Double slip switch workings?

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On the board and track charts

Postby train2 » Fri Feb 06, 2009 2:22 pm

Re: seeing it on the board:


The short answer is no. I have spent a lot of time in towers, many the same as you, but I never noticed this one detail and thus wanted to get a better understanding.

Seeing the track chart is a help. But not as much as seeing a photo of the switch set to the various combinations would be.

Sometime in the future I would like to watch one go though the various moves.
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Re: Double slip switch workings?

Postby Gerry6309 » Fri Feb 06, 2009 3:09 pm

Grand Central Station's approaches probably have the most puzzle switches in the smallest volume of railroad anywhere. Engineers aproaching the terminal are given a track number and a permissive signal and sent on their waythey have to trust the tower operators who line them up as it is impossible to have a signal at every switch. All of this is in a tunnel filled with columns and walls with several movements taking place simultaneously. The avrage train move might encounter 15 of these switches.

JAY and HALL interlockings outside the Jamaica Station of the LIRR are probably the next most hideous location since there are three possible routings east and west plus platform and bypass tracks. You wouldn't want Dan to Dash for the wrong train, would you?

A much simpler implementation of a double slip can be found at the Seashore Trolley Museum in Kennebunkport Maine. The double slip is a point - mate design, and is set up to sort passenger trips from certain yard moves. On a normal summer day at least three of the four possible moves will be made in both directions. The fourth possibility will come up maybe every other day. Although the switch is quite forgiving, failure to read the switch correctly has slowed down the qualification of many an operator. The switch is right in te middle of the public area and is easily photographed.

While you are there check out the unique "Freddy" switch at the south end of Riverside Barn. It is one of those situations where you have to make do with the materials available. The frog is probably two sizes smaller than the rest of the switch, thus there are some horrendous looking curves. Despite this it is not derailment prone. "Freddy" was Fred Perry who had a reputation for taking on impossible tasks with acceptable if not asthetic results. His talents were applied to many of the historic trolley operations running around the country. He passed on before his time about three years ago.
Gerry. STM/BSRA

The next stop is Washington. Change for Forest Hills Trains on the Winter St. Platform, and Everett Trains on the Summer St. Platform. This is an Ashmont train, change for Braintree at Columbia.
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Speeds for these switches

Postby train2 » Fri Feb 06, 2009 8:13 pm

Since someone mentioned slow speeds, what are the typical speeds for straight thru vs diverging movements on one of these beasts?
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Re: Double slip switch workings?

Postby Jersey_Mike » Fri Feb 06, 2009 9:45 pm

Since someone mentioned slow speeds, what are the typical speeds for straight thru vs diverging movements on one of these beasts?


The old Main Line double slip at SHORE on the NEC was good for at least 80mph on the straight route according to timetable speeds. Diverging speeds on a double slip are no greater than 30mph.
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Re: Double slip switch workings?

Postby nyandw » Fri Feb 06, 2009 11:45 pm

Real interesting thread guys! I posted the Jamaica slips diagam http://www.trainsarefun.com/lirr/jamaica/jam1970.gif which gives one the idea how trains travel "up the ladder"...

Image Jay

Image Hall

Anyone with photo's of the switch layouts of these areas around Jay or Hall Tower?

Thanks!
Best,
Steve
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Re: Double slip switch workings? Jay/Hall Photos

Postby nyandw » Sat Feb 07, 2009 8:23 pm

Image

Hall view East

Image
Jay view West Photo: Tim Darnell

Other photos?

Best,
Steve
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Oxymoron??

Postby 2nd trick op » Tue Feb 10, 2009 8:12 pm

Out of curiosity, can anyone think of, (or has anyone heard of) a double-slip switch that was not interlocked?
What a revoltin' development this is! (William Bendix)
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Re: Double slip switch workings?

Postby Gerry6309 » Tue Feb 10, 2009 9:22 pm

There is the one at Seashore which originally lived at Watertown Carhouse. Never interlocked or electrically thrown in either life.
Gerry. STM/BSRA

The next stop is Washington. Change for Forest Hills Trains on the Winter St. Platform, and Everett Trains on the Summer St. Platform. This is an Ashmont train, change for Braintree at Columbia.
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Re: Oxymoron??

Postby ExCon90 » Wed Feb 11, 2009 4:17 pm

2nd trick op wrote:Out of curiosity, can anyone think of, (or has anyone heard of) a double-slip switch that was not interlocked?


Dearborn Station in Chicago had lots of non-interlocked double-slips in the throat for years. They made it all through World War II and after without any interlocking in the throat; each switch had two switchstands, with switchtenders running around lining routes (for the Super Chief!! and others) as directed from the tower. They finally interlocked the throat in later years, just in time for the decline in intercity passenger service.

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Re: Double slip switch workings?

Postby JCitron » Thu Feb 26, 2009 8:25 pm

Gerry6309 wrote:
While you are there check out the unique "Freddy" switch at the south end of Riverside Barn. It is one of those situations where you have to make do with the materials available. The frog is probably two sizes smaller than the rest of the switch, thus there are some horrendous looking curves. Despite this it is not derailment prone. "Freddy" was Fred Perry who had a reputation for taking on impossible tasks with acceptable if not asthetic results. His talents were applied to many of the historic trolley operations running around the country. He passed on before his time about three years ago.


There used to be quite an interesting Freddy in the mouth of the Haymarket Tunnel where the North Station loop used to enter and exit. I saw it for years, but never bothered to get a picture of it. Sadly it's gone now. :(

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Re: Double slip switch workings?

Postby Gerry6309 » Thu Feb 26, 2009 11:25 pm

The infamous "Hospital Switch" under the remains of the Haymarket Relief Station. The northbound (RR eastbound) crossover was sandwiched between two sections of a solid wall allowing cars to access Canal St. terminal. The Southbound (RR westbound) crossover was in the open, just before the portal. It was an interesting place to snake an LRV or Type 7 through. There was also a significant grade change here as the Canal Lead was flat white the approach to the Lechmere Viaduct was on a 5% grade. No slip switches here though!
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The next stop is Washington. Change for Forest Hills Trains on the Winter St. Platform, and Everett Trains on the Summer St. Platform. This is an Ashmont train, change for Braintree at Columbia.
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Re: Double slip switch workings?

Postby JCitron » Fri Feb 27, 2009 3:15 pm

Gerry6309 wrote:The infamous "Hospital Switch" under the remains of the Haymarket Relief Station. The northbound (RR eastbound) crossover was sandwiched between two sections of a solid wall allowing cars to access Canal St. terminal. The Southbound (RR westbound) crossover was in the open, just before the portal. It was an interesting place to snake an LRV or Type 7 through. There was also a significant grade change here as the Canal Lead was flat white the approach to the Lechmere Viaduct was on a 5% grade. No slip switches here though!


I didn't recall it being a slip switch, but it sure was an interesting piece of trackwork. I would hate to have been the trackworkers that had to lay the rail down for that one. The grade is a lot shallower than I thought it was being only 5%. I'm old enough to remember the PCCs using the loop track, and the Orange Line trains using the elevated above. About a year ago, I had an appointment on Canal Street, and I was totally confused when I came out of the new North Station! I couldn't find Canal St if my life depended on it! I ended up eating crow, sucking it up and asked a policeman where Canal Street was. Without the elevated there, I was really confused.

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Re: Oxymoron??

Postby RearOfSignal » Fri Aug 28, 2009 4:36 pm

2nd trick op wrote:Out of curiosity, can anyone think of, (or has anyone heard of) a double-slip switch that was not interlocked?


In yards sure.
Hurry up and wait at the signal!
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Re: Oxymoron??

Postby ExCon90 » Tue Aug 05, 2014 2:44 pm

ExCon90 wrote:
2nd trick op wrote:Out of curiosity, can anyone think of, (or has anyone heard of) a double-slip switch that was not interlocked?


Dearborn Station in Chicago had lots of non-interlocked double-slips in the throat for years. They made it all through World War II and after without any interlocking in the throat; each switch had two switchstands, with switchtenders running around lining routes (for the Super Chief!! and others) as directed from the tower. They finally interlocked the throat in later years, just in time for the decline in intercity passenger service.

ExCon90

This is a very old thread, but on page 59 of the Fall 2014 Classic Trains there is a clear view of a hand-thrown double slip switch in 1967, complete with two switch targets, one for each end; you had to check both to know which of the four possible ways the switch was aligned. I think the train in the shot is going over another one just like it.
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