Uh no, I gave up trying to follow their antics during construction. Part of serving Marin county means that they are bat s*** crazy even by SFBA standards. They were aggressive hostile to off hour freight service and now, go figure, they are planning to buy the operator. [banghead]
What SMART does for the San Rafael ferry connection will probably redefine the use of the word ‘cluster’. The fine county citizens already spent ~10M$ or so on their bike crossing of SFD Blvd.
A question from someone with absolutely no railroad knowledge.
On the Canyon Diable bridge, why did they lay the track that way instead of just switching to one track crossing the bridge? Was it to avoid having to set the switches?
A not very informed guess was that avoiding switches was -um- the point. Someone would have to get off the train to throw the switch before and unthrow after the train passed. With a gantlet, the train would just need to slow down a bit and save a fair amount of time.
One downside of a gantlet is dealing with the frogs.
Thanks, Erik.
Still better than frogs and points…
I don’t understand.
You’re going to have to use signaling to make sure there’s only one train at a time on the bridge in any event. So why do you need the gauntlet?
Is the idea to get the weight more centered on the bridge?
You mean three RAILS, right?
Man, I’d love to see a photo of that. That’s wild. Lionel!
Until this thread came along, I was not aware of any type of gauntlet trackage, never heard the term even. This is really fascinating.
Signalling is one thing - power switches are needed if it were to be a true single track on the bridge. Power Switches are expensive.
Theory was that the bridge could handle the weight of two ‘light’ trains when built so in theory it had the structural ability of handling on ‘heavy’ train. I am not a engineer so I don’t know how close they were getting to the maximum capacity of the structure.
Read the story at the link I posted for this earlier in this thread – not only does it cover both the theory and the strengthening improvenents that were made, it has diagrams of the ‘amended’ cross-sections.
Here is the not-too-succinct-but-effective link again:
(Oddly enough no more direct combination of search terms on the Poughkeepsie Bridge put into Google listed this link!)
The chief point of the gantlet is that it requires no switching: it is two main lines that overlap, with (as noted) only frogs and not points to be negotiated. To a limited extent the ‘extra rail’ in the gauge of a given gantlet track can function as a guardrail – the absence of points close to the bridge reducing some of the need for full guardrails on bidirectional single track.
Problem with this is that the ‘center’ rail would see twice the tonnage per month, with the wear alternating by side of the railhead as well as direction. So I would expect it to need more frequent inspection and ‘dressing’ and to require replacement more frequently…
The design would also necessarily include carefully ground or relieved points – they would never need to move, of course, but they would need to be provided and reinforced. This may be more money and work than the ‘frog’ alternative…
I remember reading in an old (1953 or so) issue of TRAINS that Poughkeepsie Bridge was strengthened a second time for heavier motive power and the gantlet was installed to center the weight.
I’m in the same boat. I had never seen one of these sets of tracks until now.
Of course, my knowledge of railroading is next to nothing. My experience is what my KATO locomotive does on an N Scale track.
While I think I’ve seen examples of modelled gantlet tracks over the years, it’s not something you see often on model railroads because the conditions that cause them aren’t usually a problem on model layouts.
If it’s there, it’s because the modeller chose to include it.
Not to mention the fact that you’d have to build such an arrangement from scratch.
You wouldn’t necessarily need power switches if the tracks were operated current of traffic style. Two spring switches would do. However, power switches would be more flexible when the dispatcher wanted to run something ‘wrong main’.
The C&NW gantlet at the Cedar River ended in the late 1970s after a derailment on the bridge. I don’t believe the gantlet section had anything to do with the derailment. It was shortly after when they just single tracked the section and placed spring switches at either end. Both ends were combined into a single automatic interlocking. Eventual
Maintaining switches is always more expensive than not have switches - be they Powered, Spring or hand throw. Something that moves requires maintenance to keep it moving.
Here’s a simple image of a gantlet track. Note the lack of moving parts.
That is true in most situations. However, gantlets around high-level passenger platforms, such as on South Shore, do require a switch at each end.
Very true. IMHO, such a track would be better described as a “bypass track.” The same thing is/was done at track scales, so cars that don’t need to be weighed aren’t.