Acceleration and centrifugal force around curves is often expressed as "cant deficiency." The cant is the number of inches the outside rail is jacked up to superelevate the curve, and the gauge, is of course, 4 feet 8 1/2 inches. If the outside rail is jacked up by 6 inches, that is also roughly 6 degrees of tilt, and you can negotiate that curve at 3.5 feet per second lateral acceleration and have zero degrees of coffee slosh in the snack bar. If you run that curve at twice 3.5 or 7 feet per second lateral acceleration, you will have 6 inches of cant deficiency, and you will have about 6 degrees of slosh in the coffee cup.
In a non-tilt train, all of the lateral acceleration in excess of the superelevation is uncompensated cant deficiency. In a tilt train, all or part of the cant deficiency will be compensated with the tilt system, the remainder is uncompensated cant deficiency that sloshes the coffee.
The experience with tilt trains calls for some amount of uncompensated cant deficiency to give the passengers some sensation of going around the curve. Some passengers experience motion sickness without this.
How much cant deficiency and how much uncompensated cant deficiency are matters regulated by the FRA or corresponding body outside the U.S. The limits on the total cant deficiency are 1) the effect of high axle loadings on spreading the rails -- it is said the use of high axle load locomotives limits the Pacific Cascades Talgo to 6 inches cant deficiency, and 2) tipping the train over, a limit usually far from reached, although a 3 foot 6 inch gauge Australian tilting train tipped over from an operator going way over speed restrictions. The FRA limit on uncompensated cant deficiency is 3 inches; in Europe, they run the TGV at as much as 6 inches of uncompensated cant deficiency.
So an Amfleet train can run at 3 inches cant deficiency per FRA rules; the Acela apparently is restricted to the same conditions as the Cascades Talgo of 6 inches cant deficiency with 3 inches of uncompensated cant deficiency; the non-tilting TGV also runs at 6 inches of cant deficiency because in France they believe passengers are OK with those levels of centrifugal force; the Acela was supposed to run at 9 inches cant deficiency with 3 inches uncompensated, probably similar to what Pendolino does. That Acela is restricted to 6 inches cant deficiency, same as the non-tilting TGV but more than a U.S. Amfleet, is probably a combination of the high axle loading of the Acela power cars and restrictions on the allowed degrees of tilt.
Assuming there is already 6 inches of superelevation, the fps lateral acceleration is v^2/r with v in fps and r in feet, converting fps to MPH by factor 3600/5280 gives
Curve
Deg Radius (ft) Amfleet Acela-Talgo-TGV Pendolino
MPH
10 573 37 43 48
6 955 48 56 62
4 1433 59 68 76
2 2865 83 96 107
So is the glass half full or half empty? Cutting the tilt in half because of clearance restrictions just so happens to split the difference between conventional equipment and what they could do. They could allow 6 inches of uncompensated cant deficiency as in Europe, but the total of 9 inches of cant deficiency is probably a little bit much force on the rails for the axle loads they are running. So, the amount of tilt and how fast they go around the curves with the Acela is probably as best as one can realistically expect with U.S. operating conditions, although that amount of tilt is easily achieved with the passive Talgo and doesn't require the more complex servo-hydraulic active tilt system.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Your right on north vs east. The New Haven allways felt Boston was east of New York and Portland was "Downeast".
Tilt on the Acela is a product of speed and inertia which is recorded in the "Black Box" and tracked by GPS. Designed as 0 to 7 degrees, last I knew it was locked at 1/2 swing and speed restrictions imposed on some curves. Can anyone update.
A standing Providence and Worcester freight and a tilting Acela might violate minimum clearence. Note that the platform level will be at the bottom of the door (on the left) but the body gets very wide as it goes up. Also, all windows are "rescue windows" with instructions .
Don U. TCA 73-5735
Hard to buy the "four inches too wide" argument when the Acela Express is 10' 4" and all other rolling stock on Metro-North/CDOT (plus Amfleet) is 10' 6" wide.
To say that two AEs tilting around a curve would be a stretch, since they would both be tilting in the same direction. (BTW, it's east of New Haven, not north.)
The last I knew, the "tilt" was locked at 3.5 degrees in place of the designed 7 degrees. The Acela was built 4" too wide do to interior design.
If the two Acelas were to pass each other on some curves, with tilt at maximum, it would be too close. The tightest spot was on the Canton Viaduct outside of Boston. Built in the 1830s as a single track line for the Boston & Providence, the New Haven added a second track in a "gauntlet" operation (one train at a time). Amtrak solved the problem by adding an ugly overhang on the east side of the viaduct to widen the Right Of Way.
The speed limit south of New Haven on Metro-North Tracks, as of 2001, was raised to 90 mph, maximum. Lots of speed restrictions to 75 and 70 mph do to the numerous curves and bridges. Freight trains are restricted to 40 mph or less. (ref. M-N R Employees Time Table April 2001)
The line is 4 tracked New Rochelle to Stratford, 3 tracked Stratford to New Haven, and north of New Haven (Amtrak owned) 2 tracks to Boston with added tracks at Providence and Boston.
DMUinCT wrote:In between they have Acela Regional
The catenary wire is being upgraded and modernized on Metro-North/CDOT (for the most part, it was the same wire that dates to the first decade of the 20th century); although why the extra money is being spent for constant-tension when the speeds (and/or signaling) are not being upgraded on that line is not easily understood.
Amtrak has 20 "Acela Express Train Sets", on any day at least 15 are in service. The fastest (fewist stops) can make Boston to New York in a little over 3 1/2 hours. New York to Washington, 2 1/2 hours! A train every hour. BUT, Acela are a First Class and Business Class only trains.
In-between you have Acela Regional, which has nothing to do with Acela Express!!! It's locomotive hauled "Amfleet" cars, Business Class and Reserved Coach.
Six to seven hours (depending on stops,) you can spend more time at airport checkin than the train takes for the trip.
The Catenary north of New Haven is new, the latest design. New York to New Haven it is being upgraded by the owner, MetroNorth/ConDOT. South of New York the Catenary must be upgraded. as funds permit.
rustycoupler wrote: hahahaha they cant even get the regular acela trains to run on time
And for the record, they have a far superior on-time performance record to the air shuttles between New York and Washington DC.
new track, new engines ,new attitude out of the question!
I recall reading, a while back, that the Acela NEC upgrade project got less than half the funds promised to it. So out of the "new" things on the list to do, new catenary wire between New York and Washington DC, plus key interlocking upgrades, got excluded due to the funding shortfall, resulting in no 150 mph territory on the former PRR and slowed-down operation on curves (even in spite of the active-tilt system). Other FRA requirements (cutting back on the expected 9-inch unbalance in curves, requiring crashworthiness standards that resulted in the trainsets being twice the weight of the TGVs) have exerted their own negative effects.
I liked the idea of High Speed rail lines in New York, Montreal and California
Please add Columbus,Macon,Augusta to Atlanta, Georgia then to Chattanooga, Nashville, Knoxville, from their to anywhere.
Tks Railman
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