On30 PGB – Pt III

Main Girders
Aligning everything took a while .. align one piece .. cement .. let it set up a bit .. then measuring and measuring again .. double-checking. Since my Cross-Girders are larger then the ones in the kit I had to file the triangular braces to fit. The cool thing is that they are doing exactly what the ones on the full-scale bridge would have done .. and brace the darn thing!
Bridge Ties
One thing though. Take a look at this photo. This is the stock bridge structure with the tie assembly. While in HO the ties overhang a bit .. 30″ beyond the rail bearers. Seems to me that in ‘real life’ the ends would have been supported on something. These HO ties measure out at a little over 11′ in length.

Narrow gauge ties run let’s say 6-7′ in length .. but what about the bridge ties? I’m guessing 8′? If so .. what the heck supports the ties on the outside?

In a book titled “Notes on track : construction and maintenance By Walter Mason Camp” pub 1903 I found a diagram showing that .. yepper .. the ties overhang. If I used 8′ bridge ties .. that means they would overhang the rail bearers by only about 33″ .. which is the same (pretty much) as the standard gage overhang.

On page 847 it says .. “The size of tie required for a bridge floor depends upon the manner in which the tie is supported. If the tie is supported by stringers directly under the rails (which mine does .. aka .. the rail bearers) or nearly so, it supports the rail without appreciable bending movement, and other then this its duty is merely to hold the rails in gage and in line. Under such requirements a tie of ordinary size is sufficient, and the common sizes are 6×8, 7×8 and 8×8 ins., the first and last mentioned being the most common.”

Well. That pretty much answers that. 8′ ties will fit with clearance between the triangular braces. 7′ might be better. Will have to wait to I get to that part! 🙂

Tie Plates
The bridge was going to be right at the edge of the layout so I wanted as much detail as I could get. I drew up some On30 tie plates and had them 3d printed at Shapeways. In the photo I have painted them and piled them up for a photo. Notice that some of them have lines on the surface. This is due to the way that they were printed. Those lines are the layers of plastic formed during the 3d printing process. Depending on the orientation they show sometimes .. and sometimes they don’t. I had enough printed that I could pick and choose. I mean .. these things are small .. right at the edge of the maximum resolution of the printer.

Note: If you click the link to Shapeways you will see the tie plates arranged in a sprue of 20 plates with a $5.32 price tag. I had these printed before Shapeways tacked on a $5 handling fee so my cost was only the .32 cents bit. I need to go back and gang together multiple sprues so that $5 handling charge is minimal applied across all the tie plates.

Ties, plates and rail
Assembling everything. I printed off an overhead view of the ties and rail so I could get everything aligned. The one thing I didn’t do was put spikes through the tie plates. It wasn’t because I didn’t want to .. or even because I didn’t have any .. but .. because when I got to this point I couldn’t find them! Darn. I’ve located them since but it will be much harder to insert the spikes with the bridge in place on the layout. Still .. onward and upward and all that.

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