Allen Hazen wrote:I apologize for going on about my pet peeve of overweight passenger diesels: for the moment it is pretty tangential to GE. But...
Another tidbit from McDonnell's "Locomotives": the Alstom PL42AC locomotives for NewJersey Transit (EMD 16-710 engines in a European-inspired carbody; 288,000 pounds) have traction motors mounted on the truck frames (in contrast to the typical North American "nose-supported" traction motor which is slung between the axle and the truck bolster) to reduce unsprung mass and so reduce track damage ("hammer blow"). This is interesting. Since only one end of an American style traction motor is suspended from the axle, I would think (if there is an engineering dynamicist out there, please correct me if I'm wrong!) the reduction in unsparing mass would be roughly on the order of maybe approximately half the mass of the t.m. (more or less): so a four-motor locomotive with frame-supported traction motors would, in terms of how it interacts with the track at speed, be the equivalent of a locomotive with American-style motors weighing 12,000 to 14,000 pounds less: an improvement of under 5%. Alstom's designers felt this was worth while, and New Jersey commuter rail thought it was worth paying for.
Now, frame-supported traction motors aren't all THAT new an idea: Westinghouse and GENERAL ELECTRIC built electric locomotives with quill drive decades ago. So in principle GE could easily design a passenger locomotive with frame-supported motors. I don't think, however, that GE currently builds motors suitable for that sort of mounting. (At a guess, they could use the same internal works as used on their current motors-- certainly the same electrical arrangements-- with a new motor casing and connections to a different sort of gearing arrangement.) But whether they would think it economic to do the new engineering for an order of a few, or a few dozen, units from a commuter agency is another question.
(Another way of shaving the weight would be to use a lighter-weight engine. But getting the cautious people who run commuter trains to consider even the GEVO engine was probably a hard slog: designing an all-new North American passenger unit around the power haul engine might be, in commercial terms, risky.)
While this post is WAYYYYY over my head, I can make out a few tidbits of info and what they mean
I can say this, ive run the PL42s and the P40s over the same track at the same varying speeds. The PL42s ride HORRENDOUSLY. The P40s ride like a Cadillac compared to the PL42s. I have literally been bounced out of the seat in a PL42 (going west through Perth Amboy, NJ), and even on the relatively smooth NEC, they ride like hell. It feels like the suspension cannot handle the weight of the loco, and it feels from the seat that they bottom out at nearly every bump. Even with freshly overhauled trucks, they ride the same, or at best, "less worse".
IMO, the P40s are much better locos than the PL42s. The only real "fault" (and its not really a fault, just how it is) with the P40s is the GE loading, which for a commuter operation which I run them in, can be a drawback, or at least an annoyance...haha.
