I have 6 DCC equipped Atlas MP15 locomotives. They will typically pull 10 - 12 Red Caboose auto racks on the flat and around 18" radius curves. Like my prototype, I frequently run them in lash-ups, then the sky is the limit. Dave
The lack of 'scientific' or at least 'comparative' testing is what led me to build my own dynamometer car with a spring scale, and then later get into calculating the traction coefficients when I could see trends emerging, particularly for the horrible weight and traction of some new Atlas products. All this started when I got a new Atlas SD24 several years ago and it ran fine, the first couple laps, with its assigned train, and then got stuck on the hill as the wheels polished up and the blackening wore off. It became pretty obvious to me that not only was locomotive weight decreasing (combination of DCC cutouts + changing to non-lead alloys) but that wheels themselves were much slicker. I'm following this one because I'm really hoping that something hasn't 'changed' with new Kato products - like going to the slick alloy wheels. Historically they have outperformed Atlas consistently on the coefficient, which I attribute to a different wheel alloy entirely. Now what's strange is that it's not necessarily ALL Atlas; while the newer GP7 is a little lighter, the traction is still better than other Atlas and on the same level with the old one expressed as a percentage. But the MP15 and the GP38, wow, both pull so poorly that they got put in the display case. If the manufacturers can convince you to buy more locomotives by making the performance significantly worse for tractive effort, that's a pretty good business. I've been at this long enough I remember that the old Rapido GP9/30's (with turned wheels and flanges) could easily drag 10 cars up a 4% grade, grinding all the way, of course. "Performance" has been dramatically improved across the board, unless some old-timer remembers when you didn't need three locomotives to move 10 cars up a 2% grade.
Dynamometer Randy, I'd be interested in how you made your dynamometer....is it a car you pull with a train behind it, or do you attach it to a fixed point?
Did the real switchers actually pull out the entire train, or was it broken down into segments ??? Just wondering !!! As previously mentioned, I don't have a problem doubling up switchers if I need to. Of course, you may not have two of them. Another cure is have something a bit larger nearby, just in case. I have rightly been accused of always having an SD7 or SD9 within arms reach !!! Grab the bulk of the train with the SD, snag the head end cars with the NW, and your road units are free to go. I know it adds an extra movement, but I think we ALL like runnin' engines anyway, ya' know ??? Just an idea !!!
I have never heard that Kato made any changes to the NW-2. Where did this info come from? Anybody have specifics. Just being honest.... until someone could provide some sort of proof and/or specifics, I am doubtful.
That would at least depend upon the tonnage involved. I've watched some of the older EMD and ALCo switchers really dig in and lug. As long as they got traction and could get it rolling, some really big cuts of cars.
Boxcab, I've seen that, also, but the OP is talking about passenger trains. Sure, the passengers may be off, but there are still crew members inside. If they experienced a sudden, unexpected AA/Fuel Funny Car-type launch, the engineer of that switcher may not be very popular !!!
Well, what I was saying is that if they had the ability to lug out huge strings of freight cars, they can certainly do the same for the smaller quantities/lesser tonnage of passenger cars. Are there still crew members aboard at a terminal? Trains I have been aboard when switched outside a terminal, they generally moved us fairly easily. Probably more like car cleaners, if any, aboard an otherwise empty train.
Got it !!! I understand. It makes perfect sense. Guess I'm just trying to keep the OP's NW2 from the "scrapper's torch" !!!
When I got involved with 12"=1' railroading and started doing operational studies, one of the first things I learned was that my impressions about 'what something could pull' were way off. The 'switcher vs. road unit' based on horsepower got to be rather interesting as I was given a copy of EMD's software to determine how many locomotives you needed to power a train. And you entered all the variables, including speed over the road. HP didn't equal tractive effort, HP equaled sustained speed at tractive effort and moved that curve up higher. So here's our little NW2: http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=es-10_E425018i.gif&sel=die&sz=lg&fr= Note that the weight is 243,550. 122 tons. 60,890 lb. of tractive effort, quick ratio 25%, steel-on-steel, and likely with the ammeter in the red zone. Now lets go to a GE U25B: http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=es-10_E425018i.gif&sel=die&sz=lg&fr= Note that the weight is 270,090. 135 tons, and 80,000 lb of tractive effort at 14.7 mph. 29.6%, that's with sanders for sure, and possibly even overstated. But that TE is at a lot higher speed, I suspect. You'll see coefficients that high today and even more with AC traction, automated sanders, and wheel slip control. The point is how close they actually are at low speeds, not because the U25 is so much bigger and almost 3X the horsepower, but that the raw weight of an NW2 is more than you'd think from appearances. If you've got enough horsepower to get 25% to the drawbar for slow moves, you're there. What limits a locomotive is more often the axle loading to the rail. So on a dead-start crawl, they're actually a lot closer than you'd think, as the weight of a switcher is more closely related to a road unit than you'd imagine. It isn't until you try to move that weight at any speed that HP is kicking in and they fade out immediately. So yeah, the 'poor little switcher' dragging cuts of cars around a yard at 5mph was darn near as capable as if you'd put a road unit in there, and the assumption is correct that a model shouldn't be assumed to be so weak that it can't break up a train that a road unit managed to get in the yard. I've got advertised tractive effort and performance curves on GE 44-tonners that are fascinating; how GE rated them for traction and speed, and how rapidly they fell off the curve at the slightest provocation of either a grade or speed. But at a dead-flat yard at 2-3mph (until the traction motors or main generator overheated) you had a little mule. Today you're looking at crowding the locomotive size right up to the maximum for axle loading for road units PLUS pumping up the horsepower for speed PLUS jacking up the adhesion with all known automated add-ons; not really fair for comparing a new GE backwards but for four axle to four axle, it was always a 'huh' revelation to me when I realized that the little EMD switchers were darn near as heavy and low-speed capable as the much bigger brothers.
Randy is right. I too work in the 1:1 railroad world specializing in locomotives. I disagree however with the adhesion factor, it is overstated. The GE engine is closer to 13% adhesion with the CMR wheel slip system and the NW is closer to 7% adhesion with the old style through cable transducers. Only a really good engineer on the NW would get close to 15% by allowing the old engine to "wheel creep" Wheel creep causes micro welding to the rail and increases adhesion . The goal is to prevent the wheels from slipping at all to maintain adhesion , sadly the older systems were not able to do that quickly enough. This is why the wheel slip systems have been in a constant state of evolution. Randy (II)
