Stadium-Armory Pocket Track Use Questioned for Silver Line

Mainland wrote: Metro is also worried that extensive use of D98 will slow service across the line since trains would come from full speed out of Stadium Armory down to the speed needed to enter the pocket.

Of all the reasons cited, this one strikes me as most off-key.
How far from Stadium Armory is it? How fast will they be going by there?

farecard wrote:Of all the reasons cited, this one strikes me as most off-key.
How far from Stadium Armory is it? How fast will they be going by there?

As I recall, rail chief Kubicek was quoted as saying it was approximately a mile after pulling out of Stadium Armory. He also noted the rail grade coming out of the station within his discussions of trains needing to accelerate to reach, again as he was saying, 50mph speeds.

Operation of the signals in that area was also raised as a concern, specifically that a problem at/in the pocket may effect the D&G junction signals.

afiggatt wrote:On the viewgraph presentation, finally we get some specifics on the problems on the pocket track and the operating frequencies. In short, once the Silver Line begins operation, there will be a lot of unhappy Blue Line riders and Orange Line riders getting on the AM Peak trains in Vienna, Dunn Loring, and West Falls Church. The Metro system should be in the early stages of engineering and environmental studies on the Blue Line re-route to Georgetown & M Street so the new tunnel and route would have the possibility of starting service in the next decade or so, not 2030 or 2040.

Agreed. Blue line re-route would add service in new areas and serve as a backup for the orange/silver tracks, i say bring it on!!!

"farecard"

It looked to me as if they could lengthen it about 70 ft by sacrificing the east end switches, making it a spur instead of a passing pocket. More than that would require bridgework.

That's one option. However they can lengthen the pocket track by 15' to 20' by adding a degree or two of curve at the trailing ends of the turnouts this would increase the distance between the points at each end of the pocket track. The only disadvantage is the tangent between the mainline turnouts and equilateral turnouts would become shorter.

Washpost:

Offering what he called a rough guess, Sarles said retrofitting the section of pocket track that would be used for the Stadium Armory turnaround — if it could even be done — might cost more than $300 million.

New excus err reason:

Examiner:

There is also minimal room on the sides for workers to reach the aerial structure.


Huh????

"farecard"

New excus err reason:

Examiner:

There is also minimal room on the sides for workers to reach the aerial structure.

Huh????

A narrow stair case ascending from the ground east end of the traction power tiebreaker station to the junction turnouts.

The walkway on all WMATA elevateds is on the side opposite of the third rail.

Here's what I think is the real reason that Metro is abandoning the turnback at the D&G. If you have every pulled into Mt. Vernon Sq heading North or Silver Spring during rush hour more than likely your train has stopped short of the station. Now just west of the D&G the D line curves from a NE to E heading over Benning Road, In this turn the tracks are banked to the east (Eastbound trains are tilted toward the ground on the inside of the curve); Now with the vibration to the structure that was mentioned during a turnback just ahead, if a westbound passes that will vibrate the structure even more. What Metro management is terrified of (Dave K. alluded to it during the board meeting a something catastrophic) is a train holding short of the D&G performing a wheel climb as is crawls toward the switch, and possibility going over the side. The same applies to westbound trains departing Minnesota Ave; especially if you have a Silver pulling out the pocket and a blue line passing D98/52 and fouling the switch, the is the exact spot where ATC holds the train.

Sand Box John wrote:The 2 #6 Y (equilateral) turnouts are equivalent to a left or right hand #12 turnouts.

Are they measuring the deviation without concern that there is no tangent path? It would seem to be more consistent to measure deviation from a straight path than deviation from another diverging path.

"justalurker66"
Are they measuring the deviation without concern that there is no tangent path?

If the angle at the heal were the same with a tangent path the frog angle would be 12.

It would seem to be more consistent to measure deviation from a straight path than deviation from another diverging path.

The deviation of the path to left is the same as deviation to the path to the right. Split the deviation in half and you get 6.

If you look closely at he bottom pictures on the right side of page 15 in the Silver Line Operating Plan you will notice a short curve behind the heal of the #6 Y (equilateral) turnout. There is no curve behind the heal of the #8 right hand turnout in the picture above. If there were no curve behind the heal of the #6 Y (equilateral) turnout, the angle of that turnout would have to be a #4, 4 is half of 8.

Sand Box John wrote:If you look closely at he bottom pictures on the right side of page 15 in the Silver Line Operating Plan you will notice a short curve behind the heal of the #6 Y (equilateral) turnout. There is no curve behind the heal of the #8 right hand turnout in the picture above. If there were no curve behind the heal of the #6 Y (equilateral) turnout, the angle of that turnout would have to be a #4, 4 is half of 8.

Bottom right on page 15 is the junction east of the pocket track.
Bottom left is the west end of the pocket, obscured by a signal or cropped - the shallow angle can make rails look different than they are actually constructed.
Top left is the entire pocket looking west ... the fence and the angle not helping.
Top right is a good shot of one of the #6 switches ... but I can't see the curve you are talking about.

I'll probably need to model it to understand.

"justalurker66"

Sand Box John wrote:If you look closely at he bottom pictures on the right side of page 15 in the Silver Line Operating Plan you will notice a short curve behind the heal of the #6 Y (equilateral) turnout. There is no curve behind the heal of the #8 right hand turnout in the picture above. If there were no curve behind the heal of the #6 Y (equilateral) turnout, the angle of that turnout would have to be a #4, 4 is half of 8.

Bottom right on page 15 is the junction east of the pocket track.
Bottom left is the west end of the pocket, obscured by a signal or cropped - the shallow angle can make rails look different than they are actually constructed.
Top left is the entire pocket looking west ... the fence and the angle not helping.
Top right is a good shot of one of the #6 switches ... but I can't see the curve you are talking about.

I'll probably need to model it to understand.

My mistake, the quote above should reed:

If you look closely at he bottom pictures on the left side of page 15 in the Silver Line Operating Plan you will notice a short curve behind the heal of the #6 Y (equilateral) turnout. There is no curve behind the heal of the #8 right hand turnout in the picture above. If there were no curve behind the heal of the #6 Y (equilateral) turnout, the angle of that turnout would have to be a #4, 4 is half of 8.

Curve behind heal.


Tangent behind heal.

Aerial photography of the turnouts at west end of pocket track.

Thanks John ...
If I understand correctly the frog is a #6, which is why the Y turnout is a #6 ... the extra curve past the frog creates the angle of a #4 (the angle that the tangent rails beyond the curve would make if they ran straight to a frog) ... which matches the angle of the #8 turnout from tangent rail.

If it were tangent rail (no extra curve) the Y would have to be a #4 as you mention OR the switches on the main would have to be #12 to match the angle. The #12 would provide potentially faster speeds but would take up more space. With the entry to a pocket with the exit at STOP is speed limited to 15 mph the "potentially faster speed" would not help on entrance but could help on exit.

At the newer pocket tracks where #10 turnouts are used on the main lines an extra curve is still needed, but the extra curve does not need to be as big. The #6 Y + #10 tangent pockets would take up more space (assuming the same track centers) than the #6 Y + #8 tangent pockets.

"justalurker66"
Thanks John ...
If I understand correctly the frog is a #6, which is why the Y turnout is a #6 ... the extra curve past the frog creates the angle of a #4 (the angle that the tangent rails beyond the curve would make if they ran straight to a frog) ... which matches the angle of the #8 turnout from tangent rail.

If it were tangent rail (no extra curve) the Y would have to be a #4 as you mention OR the switches on the main would have to be #12 to match the angle.

In assents that is Correct.

The #12 would provide potentially faster speeds but would take up more space. With the entry to a pocket with the exit at STOP is speed limited to 15 mph the "potentially faster speed" would not help on entrance but could help on exit.

Yes and yes.

At the newer pocket tracks where #10 turnouts are used on the main lines an extra curve is still needed, but the extra curve does not need to be as big. The #6 Y + #10 tangent pockets would take up more space (assuming the same track centers) than the #6 Y + #8 tangent pockets.

Actually all of the existing underground and elevated pocket tracks use #8 and #6. Because of the extra space at Silver Spring right hand #8 are used instead of #6 Y. The turnouts in Wiehle-Reston East pocket track are all #10.

Breda3252 wrote:What Metro management is terrified of (Dave K. alluded to it during the board meeting a something catastrophic) is a train holding short of the D&G performing a wheel climb as is crawls toward the switch, and possibility going over the side.

Google Earth shows a train there.....

So why is the "stop & hold" location cast in stone? Could not EB trains stop earlier, at the parking lot? {See the GV photo registration ooops there, BTW ..}