Saturday 31 December 2011

Heart River Bridge

Completed in May of 1916, the Heart River bridge was the final link needed to bring rail service to Peace River, then called "Peace River Crossing". Once the trains descend the hill from Judah into the Peace River valley on a grade that fluctuates between 2.4 and 2.9% (at one time, and maybe still, the steepest mainline grade in Canada) the tracks cross the Heart River on the eastern edge of town on a beautiful bridge made up of 11 plate girder spans and a deck truss span for the river itself, all supported by 6 spindly towers that don't look like they should be able to support the weight. In total the bridge is 590 feet long and towers 140 feet above the water.

Preparing to place the last span
Twelve Foot Davis Ball Park at the foot of the bridge

Looking East across the Peace River (see the grade in the bridge?)

1978 - 3 of the 4 NAR SD38-2s headed south
The natural starting point to model this bridge was Micro Engineering's "Tall Steel Viaduct". I used 2 full kits with the 40' connecting spans and another single tower extension. For the deck truss portion, again I turned to the Central Valley Pratt Truss bridge kit as I did with the Peace River bridge, but this time I built it with 5 panels just like the prototype.



I was a little disappointed with the quality of the Micro Engineering kits as compared to the Central Valley kits. The plastic used by M.E. tends to tear and break rather than cut, even when using a new #11 x-acto blade and there are many needless sprue parts that must be cut from the castings. The level of detail was also not as good as I expected. Don't get me wrong, it still produces a very nice model but when building it you must be very careful and take your time. The model does come very close to looking like the real Heart River bridge and captures the over-all "look" of the structure very well with only slight differences that will be difficult for the non-expert to spot.

This picture was taken "upside-down" during construction and flipped. The towers are not yet attached to the girders in the photo.

I modified the kit in several ways: The prototype, as seen in the photos, seems to be built on a gradient (about 1.5 or 2% from what I can tell). So is the model bridge. To incorporate the model's 4% grade I had to build the towers with one side a scale foot and a half taller than the other so that the towers would sit vertically and not look like they were leaning once the bridge was constructed and in place on the layout. This helps mask the relativly steep incline of the bridge.
I also cut the towers to mimic the real bridge's towers, removed the top portion of the towers that support the deck truss span and added supports (I got lucky and found that the height of the top tier of the towers was almost exactly that of the Central Valley kit).
Stiffeners made of wood strip were added to the centre of the two deck girder portions to keep the bridge from sagging.

Bridge on a temporary "land form"
The model bridge measures 42" long and the rails will be 10" above the model river once the foam base is cut down 1". This scales out to 560' long and 133' high (or about 94% of the real bridge)

The bridge turned out even better than I expected and I am very pleased that I was able to capture the over-all look of the real bridge. A few details are yet to be added such as the walkway that ran along the east side of the bridge and the jutting timbers on the west side that carried telephone/telegraph lines across the chasm. The footings for the towers have yet to be installed and the deck still needs actual rails...

I was going to use Micro Engineering's "bridge track" which has guard rails and longer ties that are spaced closer together than normal track but I found that, to install the walkways, the ties were too short and the tie strips included in the Central Valley kits were much better suited to the project. This means, though, that I will have to hand lay the code 55 rail and code 40 guard rails. Thankfully the Central Valley tie strips are built for just such a foolish endeavour.

Like the Peace River bridge posting, I will be adding to this one as work on the bridge progresses, so check back when you can. Thanks.

Mike

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