Catenary Support Poles - NYNH&H vs PRR

[TheBoyFromNewYorkCity]

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Was watching some vids of the New Haven Line.

One thing has always puzzled me for years.

The difference between the trackside catenary support poles that the NYNH&H put up, as opposed to what the Pennsy went with.

The NH poles are not really poles at all.

They are huge, built like a battleship.

Like a signal bridge.

The Pennsy went with a very slender profile.

The NH must have spent a ton of money for all that massive ironwork they put up.

How many of the poles on today's NEC do you guys think are original?


The Boy


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[John_Perkowski]

Admin Note:

Topic moved from the New Haven forum, duplicate post here discarded.

[Allen Hazen]

If early 20th C versus recent bridges are anything to go by... my guess is that the PRR's slender poles might have had more weight of steel in them than the New Haven's "massive" ones. Earlier practice (labor having been cheap) was to use built-up structures -- lattices of steel strip -- rather than solid, large cross section, steel members. As for cost... I would think that (even under Mellen!) the New Haven's engineers would have compared alternatives and economized where they thought safe. The difference might come down to a change in th ratio between the price of steel and the wages of riveters.
(This is a bit speculative, I'm afraid: I don't actually have figures to go by. But the change in bridge styles is dramatic, and this is the explanation for it I hit on. ... It might also be a technological thing: maybe the making (casting? forging?) of large cross section structural forms was harder to do right in the earlier period, so fabricated structures had to be substituted.)

[Ridgefielder]

(This is a bit speculative, I'm afraid: I don't actually have figures to go by. But the change in bridge styles is dramatic, and this is the explanation for it I hit on. ... It might also be a technological thing: maybe the making (casting? forging?) of large cross section structural forms was harder to do right in the earlier period, so fabricated structures had to be substituted.)

I think it's completely a technological thing, resulting from the advances in steel fabrication in the decades after 1910.

The NH wasn't alone in using latticework pre-WWI. The poles for the trackside high-voltage lines in NYC and LIRR third-rail territory were steel lattice, and so were the catenary supports on the Chicago North Shore & Milwaukee.

By contrast, the post-WWI installations all used I-beams so far as I know: the Reading and DL&W suburban routes, the PRR, and even the New Haven's own Danbury Branch (electrified 1925.)

You can see the same thing happen with bridges: pre-WWI, the most common design seems to have been truss with steel-lattice members, but by the 1920's plate girder is far more common.

[TomNelligan]

.How many of the poles on today's NEC do you guys think are original?

On the New Haven RR end, almost all of the original early=20th-century catenary bridges are still in use. There are only a few short stretches where they have been replaced by more recent construction.

[ExCon90]

The second paragraph of Ridgefielder's post clarifies something I've wondered about: in Oakland, CA, there are latticework support poles from the SP's Interurban Electric still standing along the UP right-of-way south of Jack London Square, parallel to BART, which certainly date from the early 20th century.

[YamaOfParadise]

The PRR also had the benefit of not commencing on their major electrification projects until after the NYNH&H had electrified from New York to Stamford in 1908; they could learn off of the NH's example and experience, instead of doing something for the first time without any idea of how it'd turn out.

[timz]

How many of the poles on today's NEC do you guys think are original?

Poles have been added here and there, but aside from the ones that were in the way of new construction, or got hit by derailments, why wouldn't all the originals still be there?

[NYCRRson]

I suspect it was also decided by what size steel "I beams" the steel mills could actually manufacture.

The 1920's saw massive growth is steel mills, the Bethlehem Steel factory in Lackawana NY was built in the 1920's, at the time it was the third largest steel mill in the world.

Pre 1920's the mills probably could not manufacture the huge I-beams used by the PRR in the 30's. I think they are about 18 inches across and appear to be 50 feet tall. Perhaps In the 1910's nobody could manufacture an I-beam that big/long ?

Just speculation on my part. But the existence of factories able to make large steel parts evolved along with the railroads. Bigger rail cars to deliver larger loads enabled bigger factories.

Cheers, Kevin.

[Allen Hazen]

Re: NYCRRson's "I suspect it was also decided by what size steel "I beams" the steel mills could actually manufacture."

Where "could actually manufacture" has to be interpreted as "could economically manufacture." Let's start with simple plate. (An I-beam consists of a small number of plates: the web of the beam, and the top and bottom flanges. I'll bet there was a period, early in I-beamhistory, when I beams were fabricated by riveting these members together.) Now, fairly heavy plate COULD be made for special purposes early. (If there is a naval historian reading this… How thinck were the plates from which the turrets of later Union monitors were constructed in the American Civil War?) But I think there was a tendency to build up thick plates, for civilian applications, by laminating thinner ones. There is a late 19th Century bridge in Melbourne, Australia (originally a railway bridge, now-- after the line on one side of it was transferred to the Tramways-- a pedestrian crossing of the Yarra River in central Melbourne) that I looked at frequently. There was a part-- basically, I think, the bottom flange of an I-beam-- that fascinated me. It was clearly meant to be, functionally, an inch thick or inch-and-a-half plate, but it was in fact fabricated by laminating four (I think) quarter-inch (3/8 inch?) plates together with rivets spaced a few inches apart. Obviously, nobody would do this (riveters don't work for free! And laminated structures aren't generally as strong as comparable thickness solid ones) unless the production of thick plates was -- economically if not in principle -- unfeasible. (If there is a Melbournite reading this, you know the bridge I mean: could you take a rule down to pedestrian path along the north bank of the Yarra and get the actual measurements for us?)

[NYCRRson]

I am pretty sure that most of the Catenary posts on the PRR electrification project were solid steel I-beams. I recall seeing many of them up close.

There were manufactured by rolling red hot steel through rollers big enough to form the I-beam shape. I suspect steel factories with "rolling mills" large enough to make approximately 18 inch wide I-beams where not around early in the 20th century. Thus the NYNH&H used laminated tower supports with riveted connections. More labor and less strength of course.

I suspect that by the 1930's when the PRR electrified the large I-beams were available.

I also suspect that there is still a limit on the largest I-beam you can purchase "off the shelf".

Cheers, Kevin.

[chnhrr]

There was a change in milling technology after the First World War. I beams or W sections of different sizes and weights became readily available. Also advances in welding technology occurred. At the beginning of the Twentieth Century repetitive member and composite structures (usually riveted) were more common. What interest me is the difference between the straight and the tapered leg versions of the NH centenary bridges. The tapered post used less steel per unit, but required more time to fabricate given the different strap sizes need to make the angled legs or posts.

[jackie]

There are modern support poles in the Glenbrook CT area. This resulted because of a collision between a freight train and the "milk train" (the Pilgrim?) that occurred in 1958. It disrupted operations between Stamford and South Norwalk for a couple of weeks and probably took down the stantions in Glenbrook. Glenbrook did have a main line station until high-level platforms were installed and they might have felt the cost and the redundancy of the station (being a short walk from the branchline station) allowed for its discontinuance and destruction.
Ironically, shortly thereafter I got ticket from Glenbrook to South Norwalk). The conductor made me by a ticket to Stamford and a separate ticket to South Norwalk, despite my protests I was being punished for the elimination of the branchlike station.

[Nasadowsk]

The PRR also had the benefit of not commencing on their major electrification projects until after the NYNH&H had electrified from New York to Stamford in 1908; they could learn off of the NH's example and experience, instead of doing something for the first time without any idea of how it'd turn out.

Too bad that didn't transfer over to electric motive power - the PRR tried pretty much every idea in the book before they settled on a modification of the EP3 design...

There a bit of a learning curve with MUs, too - the early MP-54s had a lot of weird operational limitations and were dogs anyway. I was under the impression the New haven stuff of the same era was a bit better technically...

AFAIK, the PRR never adopted floating beam catenary. I'm not sure if the New Haven ever used any more conventional designs. I don't know when the now almost universal constant tension system came into widespread use, but I've seen photos that suggest it was used quite early in the UK, along with the New haven triangular style...