Does anyone know of a website with a good article and suggestions for removable bridges across aisle ways? I am building a layout in a room we use for other purposes and need to put in a bridge across the hallway. Obviously making it very quick and easy to remove and replace will encourage casual train running. I don't want to have to go through a ten minute bridge installation to run my trains for a short period of mental R & R.
Looking for the best way to build a bridge that will align adequately when "dropped into place" - want to avoid having to use rail joiners. Would love to see a posting from folks who have a favorite method that works for you.
I tried a 3' piece of plywood with track laid on AMI Instant Roadbed (matching the rest of the layout), which allowed for minor repositioning of the track for alignment purposes, supported by wood blocks at the ends. You need to be really careful to cut the track precisely so that the gaps created are minimal. I decided to insure a good connection by using a shortened rail joiner which simply slid into place to connect the sections. This worked adequately, but after a while, I really started to loath having to take it out and then put it back for a short operating session. So, I built an around-the-walls layout that is essentially a compressed oval resembling a dual-mainline with 23" radius curves at opposite ends, eliminating altogether the need for a removable section.
The best way to do a liftout isn't hard to do. First off, doing it as a hinged bridge allows for one end to be firmly located. A pair of larger hinges with just a little flex in them on one side (preferably the door's hinge side) will locate that side well. The other side wants to have a V notch in it so that it always returns to the same point in the vertical and horizontal sideways direction. The in/out direction may also be incorprated into the V if necessary to insure that the two sections of the layout are always the same distance apart but generally if the layout is well fixed to the wall, this is often not necessary. Metal is generally much more desirable for the locating mechanism as it will be a lot more robust than wood will be. A similar process is often done on turntables so that the rails match when the turntable is positioned to a particular track with usually some kind of motorized pin driving into/outof the table to do the locking. A big 60 degree V notch and point made with 3/8" steel or aluminum or even a pair on either side (keeps tilt from happening) is one good way or you can use a pair of pins with a tapered point into a pair of hole as another method. Don't forget to allow adjustment for the locating system so that you can move it in any of the 3 directions to make the position stable. Also, don't forget that the bridge coming down needs to clear the rails on the fixed part of the layout so that you don't ding them if the bridge is at the extended part of its motions. Leaving the rails on the bridge longer helps a lot.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!
MR did an article sometime in the last 4-18 months on using a hinge to build a swing-away bridge. Electrical continuity was done with phone cord or some other flexible wire.
If that's not an option then make the rails slightly longer on the drop-in. I agree with Frank Eva (?) about using metal for the mating surfaces. I'd also put in some sort of micro-switch linked with track power to shut off a section of track on each side, say the last 2 feet before the bridge, so you can't accidentally drive a train over the edge while having a "DOH!" moment. The switch can be rigged so that dropping the bridge in place closes the switch. Removing it opens the switch.
On my layout I span a 46" gap with a lift-out bridge. Deck, for two HO tracks, 3/8 inch thick plywood by 5 inch wide, stiffened underneath by a length of 3x1 timber on edge to form a Tee section. The deck overlaps the
3x1 at each edge by about an inch, and where the bridge drops in there are two ledges for each overhanging end of the deck to land on. Location is by two headless nails driven into each of the ledges and standing up vertically for 3/8 inches, with corresponding holes in the deck. All rails end flush with the gaps. Elec. continuity by plug and socket connection. This has been in use for about eight years now and there is a little bit of slogger showing up in the locating holes, but not enough to cause problems. To remove, unplug elecs., lift up bridge and stand on end against wall or wherever. No safety switches for dead sections, but they are a good idea. Regards, Bill.
For the people who are already doing this, what climates are you in?
I have never done any thing like this before but after reading this thread I was thinking that here in Canada there might be quite a swing in the size of the gap from season to season depending on where the layout is (and the size) in the house (ie basement, garage etc.). The change in heat and humidity may make the gap open and close (say 1/8 to 1/2 inch??).
Does anyone leave a little bit of play in the track feeding the bridge to correct this? I was thinking you could mount curved flex track to a floating board at each end to give you up to a 1/4" of play at each conecting point (by sligthly increasing or decreasing the radius of the curves feeding the bridge). The bridge would then connect to the floating curves with alignment pins.
Anyone have any thoughts on this, or is it completely unnessary?
I live in the Northeast and yes you'll see movement as you go through the seasons. One end of the bench work for the bridge is pretty much free standing. Even though I have four concrete blocks sitting on the bottom, movement will come from people bumping into the edge and moisture. Plus the wife loves to let the bridge bang shut as she gets stored items from under the train table. Usually two or three times a year I will nudge the bottom over with a sludge hammer. I used small screws not nails for the track over the bridge. Adjustments can be made there as well, then tighten down the screw and it will hold it in position.
I find the best way to keep it closed and secure is a brass window lock. If you want to kill the section before the gate to prevent losing a train it's easy with the brass window lock. Just drill a hole for soldering the track wire on each side of the window lock. When open it breaks the connection. I gap about two feet of track just before the bridge and run the wires through the hinge side out to the window lock.
I generally run trains in one direction so killing it on one side should be enough. I know, I know for sure I'll forget and run one the other way one day. One is planned but it's on my long list.
Yes you have to leave a gap for expansion and adjustments on each end of the bridge. Curves are going to be tough as I have just a slight start of one at the end of my swing bridge. The problem is when you cut the track, you're also cutting the ties that hold the rail in position. The curve piece is the one that really gives me the most work trying to get a smooth transition over the bridge. Eventually I'm going to buy some Tru-Scale milled road bed and lay my own rail. When you cut this on a curve the bed and ties are one piece.
I would admit they are pain to make but a bigger pain is a constant duck under.
Jeez, Mason, Do you really reckon that you're going to get 1/2 inch of movement due to weather conditions on a bridge that may be 3 feet long? I know that parts of Canada can get pretty cold but such a movement does sound a bit excessive. My 46 inch bridge is indoors in a proper room, wherein the temperature range is from about 13 deg. C to 35 deg.C (55 to 95 deg.F). Humidity not checked. I can't find a Coefficient of Thermal Expansion for nickel-silver (for the rails) but using the value for brass, the change in the length of my 46 inch long rails over the above temperature range is
0.00046 of one inch, which is pretty small and can be neglected. Humidity changes may cause the timber to change dimensions, but again these changes are unlikely to be more than 1/32 of an inch at a guess. I've certainly never had any problems with my bridge due to heat or humidity changes. Regards, Bill.
I wasn't thinking of the rails but the expansion/contraction of the bench work in combination with the walls they are mounted to. I am assuming the bridge stays somewhat constant. But it does sound like it is not something to really worry about....
I had a baseboard (4' in sections) 32' long in my garage. I found that the timber frames and the nickel-silver rail tended to move in opposite directions - hot days made the rails expand while the baseboards dried and shrank. In the cold damp of winter the movement was the other way. The really bad part was that the total rail gap on cold days seemed always to end up at one point rather than distributing itself evenly amongst the rail joins!
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