A very distictive symbol of the 1906 NHRR electrification was the unique triangular catenary assembly , the 11,000 volt "Trolley" conductor supported by two steel cables. The groved trolley was clipped to the bottom corner and the two top corners clamped to the cables.The legs of the triangle were 3/8" gas pipes. This was a "super-strong" type of suspension but was too "stiff" or ridgid; only one support cable was necessary.Another example of "over-engineering"was the size of the massive catenary- support girders spanning four tracks. Did the NHRR engineers have a proclivity for "erring on the side of strenth and durability" because what they were constructing was without presedent?.
PATTBAADid the NHRR engineers have a proclivity for "erring on the side of strength and durability" because what they were constructing was without precedent?
The triangular catenary was an artifact of observations at the time that 'floppier' solutions were subject to substantial bounce and sparking when vertically contacted by even lightweight 'pickup devices' connected to locomotives or cars running on jointed rail. Probably some of this observation was also made with an eye toward the reported German high-speed testing only a few years prior (circa 1903-4) with extreme high speed and side-bearing contact.
The idea of increasing tension to stop the bounce quickly ran into ... well, the same problems all the variable-tension catenary subsequently built ran into: to actually quell most of the sparking you have to run so enormous a tension that your anchor bridges start to look armored... and you run into more and more issues with pulloffs on curves and keeping the proper 'wiggle' in the wire path to equalize out contact-shoe wear. What New Haven decided to try was to put distributed mass into the hanging catenary system, approximating more what an 'aerial third rail' might do as far as soaking up transient shock and reaction inertially and giving better reliable contact at NH running speeds -- I would argue that this it did, and quite well. If you have Morgan's money to put up all the structure, and Mellen's enforced speed reduction with all those wrecks to keep from getting to the point that speed overcame the inertial mass damping ... the problem being that it took a lot to get the triangular cat rocking, but once it started rocking, it was hard to stop.
That the triangular cat worked might be seen by how long functional installations lasted, even after GG1s gave a reasonable speedup to ex-New Haven Amtrak trains after the PC merger. It may be notable that much of the overhead support structure is being replaced in the conversions to constant-tension catenary I have seen, which may well be because the old bridges are required to maintain frequent electrified service while the new infrastructure is being constructed at intervals 'between' the existing bridges.
Perhaps interestingly, there was still substantial triangular catenary present when I was looking at running extremely-high-speed container trains on the route in the mid-Seventies, and part of this involved the use of a two-stage servo pantograph (with a lightweight 'bottom' like a Brecknell-Willis or assisted Faiveley and a small aerodynamically-steered contact member that did the actual high-speed contact accommodation faster than a mechanical servo through linkage could push the pan up or down -- or so was the theory I held to then). This sort of approach works far better with a high-mass catenary that has not been excited into periodic motion ... in other words it was more 'optimal' on the triangular cat than on any of the subsequent improved designs in the various stages of PRR Corridor 'improvement' south of NYC. Of course PC and Conrail had little interest in an active pantograph system even for Metroliners, and adopted or bought advanced low-mass designs for the AEM-7 and successors...
Keeping in mind that the New Haven installation was the first heavy duty electrification using high voltage AC and there wasn't much in the way of experience on how catennary would behave when design work started. The first AC interurban started service only three years before the NH line was put in service.
The original triangular catennary installation had problem with hard spots where the original contact wire was connecte to the hangers. The fix was to use a new conatact wire that was attached to the original wire halfway between the hangers. One other problem was the messenger wires were at line potential which made maintennance a bit tricky as well as making the traction power system vulnerable to lightning strikes.
The expansions of the NH electrification was done with a compound catennary where the top messenger wire supported the secondary messenger wire in two places between the cat bridges and was grounded.
The Milwaukee's first phase was a bit overengineered as well, with a spare M-G set in each substation. In order to get enough conact wire area to handle the traction current, the Milwaukee used a twin trolley with two side by side contact wires with staggered hangers. In addition to gving more contact surface, this construction gave a smoother contact.
Local lore has it that A.C. Gilbert, whose factory was adjacent to the tracks, got the idea for the Erector Set after observing the catenary poles the New Haven was using.
243129 Local lore has it that A.C. Gilbert, whose factory was adjacent to the tracks, got the idea for the Erector Set after observing the catenary poles the New Haven was using.
What was your opinion on NH cat?
I remember reading about Gilbert's inspiration came from seeing electric transmission line pylons being assembled, but would not be surprised to see the NH cat support bridges being the actual inspiration.
charlie hebdo 243129 Local lore has it that A.C. Gilbert, whose factory was adjacent to the tracks, got the idea for the Erector Set after observing the catenary poles the New Haven was using. What was your opinion on NH cat?
It is still in use to this day. Poles and supports durability is evident. I liked it.
Erik_Mag I remember reading about Gilbert's inspiration came from seeing electric transmission line pylons being assembled, but would not be surprised to see the NH cat support bridges being the actual inspiration.
https://en.wikipedia.org/wiki/Erector_Set
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