YoHo1975Were the inverters a limitation for both manufacturers? When Seimens was upgrading the Sacramento plant to build the ACS-64, the German VP who came over to oversee (Who is not the person currently overseeing it) the upgrades was a member of our club. He had STRONG opinions on the drivelines in the SD90s and SD70MAC as you might expect. He was of the opinion that the Siemens gear could more than handle the SD90 output.
When Seimens was upgrading the Sacramento plant to build the ACS-64, the German VP who came over to oversee (Who is not the person currently overseeing it) the upgrades was a member of our club. He had STRONG opinions on the drivelines in the SD90s and SD70MAC as you might expect. He was of the opinion that the Siemens gear could more than handle the SD90 output.
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D.Carleton YoHo1975 Were the inverters a limitation for both manufacturers? When Seimens was upgrading the Sacramento plant to build the ACS-64, the German VP who came over to oversee (Who is not the person currently overseeing it) the upgrades was a member of our club. He had STRONG opinions on the drivelines in the SD90s and SD70MAC as you might expect. He was of the opinion that the Siemens gear could more than handle the SD90 output. EMD's MAC series had GTOs. The ACE series, retreads and DC-to-AC conversions are IGBT supplied by MELCO. Same thing with GE except they are providing the new IGBT hardware. GTO has limitations and is not as robust as IGBT but obviously work as they are still in regular service in large numbers all these years later.
YoHo1975 Were the inverters a limitation for both manufacturers? When Seimens was upgrading the Sacramento plant to build the ACS-64, the German VP who came over to oversee (Who is not the person currently overseeing it) the upgrades was a member of our club. He had STRONG opinions on the drivelines in the SD90s and SD70MAC as you might expect. He was of the opinion that the Siemens gear could more than handle the SD90 output.
EMD's MAC series had GTOs. The ACE series, retreads and DC-to-AC conversions are IGBT supplied by MELCO. Same thing with GE except they are providing the new IGBT hardware. GTO has limitations and is not as robust as IGBT but obviously work as they are still in regular service in large numbers all these years later.
Yes I know that, but in the context of the discussion on 1000HP per axle. Did the SD90 have inverter problems in the 6000HP configuration. If it did, it's not something I've heard of.
YoHo1975 Yes I know that, but in the context of the discussion on 1000HP per axle. Did the SD90 have inverter problems in the 6000HP configuration. If it did, it's not something I've heard of.
D.Carleton EMD's MAC series had GTOs. The ACE series, retreads and DC-to-AC conversions are IGBT supplied by MELCO. Same thing with GE except they are providing the new IGBT hardware. GTO has limitations and is not as robust as IGBT but obviously work as they are still in regular service in large numbers all these years later.
My understanding that GTO's themselves are robust, but the associated circuitry may not be very robust. The turn-off process for a GTO involves pulling about one third of the current passing through the GTO through the gate (hence Gate Turn Off thyristor), which could be several hundred amps. Turning off an IGBT involves pulling out a few amps for less than a hundred nano-seconds. Overall turn-off time for an IGBT may be on the order of a micro-second needed to sweep out minority charge carriers - which is a similar process to reverse recovery in a junction diode.
Another limitation of the GTO is that it they are slow, with maximum switching speed not much higher than line frequency. Locomotive size IGBT's can switch at a few kHz.
IGBT's are easier to use in a inverter per axle arrangement than GTO thyristors.
Yes 90 MACs did have problems from time to time .
I had one let go coming out of Anderson Point one morning .
Another time had a H let go in a big way on a 40,000 tonne ore train out of the Creek . I was amased the almighty lurch didn't break the train .
Also was involved in a load test with a pair of 90 MAC Hs , one in 8 against another in DB8 . The one in power let go and I nearly went through the back wall of the cab .
Museum press release from a few days ago. 6002 does still contain a HDL engine.
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BDA Yes 90 MACs did have problems from time to time . I had one let go coming out of Anderson Point one morning . Another time had a H let go in a big way on a 40,000 tonne ore train out of the Creek . I was amased the almighty lurch didn't break the train . Also was involved in a load test with a pair of 90 MAC Hs , one in 8 against another in DB8 . The one in power let go and I nearly went through the back wall of the cab.
Also was involved in a load test with a pair of 90 MAC Hs , one in 8 against another in DB8 . The one in power let go and I nearly went through the back wall of the cab.
How exactly did they "let go"? I love gruesome details about mechanical failures.....
I've always gotten the impression that out of the two 6000 HP designs, GE had the worse diesel engine but EMD had the worse overall locomotive.
The first one out of the Port lost an inverter and under relatively light load , it was the middle of 3 units . Basically squeeled in fright .
Went back identified the fault (one inverter) and isolated it . Control asked if I cut a traction motor out , no cut an inverter or effectively 3 motors or one truck out .
Second time had 3 units on 42 000 metric tonnes , Dirty Harry was again in the middle and let go under full load at about 20-25 km/h . The sensation was a almightly reef then back to the other two units . As I said I was surprised it didn't break a nuckle or drawbar given the trailing tonnage involved . The unit was isolated and went through with the other two , which from memory was a 70ACe and a Dash 9 .
The last one involved a couple of 90Hs in a yard . The idea was to have one loaded in run 8 against another in DB8 . Noisy as you'd imagine and short lived as the one powering in 8 , probably at 7-8 km/h , let go and offloaded very quickly against the other loaded up in DB8 . As mentioned it stopped so quickly I would have slamed into the back wall of the cab if I'd not braced myself .
I personally don't agree that the H engine itself was the only issue with these units . At the time it was said that the Siemens control system was not as evolved as it could have been , also whispers that the relationship beetween them and EMD could have been better .
We mostly ran units converted to the 16-710 and while more reliable they still seemed fragile control system wise . As I've mentioned in other threads that Earthquake effect was not fun though it didn't happen all the time . Basically the control system cycled through rapid on and almost off load and the isolated cab danced around with everything (human and otherwise) trying to shake itself to pieces .
A little off topic but I think EMD would have been better off trying to refine the SD80MACs , the 20-710 was a lot less problematic and a control system upgrade ACR style would have made them a far better thing . I guess the proof is that 80MACs are still around ? 90MACs and AC6000s are not .
IMO the ony way you will effectively utilise much more than 4500 Hp is with heavier locomotives , traction control systems can only do so much and then there's nowere to go but higher axle loads .
IMO the ony way you will effectively utilise much more than 4500 Hp is with heavier locomotives . Traction control systems can only do so much and then higher axle loads is the only place left to go .
You have to admit that FMG's SD90MAC-H units weren't exactly fresh out of the Factory... All of them had been discarded by UP as too much trouble. Only a few of them were rebuilt at Juniata with 16-710s (and those had the Juniata "AC" symbol on the cab side.). The locos with the 265H basically got a coat of paint...
They were bought to ship ore during the mining boom and most days they did that. FMG earned a lot of money from them, even those with the 265H. When the boom ended they were stored. Now the Brazilians found that they couldn't build tailings dams twice, FMG are running anything they can lay their hands on including very sad looking Dash 8s still in BNSF paint.
There are serious rebuild units coming from GE with new FDL enines, new inverters and AC6000 radiators (so something lasting came from that program, with 150 radiators of AC6000 design running on EVOs in the Pilbara already).
I recall a day on the Mt Newman line when it was raining on the Chichester range* and we had tumbleweed blowing across the track. and the two C636s trailing had no sand. We had 144 wagons, so maybe 20 000 tonnes. Whenever a trailing unit slipped, you could feel the train slow, long before the wheelslip alarm bell rang. Eventually the driver made a partial application of the independent brake to control wheelslip. We stopped at the loop at the top of the hill and I was told "go back and check that none of the locomotive wheels are cracked but under no circumstances touch them" while the driver did the other side...
*equivalent to hades freezing over....
Peter
Yes well both brands of 6000 hp diesels were discarded though quite a few of the 9043s are still running around .
Shame that the ACe type rebuild wasn't available at the time . I suppose you could say that the AC6000 may have had a similar option but no .
Anyway good to see that an AC6000 has been preserved , probably not much chance of a 90MAC H being kept .
BDA Yes well both brands of 6000 hp diesels were discarded though quite a few of the 9043s are still running around . Shame that the ACe type rebuild wasn't available at the time . I suppose you could say that the AC6000 may have had a similar option but no . Anyway good to see that an AC6000 has been preserved , probably not much chance of a 90MAC H being kept .
My recollection was that the original intention was to rebuild six of the SD90MAC-H units at NS Juniata, and this was to include a complete replacement of the inverters and control system to SD70 ACe standards.
Apparently the first unit was stripped to the frame at Juniata when FMG decided that they needed more power immediately and six more units were obtained intended for delivery "as is".
The first unit at Juniata was felt to be in the best condition of all the units and it was reassembled as it was and was shipped with the first batch. Six units were rebuilt at Juniata with 16-710G3 engines, but these kept the original GTO inverters, probably to allow an early delivery.
So as I understand it, the ACe option was there but not taken up to ensure quick delivery.
Perhaps they learned a lesson and the AC44C6M units coming now are fully rebuilt, although they have bought some used Dash 9s to meet the urgent need for new power.
From what I've been told, apparently it came frpm Wabtec in mint original condition with the FDL and everything, all really required is rewiring rear traction motors, and refilling water, lube oil fuel replace the batteries etc. It would run
Wouldn't "mint original condition" involve a HDL? (Which is what I did think this particular unit still had... and is a major part of what makes it such an important piece of GE locomotive history.)
(It occurs to me that the museum would benefit further from whatever parts and documentation GE has about the 6000hp locomotive engine development up to the time the 'demonstrator' running stopped...
She still has her 7HDL-16.
Nice to be original but the Evolution engine would probably be better if it was to be kept in running condition .
This is an interesting thread though it does tend to wander around the whole 6000+ HP/1000 horse TM topic . Possibly grounds for a seperate thread .
Anyway my opinion on the general topic is that I agree with the 4500 odd HP 6 axle/TM layout at around 190-200 metreic tonnes - in other words USDM specs .
To get greater real world hauling performance IMO involves higher capacity permanent way (rail infrastructure) combined with higher locomotive axle loads . You would have to know that more horsepower beyond this doesn't equate to dragging higher tonnage per unit . We know this in Australia because outside the Pilbara and arguably NSWs Hunter Valley locomotive performance is very much limited by our lighter ie 22.3 tonne axle loads . Our units cannot hope to pull anything like what your 30 TAL units can , not a hope . Things like EMDs Super Series allowed us to put 3000 Hp to rail with engines like a lightweight 127 odd tonne SD40-2 ie 81 Class G class . Previously 3000 horse units could not pull the same loads as these SS ones . They probably performed more like the Goodwin Alcos of more like 2000 Hp , but faster when not traction challenged . AC traction was probably as big a jump again as SS and made it possible to use most of the 4000/4500 Hp out best units currently have .
I'm not up to speed on where Adani's narrow gauge GT46ACe's are performance wise . I think I read that they didn't perform that much better than the NG GT42ACe does - possibly because they use same or similar NG traction motors . I think the 46 is something like 17 tonnes heavier and 4500Hp vs 3200Hp in the 42 .
Back later .
BDANice to be original but the Evolution engine would probably be better if it was to be kept in running condition.
I didn't get much feed back on exactly what went bang with the H engine , I just remember the 90s falling over a bit too often . They also had electrical and control system issues . Elec compressors were expensive to rewind so they were changed to shaft drive ones .
Yes a preserved AC6000 wouldn't be worked too hard , I was thinking Evo bits would be more readily available .
Anyway , back to the higher horsepower subject . If (big if) manufacturers wanted to get extra real world performance the axle lods need to increase . I don't think there is any other way to increase tractive effort to get more potential on a per locomotive basis . 1000 horse traction motors are already here and reliable engines in the 5000+ horsepower range are too . As mentioned the 80MAC config worked , and I think an 80ACe is available for export . Not T4 obviously but any rusty 90 hulk could be rebuilt to 80ACe spec .
The big issue is would the operators consider heavier perway , probably not .
BDAI didn't get much feedback on exactly what went bang with the H engine; I just remember the 90s falling over a bit too often.
The explanation we came up with is a bit scientific, but it may explain some things you observed or heard in the field. Increasing the governed horsepower output involves increasing the BMEP in each cylinder and hence its peak firing pressure. The generation and then exhaust of this pressure causes vibrations in the cylinder and crankcase structure, with the usual 'harmonics' and resonant interactions you might see in other structures 'excited' below their yield point -- as in bells.
The design of the 265H involved a thin-wall cast block, which was almost certainly designed to 'put the metal where stress analysis said to' (not where resultants of vibration would be minimized). In practice, governing the engine at highest setting produced ultrasonic vibrations in the crankcase structure, which happened to be communicated into the coolant spaces where they coupled with the coolant mass... sometimes being focused into a small volume.
At ultrasonic frequency, this 'ringing' would produce tiny "vapor" bubbles which would then rapidly collapse. Unfortunately the speed of their collapse is determined by physics, and is much faster than their generation was -- and the speed of convergence of the volume in the last stages of contraction is fast enough that you can observe visible light from the heat generated -- this is the innocently-named 'sonoluminescence' referred to earlier. The aggregate result of many of these bubbles forming and contracting is that the area adjacent to the 'action' is eroded, and this is one form of 'cavitation' (as observed in structures like propellers).
Now there was at the time an ongoing discussion of very similar 'cavitation' in one of the early higher-output light diesel engines Ford was installing in its large pickups -- I believe this was somewhere in the transition from the 6.9IDI to the 7.3 "power cerebrovascular accident". What was being observed was mysterious erosion in some of the coolant spaces, which was first thought to be some kind of facilitated electrolytic corrosion because it was smooth but led to thinning and eventual perforation of the block 'from the passages outward' -- and unless you were monitoring your coolant for metallic content, which let's face it no one really ever did, you would have no visible warning of the progress of this issue, except for small decrease in visible reservoir volume, until pinhole leaks started developing and then widening under pressure when the engine was working under hot conditions.
The understanding I had at the time of the initial 'fun' with the 265H was that just this kind of leakage was starting to be observed, and that once the first few were observed, there were thousands of others that were just a tiny fraction of a mm from becoming leakage themselves. Finding them all, cutting them out, and welding spot patches into the cast crankcase would have involved very fancy borescoping-style inspection of the coolant spaces --this being eerily similar to a post on RyPN by Bruce Mowbray describing pitting damage in superheaters observed on his 'watch' at Steamtown.
They also had electrical and control system issues.
Combine that with the el cheapo using one inverter synthesis for three motors at a time. As Wayne (and Crichton) noted: what could go wrong... wrong... worng.
Yes a preserved AC6000 wouldn't be worked too hard, I was thinking GEVO bits would be more readily available.
Anyway, back to the higher horsepower subject . If (big if) manufacturers wanted to get extra real world performance the axle loads need to increase. I don't think there is any other way to increase tractive effort to get more potential on a per locomotive basis.
For a little context, this was the age where 'magic wear rate', head-hardening and bainite, and 315K axle loading were starting to converge. For a while in this period, there was serious consideration being given to making a three-axle replacement (with radial steering) for the traditional three-piece truck, to facilitate less disaster from using only the axle load that rail and wheel metallurgy would cost-effectively support while still "optimizing" (meaning increasing at lowest cost to the railroad) the capacity of a given car.
One solution we saw 'aborning' over on the EMD side was the obvious thing you did for increased practical adhesion for a 600 or greater hp unit: more axles in each 'truck', but not with the issues observed with the D trucks under the Centennials. You could get a version of this, of course, using HTCR-style radial steering (but still with a long truck sideframe extension and residual rigid wheelbase if you did) or you could do as EMD actually tested, which is to build a relatively short-wheelbase B-B truck that would fit in the rough frame space of a HTCR C truck. (And then take advantage of the electronics revolution to get better and better power and control of AC motors, but now with lower peak power required per axle, and a larger contact patch...)
The best person to take up the discussion of 6000hp locomotive adhesion is probably Dave Goding, who has firsthand experience with all this.
[quote]1000 horse traction motors are already here and reliable engines in the 5000+ horsepower range are too.[quote]An interesting thing to note, though, is that there was testing of the large-horsepower QSK45 in a typical C-C form factor (on the Indiana Railroad) and this went, and went, and went without much report of successes leaking out, and I believe now has been given up. This is in line with my other observations that 4300-4500hp is 'rightsized' even with comparatively large or long six-axle chassis required for the weight and the radiator capacity for tier 4 and above without SCR/DEF. (I would have dearly loved to see the renewed application of 1000+hp AC motors in four-axle units... or even BoCo-types a la 2400hp passenger FMs... but you will note their absence in practice outside of passenger work.)
[quote]As mentioned the 80MAC config worked , and I think an 80ACe is available for export. Not T4 obviously but any rusty 90 hulk could be rebuilt to 80ACe spec.[quote]Yes, but look at where the SD80MAC sold domestically... and how many were built after the initial batches. Holy Hanna, was that thing a fuel hog when you used it for anything other than operation at sustained 'best output' (as we might note its 'successful' use basically involved anywhere it was run effectively). And it had many of the long-term cost issues and concerns applicable to the early 20-cylinder engines.
In any case, 'until the revolution' we appear to be on course to hydrogen/BEV hybrids for longer-term power, so a two-stroke diesel is not particularly futureproof, even compared to four-stroke or high-speed alternatives.
The big issue is would the operators consider heavier perway , probably not.
And meanwhile the world under PSR has gone back to a neo-drag-era operating model, with fifth-notch restrictions 'and all that', in which the higher speed that is the principal actual benefit of higher-horsepower six-axle locomotives is no longer an economic priority or even particularly desired.
I personally suspect that rather than improve track standards or even FRA class, railroads would go back and dust off some of that steerable three-axle tech if they wanted greater capacity per car/wagon -- which would show up first in the center trucks of 'longer' articulated stack-train equipment. You will notice they appear perfectly happy with sticking 53s over 40 to 48s and 'cubing out before they're weighing out' to keep any reinvestment in track structure to a minimum... even as income from containerized traffic falls increasingly toward commodity level.
All food for thought ,
It's hardly surprising that an 80 MAC would use more fuel . More cylinders/injectors and more power .
I think I remember reading that EMDs thoughts in the 90H development times was that two stroke diesels were not going to meet emissions limits and I assume this would be going into T1/T2 era . Shame if that's the case given that the 710 made it as far as T3 . Its possible that someone here mentioned EMD looked at another slightly larger ie 810 cu/cyl 2 stroke V16 . That would have been an interesting idea . The T4 V12s (both) must have fairly large capacity cylinders to make similar power to the previous generation V16s .
Anyway I agree that different fuels are probably the way ahead given the stranglehold of emissions laws . Personally I think the battery electric fad will be a passing band aid because of charge time and unit availability .
Thing is that the 80MAC 20-710 'mac-xed out' at around 5800 nominal hp, and I believe that was at rpm where torsional resonances in the crank could develop in governed power regulation in high notch. As you note you'd have to go to larger displacement -- which leads to injection concerns and additional reciprocating-balance issues with the equivalent to balance shafts still carried up in the timing gears somewhere, so god-awful peak torsional stress a la 16-244... someplace you would NOT want to go if your competitors didn't have the concern at all...
The 710 was close enough to Tier 4 final without SCR/DEF. If you look at the EPA stats, the engine produced only somewhere like 1.5% high (yes, that's .015 over requirement) on about 4% at most of the test duty cycle. Since the Tier 4 NOx standard for locomotives was completely made up by regulators, you'd think a waiver preventing multi-hundred-million-dollar trade losses (involving additional NOx in service measured in pounds) would be feasible. Not at an agency with an employee on record who noted the NOx standard was explicitly written to force the railroads to SCR...
In my opinion, battery-electrics like the GE FLXdrive are the wave of the future... in consists of fueled power, as the electric part of hybrid power. Their use in 'zero-carbon air-quality management districts' is an additional synergy. This is the same set of arguments Iden et al. make for their 'tenders', but keeping the cab extends utility to two-unit cabs-out power comparable to some of the road-slug combinations.
Hydrogen fuel-cell locomotives without substantial battery/supercap capacity are not going to be the answer to much except the equivalent of that old boating joke about setting thousand-dollar bills on fire one after the other for the service life of the power... you may have noted that the only successful use of hydrogen so far is 'tripower'-style road charge of battery trains
My guess is that the battery electric will be a short term thing , partly because of existing battery technology and charge times . At best these things can charge in dynamic and possibly take a feed from adjacent diesels in DB mode . It's hard to imagine the operators affording the time to charge them from ground supply .
My guess is that bulk charging of the 'battery-electric' component of a consist would be ground-charged in massive parallel at conventional fueling stops. That is less likely to be fully safe for hydrogen-capable infrastructure as for straight diesel.
But the real charging will be from early stages of punctuate catenary (installed for grade snapping and dynamic regenerative braking) which by definition offers an extended charging time with the locomotives and train in motion. One of the advantages of the dual-mode-lite approach is that the OHLE (or smart third rail) can source enough for both 'diesel-equvalent' traction horsepower and incremental fast charge simultaneously.
The majority of the problems with the old H motors are they required antifreeze for their cooling systems not just treated water. The railroads weren't ready for a locomotive that required antifreeze to stay cool and needed more than treated water when refilling it. Also the H series supposedly had massive cavitation issues with the liners on the engine. Now as for the 710 series and emissions issues blame the EPA for this. They literally moved the goalposts back further to prevent the 710 from being able to meet tier 4 for emissions. But why the EPA are not allowed to care what businesses want to them anymore anything that is harmful to mother earth in any way must be destroyed unless it's part of the holy green environment kingdom such as wind solar or battery it seems.
Overmod what do you mean by that 315K reference .
Shadow the Cats owner Now as for the 710 series and emissions issues blame the EPA for this. They literally moved the goalposts back further to prevent the 710 from being able to meet tier 4 for emissions.
Now as for the 710 series and emissions issues blame the EPA for this. They literally moved the goalposts back further to prevent the 710 from being able to meet tier 4 for emissions.
The worst part about this mess is that there would likely be LESS pollution from locomotives had the EPA adopted "tier 3.9" limits. This is because the railroads would have been more likely to buy a "tier 3.9" locomotive than a "tier 4" locomotive.
BDAOvermod what do you mean by that 315K reference?
The problem with 315K axle load, particularly if there is any particular shock from flat wheels, low joints, etc., is that no matter how hard you make or coat the surface of the railhead contact patch, you're still going to induce cold flow in the metal further down (since you can't harden the bulk of the railhead so much that it becomes brittle in service; you need to maintain field weldability with sometimes-crude methods; etc.). I suspected that the experience with hard coatings would translate over into the railroad context, and it seems to have done so: the work-hardened layer on rails tends to break up into lamellae which then work against each other and can actually tip a bit, causing high (and virtually invisible to practical inspection) cracks propagating vertically into the rail metal. It doesn't take too many broken or spalled rails to eat up the putative "big savings" from heavier load per axle -- and we haven't gotten into the issue with wheels on the 'other side' of the contact patch yet, or concerns with side-bearing binding, center-pin lubrication, and other things.
It was in this context that the Canadians developed the 'magic wear rate' theory, which in essence said that you wanted the rail to wear away just as fast as the microcracks were propagating down past the work-hardened surface... and that it would be no loss to grind the rails repeatedly (and get the effect of reprofiling and removal of cold flow over or into the gauge corner) to produce the magic rate. (It followed that regular dressing or reprofiling of wheel treads would be valuable both in load transfer and in reducing shock and noise.)
There is certainly active practice on the heavy coal trains through the Memphis area to keep the wheels well dressed, since the late 1990s -- in conjunction with regular passes with the Loram-style grinding trains. I grew up with the typical clattering roar, pings and pops that accompanied even 55mph road speed, and it was eye-opening to observe a coal train passing at 45mph loaded with only a low hum, even though you could observe the track 'breathing' between trucks passing.
Thank you that is most interesting , it leads to another question - but first .
Here in Australia we don't measure locomotives , axle loads or rail weights in pounds . A locomotive like say a NR class weighs 132 metric tonnes and its axle load is 22 tonnes . On our national standard guage network the max axle loads AFAIK is 25 tonnes . So x 4 is a 100 tonne gross mass wagon (car) . The faster Intermodal trains are allowed 115 km/h (70 mph) at 19 tonne axle loads 76 tonnes gross .
We measure rail weights in kilograms per metre ie 60 = 60Kg/m . It used to be lb/yard ie 135 pound rails .
Our Western Australian Iron Ore Railways are basicaly isolated systems built to North American standards , or if anything heavier duty - possibly . The operator I worked for there uses 68kg/m rail and the locomotives are approximately 190 tonnes or 31.67 tonnes axle load . Currently their loaded ore cars gross 168 tonnes or 42 tonne axle load x 4 . 250 car trains gross 42,000 tonnes . Maximum speed is 80 km/h or approx 50 mph .
So I gather by 315k you mean 315,000 pounds or 157.5 2000lb short tons ? If so then that means individual car axle loads of 39.375 tons .
Any way I still wonder how a USDM style locomotive of say 5000 Hp would go with a gross mass of around 200-210 metric tonnes , and with attention given to minimising unsprung mass .
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