to the main rotor's pole pieces.

AC drives can provide 100 percent continuous torque (not HP), even at zero RPMs. This should account for the reduction of stall outs. DC drives can vary torque, but can not maintain constant torque through varying speed ranges.

DC motors will "run away" if one of the stationary fields are opened. While not a concern while the motor is under heavy load, a DC motor that runs away under light to no loads will continue to increase in velocity until it destroys itself. This is hazardous to not only the motor, but the attached load and any personnel in the area.

AC still has faults. The system has a higher initial cost (as mentioned earlier). The space requirements are also greater. In the world of big trucks, production is King, and space reduction due to physical size usually means payload reduction. Poor VFD design or application can lead to nasty voltage harmonic imbalances, which will eventually lead to premature failure. Regenerative braking is not inherent to an AC motor's design, so passive elements must be used to retard the energy created under coast conditions.

Both technologies have their place. There are still mines that employ both technologies and will spend the time and money to keep their DC trucks in production. I believe in the long run it all comes down to intended applications, ability to support maintenance/tooling, and perceived advantages.

[Jessikah]

Hmm that is interesting

[JASON M]

Maybe I was gone that day at school when they taught us how a 400 HP engine could provide 800HP at the wheels:spaz
Something don't sound right about this

I'm with you on this; Losses will be incurred. Horsepower is the rate at which work is done. You can't convert 400 hp into 800 hp............ but you can definitely convert 800 hp into 400 hp with driveline losses (in theory)

[surfer-joe]

Hmmmm. Takes about 400 horsepower to make 350KW. For a machine the size and weight of a 657, and to make the required speed on the haul is going to require more than 350KW. The standard engine in the 57 is about 550HP in front, 450 in back, about 1000KW. To retain the capability of the now existing 657 means the KW rating from a single engine on an electric drive 657 would need to be about 1300HP.

WABCO built a double barrell elevating unit in the early seventies that had a V12 Detroit fore and aft. It went like hell and loaded very well. I believe the engines were about 425HP each. 850 HP in all, and that machine was about the size and capacity of a 633 CAT.

LeTournau electric drive loaders and trucks in the early nineties used 150-200HP wheel motors in the rear wheels on the trucks, all four on the loaders. Minimum engine size was about 2000HP on the trucks (150 tonners), and about 2500 on the loaders (L1100).

I'm no electric expert, just have a little experience with a few electric drives. All in all, I'd rather have the mechanical setup as is.

Fun speculation, be interesting to see if more info comes out of CAT, or maybe in CE.

[Gavin84w]

Cat ED scrapers, agghhh no. EOS

[JTL]

This is kinda of an old thread, (started in 2007) but Im glad it got brought back up, after all it is 2010 now!:drinkup

Very interesting topic. I actually think I learned a thing or two about electric motors this morning! I had a mechanic working for me last summer that use to work in a coal mine in western Washington state. He was explaining to me how the haul truck drives worked, but I kept getting confused. After reading how the work, I kinda understand now. Might be interesting to see Cat try this concept. Although I not belive now is the time to try it with the economy the way it is.

On another thought- since it is 2010, and our president is black, I want to know one thing. WHERE THE %@&* IS MY JET PACK!!:)

Jason

[Gavin84w]

Cat is hurting a lot i think and keeping the company afloat profitably is priority No 1. I would think a lot of development projects have been cancelled. Think how many 793,s they sell vs scrapers and they have canned the electric drive 793 for the moment.

New product introduction always comes with a premium % higher cost than the previous models sold and with scraper prices today and higher prices for new models in the future a certainty i don,t think we will ever see ED scrapers from Cat, who would they be trying to keep in front of with a higher technology?

[Greg]

Makes sense to do it. The reports on the new D7E's being tried are all good. Reports are 20% less fuel than previous models and more push. I don't know why it has taken so long to get to this point as rail road locomotives have been doing it since the 1940's.

[OC(Outside Cat)]

If I remember correctly, Cat bought a company a few years ago,that used electric drives in something, (might have been a haul truck company) I thought at the time it would be interesting to see how they would use the electric drive set up.

OC

[malcolm]

May bee after 50 years cat are going to make a crowd pleaser like this cheers malcolm