My HO trackplan includes a bridge over tracks that run underneath at only a 20-30 degree angle to the track above. I need bridge supports that allow a wide opening underneath to allow the lower track to pass between them. Any suggestions? Thanks!
This car stops at ALL railroad crossings!
Bridge piers and abutments aren't always at 90 degrees to the bridge. If you skew your supports, you won't need an especially wide opening.
The real guys do this because using a longer bridge to make the span costs more.
Here's a cute little example from down New Zealand way (a former railroad bridge, by the way):
Typically, for a truss bridge like this one, the "offset" is in increments of panels (this bridge being a 4 panel or 6 panel, depending on how you count). I've seen plenty of one panel offsets. Two panel, I don't know. But I see no reason why it couldn't be done.
For a girder bridge, the same holds. There are more panels, so there are more choices.
For a concrete road overpass, it's easy. No panels. Sort of.
Anyway, do a search for "skewed truss bridge" or "skewed girder bridge", and you'll see lots of examples.
Ed
I agree. The support piers need to have their long edges parallel to the lower track. You will need a longer bridge than for a 90 degree crossing. it
It takes an iron man to play with a toy iron horse.
Skewed bridges in HO are rare. And usually expensive. And likely not of a size you need.
I'm pretty sure your choices are:
Make a skewed bridge and your own abutments/piers. It's not horribly difficult. With the least care, you'll have a very convincing bridge, that is visually appropriate (if what I'm imagining as your track layout is correct--you haven't described it in any depth).
OR.
Buy an off-the-shelf bridge that is bigger and longer. And install it on off-the-shelf abutments/piers. Won't be as good, but it'll do. Nobody's likely to argue about it.
Maybe a plate girder bridge might be easier to kit bash, for a scewed bridge than a truss bridge.
There are plenty of kits out there, along with truss bridge kits. You might have to add two kits together to get the length you need, and then set up sides on the skewed angle your looking for.
Here's what Walthers offers for abutments and piers, maybe you can combine some kits to get what you need.
https://www.walthers.com/products/layout/scenery/scenic-structure/bridge-piers-abutments-wing-wa/scale/ho-scale
Building your own abutments to fit your situation is not all that hard.
Mike.
My You Tube
For a bridge at a 25 degree angle over a track, and for a track clearance width of 2.5", and for a bridge width of 2.5"; and adding a quarter inch at each end for the supports:
a skew bridge will need a span of 6.4"
a "square" bridge will need a span of 12.3"
Microengineering makes a deck girder bridge 11.8" long. It is obviously not 2.5 inches wide, so the bridge can be shorter than the 12.3", above (That number would be more for a through truss):
Microengineering makes deck and through girder bridges 6.9" long:
and
You will obviously have to modify the short ones to skewed. And to consider the panel count, if you're in the mood. Although no one is likely to call you on a half-panel error.
The Micro-Engineering bridges Ed suggested are great.
.
To keep it as simple as possible you can use the Deck Girder bridges with closely spaced ties, or the through girder bridge with a ballasted deck. That way you only need to run the girders at the skew and not model, or modify, the bracing underneath. Not quite "out of the box", but easily do-able.
-Kevin
Living the dream.
Depending on the length required, pretty-well any bridge can be built skewed. For girder bridges, even the one-piece Atlas through girder bridge could work: simply cut the sides from the floor, move them appropriately, then re-attach. If the full length of the girders is needed, you'll need to add triangular pieces of deck at both ends (.060" sheet styrene will give you a good start). If you don't need the full length of the girders, you may be able to simply cut-off the girders, shorten them as necessary, then modify the shape of the floor to match the needed amount of "skew". Re-attach the shortened girders, ballast the deck, and put your bridge into service.Deck girder bridges and deck- or through truss bridges can be modified similarly, but require some extra work and materials on the floor bracing and the ends of the top crossmembers. Basically, you re-locate the sides, putting each at the required offset, then fill-in the necessary bracing members at both ends, using either leftover parts from the kit or with Evergreen structural shapes.You can buy ready-to-use bridge abutments, or make moulds and cast your own.
Wayne
Good replies. I will add one comment, that if it is an open deck (instead of ballasted) the bridge ties can get tricky if you want to avoid the nitpickers. They do not usually extend across the gap between the bridge and the skewed abutment. I have seen two approaches used by the prototype. More common is having a tie at each end angled to match the bridge, and some fudging in the triangular portion. Much the same in the ballasted section off the bridge. That works best when the skew is moderate.
The second method has the stringers that support the bridge ties extend beyond the end of the main girders, resting on their own abutment seats instead of tieing into the end floorbeam. This requires the abutment to be more complex, as the top ballast wall steps first of all at 90d to the track, and then forward to meet the other girder. Usually the lower part of the abutment will match the skew, at least on the front face.
Ballasted decks are rather simpler!
I am no authority figure here on this kit-bash. I am just using it for reference.
I am probably going to redo the deck of this bridge. But if you're going to put a bridge across at an angle. Kitbashing is the way to go.
I wanted to combine two Warren Truss bridges going across the tracks below at a 40-degree angle here. To put the cross members below the trusses after I cut them apart and staggered them, the supports did not match up with the truss angles because the Warren truss Bridge by Atlas is not symmetrical.
Normal Bridges have under support in between the trusses at a 90 degree angle. I will redo the deck under this bridge because the angled supports between the trusses is not prototypical.
I think you get the idea though.
An angled trestle support will be put between the two truss bridges when the deck is rebuilt correctly and it is finished.
Hello all,
I managed to kitbash a span of 14-5/8-inch (106' 1" scale), in HO, from three Warren bridge kits from Life-Like, two Straight Pier Girder #32 by Atlas and 2.0mm x 5.00mm strip styrene.
I only used four of the side trusses; cutting off two of the angled ends and cutting off the last vertical member along with the angled ends of the other two.
Thus keeping the "W" angled truss members in the center of the span.
From bridge shoe to bridge shoe it's 17-5/8-inch (127' 11" scale).
The track passing below the span is a curve. Adding even more challenge.
Even though the span is angled over the track below I set the abutments 90º to the bridge, not skewed.
One end is set in bedrock while the other end is set in a large cribbed abutment filled with rip-rap.
This span is not a prototypical length for a Warren truss bridge- -it is too long to carry modern diesel traffic on a single span.
I am in the process of "upgrading" this span to handle modern traffic by adding external arch support from a Faller through arch bridge kit.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"