Re: Dual gauge trestle


John Stutz
 

Nigel

Probably none of the original trestle bents survive, since pre-WW-I piles were rarely creosoted and only had a lifetime of about 15 years.  By then they were getting rotten just below the ground line - just like an untreated wooden fence. The usual practice was to pull the rails and deck, drive new pile bents offset about 3-4', and rebuild the deck offset to the new bents.  If you look closely under a pile trestle, you can often find evidence of previous bents.  I once found a trestle that had been rebuilt three times.  The previous generation had piles cut off about 1' above ground level, the next had hollow shells of cutoff piles, and the oldest was just holes in the ground. 

The 150' length given for the Howe truss bridges near Cardston is probably correct.  This was a fairly common length for the longer Howe spans, and is well documented in the engineering literature, including several excellent drawings.   It is the longer spans that are rare, although there were some, and Southern Pacific built a 250' covered Howe over the MacKenzie R at Eugene Oregon to connect to the former NG Oregonian RR's south end.  This was at the site later occupied by the preserved 400' Whipple-Murphy still visible from I-5.  But combination timber and Iron bridges, with eyebar ties and lower chords, were more common at such lengths.

John

On January 10, 2022 7:59 AM Nigel Phillips <nigelp18000@...> wrote:


Hi all,

Found some interesting information on trestles used on the Gault lines in Southern Alberta. The line between Lethbridge and Dunmore junction had a small trestle over Persons Creek, with 6 pile bents. Bents (probably not the originals) are still in place along with some CPR track. The St. Mary Railway had 3 trestles, the one at Spring Coulee being reported as 685 feet long. The one over the St, Mary River near Cardston was sandwiched between 3 Howes Truss bridges over the river channels, the bridges being reported as 85 feet for the north channel. and 2 x 150 feet for the south channel. If that is not a typo (150 feet total with 2 spans of 75 feet?) then that was a very long Howes Truss. The crossing over Pothole Creek east of MaGrath was a low level trestle bridge, which from the old track right of way on Google Maps would have been about 75-100 feet long. If double gauged it would have been during 1907.

Nigel

On Thu, Jan 6, 2022 at 1:20 PM Earl Knoob < earlk489@...> wrote:
There were/still are several short ones between Alamosa and Antonito.



From: HOn3@groups.io <HOn3@groups.io> on behalf of Scale Brass Mechanic <scalebrassmech@...>
Sent: Thursday, January 6, 2022 7:01 AM
To: HOn3@groups.io <HOn3@groups.io>
Subject: Re: [HOn3] Dual gauge trestle

The bridge over Arkansas in Salida was dual gauge. Yes Steam plant on south side was dual gauge as well as a track in the marble monument facility. 🚂👍Fz



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