I'll use this thread for topics that don't deserve a full build thread on my Sandy Lake & Northern (standard gauge) and Sandy Lake & Rangely River (narrow gauge HOn30) 1890s era railroads.
dave
My current small project is a farm road bridge over the tracks.
The bridge goes over these tracks in a relatively deep cut:
IMG_1347.jpeg
A mock-up:
IMG_1346.jpeg
To get the clearance worked out with the cliffs, I built a template of the bridge center span and bents from sturdy 1/4 plywood. That's a level on top of the template.
IMG_1348.jpeg
Next step is to seal the base of the template, so that I can use it to 'smush' plaster in place where the bridge footings will be.
IMG_1349.jpeg
Once this is sealed, the idea is to put some Vaseline on this, put a bit of plaster or sculptamold into the hole, then push the template into position level in both directions. When the plaster dries, hopefully the template comes out without bothering the plaster.
dave
That worked as expected. The plug separated from the damp Sculptamold (colored with some paint). After I removed the plug, I worked the edges down so there wasn't quite the obvious ditch for the footers.
IMG_1351.jpeg
Now to let the Sculptamold completely dry, and do a test fit of the actual bridge...
dave
This will be interesting to see how this comes together, but to me right off the bat that ramp on the right looks very steep.
The center span and trestle bents fit into the holes from yesterday. (The Sculptamold is still damp, but no adjustments needed....) The right side ramp needs a bit of work to get the road to align. I'll need to build up the left side to reduce the slope of that ramp.
IMG_1354.jpeg
dave
Howdy Dave,
The farm road bridge looks terrific. Thanks for describing the process you used to create the cut and abutments.
Have fun,
mike
An update on the farm bridge: I've been struggling with how to get the two ramps aligned at the correct angle to the terrain. In the process, I've had a bunch of failures, including some stuff that broke loose and had to be reglued. The bridge as a whole needs to be sturdy, in part so I can attach the railings and so I can remove it to do scenery and ballasting. Once I have a technique that works, I'll tell you what it is. :P
dave
OK, I finally got the farm bridge ramps attached
IMG_1361.jpeg
Here's the approach that finally worked.
1. I put a piece of tape across the top of the span to hold things together. I put the bridge on location, making sure it was correctly positioned (center was level, ramps touching the abutments.)
2. Then I used a protractor to measure the two angles.
3. I drew the bridge to scale on a piece of graph paper, including the two ramp angles.
4. I measured the offset from the bottom of the truss to the top, the "batter". I cut 2 pieces of wood that thickness.
5. Then I laid the center span on one of the wood pieces, and clamped it to a 1-2-3 block to hold it into position and perpendicular/plumb.
6. I put the other piece of wood aliong the angle of one ramp (measured in step 2, drawn in step 3.) I glued the ramp to the center span, and after the glue was mostly set (about an hour for yellow wood glue), I moved the bridge back to location. I made sure the bridge trestle bents were in position, the center span was level in both directions, and the ramp rested on the abutment on the scenery.
7. After the glue was fully set, I carefully removed the bridge, and added the 2 diagonal pieces that go from the trestle bent to the joists under the ramp. I -carefully- clamped those into position.
8. The next day, I did steps 6 & 7 for the other side....
Now all I need to do is add the railing on both sides of the bridge. I've stained the wood pieces, I need to cut and glue them.
dave
Howdy Dave, congrats on finishing the farm bridge. It looks good. Have fun, mike
Dave, those angles look better now.
Nice job.
Dave,
Nice job on the road bridge. When looking at the mockup, the ramp angles looked to steep.
On the finished model, they look more natural. Well done.
Tom