Hello everybody,
in the new trains issue it was mentioned that the BNSF has a order for some of the new SD70ACe-P4's. The axle configuration is a B1+1B. A couple of years ago there was a excellent article in TRAINS about CSX and how they added extra weight to the AC4400's as well as changed the programming for the traction motors. The programming was such that the outer traction motors would exert less tractive effort under slippery rail conditions and basically condition the rails, while the inner traction motors would be allowed to increase the tractive effort to make up for the shortfall. I thought this was a great idea,
So when I read that the new EMD locomotives would be of a B1+1B design I thought it was strange. They are essential doing the reverse as to what GE done with the AC4400's. It would make more sense to run the non traction motor axles as the outer axles so that the lead non powered axle could condition the rails. Ie have a 1B+B1 axle configuration.
This is just my thinking, what are your thoughts on this situation?
Frank
"If you need a helping hand, you'll find one at the end of your arm."
Frank,
From what I have read, the GE truck design does not automatically transfer weight. Under heavy loading, it is typical for the traction motors to unload the rear axle of a truck(sort of like the rear axle of a rear wheel drive car lifting). The GE 'software' makes up for this with those CSX engines.
GE later used a 'lift' device to unload the center axle on the ES44C-4 engines for BNSF. This was to maintain adhesion with the A-1-A configuration of the locomotive.
The EMD locomotives have used their HTC truck design since the SD40-2. This truck design will transfer the weight/power automatically(within reason).. EMD feels that having the outboard axles powered will eliminate any wheel slip issues and has gone with the B1+1B configuration. This eliminates the need for the 'lift' device that GE is using.
Time will tell which system works out best, or if it is a 'wash'....
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
The topic title reminded me of a question that I don't think has yet been answered.
In the GE ES44AC4, where each motor has its own inverter, it is easy to see where the money is saved. Two motors and their inverters are left out, saving enough money to reduce the cost to that of a DC unit.
Since the EMD units have one inverter per truck, to make an appropriate saving, two smaller inverters or one slightly larger inverter must be used, to power the four motors. Does anyone know how EMD did this?
Deleting the motors while using the same inverters would not seem to reduce the cost sufficiently to match the GE offer.
M636C
The traction motors within a truck on EMD AC locomotives are wired in parallel, deleting two motors doesn't affect the Inverters, just more Amps to each motor.
beaulieu The traction motors within a truck on EMD AC locomotives are wired in parallel, deleting two motors doesn't affect the Inverters, just more Amps to each motor.
My concern was not that the existing inverters wouldn't work. I am concerned that the cost saving by deleting only the motors and not, as in the GE unit, the matching inverters would not be enough to make the four motor EMD cost competitive with DC.
I recall hearing that the Alaska Railroad SD70MAC equipped for passenger service used one inverter for HEP and that the other inverter supplied four motors at reduced power, suitable for passenger service. I think the Indian GT46 PAC operates the same way.
So if it were possible to use one inverter to power all four motors on the SD70ACe-P4, it is very likely that the reduction in cost would allow it to be sold at the equivalent price of a DC unit.
M636C Since the EMD units have one inverter per truck, to make an appropriate saving, two smaller inverters or one slightly larger inverter must be used, to power the four motors. Does anyone know how EMD did this? M636C
M636C: I have to take on opposite tact. At low speeds the EMD will exceed the adhesion so the HP output will have to be reduced. At some speed ( anyone know ) probably below 30 MPH the full out put of the EMD inverters will provide the full HP rating of the 4 AC motors. So EMD will need the same inverters as 6 axel powered units.
On the other hand a GE C44AC4 will need larger capacity inverters to provide 1100 HP max ( at higher speeds ) to each of the traction motors. Am I on the wrong track ?? So either the GE inverter on 6 axel powered locos has enough spare capacity to provide 1100 HP instead of 730+ HP or a new inverted had to be installed ??
blue streak 1 M636C: Since the EMD units have one inverter per truck, to make an appropriate saving, two smaller inverters or one slightly larger inverter must be used, to power the four motors. Does anyone know how EMD did this? M636C M636C: I have to take on opposite tact. At low speeds the EMD will exceed the adhesion so the HP output will have to be reduced. At some speed ( anyone know ) probably below 30 MPH the full out put of the EMD inverters will provide the full HP rating of the 4 AC motors. So EMD will need the same inverters as 6 axel powered units. On the other hand a GE C44AC4 will need larger capacity inverters to provide 1100 HP max ( at higher speeds ) to each of the traction motors. Am I on the wrong track ?? So either the GE inverter on 6 axel powered locos has enough spare capacity to provide 1100 HP instead of 730+ HP or a new inverted had to be installed ??
M636C: Since the EMD units have one inverter per truck, to make an appropriate saving, two smaller inverters or one slightly larger inverter must be used, to power the four motors. Does anyone know how EMD did this? M636C
I recall reading the all the Evolution series AC locomotives use the same inverter as the AC6000CW so ther actually is no problem with the higher output...
In regards to the SD70ACe-P4, EMD already supplied a number of 70 series derived locomotives to Indian Railways called the GT46PAC. The first series of the model suppled use an identical truck/traction motor arrangement to the SD70ACe-P4 so there really arten't huge changes (other than the fact that the Indian units are broad gauge) needed to design the BNSF units...
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
I still don't get why they don't eliminate the extra weight and cost of the extra axles and go with an AC B-B design. On the GE units, I vaguely remember something about spreading the weight when on light rails, but being able to to put more weight on the driven axles when needed. If you are not going to shift the weight, why not eliminate the extra axles and make the whole locomotive lighter while keeping the weight on drivers the same? (Steam thinking: "weight on drivers.")
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
Because the locomotives weigh far too much to be on only 4 axles.
The Dash8s and GP60Ms already had problems with their weight.
The Only way on the GP60M that EMD could meet Axle loading was to limit the Fuel tank to 3200 gallons and then limit the fuel load to 2900 Gallons total. The crews said they rode like a Bucking Bronco. Then you have the B-40-8-W that had roughly the same issues. No way are you going to get a AC driven Freight Motor with a decent Fuel Tank size and also have it ride decent with Modern Emmisons Equipment on it. Sorry but the EPA crap that is Mandated in the OTR side has ADDED close to 1000 LBS of weight to the normal OTR truck. Yep the DPF DEF and all the extra stuff the EPA screamed was needed has cost them 1/2 a ton of cargo weight. This is just teh equipment and does not include the extra heat insulation needed to keep the trucks safe from the 1500 degrees the DPF creates.
Flatbedders that could carry 50K before can now only get 48K now. Reefer Drivers are barely getting 46K when some could and did scale 48K same with Dry vans. Yet oh all is well with the EPA. Wait til the Locos get to heavy even for a 6 axle setup.
So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job.
daveklepper So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job.
Yup. Without sacrificing range or increasing the complexity of doing wreck repair at the same axle loads while supporting all the hardware needed for emissions, crew environment, etc. Not an easy task.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Everything I've read says that to build a Modern high horsepower BB locomotive within reasonable weight tolerences and accomodating all the added weight from the upgraded cooling systems,ect. necessary for meeting current emissions requirements it is necessary to use a monocoque style carbody rather than a roadswitcher frame. That body style is not optimal for freight service..
Also keep in mind that what BNSF has asked the builders for is essentially SD70M-2/Es44DC equivalent using AC traction motors rahter than an upgraded GP60M/B40-8W.
As previously noted, the fuel tank requirements for long haul freight units do not make a BB design desirable..
carnej1 daveklepper: So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job. Everything I've read says that to build a Modern high horsepower BB locomotive within reasonable weight tolerences and accomodating all the added weight from the upgraded cooling systems,ect. necessary for meeting current emissions requirements it is necessary to use a monocoque style carbody rather than a roadswitcher frame. That body style is not optimal for freight service.. Also keep in mind that what BNSF has asked the builders for is essentially SD70M-2/Es44DC equivalent using AC traction motors rahter than an upgraded GP60M/B40-8W. As previously noted, the fuel tank requirements for long haul freight units do not make a BB design desirable..
daveklepper: So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job.
Yup. That's why what's happening is happening. But, that is not to say that if a decent way to save 50 tons a locomotive isn't a good idea. You'd get slight bump in trailing tonnage and/or a slight bump in fuel economy - for free.
Heck a GP 60 is overkill on the Locals that NS runs here and the Crew know it. The best engine for Yard and local service anymore is going to be a Genset put on a old GP frame. Why when lightly loaded only as much HP as needed to the rail and saves on the Prime Mover wear. The last GP series was built 20 Years ago so their is a demand for them just not yet and no one yet has the Perfect replacement for them. Trust me if someone came up with an AC driven GP series rebuild that was cheap enough the RR's will be beating their door down with CORES to be overhauled.
oltmannd carnej1: daveklepper: So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job. Everything I've read says that to build a Modern high horsepower BB locomotive within reasonable weight tolerences and accomodating all the added weight from the upgraded cooling systems,ect. necessary for meeting current emissions requirements it is necessary to use a monocoque style carbody rather than a roadswitcher frame. That body style is not optimal for freight service.. Also keep in mind that what BNSF has asked the builders for is essentially SD70M-2/Es44DC equivalent using AC traction motors rahter than an upgraded GP60M/B40-8W. As previously noted, the fuel tank requirements for long haul freight units do not make a BB design desirable.. Yup. That's why what's happening is happening. But, that is not to say that if a decent way to save 50 tons a locomotive isn't a good idea. You'd get slight bump in trailing tonnage and/or a slight bump in fuel economy - for free.
carnej1: daveklepper: So, for EMD to recapture market share, it should try to reduce locomotive weight to the point where 4 axles can do the job. Everything I've read says that to build a Modern high horsepower BB locomotive within reasonable weight tolerences and accomodating all the added weight from the upgraded cooling systems,ect. necessary for meeting current emissions requirements it is necessary to use a monocoque style carbody rather than a roadswitcher frame. That body style is not optimal for freight service.. Also keep in mind that what BNSF has asked the builders for is essentially SD70M-2/Es44DC equivalent using AC traction motors rahter than an upgraded GP60M/B40-8W. As previously noted, the fuel tank requirements for long haul freight units do not make a BB design desirable..
I don't doubt that it would be technically possible to build a high horsepower,AC drive,Tier compliant four axle freight roadswticher unit using one of the newer high speed diesel powerplants (GE has the Powerhaul-Jenbacher and EMD has access to the new Cat high speed diesels) but I still think the fuel capacity issue would remain. I also am dubious that it would cost less than what BNSF is buying now..
Goal: 1100 A.C. hp for each axle, long range from fuel capacity, low locomotive weight and mass with compatibilty and flexibility.
How about: 4-axle control cab with complete engine-main gen., converters, but small fuel capacity, controlling another 4-axle fully performance equal unit with lead locomotive equivalence but incidently provides fuel for the engine that has the EVO or the 710. Fuel consumption balanced by transfer from the tank on the cow milked by the engine, control cab, makes tractive effort dependably constant between the units.
Put's us back to the A-unit, B-unit problem.:
The above proposal sounds like an incredibly complicated way of getting back to four axles per unit. I would assume that the two units would be joined by solid drawbars since one unit has minimal fuel capacity and the other unit has no control cab. What's being proposed is an 8800 HP, eight-axle, two-unit locomotive of unnecessary complexity.
How about a 2000-2500 HP, two axle, AC locomotive? Power could come from one of the numerous high speed diesels, an 8-710 or a 6 cylinder in-line GE. Put a cab on one in three. Put remote control and DPU on all of them. You can use them for any kind of service.
Smaller chunks of HP make it easier to build consist with the right HP and TE for the train and route. You could apply one or two to each block when building trains and aggregate trains up to just about any size, then split trains apart at block swap/block destination locations. The power stays with the tonnage.
Lots of engineering challenges though.
oltmannd How about a 2000-2500 HP, two axle, AC locomotive? Power could come from one of the numerous high speed diesels, an 8-710 or a 6 cylinder in-line GE. Put a cab on one in three. Put remote control and DPU on all of them. You can use them for any kind of service. Smaller chunks of HP make it easier to build consist with the right HP and TE for the train and route. You could apply one or two to each block when building trains and aggregate trains up to just about any size, then split trains apart at block swap/block destination locations. The power stays with the tonnage. Lots of engineering challenges though.
Better yet, come up with an unballasted version with a 20-ton axle load (If you can do 6000 HP within 6-axles at 35 tons/axle, surely you could meet this with a 2000 HP 4-axle locomotive).
And even better yet, give it Cardan-shaft drive to a large, easily cooled frame-mounted electric motor, one motor for each truck. One knock on the Diesel hydraulics with shaft drive was that you had to keep all the wheels the same diameter to high tolerances, but you have to do that anyway with the EMD system of one AC-drive inverter per truck.
And even much better, give it a radial-steer B-truck qualified for 125 MPH operation. With respect to passenger specific features such as streamline cowl, HEP, those could be options. If the unballasted locomotive unit can be kept to 20 tons per axle, I don't think you need to go to a special monocoque shell as on the Genesis for weight control and then have to worry about cutting into the shell everyone time you do a major engine overhaul. That axle load (and the radial-steer truck) would allow higher speeds on curves with passenger trains that allow it (Talgo, outboard spring Amfleet).
That way you get rid of the track-pounding nose-suspended traction motor. There was some discussion that everyone worried about the hammer-blow of steam locomotive drivers but that the pounding from the unsprung mass of nose-suspended traction motors on Diesels, even in freight service, made up for that in providing full employment for track maintenance crews.
Actually, this "building-block" concept of a mixed passenger-freight locomotive unit was tried -- I think it was called an RS-2 by ALCO, a GP-7 by EMD.
So why did Union Pacific go with "double Diesels" like the DDX-40, DD-35B, U50, U50C, and whatever the Alco model they tried? Why were the railroads so big on "unit replacement." There may be some maintenance costs that are per cylinder or per traction motor or per wheelset. There may be other maintenance costs per locomotive unit -- FRA-required inspections are always brought up as an example.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
A lot of interesting ideas on this thread but many of them would seem to violate the old design principle of K.I.S.S..it's difficult to see how any of them would fulfill BNSF's specification better than the 4 motored Evolution/SD70 derivatives..
I do think it's possible that we could see Asynchronous traction 4 axle freight units in the coming years, though..there are a number of switcher/roadswicher locomotives in Europe that use AC drive and Republic locomotive is marketing a 500 HP "Critter" industrial switcher with AC motors:
http://www.republiclocomotive.com/rx500_industrial_locomotives.html
I thought CSX had tried the Slug Mother combo to get the most out of the GP40 Series and to get the most out of the slow Branches they had. I know I used to see them all the time in Ottawa on the old RI line they have there. Mother would be a GP40 slug was always a GP30 or GP35 with a concrete block where the 567 motor should have been. Great for low speed but High Speed you run into an issue the Slug becomes Dead weight when the Engine in the mother can not produce any spare current for the slug. See the issue is always Amperage the faster you go the less amps their are to spread around even with AC current. Until we come up with a Alternator that can violate Ohms law we have to live with it.
edbenton I thought CSX had tried the Slug Mother combo to get the most out of the GP40 Series and to get the most out of the slow Branches they had. I know I used to see them all the time in Ottawa on the old RI line they have there. Mother would be a GP40 slug was always a GP30 or GP35 with a concrete block where the 567 motor should have been. Great for low speed but High Speed you run into an issue the Slug becomes Dead weight when the Engine in the mother can not produce any spare current for the slug. See the issue is always Amperage the faster you go the less amps their are to spread around even with AC current. Until we come up with a Alternator that can violate Ohms law we have to live with it.
CSX has both yard and road Mother-Slug set ups. On the Road set ups, originally both units had fuel tanks and the Mother thereby had double the fuel capacity and in service where a unit would need to be fueled weekly, the Mother-Slug that shared fuel capacity could last two weeks. Fuel sharing has been eliminated as it was a maintenance nightmare. The Slug has the same max tonnage rating as the Mother - the tonnage rating is based upon the maximum tonnage a DC traction motored engine can haul at it's Minimum Continuous Speed (the speed that the traction motor can handle their maximum current without overheating). The Road Slugs are designed to stop drawing current from the Mother at 25 MPH. When Road Mother-Slug combo are operated with the Maximum tonnage, their real speed over the road will be very close to 25 MPH on level terrain as there is not enough horsepower to generate any more current to turn the working traction motors over any faster.
Never too old to have a happy childhood!
thank you for all the great replies. It is very interesting following the thoughts about the subject. Personally I it would be great if they could bring back a 4 axle diesel. Bombardier in Europe has such a unit and EMD in the past has worked very closely with Siemens on locomotive development in North America making it a feasible task to employ one of their designs over here.
Thank you
How about putting a high-speed light-weight diesel in a BB locomotive, with an alternator designed for the higher speed? It'd probably make a good passenger locomotive, too.
In a slightly earlier thread titled "EMD SD70ACe-P4 for BNSF" it was stated that EMD C-C engines with HTC trucks have their motors mounted on the axles toward the inboard side, so that the axle closest to the center of the engine apparently has its motor suspended outside the trucks wheelbase, so it seemed the most expedient to eliminate in order to create a 4 motor model.
If you wish to go to the two-unit concept, piping fuel between the two units is more expensive and more suseptible to problems than jumpering electricity. So for a total of eight axles for the two units, only one unit has the cab, and its air-conditioner, and potty, and heater, and controls, and the other unit has all the electrical equipment that can me moved, load regulator, dynmic break grids, inverter, frequency controller, air compressors, transformers, radio and signal equpment. That ought to bring weight down to where both units have a large enough fuel tank.
You know in writing up my question about Canadian wide cabs, I got to thinking, would it really be that hard to get at least close to a 4 motor 4 axle AC unit?
I don't know the particulars of how much the different parts weigh, but what if we took away the wide cab and just put a modern crash worthy spartan cab on it? The GP60 got 3800HP out of it's 16-710-G3A engine. Presumably if one dropped in a 16-710-G3B you would get 4k HP or a G3C would get you 4300HP without any significant increase in weight. It is after all the same engine block.
So the question becomes one of the weight of the inverter, AC/DC traction motor weight and the weight of the Tier 2/3 split cooling. (and soon Tier 4)
I suspect it's the cooling that would do it in.
Paul of Covington How about putting a high-speed light-weight diesel in a BB locomotive, with an alternator designed for the higher speed? It'd probably make a good passenger locomotive, too.
EMD is looking at just that design (using a CAT high speed prime mover) for the high speed passenger unit it is developing. It won't be a roadswitcher however...
the biggest problem with any potential high horsepower "super Geep" for road freight service is the fuel capacity issue. The big Class 1's want to be able to move trains as far as possible between fuel stops and a GP60/B40-8 sized tank (with or without fuel tenders) won't meet their requirements..
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