So I pose this question on the "seldom powered vehicle" on account of just about nothing of substance that I can find in my research as to what left them... Well, seldom powered. The only point of some substance I could find was issues with the fuel pumps. Something about unreliable electric fuel pumps with no backups near as I could understand.

So what was the issue with the SPV? Was it the fuel pump, or was there more than that? It seems to me that the failures were restricted to the mechanical side of the equation.

When I look at it's failure, it makes me think that it probably killed realistic hopes for DMUs here in the US since then, given that it's probably only within the last decade or so that products from the likes of Siemens, Stadler or Nippon Sharyo have shown up in any notable numbers. And even fewer of those are certified for running outside of a light rail classification.

HOO boy, as someone I knew from New Jersey once said, "you're really treadin' on sore water!"

The single biggest problem might be called a detail-design oversight, but it had multiple terminal ramifications. One problem with the SPV was the decision to dedicate the two 8-cylinder turbocharged prime movers only to propulsion: the engines did not even have so much as a small alternator or exciter on them. All the ancillary loads were handled by a separate 4-cylinder "APU" -- and that was not only the lighting, air-conditioning, and control voltages, but the FADEC or whatever it was for the main engine control. (And yes, the fuel pumps for them...)

This was a highly durable Perkins genset, but it was given somewhat insufficient cooling radiator area -- in a part of the car that routinely got clogged with leaves and trash. When the Perkins shut down for any reason... instant Seldom Propelled Vehicle.

The larger, heavier Metroliner-derived shell and suspension were overdesigned to make the cars 120+mph capable. While that was certainly doable, I would question whether anyone remotely interested in this sort of thing would use SPVs for a modern version of the Roger Williams, rather than using either top-and-tail or some sort of cab-car arrangement with less expensive (and more easily-suspended) unmotored passenger cars.

Additionally, with the added weight, the cars really, really needed eight-wheel drive. And accordingly kits were manufactured to conjugate the two axles in each truck... but nobody bothered to check whether this might put the SPV in a different class where union representation was concerned. Rather than pay the extra wage or attempt to negotiate something, the cars were left with the RDC-style single-axle-per-engine drive, which would be laughable if it weren't so appalling in regular practice. Remember that the SPV2000 was intended to run at very high speed, with appropriate acceleration. (If I remember correctly, the main engines were 8V-92TAs or something in that family) When the throttle was advanced, slip of one of the axles was almost guaranteed at some point, whereupon the governor would abruptly derate the engine, throwing the load suddenly on the other one, and that was almost computer-guaranteed to make that one slip... with the result as above. Apparently many of the Metro-North ones had a slippery, bucking alternation like this for multiple cycles at nearly every station stop if the adhesion were anything less than ideal... and perhaps even then.

I had a great deal of fun working out a torquemeter-equipped driveshaft that communicated via LEDs and detectors and was inductively charged... not that it ever went much of anywhere with the other problem so great. I think the conversion gearsets are long since gone to scrap, but it would be interesting to gin two of these shafts up and use them on an eight-wheel-drive car... a sort of dieselized equivalent of the T1 Trust effort.

Someone has pointed out the "automotive" design approach of the people who developed the car: apparently the wiring was something of a triumph of complexity. You may recall that rugged simplicity was one of the important principles of the original RDC -- that was certainly NOT characteristic of the SPV. And all the fancy electrics ran the battery down right quick as soon as the Perkins stopped perking... with the results we know so well.

Overmod,

Thank you for the rest of the story.

Wesley
from the back row of the Self-Propelled 101 Classroom

If I had a trophy, man would I give it to you. This is EXACTLY what was missing from the story that I couldn't readily find.