• Acela II (Avelia Liberty): Design, Production, Delivery, Acceptance

  • Discussion related to Amtrak also known as the National Railroad Passenger Corp.
Discussion related to Amtrak also known as the National Railroad Passenger Corp.

Moderators: GirlOnTheTrain, mtuandrew, Tadman

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  by Gilbert B Norman
 
electricron wrote: Thu Jun 17, 2021 9:56 pm 15kV 25 Hz impedance (Z) and 25kV 60 Hz impedance are not the same.
XL = 2π * f * L
Where XL is the inductive impedance, f is the frequency in Hertz and L is the inductance in Henrys.

If the only variable is frequency, the impedance of a circuit as 60 Hz is more than twice that at 25 Hz. But frequency is not the only variable because a different inductor (L) and its value would also change.
Ron, why didn't I become an Electrical Engineer in this life rather than a CPA?
  by electricron
 
Gilbert B Norman wrote: Fri Jun 18, 2021 7:46 am Ron, why didn't I become an Electrical Engineer in this life rather than a CPA?
CPAs live in a 2D world, on a timeline that can be expressed with x and y axis, one for money and the other for time.
Electromagnetic forces live in a 3D world, with x, y, and z axis. In a CPA world the math is much easier.
  by STrRedWolf
 
electricron wrote: Fri Jun 18, 2021 1:55 pm
Gilbert B Norman wrote: Fri Jun 18, 2021 7:46 am Ron, why didn't I become an Electrical Engineer in this life rather than a CPA?
CPAs live in a 2D world, on a timeline that can be expressed with x and y axis, one for money and the other for time.
Electromagnetic forces live in a 3D world, with x, y, and z axis. In a CPA world the math is much easier.
It could be worse. You could be a computer programmer, and depending on the subject matter, you'll end up in a world with too many dimensions and not enough resources to handle it. :(
  by Matt Johnson
 
NRGeep wrote: Sat Jun 19, 2021 3:33 pm Will these new new units be limited to present 150 mph through Attleboro and Mansfield Ma or will the Liberties be allowed more speed?
160 mph where the Acela currently does 150 is the plan, and also through Princeton Junction I think where the current speed limit is 135 but new constant tension wires are in place.
  by Fan Railer
 
Currently 135 from COUNTY to HAM with a 130 restriction at the curve in Deans. As I understand it, with the new trainsets, it will be 145 COUNTY to MIDWAY, and 160 MIDWAY to HAM.
  by bostontrainguy
 
hxa wrote: Thu Jun 17, 2021 1:22 pm
Fan Railer wrote: Mon Jun 14, 2021 10:26 am
photobug56 wrote: Thu Jun 03, 2021 7:17 pm I do admit to being very puzzled. All this testing on the NE corridor with one of the 2 test trains, not a single hint of problems during the testing. One would think that if problems were found, that adjustments, fixes would have been made even if the set had to go to a yard or the factory for a month, then resume testing, but we never heard of that happening.
As test speeds gradually climbed higher from the 90 mph mark, the aforementioned issues with the pantographs was discovered (excessive pan bounce when operating in the rear-pan-up configuration, which is supposed to be the normal operating configuration)...
Under such a configuration, the wind blowing from the front would reduce the force applied to the contact wire (amount of which increases with speed), making pantographs more easy to come off-wire under higher speeds.
The mod applied to the pan consists of two small spoiler fins designed to induce lift (like a plane wing) at the higher speeds, which keeps the pan in contact with the wire more consistently when it encounters areas of poor wire geometry which induce oscillation in the pantograph height.
This "genius" solution was originally proposed by engineers from British Rail and Brecknell, Willis & Co. in roughly 1970s. These fins induce a second counter force that also grows with speed, effectively making the pantograph applying an almost constant, speed-independent force to the catenary. Every single pantograph designed for high-speed operations in UK or US has adopted this design since then, except for the (original) ones on the new Acela.
The fin idea sounds good but I was thinking that Amtrak plans to run with the rear pantograph up, so if there ever was an issue (like snagging the wire), the Acela can raise it's front pantograph and continue on it's merry way. However, wouldn't the fin now be working to bring the front pantograph down and cause it not to contact the wire under speed?
  by west point
 
The "fin" can be a common airfoil with both directions being built symmetrically. Jus look at it from the side as a common ellipse with the mid point being higher than front and back. Do not get me wrong the design can be more complicated than that but symmetrical.
  by Gilbert B Norman
 
Over at the Disposition topic, Mr. Approach notes:
ApproachMedium wrote: Just as little tiddys of info here. The new trainsets it has been confirmed that due to the single pan operation, they can now do 165mph with non constant tension wire. So much more of the railroad that currently offers only 135mph max operations can now run close to 160. Single pan ops eliminates the rear panto bounce at higher speeds as well as the rear panto bounce from two trains passing at high speeds.

Also the max curve speed for the new set is now 150mph vs 130mph of the old sets. Likely the rollout of these trains will be in current time slots, with trains that see the most ridership.

As far as speeding up service goes until you get rid of the station area slowdowns, you wont see any major decrease in time to travel. 30mph thru balimore for a few miles, 30 for about 3 or 4 in Philly, Wilmington, Shore curve etc. Thats what really kills the running time for anything.
Now could this apparently positive development mean that an Acela-II could be inaugurated in revenue service sooner than the one year delay earlier noted?
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