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Trains for the curvature of the Shasta Route -
adapting to regulations in a less than perfect world

In general, location-based active tilting is superior to "natural", gravity-controlled tilting. The users of "natural" tilting in Japan have replaced these trains with faster ones, that use a location database and active control.
Not all gravity-controlled tilting is created equal, though. The Japanese versions use a carbody, that rolls on the bogies. This results in more resistance than given by the Talgo system, which tilts in its air suspension bellows under the roof. This quite unusual location for a suspension makes it tilt faster and smoother than other passive systems.

This tilting system will not react as fast as a location-based active system, but is expected to work rather well with the tight curvature of the Shasta Route nonetheless - much better than a sensor-based active system. Gravity is less easy to fool than a computer with sensors.
It needs to be added, however, that Talgos are not usable for this route without a modification: Normally, their tilting system is switched off at 43.5 mph, in order to avoid excessive sway in station throats. This "feature" needs to be replaced by something better, in order to avoid cutting out the tilting system in the tightest curvature.

When writing "Talgo", the author does not mean "Cascades Talgo". The locos for Amtrak's Cascades service are not usable for the Shasta Route. They are far too heavy for their power, and their center of gravity is too high. This does not come as a surprise, since the Amtrak F59 PHI are little more than freight engines with HEP, plus some composite added for streamlining and cosmetics. A comparison to Spanish Talgos with purpose-built engines shows the deficiencies:

In order to accelerate a train from standing start in a steep grade, and to reach an acceptable average speed on mountain routes, 14 - 15 horsepowers for the ton of train, plus a similarely powerful dynamic brake, are necessary. This means 14 - 15 hp traction power, HEP not included. This is no problem with electric locos, and no major problem with high performance diesel locos.

The heavy, medium speed prime movers of GM and GE are second to none, if the task is "moving heavy freight with lowest maintenance costs". But they add 5 - 10 tons, in comparison to high performance diesel motors. This is the first weight penalty. Second penalty is added by the FRA regulations: 4.5 tons of deadweight had to be added to the ALP-46 for NJ Transit, in comparison to its European counterpart (Lutz Schwendt, Bombardier Transportation: "Eine neue Lokomotive für die Neue Welt - die ALP 46 für New Jersey Transit (USA)", Eisenbahn-Revue International 4/2002, page 180-185). Electric transmission means even more weight in comparison to the hydraulic transmissions of the Spanish Talgo locos, and after adding the heavy frame of a freight loco as the 4th penalty, the resulting product needs 2/3 of its power just to move itself uphill at passenger train speed.

Judgement about possible high performance diesel locos has a framework of facts and conclusions:

• In order to achieve high curve speeds in tight curves, loco weight may not be much higher than 80 tons. (Slightly higher weight might be possible with very high quality steered axle bogies, as shown by the Swiss Re 460 loco.)
• In 1982, it was possible to deliver 4117 hp in 88.2 tons, resulting in 46.7 hp/ton. These locos are still used by the Spanish RENFE, for Talgo express trains on demanding routes without catenary.
• Today, and with the European ruleset, it should at least be possible, to deliver the same as in 1982. Example: 3526 hp in 75.5 tons, for a result of the same 46.7 hp/ton as in 1982.
• The weight penalty for conformity to FRA regulations is about 4.5 tons, or a little bit higher for true lightweight construction.

Conclusion after adding up these results: Today, and with the FRA ruleset, it should at least be possible, to deliver 3526 hp in 80 tons, the same power as in a European 75.5 ton loco.

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Last modified: 2003-10-07