Chicago Metra Switching Tower - Technology Dates Back to Early Parts of 1900s

[richhotrain]

I wasn't sure if this is the best forum for this topic, but I will give it a try.

This morning, I was watching the local Chicago news on TV, and a video segment came up about the Metra’s tower at the A2 interlock near Grand Avenue and Western that was built in 1907. The switching system inside was state-of-the-art when it was installed in 1932.

The problem is it’s still in use.

"A lot of care and a lot of maintenance and a lot of attention has gone into keeping this operational," said Metra’s Rich Oppenheim. "This was the best thing that could be purchased in the 1930s."

I think you will enjoy the video.

 http://www.nbcchicago.com/investigations/metra-a2-switching-tower-221887391.html#ixzz2ddU4eqKF

 
Rich

[BaltACD]

I would be willing to bet that when A-2 is replaced - the replacement will have about 1/2 the functionality that the present machine does and that it will be handled by a Train Dispatcher, not a on site Train Director and/or leverman.

[tomikawaTT]

Old mechanic's adage:

If it ain't broke, don't fix it.

I agree with Baltaco.  If they replace it, the replacement will have about half the functionality - and will be lucky to have half the lifespan.

Chuck

[BroadwayLion]

That is a US&S pneumatic interlocking plant.

LION uses a interpretation of a GRS Model-5 Interlocking machine...

A GRS machine typically has the signal levers (painted red) on either end of the row of levers. Trains arriving from the left would have all of their levers on the left, trains arriving from the right would have their signal levers on the right.

In between are the black levers that control the switches, they are numbered from left to right across the model board.

The way that a machine like this is supposed to work, is that when you try to pull a lever, if it will not move at all, it is locked by the position of another lever. Typically you would start aligning the levers from the track where you want the train to go, through the plant to the place where the train is.

So when you pull a lever it will (if it is not locked) move half way. In this position it will lock all levers that would conflict with its new position, and it would throw the switch. The switch machine will send a back current to the machine confirming that the switch points have moved to the new position and are locked in place. This permits the lever to complete its travel, and will release other levers that are no longer in conflict with its new position. This is repeated across the plant until every thing is lined up, and then the signal lever will be free to move and give a clear signal.

The normal position for levers is in: all switch points will be in their normal positions and all signals will display RED.  Pulling a lever places the circuit in the REVERSE position.

The old US&S (Armstrong) machines required two levers to move a switch. One was for the lock and the other was for the points. So first the tower man had to unlock the switch with the first lever, move the points, and then lock them in place again. If he could not close the lock, he could not give the signal to use the track, instead he would have to go down to the track and find out why it would not work, and would probably have to remove some ballast, or some ice.

Below the floor of the old US&S Armstrong machines was the interlocking bed consisting of vertical and horizontal brass bars, about 1/2" x 1" in dimension which controlled the interlocking logic. On the GRS machine these were much finer bars with only an inch of vertical travel, and were about 1/4" x 1/2" in size. They could be smaller because that hand lever could not apply the same power to them as a lever man swinging on a four foot long lever.

The later GRS product was the NX machine. A light would display when a train entered the plant, and a button was pushed where the operator wanted the train to exit the plant, and the plant would do the rest all automatically.

Today they have mice, which work fine unless a cat gets into the tower room.

ROAR