Yet another of the supposedly preserved F40PHs getting modefied. http://www.nctrans.org/Media/Releases/U ... -For-.aspx

What's the point of an 8000-hp locomotive when nowhere near that much power is needed to pull the trains?

Some years ago, a major locomotive manufacturer attempted such high horsepower in a single unit and found out quickly that there are electrical, mechanical and adhesion limits to a four-motor locomotive.

It's good for rail burn and keeping the track gang busy.

Makes all the difference in the world to a commuter train. The toughest part for them is from 30-80 mph, where adhesion is no longer an issue and train acceleration is limited to what the engine can put out. They spend a lot of time in that zone. Having 8000hp peak instead of 3000 could significantly increase the stop-to-stop average speed of the train. That's very hard to do short of switching to EMUs.

Back in ancient times, when the Pennsylvania Railroad replaced the K-4s Pacifics with EMD E-8's on commuter trains on the New York & Long Branch, legend says the timetables had to be adjusted because the diesels could not accelerate as rapidly as the steam engines could. That may have been the case, as the E-8's had gearing for sustained high-speed running rather than for acceleration. On the other hand, I recall watching BN E-8's that had been modified for rapid acceleration roar away from stations and reach near maximum speed in a couple of train lengths. Horsepower is not necessarily an indication of speed or acceleration.

WhenI was working in the shortline railroad business, I learned a lot about the power to weight ratio of locomotives. An 800-horsepower switcher, ballasted up to 120 tons, would dig right in and pull whatever you put behind it without slipping a wheel. You could yank the throttle right out to Run 8 in one motion and away you'd go! A 1200-horsepower unit of the same weight would wheel slip like crazy if you tried that same trick. The SW-8 used less fuel than an SW-9, too.

Sounds like it'll be governed to 54mph and will only run wrong main (ie, the left lane).

Horsepower, properly used, subject to adhesion limits, vs weight, is exactly what makes acceleration, and top speed. In fact, the drawbar horsepower is computed by the speed times force at the drawbar. The confusion comes in because the drawbar HP is limited by wheel slip. The drawbar pull will remain mostly constant as the speed increases, multiply the two is the HP. Once the drawbar HP is as high as the engine, the drawbar pull will go down as the speed increases, keeping the drawbar horsepower level constant.

BTW my Prius can exceed 100 MPH and does it at a fairly respectable acceleration. The basic idea works quite well and should implement very well in the rail environment. The question is if the fuel savings will exceed the increased costs. I've come out well ahead on the Prius, but they have built several million and Toyotas are known for being pretty reliable. If the loco isn't very reliable, it will just cost tons of money.

The HHP-8s were nominally 8,000 hp, they kinda worked.

I'd like to know how they plan to do that and keep the weight down to a reasonable level. There were not only electrical and adhesion problems with 3,000+ hp B-B freight engines, there were axle loading issues, too.

Umm first of it's kind... Apparently they never heard of the Green Goat, or the turn of the century battery powered dock pusher locomotives.

Weight and adhesion are important, of course. The AEM-7 weighed in at about 100 tons, if I remember correctly... While capacity and acceleration were very impressive on the high-speed locomotive, and it did what it was designed and purchased to do. I can attest, however, that under the right conditions, like wet rail and a heavy train, it was certainly possible to slip the wheels. Computer controls did and can do wonders in keeping the locomotive at maximum traction, just short of wheel slip, load, environmental conditions and weight of the unit will determine success. Also there is always the ugly truth about axle loading imposed by the host railroads. Given the modified F40 retains it's present trucks and carbody, I don't see how the new, well, really the green modified fully loaded locomotive will weigh in at more than 286,000. Depending on fuel capacity the F40 weighted in at in at a bit less than that.

G.F.Payne
B'more MD

I think this should be an option vs the f40
http://www.rrpicturearchives.net/pictur ... 0_2173.JPG

What they are discussing is not so much the "Prius of Locomotives" as it is the "Tesla in Ludicrous Mode of Locomotives" (I would be tempted to add that at least some of the design team might really want to stick it to the furries ... but most people here are unlikely to consider that important...)

Engineer types note the permissible output in kW sourced from the battery (note the term itself is plural, so 'battery pack' or 'battery array' is nominally redundant!) as adjusted for transmission and motor losses, and convert this into 'horsepower' Sounds really good, like PRR's "9000hp" steam turbine in the '40s.

Naturally it would still be adhesion-limited, and perhaps TM/semiconductor limited in the speed ranges where "8000hp" begin to be usable. I continue to have my doubts on how effectively the Tesla engineers have built their battery structure to withstand the high discharge cycle stress of Ludicrous Mode - I understand the cycling is less of a problem with some of the latest high-power-density battery chemistries, and active heat management is not that difficult an art even at this size.

If you are concerned with dividing up the HP cost-effectively, you could use a cabbage with its traction motors restored, or resurrect the MATE.

Strange this thread comes up now; I was in Roanoke over the weekend and my son saw poor NS 888 sitting on her own little track. At least her green paint is still clean and shiny!

I hate horsepower as you don't have solid rating TE conversion.

I looked for HP vs TE conversions and the calcs seemed way off.

so I looked up the HHP-8 and NKP Berk

https://en.wikipedia.org/wiki/Nickel_Plate_765

https://en.wikipedia.org/wiki/Bombardie ... stom_HHP-8

The Berk has 8 active wheels as does the HHP-8 for power and the weight is very close

then I look up the GP-7 and look at the HP and TE and I get more confused.

https://en.wikipedia.org/wiki/EMD_GP7


someone needs to post a correct HP vs TE calculation or somebody out there made some bad calcs.

The general formula is TE = 308 x HP / MPH, subject to adhesion limitations at low speeds. The "308" might vary a bit depending on the efficiency of the electric portion of the diesel-electric system, but is a good number for early diesels with DC generators and traction motors. Those early diesels couldn't exceed TE of 25% or so of weight on drivers without slipping, but more modern ones can go above 40%. The effective HP limit for a 2nd-generation 4-axle locomotive was about 2,300 HP without introducing a de-rating feature at low speeds, such as that found on the 3,000 HP EMD GP-40. Locomotives can weigh slightly more than the freight car load limit because their wheels are bigger, thus reducing contact stress at the rail head.

Speed/tractive effort curves used to be readily available from the locomotive manufacturers, but are closely-guarded trade secrets today.