Canadian Railroads > MLW M-640

Can you guys tell me about this one of kind locomotive. I have seen several photos of this loco where it is stuffed and mounted today but can't really find any info about it's design. I know in later years was used to test AC traction but thats about it. Was it a success or failure? Could or should it have kept MLW in business longer? Thanks for any help!

Here it is in 1987 at Cote St. Luc, PQ.

©John C. Benson

Mr. Slides®

http://www.mr-slides.com

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18-251 , Blt@1972 only unit but was a "production" unit. Was designed by ALco (18 cyl) in the late
'60's but Alco shut down around 1969. MLW inherited a # of Alco employees who brought the design with them. 4000HP . The AC motors of German manufacture were part of a rebuild in the late '80's
resulting in a A1A-A1A arrangement. I think the truck wheelbase was to short to accomodate the
larger motors, retired in the early '90's , now in the Canadian Railway Museum Delson Quebec.
I don't think the 18 cyl prime mover was aq problem, but it suffered reliability issues like all
other ALco's/MLW's . I think lack of attention to body , internal equipment design , somewhat
lack of quality of construction were the issues.The 251 motors and GE Generators/Alternators were
a positive. Railways that did good timely maintenace held them in high regard..BCR, D&H to name
two. MLW quit building heavy haul road freight locomotives in the early '80's before advanced
computerization really could effectively use 4000 HP. BUT as long as MLW continued to use a compeititors compenents, paying retail for them while GE sold the same to their loco division at
cost put MLW and ALco at a price disadvantage. And assumimg MLW didn't improve their quality and
factory follow up the 640 wouldn't have made any difference. In the early '80's CP tested a group
of HR616's for 6 months, and they weren't impressed. The HR616 was a essentially an updated M630
in a cowl body, like CN 2400's/5400's /5500's. Apparently in the mid '80's some HR616's were
re-ewquipped with Hitachi traction motors, likely with the view of breaking away from being dependent on GE, but nothing came of that.
The M640 was ahead of it's time in the form of 4000HP & especially with AC motors later on, but
MLW gave up the ghost on freight diesels not to long after. Less than good reputation for quality
did MLW/Alco in and RR's have long memories. I think the AC motors are still on the unit.
To bad isn't it
Ron Aboussafy

Wow thanks for the insight on this one of a kind cool unit! Refering to the beautiful slide scan that Mr. Slides showed us what is the box directly behind the exhaust stack and above the GE like radiator? Also, refering to the quality statement, I thought that's what alco's were mainly known for. Being bulky rugged industrial machines! How did CN and CP like the fleets of M630's and M636's? They seemed to have lasted quite awhile pulling trains. Cartier mining loved there's, I know that from a video my buddy showed me.

Cartier was a little bit of a different mindset. The were isolated to the extreme. No roads along most of the route. So every train, a set number of cars out of each train and engine consists, went into the shop every trip for a good check over before heading out into the wilds of Quebec. Cartier, or QMC, did real maintaince. QMC's were the only Alcos/MLW's I NEVER saw smoke!

When I say the mindset was different, the railroad was only a conveyor belt to the mining company. Had the mine and port been closer I am sure they would have used a conveyor belt instead. Crews were US Steelworkers union, due to ties with US Steel if I remember correctly. If the trains didn't run the raw material did not make it to the pellet plant and everything came to a halt.

In the end, QMC rebuilt a group of M636s into what the shop supervisor was quote as being "Dash-8 Alcos." Those may still be running today. But it is a small fleet, maybe 5-6 units.

QMC shop people told us they had to go to new power because whoever still supplied parts and support, possibly GE, was ending that support around 2000.

Any additions welcomed, its been 7 years since I had those conversations!

The CP's 4744 M640 was rebuilt with only four (4) AC traction motors because the engine-and-alternator did not have enough horsepower to successfully power six motors! It was rated 4000 traction HP on 4 powered axles. A total of $6 million in Canadian dollars (back in the early-1980s) went into converting the locomotive to AC traction. The program partners were CP Rail, BBC or Brown Bovari Canada and Bombardier; the Canadian Department of Regional and Industrial Expansion was also a funding partner.

The 18-cylinder engine, again, was rated 4000 HP for traction (into the alternator) while it's gross HP (for traction plus auxiliary loads like fans, blowers, etc.) was about 4300 HP.

Each of the BBC AC traction motors had a continuous rating of 881 HP, so 4 of those motors represented a continuous power demand of 3524 HP on the 4000 HP Alco 251C engine and the alternator. If all 6 axles had been powered, the motor demand would have been 5286 HP or 32% greater than the engine's (and the alternator's) traction output.

CP tested and documented the 4744 with AC motors as being able to develop about 93,000 pounds of tractive effort at start (about 23% starting adhesion, the percent of weight converted into tractive effort) which was about 33% more than the typical 18% rating for an SD40-2.

You can see right here, with this locomotive as it was rebuilt, the challenge which faced locomotive builders in the early stages of getting into AC traction ... Previously, diesel engine power had eclipsed the ability of DC traction motors in power ratings. (An SD45 or SD45-2, for example, was rated 3600 HP for traction but only at speeds above about 15-18 MPH ... below that speed range, the units derated to the equivalent of 3000 HP SD40s or SD40-2s because the traction alternator wasn't big enough to pump out the equivalent of 3600 HP at low speeds.)

When EMD introduced the SD70MAC on Burlington Northern in 1992, they married the 4000 HP 16-cylinder 710 engine with 6 Siemens AC traction motors. When GE introduced the AC4400CW in 1993, the 16-cylinder FDL engine pumped out 4400 HP. The 10% extra horsepower GE carried gave the AC4400CW an advantage over the SD70MAC in low-speed high-tractive effort service, which is why the GE's quickly gained supremacy in western coal service on C&NW, CP and UP. (The first AC4400CWs in the west were UP 9997-9999 which were considered experimental, but UP primarily used them in intermodal service. It's first production GE ACs were the first 35 C&NW AC4400CWs, followed by C&NW's 2nd order for 50 were were delivered in late-1995 shortly after the merger. CP likewise put its AC4400CWs into heavy-haul service in the western Canadian Rockies replacing SD40-2s in coal service.)

So, when AC traction finally started catching on here on North America, the "power challenge" suddenly switched from insufficient traction motor power to making the diesel engines catching up.

The relatively short-and-limited excursion into 6000 HP AC technology on BHP, CP, CSXT and UP also drove this relationship. In fact, after EMD got the SD70MAC into production, rated 4000 HP on 6 AC motors (each rated for 4000/6 = 667 HP), EMD and GE both bit the 6000 HP carrot and developed their 6000 HP versions. This was one time when being "2nd in the race" was an advantage for GE, because it had designed the AC4400CW with 1000 HP AC motors (even though the 16-cylinder FDL engine was only sufficient for 4400 traction HP), knowing that a 6000 HP engine was coming. EMD responded with the 4300 HP SD90MAC "convertible" units which have 1000 HP AC motors.

A paper published by CP, BBC and Bombardier in 1986 also closed by speculating on the development of 6000 HP AC locomotives to replace 3000 HP DC locomotives on a 2-for-3 basis.

Don't hold your breath long for the return of 6000 HP AC technology. At least not in the "west". Coal trains today are all sized (at the mines, on passing tracks, in yards and at the power plants) for train lengths which are accommodated generally by either 3 or 4 4300-4400 HP AC units. And, the reliability of the 6000 HP units was not what it had to have been to replace SD40-2s, SD60s and Dash-8s.

By the way, perhaps the most important sentence in the entire CP paper about the AC-motored 4744 was this:

"An AC traction package is not seen as being a viable retrofit item for two reasons: today's retrofit cost is too high; and maximum benefit would not be achievable unless the remainder of the locomotive could be upgraded to comparable levels of performance, particularly in the diesel engine rating."

Um...the motors don't "demand" any particular amount of power. You pump in what you have so long as it doesn't exceed the capacity of the motor, taking into account continuous duty and short term overload. I presume the A1A-A1A came from size and clearance issues with those motors. Or maybe they just didn't want to mess with the added complexity. (Was this inverter-per-axle or inverter per truck?) Even if the prime mover had had far less HP you'd still prefer the 50% greater weight-on-drivers of a C-C for the greater starting tractive effort.

Not to mention that just in general it's kind of silly to think that 4000 HP isn't enough for AC traction. I don't see anyone calculating what the maximum possible HP of Siemens or GE AC traction motors and seeing if it's greater than the diesel engine output. It doesn't work that way.

There is/was a "power demand": The alternator created a torque load (which is a power "demand") on the diesel engine, and the inverters-and-AC motors put a "power demand" (an electrical load) on the alternator. Think finger, hand, wrist, elbow, OK? Or maybe film, sprocket, gear, motor.

The diesel engine (like that on all diesel-electric locomotives) was regulated (by a device called a LOAD REGULATOR) to a pre-set maximum power output, which was ... 4000 HP. Otherwise, the engine would bog down and you exceed the design loads for various components like engine bearings, run the risk of piston rings scuffing the cylinder liners, breaking a crankshaft (... all apparently minor problems, right?). Picture load noises, smoke out the stack, engine pieces blowing through the carbody doors. If the engine did exceed 4000 traction HP and did not fail, then you also run the risk of electrically and thermally overloading the alternator. Picture fire and smoke.

The CP 4744 had four 3-phase inverters, each rated a maximum of 1000 HP, connected in parallel to the DC bus (2 cables) coming from the GE alternator.

The inverters, connected in parallel as one group (one big inverter), were connected to the four AC motors, with all four motors in parallel.

So this locomotive was neither one inverter-per-motor (like GE) or one-inverter-per truck (like EMD), but one (big collective set of inverters) per (complete locomotive with 4 motors).

Yes, had there been enough space, they could have installed six inverters, but the GE GTA9 alternator could only produce enough electrical power to support 4000 HP. And the diesel engine ... well, go back and READ the entire post. Please. It was rated 4000 HP.

Installing 6 inverters and 6 AC motors (which would have fitted in the trucks) would have produced a 6000 HP (electrical) locomotive powered by a 4000 HP (engine) prime mover. Since the entire purpose was to demonstrate the feasibility of replacing SD40-2s, your 6000 HP (electrical)/4000 HP (engine) locomotive WOULD have pulled even more tonnage BUT at significantly lower speed.

4000 HP engine.

4000 HP alternator.

4000 HP inverter package.

3524 HP in AC motors (technically each motor was rated 1000 HP).

Finally, if you STILL think they should have installed six AC motors (and ended up with a locomotive which could pull another 50% tonnage but at 33% lower speed) ... the end result would have been no net improvement in locomotive productivity. A locomotive which pulls more tonnage but at a lower speed does not produce any more transportation work per day. Transportation work in the railroad world means moving tonnage from A to B in a given amount of time. If you move more tonnage but in a longer period of time ... you gain LITTLE TO NOTHING in overall railroad productivity.

CP wanted a replacement for SD40-2s. Having a replacement locomotive which would pull more than an SD40-2 but only at a lower speed would slow down the railroad. No gain. No reason to do that. Waste of money.

Last, hanging 6 AC motors under a 396,000 pound locomotive, with each AC-powered axle capable of 23% adhesion, would have traction-wise overpowered the locomotive. Twenty three percent of 396,000 pounds is 91,000 pounds of tractive effort (which 4 AC motors produced). If enough engine and alternator power had been available (... like 6000 HP), the locomotive would have had to have weighed a ridiculously impossible 593,000 pounds to use the same 23% adhesion capability with 6 AC motors.

I never expressed an opinion on what they should or shouldn't have done. I'm saying you're wrong that more motors would have overloaded the engine because the motors do not create a demand. They take what you send them. If you only have 4000 HP then your load regulator only puts 4000 HP load on engine. The fact that the motors *could* take more is beside the point. Heck, at some intermediate throttle notch the engine is only putting out 2000 HP and the that's fine because between the governor, the load regulator, and the inverter circuitry the engine is then only being loaded to 2000 HP. Likewise at full throttle the engine is "only" putting out 4000 HP and the load is matched to it. Bottom line is that whatever decisions were made in the design as regards number of motors whether size, weight, simplicity, inverters, etc. it seems highly unlikely that the decision was based on the engine not being powerful enough. There is plenty of 6 motor AC traction power out on the road right now of similar horsepower. Please don't say well that's because they used less demanding motors because that's just flat out ridiculous. Motors (in this situation) do not demand. And the desirability of having more locomotive weight converted to tractive effort in heavy freight service is going to be the same. There was something working against a six motor design and it wasn't prime mover horsepower. I'd wager motor size but that's just a guess.

Unless someone can cite authoritatively from someone involved in the design we'll just have to agree to disagree.

greendot Wrote:
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> You can see right here, with this locomotive as it was rebuilt, the challenge which faced
> locomotive builders in the early stages of getting into AC traction ... Previously, diesel
> engine power had eclipsed the ability of DC traction motors in power ratings. (An SD45 or
> SD45-2, for example, was rated 3600 HP for traction but only at speeds above about 15-18
> MPH ... below that speed range, the units derated to the equivalent of 3000 HP SD40s or
> SD40-2s because the traction alternator wasn't big enough to pump out the equivalent of
> 3600 HP at low speeds.)

That's not the primary reason they derated at lower speeds. The main reason was for power matching with other types of locomotives. If locomotives of similar adhesion capability, but different horsepower per motor, are coupled together, their tonnage ratings are reduced, compared to the locomotives operating alone. This is because the tonnage speed of the locomotive with the lowest horsepower per axle is so low that they would overheat the motors
of the higher horsepower locomotives with full tonnage assigned in a combined consist.

Consider that the GP-40, which had the same alternator as the SD-40, but fed into only four motors, was derated at low speeds so it would marry up with SD-type locomotives without overheating or heavy wheelslip.

All the manufacturers standardized on 500 hp per axle, and locomotives that had higher power were derated to that standard at low speeds. This included locomotives like the SD-45, GP-40, U-30B and C-425. It was only after adhesion control systems improved that the derating was no longer needed.

Very low HP locomotives like the SD-38 were considered to be applicable in other types of service, and not normally MU'd with higher HP locomotives in drag service, so their low HP per axle was not considered a problem. Railroads that owned them simply had to keep them in separate pools.

> By the way, perhaps the most important sentence in the entire CP paper about the
> AC-motored 4744 was this:
>
> "An AC traction package is not seen as being a viable retrofit item for two reasons: today's
> retrofit cost is too high; and maximum benefit would not be achievable unless the remainder
> of the locomotive could be upgraded to comparable levels of performance, particularly in the
> diesel engine rating."

Exactly. CP dispatched their SD-40s at the time at 18 percent adhesion, which meant that full tonnage trains would operate up the ruling grade at about 12 mph. If the AC traction locomotives could deliver 50 percent more adhesion, then with 3,000 HP, AC traction locomotives could handle 50 percent bigger trains, but they would only operate at 8 mph up the ruling grades, which is pretty slow for a long grade. Hence the need for a proportional increase in horsepower. At the time, CP's ideal AC traction locomotive was 5,000 HP, which is why they pushed EMD to offer the SD-80MAC.

filmteknik Wrote:
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> There was something working against a six motor design and it wasn't prime
> mover horsepower. I'd wager motor size but that's just a guess.

It was the engine horsepower, but not because more motors would overload the engine. It was because CP had their heart set on an AC locomotive of 5,000 hp with six powered axles, and wanted to test their theories on motors rated at 1,000 hp per motor. The only way they could do that with a 4,000 hp engine was to use 4 motors.

DeutzHDL Wrote:
-------------------------------------------------------
> Wow thanks for the insight on this one of a kind
> cool unit! Refering to the beautiful slide scan
> that Mr. Slides showed us what is the box directly
> behind the exhaust stack and above the GE like
> radiator? Also, refering to the quality statement,
> I thought that's what alco's were mainly known
> for. Being bulky rugged industrial machines! How
> did CN and CP like the fleets of M630's and
> M636's? They seemed to have lasted quite awhile
> pulling trains. Cartier mining loved there's, I
> know that from a video my buddy showed me.


Nacionales de Mexico liked their ALCOs so much they repowered a few GE U36Cs in the mid 1980s with ALCO 251s. Apparently it was unsuccessful as the program ended.

Mr. Slides®

http://www.mr-slides.com

greendot Wrote:
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> A locomotive which pulls more tonnage but at a lower speed does not produce any
> more transportation work per day. Transportation work in the railroad world means
> moving tonnage from A to B in a given amount of time. If you move more tonnage but
> in a longer period of time ... you gain LITTLE TO NOTHING in overall railroad
> productivity.

I disagree with that. You will still gain in productivity, and save fuel, but at the cost of running time. The question is whether the running times will meet market expectations.

Espee, as an example, happily ran SD-9s on heavy haul trains, like beet trains, for many years.

> Last, hanging 6 AC motors under a 396,000 pound
> locomotive, with each AC-powered axle capable of
> 23% adhesion, would have traction-wise overpowered
> the locomotive. Twenty three percent of 396,000
> pounds is 91,000 pounds of tractive effort (which
> 4 AC motors produced). If enough engine and
> alternator power had been available (... like 6000
> HP), the locomotive would have had to have weighed
> a ridiculously impossible 593,000 pounds to use
> the same 23% adhesion capability with 6 AC motors.

That analysis makes absolutely no sense.

So new you can still smell the paint.

CP M640 4744 leads a pair of C424's on a westbound freight through Dorval QC, March 24th, 1971

eminence_grise Wrote:
-------------------------------------------------------
> So new you can still smell the paint.
>
> CP M640 4744 leads a pair of C424's on a westbound
> freight through Dorval QC, March 24th, 1971

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I see no mention about wheel slip control. I think GE won the race AC by useing individual invertors and micro processer control. You can generate all the HP you want but controlling it at the wheel to rail interface with varring conditions is another battle. A pair AC six axel GE at full throttle on a steep grade starting a 15,000 ton train was some experience...the wheels would actually creep and not spin out of control

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