Apr10 Written by:Tom Farin
4/10/2008 6:43 PM
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Visitor comment - If you are taking requests, I'd love to see a bridge spanning that pond :-)
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A bridge spanning the pond? Yow. That pond is about 40' wide in the center. And about 4' deep in the middle. Let's see, that would be an 800 foot bridge at scale. A trestle is out of the question as because of depth and the fact the pond freezes solid in the winter.
But a bridge on piers ... The bridge over the Russian River at Duncan Mills for example? Piers?? The pond has a clay bottom. Maybe if I drove some 10' rebars into the clay !!! Slid them into holes drilled along the axis of landscape timbers ... The landscape timbers could be the base of the piers to just below water level. Then some formed concrete piers emerging from the water. Bridge sections between the piers ...
I'll have to think about that one. It would be spectacular. Of course, the NPC had a reputation for running trains off bridges and trestles ... I'm not sure I want to be fishing my rolling stock out of the pond.
How about a re-creation of the Austin Creek disaster in my pond?
Jim, this is exactly the kind of comment that gets me in trouble. Let's assume your comment was in jest. But I start to think about feasibility. The next thing you know one project gets dropped and I start another. Don't believe me? Just ask Fletch about Farin and his projects. I promised myself I wouldn't do that this time.
I'll put it on my winter list of things to think about when the snow is blowing and it is around zero outside.
But ooooh, maybe I could shorten the span and the depth and distance by taking it across a corner of the pond ... Oh my.
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Post by Dwight Ennis - Hmmmm... howzabout real concrete piers poured around the rebar? 
Actually, this is something you could come back to in a few years IF you planned your track accordingly - say with rerouting this section over the pond in mind. In the early stage, you could route your track towards the pond, then curve around it, curving back to meet the straight-across route on the other side. Later, you could come back and with some minor realigning either side of the pond, relay the track over the bridge and across it.
Such practices weren't unknown in the prototype world. NPC's Strawberry Point Trestle is an example, later replaced by the tunnel through White's Hill, which itself was later replaced by the Bothin cutoff after the NPC became the North Shore.
Not trying to sidetrack you btw... just provide food for thought while planning things. 
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Dwight,
Thanks for throwing some gasoline on the fire. 
I just got off a 3 1/2 hour flight to Sacramento and spent part of it staring at the 'Narrow Gauge to the Redwoods' photo of the original Howe Truss bridge over the Russian River at Duncan Mills with its nice concrete abutments. I've wanted to model that bridge but until the 'cross the pond' idea surfaced, I didn't have a body of water that would justify such a long span.
I like the idea of the concrete piers (rather than the landscape timbers) around the rebar but they would have to be more heavy duty than the piers on the Russian River Bridge scaled at 1:20.1. So here is what I came up with.
I'd pour the lower piers using the tubes you can pick up at Home Depot used to pour deck footings. 2-3 rebars would extend out the bottom of the tubes. I'd cast a hole into the top of the large piers using a greased dowl.
After the Rebars are driven into the mud, the lower piers would come to within 3-4 inches of the pond surface.
I'd place an upper pier section that models the Russian River Piers on top of the lower piers pegged in place with a Rebar cast into the scale upper piers. The bridge sections would ride on top of the upper piers.
In the winter, I could remove the model upper piers and the bridge sections to avoid any damage from winter weather and ice heaving and shifting. In the Spring I'd realign the lower piers and drop the scale piers and bridge sections back in place.
I also like the idea of a temporary track. At Duncan Mills the main line crossed the Russian River and proceeded on to Cazadero. A branch line headed down to Markam. I could use the Markam line as the main line until I'm ready to build the bridge. It would run along the edge of the pond connecting with the main line on the other side of the missing bridge temporarily. That way I could model Duncan Mills accurately except that the main line would go to the edge of the pond and stop.
Once the bridge is constructed, I could stub the Markam Branch and connect the other side of the bridge to the continuation of the main line to Cazadero.
Guys, I'm putting this idea into my layout plan. Thanks for the ideas.
Now, there was this really cool NPC truss bridge crossing Brown's Canyon. It was 300' long and 137 feet above the stream bed - at the time the tallest timber bridge in the United states. I have to build that one too. Any thoughts on that one?
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Jason Kovac Post
I wish I had that much room for a track. Can't wait for next year when you have it completed. Looking real good.
As far as the trestle or bridge over the pond, you can always dig a small bay on the pond and cross over a scale length. Now with the piers there was a article in Garden Railways a few issues back about piers, the author had made cast piers with rebar and over a few years they fractured and cracked from the rebar rusting in the concrete. He stated he would rather use a fabric or mesh. I'm sure there are people that know what would be best to use for the long term.
Another option is 6" PVC driven onto the pond and poured with concrete then cut just below the surface. I was going to cross my pond when designing my railway and was going to do something similar but using a cinder block as a base for the pipe as it is a lined pond 4' deep. It may take a while to fully cure but it is a strong option.
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