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Hello Gang,

I have an amazing 48" bridge that works very well, but I have to get on my hands and knees all the time to operate my layout, fix derailments, etc. The mind is willing but the knees are shot!!

Is there such a thing as a hinge kit, or plans to make one? Or do I buy a hinge, get out the Dremel and play surgeon??

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Last edited by Rich Melvin
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There are a number of threads on OGR about lift bridges, both manual and powered, including a current thread called "lift up bridge".  There are three key features to such a bridge:  First, the hinge point need to be higher than the top of the rail.  The other thread shows this quite nicely and I think something you could easily incorporate into your bridge - e.g., a short aluminum plate (say 6 inches long) the goes under one end of the bridge with two 'ears' for the hinge (which would be two short threaded screws).  On some of the other threads, you'll see using a pair of simple butt hinges mounted on wooden blocks, so the hinge point is above the top of the rail.

The second important feature is to have some sort of alignment pin or slot at the other end of the bridge so the track will be aligned when the bridge is lowered into place.  In the current 'lift up bridge' thread, the author claims that his design is rigid enough laterally so that there is no mis- alignment when the bridge is lowered.

The third feature is to have some sort of control block on either side of the bridge and a microswitch or other type of switch that would kill power to the rail in those blocks when the bridge is raised, so you don't inadvertently drive a train into the raised bridge - or into the abyss on the other side...

Searching for 'hinged lift bridge' will bring up a good discussion and, courtesy of Susan Deats, this link:  https://slsprr.net/features/bridges1drwgs.htm which shows some construction info.  I don't think you need a gas-spring for what you are doing - I should think just designing it so the bridge goes a couple of degrees beyond 90 deg and a stop to rest the bridge on when up would be sufficient.  If lifting the bridge is an everyday occurrence, you could use a linear actuator to actually lift the bridge up from below.  These devices come in lots of sizes and power and some run on 12VDC.

Tom Tee -- I don't think you need to cut the rail on the diagonal - certainly not at the hinge end when the hinge point is above the rail top, as the first movement of the rail on the bridge is 'out and up' away from the fixed rail at the abutment.  At the opposite end, due to the raised hinge point, there is a slight movement that closes the gap between the fixed and moveable rail, but not by much before it 'clears'.  Consider the geometry, what one has in cross-section is a rectangle whose length is the length of the bridge/moveable rail (in this case, 48 inches) and whose height is defined by the thickness of the bridge plus roadbed plus rail.  The clearance distance between the two fixed rail ends is defined by the length of the diagonal of that rectangle.  Suppose the total height of the bridge bottom, roadbed and rail is 1 inch, so whipping out my old high school geometry, the length of that diagonal is 48.01 inches (you can do it either with Pythagoras or tangents and cosines) - so that means the gap is 0.01 inches (all of this is based on having the hinge point at the top of the railhead = top corner of the rectangle).  As a practical matter, a 1/32 gap would cover this requirement.  Better would be to have the rail ends on the lift side of the bridge slightly proud of the rest of the roadbed, etc. - say ~1/8 inch.

This reminds me that in fact there is a fourth feature to consider, which is the stability of the fixed distance between the two rail ends on either side of the bridge.  That needs to be pretty stable.  Some of the designs/pictures of moveable bridges shown on the various threads here show a connection between the two table sides at the bottom - which means a 'step across' - to maintain that distance

Chris (Lehighline)—

I tried searching for Mark Boyce/ bridges but did not come up with anything useable. Do you have any links to Mark’s powered bridges?

I am always puzzled that with all the layouts with “duck-unders” that none of the custom manufacturers have not put together a commercially purchased operating bridge! I certainly would see a powered bascule bridge as a layout focal point. Even a basic platform that is motorized with adding my own Atlas double track bridge to the platform might be something to easily adapt?

Carl J

LAST THING: the gap between the layout track and the lift bridge. Using a Dremel with a cutting disc to make the gap very close and fine isn't the best approach.  You should make the gap 1/16" to 1/8" to account for movement of your layout as you work on it as well as temperature, humidity and connections change.

I find that bridges I made that were perfect fits were actually too closely gapped. And after time will stick and not lift.

@lehighline posted:

Carl,

Click HERE! Mark changes the topic as he posts about his work.



Chris

LVHR

@Carl J posted:

Chris,

Thanks so much for the link to Mark Boyce’s operating bridge(s) — big help to see his results for making his own motorized platform and adding the Atlas bridge! Pretty cool! 😎

Carl J

Sorry I am late to the show, but I just saw this topic.

Chris, thank you for finding the page where I get suggestions for hinges and cutting and then show what I did.

Carl, I see you have a 48" bridge as I do, plus I have the shorter one.  Both are Atlas that I bought used.  I must give credit to mike g. for the idea.  Quite frankly, I was at a bit of a quandary with how t do mine until I remembered mike g. had built a two bridge lift up system where the bridges are separated vertically.  That was the help I needed to move along.  I just modified it to suit my situation.  Notice the lower bridge has the pivot point below track level, which is nice so I can make more realistic scenery.  Building it was much trickier.  The upper 48" bridge had a lot of superstructure under track level, so the only way I could think to do it was to put the hinge on top with perpendicular rail cuts. 

Alan has really done a fine job with so many lift up bridges.  Sparty's is looking good so far in construction. 

I’m glad I got clued in to comment on your question looking for help on lift up bridges.  I’m glad Chris thought of what I had posted a few months ago.  I was like you, not knowing how to approach the problem.  You are right, there is no sense trying to reinvent when multiple methods are right here on this forum.

Please keep us posted on your decisions and progress.

Thanks Mark, The wheels are  turning!, as the say. I was going to make this a winter project, but I'm finding new energy here with all the help from everyone. That, combined with the incessant rainy, crappy weather here in NH = indoor play....'er projects that is!

I know what you mean.  I find that sometimes I need a kick start to get me going on a project of any kind.  A good Forum discussion often provides that kick start on train and layout projects.  We had lots of rain here in Northwestern Pennsylvania up until this last week.  Now it is too humid!  Never satisfied! 

Mark,

Actually, I'm using a linear actuator (LA) for my bridge. (See Run 317 for an article on building the bridge.) I took a different route for mounting the LA, as I did not want it to show. That and a few other considerations have complicated things a bit. But I'm slowly working through them. The hinge is installed, and the bridge mounted. I went online and found a circuit that incorporates limit switches for both ends of travel. I still need to decide where to locate them. I'm using a salvaged and repurposed computer power supply for my 12vdc power source. Once I have things far enough along, I'll post some pictures and a video.

Chris

LVHR

Alan, that’s an interesting thought.  I left mine in the up position before back surgery, and just lowered it last week for the first time in two months.  The lower of my two bridges had expanded just a smidgeon; enough it just barely hit the tabletop.  I have an air conditioning vent and dehumidifier, so I didn’t think it would expand.  🤔  🤪

Last edited by Mark Boyce

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