The press release in the first post says:
as the official launch date approaches, customers should look for more information from Amtrak about how to locate and select the NextGen Acela train options. In the coming months, Amtrak will be operating both the current Acela equipment and the NextGen Acela trains as the new trains transition into the fleet.
Iām wondering if that is due to the close spacing of the tracks on the NE Corridor?
Not in the whole corridor, just the parts above New Haven where there are potential interferences. I think the concern is as much with failures of the tilt to full extension as with a train with tilt coming into contact with one that doesnāt.
Iād look forward to reading something conclusive that states their reasoning.
I donāt think we have any conclusive information on that, just informed speculation and comments with no indication of source for the information.
Something that may (or may not) be related is the experience with the outside swing hanger truck made by Commonwealth/General Steel Castings. On page 510 of Whiteās book on American RR passenger cars, he wrote the āfull potential was never realized because it was necessary to restrict the free swing of the links to stay within existing side clearancesā. The footnote proceeding that referred to data provided by W.D. Edson.
Yes, and he specifically noted the truck in question was used on the New Haven.
He also noted that the New Haven was the first customer. I wonder what would have happened if the first customers were western roads with presumably more generous side clearances.
One of the nifty features of the truck design is that it tilts the car towards the center of the curve when train speed is above the balancing speed for a given superelevation.
Erik: How would that truck compare with the Nystrom trucks on the Milwaukee Road,? Hiawathas ran very fast (100+mph) on curvy track in places.
The Nystrom truck is primitive by comparison ā stiff suspension optimized for high speed meant poor ride quality below 40mph. I believe Nystrom himself has documented the design philosophy.
The improvements in various kinds of outside swing-hanger trucks (OSH) are in the secondary-suspension ride quality and the lateral accommodation and damping ā improvements in perceived ride quality more than better guiding at high speed. The trucks in question move the bolster support points as far outboard as the loading gage at that height would permit, and as Erik notes, the swing-hanger arrangement can roll the carbody when high lateral force occurs in curving.
Note that the more definitive solution for indeterminate-spring-rate secondary suspension is air bags. These cannot be used in place of coil springs in these OSH trucks as the required diameter of the bag system is greater, and transverse elliptic springs as in the āBlombergā B truck would also project too far.
The NEC is a higher speed corridor (over100mph). What type of trucks are being used on the new Acelas?
Itās surprising how difficult it seems to be to find a labeled drawing of the truck and the pivot arrangement. Best I can find so far that isnāt an artistās rendering is Dan Cupperās picture from TrainsPro;
Many of the bogie components are apparently common to the Avelia Horizon āTGV Mā double-decker, but the latter uses spring secondary suspension. The tilt mechanism is Tiltronix (Alstom notes it is derived from the Pendolinos) and there is an Instagram video of the tilt mechanism being exercised ā you will understand the weird mismatch between the power car side profile and that of the cars.
Nystrom specifically said that a high speed truck would ride poorly on a low speed branch line suffering from too much bounce. His high speed truck design used stiff primary springs and soft secondary springs.
Moving the support points out as far outboard as possible is the roll resistance goes up with the square of the spacing between support points. Looking at it another way, the wider support points allow for softer springing while maintaining roll resistance.
Looking through Kratvilleās book on UP Streamliners, the UP had the OSH trucks on most of the cars ordered after 1950.
We need trains that tilt over here in western PA. I want to ride the tilty train.
" Amtrakās New Acela Trains Are Here. Theyāre Moving Slower Than the Old Ones."
Found a new GO effective August 2025 showing the new Acela 2 speeds. Note that they are temporarily running under column B due to restrictions on the tilting speeds which are lower than the speeds on curves allowed for Acela 1 speeds.
Hopefully this is a temp issue, which accounts for the slower running times at the moment.
Alstom says it tweaked the design to meet Tier 3 requirements, which ultimately affected the trainsā performance during extensive testing. That, in turn, prompted additional minor modifications to the equipment, including dampers on the suspension of the trainsā power cars, an independent source tells Trains.
Further complicating matters: The new trains ride on a TGV wheel profile, which is different from any other Amtrak equipment. The Northeast Corridor, Jagodzinski points out, includes significant mileage shared with freight and commuter traffic, which raises tonnage beyond what TGVs experience on dedicated high speed tracks in France.
So, it seems to be a vehicle dynamics issue. As of now, the tilt mechanism is essentially useless, as the trains arenāt even allowed to match the first gen Acela performance on curves. If after four years of delays they havenāt gotten this worked out, I have to wonder if Amtrak is just giving up and accepting the possibility that the trains will never operate as intended. I certainly hope not. That ugly mismatch between power cars and coaches needs to be justified somehow!
The Acela 2 like all French trains use a cylindrical wheel rather than a conical wheel. The Amtrak Turboliners back in the day did too. As did all locos on the Santa Fe including Amtrakās SDP40Fs. They hunt less at speed.
The North Shore back in the 20s started this. Santa Fe copied. Then the French. Interestingly the CTA still uses cylindrical today.
The Japanese use 1:100 on their Shinkansens which is nearly cylindrical. They started with I think 1:30 and had bad hunting.
Typical low speed trains are 1:20 to 1:40. Iāve not ridden the Acelas 1st or 2nd gens but Iāve ridden the NEC regionals a fair amount. I wouldnāt compare the NEC to either Japan or France in terms of smooth track.
https://dn721508.ca.archive.org/0/items ā¦ -19SUM.pdf
I wouldnāt compare our track with that of Italy, Germany or China either. Question is poor engineering and construction or overly heavy loadings?
Iām not an expert but I know in France and Japan and China only the HST with axle loadings below 17tons are permitted on the HSR tracks.
Germany allows freight trains on their 250kph lines (but not their 300kph lines) but their freight trains are smaller. Looks like about 22.5tons.
I believe Italy no longer allows freights on their HSR lines.
US freights can be up to 39tons. Oof! Thatās got to beat the track even at slow speeds.
Every book Iāve ever read on HSR says freights and HSTs are contra indicated.
I donāt think anyone on here anymore (NH/PC/CRlAMK Joe was in the past) is an āexpertā on high speed trains. Only a handful have ever even ridden one!!
I do try to buy models of every high speed train Iāve ridden. Got quite a collection. Even the Shanghai Maglev! (Maglev doesnāt run, just a static model. Not sure how theyād make it levitate!)
Will be hitting Germany and France in September and next September Japan and Taiwan. And Iām already planning to try the new Acelaās this fall or next spring.
If youāve never seen it this PDF has buckets full of HSR data. Published annually. Youāll be an expert in no time!
One of the videos stated the northbound inaugural run was delayed due to issues with the platform gap fillers and doors. Winter may be interesting for those.
Also one of the bathrooms (only one per car) went oos.
