One of the bridges I have for the layout is the Walthers operating bascule bridge. I am using Micro Engineering bridge track, but I have no idea where to cut the track to allow the bridge to move and trains still run reliably. I have read, re-read, and re-re-read the instructions and find nothing more than the recommendation to use the Walthers bridge track and install it in the moving part of the bridge on the first page. I am guessing the track should be cut flush with the pivot end of the bridge, but what about the other end? Any tricks to make sure it will align with the track on the layout? Shoukd the tracks be cut squarely or at some angle to help line up a little better? I really would like to get this right the first time, so if anyone with experience building one of these will chime in I would appreciate it. Thanks!
Good Luck, Morpar
Let's see, well it's been 25 years since I built my Walthers Bascule bridge. I don't recall fretting too much over the track details. At the time the Shinohara bridge track had just become available but they didn't offer the separate ends until later.
The pivot points of the main movable section is slightly above rail height and this allows for the arc of the cut ends to swing away from each other which is a good design.
Bascule-DB tower by Edmund, on Flickr
I simply allowed about a quarter inch of the rail to stick out, unsupported and eyeballed a reasonable gap, maybe 3/32 inch between the rail ends.
Bascule by Edmund, on Flickr
I used Teflon wire to supply power to the span rails and this stuff doesn't take paint well so you can see the colors of the wire if you look straight down in the gap but in normal viewing angles you can't see it.
Bascule-pivot by Edmund, on Flickr
On the far end I made a spring plunger that activates an under the benchwork microswitch and relay which stops the lowering motor so I don't strip any gears and it also drops the home signals to red. I used to kill the track power here' too, when the bridge was up but keep alive capacitors negated that need.
Bascule-far end by Edmund, on Flickr
My bridge is in a somewhat hard to reach area so I really don't dust it as often as I should The alignment shoes do a good job of keeping the track laterally aligned and, if I recall, I used thin strips of styrene under it until I was satisfied with the rail height alignment, then cemented them permanently. I don't recall ever having a derailment issue with the bridge at all.
Bascule gap by Edmund, on Flickr
Not long after I put the bridge into operation I found that the trunion gearing at the racks was not sufficient for the loads involved. I drilled out the halves of the guides and the gears and inserted steel pins, maybe 1/16" but I forget the exact size.
Bascule trunion by Edmund, on Flickr
I've got to get the handrails back up! I might have replaced the actual pivot pin with steel as well. I don't recall how the actual pivot point was made but it looks like I might have beefed that up, too.
I remember having to do some repairs and modifications to the motor gearing, too. The kit might have come with limit switches but in typical Walthers fashion, these were somewhat inadequate. I don't use an up limit and the down limit is through that plunger I showed earlier.
Hope that helps, Ed
Wow! Great work Ed, this is very helpful. I figured I was overthinking the whole track thing.
I have a series of three side-by side Walthers Bascule bridges. Unfortunately, Walthers never made a double track bascule bridge because I needed two of them side-by-side. I settled for three single track bascule bridges based upon the configuration of my layout.
I applaud you for succeeding in making your bridge operational. I did so with the first of my three bascule bridges, but I had ongoing performance problems so I disabled the motor. None of my three bascule bridges are operational and that suits me just fine.
Ed got it right with where he cut the gaps in his bascule bridge. To ensure proper alignment, I used the turntable principle of cutting angles in the ends of the rails where the bridge meets the grade.
Rich
Alton Junction
All good advice. You lay the trackage with a bit of putty or something to add a hand to keep it still, with one already-cut end nearest the pivot point rails. The two ends must clear, but not be so far apart when the bridge is in place and flat that cars wobble unnecessarily. That tends to spoil all the work. So, you fiddle with distance until the clearance is met.
Then, with the bridge deck level, and the tracks not moved at all, you mark where they should be cut at the other end, probably needing even less clearance, but let your intuition guide you here.
Remove the length of bridge track, nip, use a needle file or kiss the inside flange face with a cut-off disk on a Dremel and make a beveled edge. Do this for the oncoming rails outside the bridge deck as well. Try for a 20 degree angle, no steeper. Take your time...there's no hurry, and you want this to be perfect.
Once all your rail ends have been treated, restore the newly-custom-cut length of bridge track to the deck and adhere it with whichever glue you like. I like thin beads of Parr Bond, a clear sealant and adhesive that can be painted. Before it sets, use that Opti-Visor and a trail rail car to align and to run over both ends of the bridge to ensure it all works.
If there's room, and the gaps aren't too wide, I would even use a slightly shortened joiner (razor saw or cut-off disk) and align the rails that way. When the Parr sets, or whichever adhesive you use is set, gently remove the joiners by sliding them the required distance, and raise the bridge to free those closest to the pivot.
OK, I don't have the bridge, but how do you provide a positive lock of the far end of the movable span to the abutment to guarantee the tracks are alined?
The pair of wedge-shaped projections engage the inside edges of the movable section of the bridge. It is a snug fit but not overly tight.
In 25 years it hasn't worn or loosened on my bridge. The motor has to stop within a second or two of engaging these wedges or you run the risk of damaging the rack or gearing, or lifting the motor end off its anchoring — there's that much downward force.
Regards, Ed