My question is why? I read that they are supposted to be used on the Transcon but wouldn’t 4 axle engines do the same? And what would the trucks look like?
There are some interesting discusssions going on about this on some other web forums and the best explanation I’ve read on why BNSF isn’t ordering ES44BAC’s(BES44AC?)) is that a LOT of money and development time would have to go into creating such a locomotive and it would very likely cost just as much as one of these ES44AC-4s. In addition the hypothetical BB would need to have the same “souped up” cooling system as a 6 axle EVO(for emissions Tier compliance) and shoehorning all of this into a B40 series frame (which IINM is already pretty long for a roadswitcher) would be tricky, although some have speculated about a hypothetical freight version of the “GEVOSIS”(Evolution series, Gevo powered, Monocoque bodied passenger loco GE is trying to market)…
If what I’ve read is correct BNSF is getting a unit priced about the same as an ES44DC(with similiar train handling capabilities). They will be somewhat lighter than a standard Evolution series(with corresponding reduction in fuel consumption) and have somewhat lower maintenance costs (2 less traction motors and inverters, ect)…I do wonder about cost/performance figures of a lashup of 3 ES44AC-4s versus 2 standard, six motor ES44ACs (or how best to deploy 12 AC powered Axles)?
Pretty much what has been said by carnej1.( an on other forums ) It will still be a ‘standard’ 6 axle loco but with traction motors missing from the inside axle of each truck. I shouldn’t think you will notice much if any difference. It will just have more power available for speed, plus with modern AC adhesion technology wheel slip will be controlled to the minimum. The alternative would be designing a new 4 axle loco. GMS
A V-12 engined GEVO would be too heavy for B-B trucks, with any reasonable sized fuel tank. The Dash-8-40BW had to have smaller fuel tanks and rode like a Sherman tank. a GEVO version with a more sophisticated cooling system, and a stronger cab, would be much worse. I don’t think the 12-cylinder EVO diesel is much lighter than the 7FDL-16.
Why would a class I railroad order a high hp A1A freight loco these days? Back in the 1940s and 50s there were A1A RSC versions of Alco switchers for branchlines, and later EMD had the C-C SDL39 built on a shorter, lighter frame. The most common EMD’s with A1A trucks were E-units. As passenger operations were phased out in the late 60s/early 70s, some passenger A1A E-units were pressed into freight service, and from what I’ve heard they weren’t very suitable for this type of operation. EMD’s GMD subsidiary in Canada also produced the GMD1 switcher, which like the Alco RSCs had A1As. Santa Fe, SP and NS ordered high-HP 4-axle B40-8s and GP60s in the late 80s/early 90s for intermodal traffic, but were displaced by C-C for this service as time went on.
We are forgetting one thing about AC traction motors THEY DO NOT have a SHORT TIME RATING. You can load them to full power right out of the gate and if they can grip the rail they will pull. Plus one AC motor is worth 1.5 DC’s so in a way BNSF is getting the pulling power of a DC44GEVO anyway but saving the cost of 2 invertors and 2 traction motors worth of Maintance. BTW it was the GP60M that had to have the Smaller fuel tank 3200 gallons instead of 4000 gallons when the wide cab was put on it and rode rougher than a Rubberblocked suspension truck going across Arkansas on I-40 EMPTY that and they could only give them 2900 gallons of fuel in the tank MAX to keep within axle loading.
Mentioning about a 4 alxe engine with a GEVO engine in it, I had saw a GE presentation on the internet and they show on one of the powerpoint slides that they were developing a engine that you could fit into older GE’s like the Dash 7’s. And I know they tried 4 axle AC motors before so could they do it again?
My problem with the design is that I question how much trouble the ES44C4 will have producing a factor of adhesion of 42.8%, compared to a ES44DC producing a factor of 28.5%. That is what each locomotive has to achieve to produce 120,000 lbs. of TE, with a locomotive weight of 210 tons. And if an inverter or traction motor goes down on the C4 you stall. And both locomotives are at 70,000 lbs on axle so there isn’t much room to lower the need factor of adhesion by raising locomotive weight.
Can anyone explain why it should?
It would probably be possible to produce a GP70ACe or SD70ACe with A1A trucks too, though’s EMD’s is one AC inverter per truck whereas GE’s is one inverter per axle.
Seems foolish to take away 2 powered axles. Must be forgetting about snow, ice, wet leaves, etc.
Maybe just get ES44ACs, and have the computer cut out the 2 center axles above a certain speed.
At least there should be room to put the center traction motors back in when the experiment fails…
The above is not strictly true in that GE has designed and is trying to market a 4 axle (and 4 motor)passenger locomotive using the GEVO-12. This is confirmed in a recent book about the Evolutiion series. The “Gevosis” (my own nickname) would use a new Monocoque carbody rather than being built on a roadswitcher frame. However, It still seems putting that machinery and electrical system onto a Dash 8 B size frame might not be practical…
It would do exactly what a 4 axle AC or 6 axle DC locomotive would do.
The advantage a four axle would have would be less weight and one less pair of wheels to maintain.
But, you’d have to do some fancy engineering in order to figure out how to shoe-horn in 5000 gallons of fuel and keep the axle loadings down to a managable level. And, BNSF is already set to maintain the new locomotives. They won’t need one additional spare part or have any training to do.
The kicker here is GE could sell BNSF an A-1-A for the same price as a 6 axle DC and it will the same job and, being AC, will cost less to maintain. And then can sell them to them right now with almost no risk to BNSF. A good deal for BNSF!
So why does anyone want ES44DCs?
An ES44DC costs what-- 20%? 25%? less than a C-C ES44AC? Can an A1A-A1A match that discount by deleting two motors and two inverters?
What locomotive give a better performance EMD or GE?
That’s the theory! (apparently, it’s practice on BNSF, now)
Timz,
An A1A (4 motors/4 drive axles & 2 unpowered “coaster” axles) will have more power per axle giving a higher top speed, as does any B-B (two 2 axle trucks with one electric motor per axle = 4 motors) loco over any C-C (two 3 axle…= 6 motors) given the same engine power.
This is because a given diesel prime mover puts out a certain amount of maximum horsepower for which it is rated. For example an SD40-2 is rated at 3000hp max. The ES44AC & DC puts out 4400 hp max (hence the name “44”).
At rated horsepower, the generator, which is directly driven off the prime mover, makes its maximum amount of electric current (amps). Just for example, say that it is 1000 amps. 1000 / 4(motors) = 250 amps of torque applied per motor/axle. 1000 / 6 = 167 amps per axle. More torque means more power to push the train faster.
The tradeoff is that if you have a very heavy train or steep grade to climb, and are going slowly or just starting out, getting all that torque to the rail without the drive wheels slipping is difficult or impossible. Having 2 extra axles worth of drive wheels allows you to spread out the work load.
But if the train is lighter, like the intermodals BNSF has these A1A’s in mind for, you don’t need the extra traction of 6 drive axles with motors. 4 drivers and two “coaster” axles will do the slow work fine and then have that extra torque available as the train speeds up to keep adding more power and hence more speed.
They could just delete the “coaster” axles, but that would require a whole new design, and the whole point of this “experiment” is to save money, not spend more. Also, if the experiment flops, they could reco
Ah…The more conventional term for an unpowered axle on a diesel locomotive is “idler” axle, not “coaster” axle.
I stand corrected.
So do we know when these units are supposed to hit the road?