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How to build a hinged track bridge?

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  • Member since
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  • From: Bradford, Ontario
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How to build a hinged track bridge?
Posted by hon30critter on Thursday, October 04, 2018 12:44 AM

Hi gang:

My club, the Barrie Allandale Railway Modellers, has wisely decided to add some staging to our new layout. The original plan was to use one of the tracks in the main yard but in the little time that we have been able to run trains (on the mainline only) it has become obvious that using the yard is going to cause problems. (I can hear the chorus now saying "told you so!").

The staging will be four tracks each 16' long with a run around and a caboose track at the far end. So far so good. The challenge is that we have to get past an electrical panel to access the staging. The electrical code requires 36" of clearance so we need a removable section at least 36" wide.

We have decided that we want a hinged bridge as opposed to a liftout for two reasons. One is to avoid problems with a loose piece getting banged around. The second is that we want to be able to make the bridge as easy to open and close as possible. It will have to be in the open position whenever the layout is not in operation so that the landlord can always get access to the electrical panel.

One thing that complicates the bridge a bit is that it will hold a wye so it has to be narrow (12" - 15") at the hinged end but it will be about 36" wide at the other end. Another limitation is that it must lift up as opposed to swinging to the side because of the geometry of the hinged section.

So, please show me how you have built your bridges. I am particularly interested in how you keep the track lined up at the open end.

Thanks again,

Dave

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Posted by doctorwayne on Thursday, October 04, 2018 3:19 AM

Dave, I use lift-outs on my layout...

...but you could do yours as a hinged lift-up (a pair of door hinges atop the layout and lift-up would be simplest) with a U-shaped receiver for the free end, to maintain good track alignment...

I laid my track continuously from layout, to lift-out, to layout, then spiked the rails and/or ties on both sides of the gaps before cutting the rails with a cut-off disc....

Leave the rails on the lifting end long, as I did with my lift-outs - this lessens the chance of someone's clothing catching on rails sticking out from the layout.

For the hinged end...well, I didn't want hinged ones anyway, but I'm sure someone will have a suggestion that won't mangle the rails on the hinged end when the bridge is lifted....thinking as I write, you could leave the rails on the hinged-end of the lift-up long (so that they project onto the fixed postion of the layout) but cut away the portion of the layout immediately below just those rail ends - a SkilSaw or router would do the trick.

Wayne

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Posted by gmpullman on Thursday, October 04, 2018 3:53 AM

hon30critter
So, please show me how you have built your bridges. I am particularly interested in how you keep the track lined up at the open end.

Hi, Dave. 

A staging yard is definitely something worth having even if it requires some creative engineering.

I realized during my planning stage that I wanted to fit in some additional sources of revenue and my "drop bridge" carries a single track connecting railroad and a siding to the ore unloading dock.

 DB_6 by Edmund, on Flickr

My bridge sits at a 10° angle but does not affect its operation in any way.

 DB_3 by Edmund, on Flickr

I visited a local layout that had a lift bridge and in talking to the owner he said he wished he had done it some other way as the bridge had been bumped more than once causing it to fall. He finally put a safety chain on it.

I like my design to have the bridge drop out of the way. Here is a view of the alignment plate at the open end.

 DB_5 by Edmund, on Flickr

I use two 1/4" hard steel dowel pins with a chamfered end. A phenolic handle with a threaded insert is the "keeper" and two dog-point 1/4-20 set screws with jam nuts allows me to fine-tune the rail height if needed (rarely have I ever adjusted these.

 DB_2 by Edmund, on Flickr

 DB_1 by Edmund, on Flickr

At one time I used that Molex plug to carry layout block wiring. I also had a "loop back" circuit that would open a relay, kill the track power and set the signals to red. When I re-wired for DCC I eliminated that feature.

The bridge spans two walls and I made a hardwood anchor that spans two studs on the hinge side. I found a very heavy duty commercial hinge and screwed it to an aluminum block machined to the 10° angle.

 

 DB_7 by Edmund, on Flickr

 DB_8 by Edmund, on Flickr

When I set the track in place I simply used a few extra spikes to hold things in place. I have small squares of lauan plywood that is the same thickness as the cork roadbed for extra support.

 DB_4 by Edmund, on Flickr

At the time Shinohara didn't have the bridge track with guard rails but If I were to do it over I would have used that, more for appearance than for tracking ability. I've never had any derailments at the gap.

 

I hope you can find something useful here, Dave Yes

Regards, Ed

 

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Posted by hon30critter on Thursday, October 04, 2018 4:11 AM

Wayne and Ed:

Thanks for showing your bridges.

Wayne - I like the 'U' shaped alignment plates. They would be easy to do and they don't take up much space. The suggestion of having a small depression for the projecting ends of the bridge track to fold into is great.

Ed -  I hadn't thought about having the bridge swing down but it obviously addresses the issue of how to deal with the ends of the track too. The bridge would have to be a few inches longer so that there is still 36" of clearance when it is swung down, but that would be easy to do.

Dave

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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Thursday, October 04, 2018 4:30 AM

hon30critter
I hadn't thought about having the bridge swing down but it obviously addresses the issue of how to deal with the ends of the track too.

Here's a better shot of the hinge-end with the bridge down.

 DB_9 by Edmund, on Flickr

As you can see, with the pivot-point of the hinge well below track grade you don't have to deal with a pinching effect that you would with the bridge swinging up. Wayne's design avoids this issue. Anyone building a swing up bridge would have to place the hinges on the top-side of the roadbed.

I forgot to mention that the bridge itself is a "trough" made from two 1x4 clean pieces of poplar with a 3/8" furniture-grade plywood base rabbeted into the side rails. Then filler pieces were added at the ends for the hinge and alignment plate to mount to. I built this in 1995 and it has never given me one bit of trouble (insert knock-on-wood emoji here).

Some people ask me about the door knob.

Well, it IS a conversation piece so... Also, when this old man has a drink in his hand and I duck under the bridge, I can grab that knob to help steady myself so I lessen the chance of spilling my drink Whistling

 

[edit] One other design feature I would probably have used is to have a "De-Sta-Co" type toggle-lever clamp to hold the bridge in the closed postiton in lieu of the threaded knob I used. You've seen these things in hold down fixtures.

With a single-lever clamp like that you could lower the bridge one-handed.

https://www.destaco.com/vertical-hold-down.html

 

 Cheers! Ed

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Posted by hon30critter on Thursday, October 04, 2018 5:16 AM

Hi Ed:

One of the clubs that comes to our February show uses a pair of those clamps to do exactly what you are talking about. Their bridge gets opened and closed many times during the show and they never seem to have any trouble with it.

Thanks,

Dave

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Posted by snjroy on Thursday, October 04, 2018 12:43 PM

Hi Dave. My advice: overbuild and goofproof the thing given club conditions. I built mine a few months ago and I have zero derailments (so far) and the thing goes up and down every day when I enter the train room. As shown in the following pictures: 1) I raised the hinges by one inch to allow me to align the tracks as close as possible; 2) I put two blocks on the sides to ensure a dead-on alignment; 3) I wired the track from underneath and put a switch that shuts off the ENTIRE system when the bridge is in a upright position. I would say that the on/on switch is a must for a club. I caught myself many times trying to get a loco moving with the thing in a upright position…

Simon
  20181004_073416 by on Flickr" alt="" />
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  20181004_073338 by on Flickr" alt="" />
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Posted by cowman on Thursday, October 04, 2018 7:46 PM

Going along with snjroy, one club that brings their layout to local shows has the top hinge, lift up type gate.  They hide the higes under a grass mat or similar piece of flexible material.  They can also be hidden by removable buildings.

I prefer the idea of a lift up to a drop down bridge is that when you walk by the bridge the bottom is facing you, if you bump it you don't damage scenery on the bridge.  Another reason is that the rest, where the bridge end sets on the layout is a solid part ot the layout.  I plan to use a lift up when I get that far.

Good luck,

Richard

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Posted by hon30critter on Thursday, October 04, 2018 8:38 PM

Hi Simon:

Raising the hinges is a great idea. As Richard said, they can be disguised. I also like the idea of the adjustable blocks for alignment on the open end.

Have no fear, I overbuild everything! I built a $4000 deck on the back of our house for $7000!Smile, Wink & Grin That was 22 years ago. There has never been a squeak.

Thanks,

Dave

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Posted by snjroy on Thursday, October 04, 2018 8:59 PM

Thanks. I can't take credit for any of these ideas. It all came from this and other forums. 

Simon

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Posted by hon30critter on Saturday, October 06, 2018 4:03 PM

Those of you who are following this might want to have a look at the power shut off system in this thread:

http://cs.trains.com/mrr/f/744/t/272373.aspx

The bridge in the example drops down but the system could easily be adapted to one that swings up or sideways.

Dave

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Posted by hon30critter on Wednesday, October 10, 2018 9:21 PM

Can anybody tell me what the radius of an Atlas wye turnout is?

Thanks

Dave

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Posted by rrinker on Thursday, October 11, 2018 7:03 AM

 Pretty sure each diverging route in the Atlas Wye is the same as a #4. Not something you'd probbaly want in your main line.

                                       --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by hon30critter on Thursday, October 11, 2018 4:15 PM

Thanks Randy.

I was pretty sure that the Atlas wye was too tight for what we wanted. Interestingly, using a #6 doesn't take up any more space as far as the size of the bridge is concerned, so that is what we will go with.

I have another question. Has anybody built a bridge out of steel drywall studs or other lightweight metals? I recognize that it would have to be reinforced in the area where the hinges are mounted, but it would reduce the weight. We are also considering using 1/2" plywood instead of the 3/4" that we used on the rest of the layout.

Dave

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Posted by rrinker on Thursday, October 11, 2018 5:22 PM

Steel studs like to twist too much if used as just a single element. But if you use plywood, 1/2" should be fine if you make a U shaped box out of it - the sides will keep locos and cars from falling ont he floor if someone bumps the bridge or something derails, and a U section of 1/2" plywood will be more than sturdy enough to not sag.

                                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by hon30critter on Saturday, October 13, 2018 9:28 PM

Here is the plan for the bridge. We still haven't decided on materials but regardless of what we choose it won't be a huge investment so we can afford to experiment.

 

Dave

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Posted by snjroy on Tuesday, October 16, 2018 5:32 PM

Hi Dave. There is going to be a lot of weight on those hinges when the bridge will be an upright position. I wonder if they would work on the other side of the bridge.

Simon

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Posted by 7j43k on Tuesday, October 16, 2018 6:50 PM

Dave,

The shape and design of the bridge look just fine to me.  I would recommend making the whole thing out of 1/2" ply.  Making it four to six inches thick should do nicely.  And glueing and screwing it together.  If there's no scenery (or "thin" scenery), I doubt it will weigh much more than 20 pounds.  Most hinges you'd pick would handle that weight.

Because there's no "bottom" to the assembly, it will twist a bit when it's not down in place.  There are fixes for that, if you guys care.  Which you might, if there's scenery.  Cracking, and all.

As you may know, I work in Free-mo, where everything is like the bridge you want, in that things get moved around.  A lot.  So I do have, in a way, experience with this.  I also work construction.  More experience.

 

Ed

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Posted by hon30critter on Tuesday, October 16, 2018 10:29 PM

Hi Simon,

Unfortunately we cannot put the hinges on the wide end because of the location of the electrical panel. We have already stretched the rules by having the large loops of the mainline located partially in front of the panel. If we were to hinge the bridge on the wide side, the bridge framework would intrude another 5" into the gap when in the up position. That would make access to the panel much more difficult. We are hoping that the current panel overlap can be excused.

We are seriously considering using metal drywall studs or floor channels for the framing. That should keep the weight down. Also, I plan on using heavy duty hinges with nylon bushings so there will be little slop at the joint.

The bridge structure will obviously have to be reinforced at the hinges. The adjoining staging will also have to be reinforced because we are only going to use Homasote as a roadbed. The frame will be about 9" wide so 1/2" Homasote alone should work fine. Nobody is going to be climbing on it.

Thanks for the suggestion.

Dave

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Posted by hon30critter on Tuesday, October 16, 2018 10:41 PM

Hi Ed,

7j43k
I would recommend making the whole thing out of 1/2" ply.

As I mentioned above, we will give the metal drywall studs or floor channels a try first. If they are really wobbly we can double the beams by running them back to back. Assembly will be much easier than using wood (theoretically any how) because we can use screws and construction adhesive to assemble the frame. The metal drywall studs can also be cut so as to add additional or larger tabs at the joints, and we won't have to cut mitres at the odd angle joints. Just cut the stud with tin snips and bend the steel to the desired angle.

If the drywall studs prove to be too flimsy then we will go to wood. We will decide on what type and size if we get to that point. I will include your suggestion in the discussion.

Dave

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Posted by snjroy on Wednesday, October 17, 2018 8:01 AM

Ok, let us know how it works out. 

Simon

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