I still believe that six-wheel trucks with one axle idle is not an opitmum solution for high horsepower freight locmotives for intermodel and other premium frieght trains.
1. The four wheel truck should have a longer wheel-base than conventional, similar to the wheel-base of a six-wheel truck. If the technolog is up to it, radial self-stearing axles should be employed to insure wheel tangent to rail on curves. The space been axles might permit one large longidunal ac AC-hysterisis synchronis motor with worm drive on both ends to replace two motors, with the mating gears quill connected to the axles, dropping unsprung weight considerably and thus resulting in a ride quality better than diesel electrics with asle-hung motors. (PCC and most modern light rail cars have longitudinally mounted motors.)
2. There is no reason why monocoque desing has to restricted to covered wagons. The same principle can be applied to hood units, with the side walls of th hood reducing the weight and depth of the centersill, allowing a large fuel tank as well as reducing weight. The Stillwell passenger design side walls are the key, with the side walls of the hoods being designed as trusses, like bridge trusses, and doors for access located so as not to compromise the rigidity of the truss/ Just like the window and doors in a BMT or H&M subway car or NYW&B commuter car. The roof of the hood would be analagous to the roof trusses of a truss bridge.
The length would be as long as required to install a fuel tank of required capacity/
Speaking to your second point a monocoque carbody is not optimal for any kind of reverse move/switching so how do you overcome that issue?
Your proposed locomotive also would require a considerable development effort and I question what the price per unit would be compared to the modification of current production six motored units...
If I'm the chief mechanical officer for BNSF why would I want to buy something with such a radically different truck/motor arrangemetn than the rest of my locomotive fleet? Would the lighter weight result in a significant advantage in fuel consumption with the same locomotive performance?
It would certainly be possible to build a high horsepower roadswitcher using one of the newer lightweight, high speed prime movers. Conversely a monocoque passenger design could be adapted for freight service (such locomotives are used in Europe), but I do not think either of these would meet BNSF's requirement.
The ES44C-4 is really intended to be an AC drive replacement for the ES44DC rather than an AC equivalent of a DASH 8-40B, ditto the new SD70ACe variant..
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
With the advances in power electronics, we should get to a point where the size/weight of the AC traction motor electronics becomes less than the necessary hardware for supporting DC traction motors. This could make 4 axle power practical again.
- Erik
It would take a major weight reduction to shrink the control electronics enough to go back to four axles. Remember that the ATSF GP60M's were already quite heavy even with DC traction motors.
Weight reduction in the control electronics (i.e. inverters) would come from replacing the oresent silicon based power devices (GTO's and IGBT's) with either GaN or SiC devices, more likely the latter. Both can operate an order of magnitude faster than the IGBT's and two orders of magnitude than GTO's. The higher frequencies will allow for smaller capacitors and inductors. The SiC devices can operate at higher junction temperatures, which reduces size and weight of cooling.
AC motors are lighter for a given capacity than DC motors, and should be capable of higher operating speed, which could further reduce the weight. Lighter motors would also reduce unsprung weight, which should reduce dynamic forces on the track.
The traction alternator may be lighter if designed specifically for constant inverter input voltages as alternator output current would depend only on throttle setting and not locomotive speed.
Certainly the advanced design four axle high horsepower locomotive will require component testing and then prototype in-service testing before production. But the technology is not new. In fact, except for the anvanced truss-design carbody, you could mate a truck design from high speed European electric locomotives, the two motors large ones from Brown Bravory, and adaptations of the latest existing ac technology and a Tier 4 prime mover as available. The locomotive might also be a fuel saving advance over existing intercity passenger and commuter locomotives.
The limiting factor on a modern 4 axle unit would be its incredible weight. The track structure had/has lots of trouble handling Geep 60's, put AC transmission electronics in and you will simply over load the axles.
The difference between 4-axle and 6-axle power for premium mainline freight service began to narrow about the time the horsepower race began, roughly the mid-1960's. As mentioned in the previous post, weight and axle loadings are an issue at present so why offer for sale a type of motive power that nobody particularly needs or wants. As things currently stand, the only place for four-axle power is in secondary service and that market is being served by rebuilds and gensets.
Why? Because the unpowered axle in each truck is added useless weight and a maintenance item in addition as well as an example that the present solution is not the most efficient.
If you really want a Modern 4 axle Locomotive and in a 2000 HP range with 4 Axles that is Easy to do take 3 700HP complete Power packed Cummins engine assemblys complete with Cooling systems and install them into the Locomotive Shell Each Powerpack and Gen/Alt would weigh around 15K rough Estimate then add the Frame Cab Switch gear and if you want even make it AC. You could get an AC drive 4 axle loco that would have the space in the Unit for a 4th engine that could go up to almost 3000HP at the rail. Would just be a Genset Design but would work and if a Powerpacked motor goes out remove it and replace it and Get it back on the Ready track. See by having them complete with Cooling Systems it is just unhook the Fuel line Electircal lines and go.
Good thinking, but the design I first proposed was for the 3600-4000HP range, The equal of the ac four-motor six-axle power BNSF is buying from EMD and GE.
There are 6 Clyinder 16 Liter Motors that can do that easy in a 900 HP range 2 of them to replace a GP38 3 to replace a GP40 and 4 to replace a GP60 and those same motors can be bumped up to 1000HP and last. Cat has a 16 Liter engine that does 1200 HP in Marine and 1000HP in Industrial Situations. Cummins has the ISX that can go to 1000 HP also. It is 16 Liters also.
Weight and axle loadings are still the big issue. The situation is analogous to using light SD7's and SD9's on branches because the light rail couldn't support GP7's and GP9's. The weights may be greater and the rail may be heavier but the issues are the same.
The use of idler axles may not be an "elegant" solution but it works.
Lets see here a set of 3 C16 that are Truckengines that have in Industrial settings a 1000HP rating also with a Differant Cam and Injectors they are only 2700 LBS Each. Then add 11 Gallons of Lube Per Engine and 10 Gallons of Coolant Doubleing the Reserve of coolant. With a radiator and CAC your adding around 1000 Lbs Each. Gen/ALT is around 4K so we are still less than 10K even with the Structure to hold them. IIRC the engine is 45K the Alt is around another 20K lbs so we are 20K lighter if not more and we have room to play with as the C156 burns LESS fuel per hour than a 710. It could be done. However who is going to Buy it.
Well, EMD as far as I know will gladly build you a GP32ECO if you ask them to. I assume that the V12 and added cooling can fit. Question is, how much would that 3200 HP weigh?
Tugboat Tony The limiting factor on a modern 4 axle unit would be its incredible weight. The track structure had/has lots of trouble handling Geep 60's, put AC transmission electronics in and you will simply over load the axles.
AC transmission electronics will become significantly lighter in a few years and AC traction motors can be made significantly lighter than an equivalently rated DC traction motor.
Ed Benton:
Using an AC electric transmission can make gensets a lot more practical as the genset can provide a fixed voltage at varying current for the inverter DC bus. With proper design of the inverters and DC bus, the locomotive can still be largely functional in the event of a genset failure or inverter failure. This would be in contrast to the various double engine diesels (e.g. E units, DD40's, etc) where loss of one prme mover cuts the tractive effort in half.
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