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  • Maine Central Searchlight & Semaphore ABS

  • Discussion relating to the pre-1983 B&M and MEC railroads. For current operations, please see the Pan Am Railways Forum.
Discussion relating to the pre-1983 B&M and MEC railroads. For current operations, please see the Pan Am Railways Forum.

Moderator: MEC407

 #781410  by TomNelligan
 
gokeefe wrote: What are smash boards?
Pretty much what they sound like... things you smash. :-)

Well, hopefully not, if you're paying attention. They're big, low, semaphore-like swinging panels or sometimes arms with disks that hang across the track at about cab level when the bridge is open as a additional obvious visual to the engineer that it is not safe to proceed. And if you ignore it and don't stop, you smash it as you go into the drink. They were once fairly common on drawbridge approaches and a lot are still around.
 #781415  by gokeefe
 
Thank You, Mr. Nelligan! :P

I mentioned to the author that I was surprised an automatic derail of some sort wasn't positioned well before the train actually got on the bridge. I would think that if there is a true emergency the chances of the train stopping in time once these boards had their effect might be quite poor.
 #783737  by jbvb
 
Smashboards had a second purpose: If the board was smashed, the fault wasn't with the signal system or draw operator.

B&M and MEC were jointly managed through 1954, so semaphores were subject to the same replacement scheme as on the B&M: From the 1930s on, as they needed major work, they were replaced with first multi-lens color-light (till about WWII) and searchlight (after WWII). This didn't apply to lines where traffic was declining and passenger service expected to end; their semaphores were maintained until the end, then left in place with arms removed (like the B&M's Concord - Woodsville line or the Cheshire branch). Eventually the old cases and masts rusted out and most have fallen or been pushed over. They were quite evident on RRE fantrips in the 1970s.
 #912251  by gokeefe
 
I made a trip down the Augusta Lower Road today from Augusta to Bowdoinham and observed the following...

I happenned to notice, perhaps for the first time the exact intervals at which the old signals are spaced on the Lower Road. They are remarkably close together. In fact the blocks appear to be only 1-2 miles long at most. I would like to know more about why these signals would be so tightly spaced together. This seems to point towards previous heavy usage by the Maine Central and also to efforts made on their part to allow for 'higher' speed operations (perhaps in the 50-70 MPH range) for passenger trains. I'd like to know if my impression is correct.

This request was first posted in the "Augusta Lower Road" thread in the New England forum.
 #913810  by jbvb
 
When electric track circuits for occupancy detection were first developed, they simply connected two DC polarities to the rails. When a train shorted it, the relay opened and the block was occupied. However, depending on thequality of your rail bonds (those doubled wires between pins driven into holes at the end of rails at joints), the resistance of your ballast (and salty slush at grade crossings), block length had to be limited to perhaps 2 miles under the best conditions. Talk to an EE or a signal maintainer to find out exactly why.

Though this cost more, it did allow trailing sections of scheduled passenger trains to run fairly close together at 50-70 MPH (you need a minimum of two blocks between trains at all times). It also made it easier to "fleet" freight trains (an operating plan where several trains in the same direction are scheduled for more or less the same time, in order to get more capacity out of a single track line with a limited number of sidings).

As CTC came into wide use, the vendors developed "coded track circuit" schemes. I've never seen details of how these work, but I know they allowed much longer blocks and so a side-effect of CTC work on a number of RRs was a big increase in signal spacing on lightly-used lines. The most visible case I recall from circa 1970 was the B&M from North Beverly to Newburyport - the searchlights in service were placed 2-3 mi. apart but you could see the old semaphore foundations every mile or so.