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In lugnet.trains, Scott Lyttle wrote:
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In lugnet.trains, Dave Sterling wrote:
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Stacy and I are designing a small layout for Brickworld this year and we
want/need to have a bridge in the layout. We’ve been working to design the
layout using banquet tables (so I don’t have to bring my own tables), yet we
still want an open space in the center. The way we have it designed
necessitates us to try and span 40 inches (128 studs) unsupported.
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SNIP
If you do want to make a truss bridge, I recommend using layers of plates (as
there is a greater surface adhesion (clutch power) of plates when compared to
bricks. One thing that I have found that works well to to use two layers of
plate between two technic bricks. The spacing of two plates between two
technic bricks is such that you can position a 3-stud wide technic beam
upright, where the technic bricks will match holes 1 and 3 perfectly. You
will most undoubtedly need one baseplate on either side of the span to build
some supports.
My bridge has been holding together well, and is not covered with plexiglass
sneezeguards on our layouts, so it has born the bront of many children’s
fingers leaning against it.
I’m trying to remember if I’ve brought the bridge to a BrickFest. I can send
you some pictures if you’re interested.
Scott Lyttle
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Wow! This has all been great information and the pictures are wonderful. I’m
really excited to get a closer look at some of these bridges at various shows
this summer. :-) I might even have to get out to somewhere where SCLTC is
displaying sometime!
So, last night I went home and quickly put together a 92-stud prototype bridge
and tested it. My design works, but needs a little reinforcement to make it
viable for the long haul. I’ll probably add plates to strengthen it and maybe
try sandwiching the plates the track sits on using the upright Technic beam
method Scott mentioned.
More Images
The next step is to do a Bricklink purchase to get the pieces for the 128-stud
bridge. The scaling from 92-studs to 128-studs shouldn’t be a big deal. This
bridge held the pictured engine and three hopper cars with no noticeable
deflection. The cars weren’t moving though, so I imagine I will have to
reinforce it more to deal with the vibration. I don’t want it crashing down in
the middle of a show. Oh the horror! The Minifig carnage! Minifig bodies
everywhere screaming for help as they are trapped inside a burning Santa Fe
dining car. Yeah...not a pretty sight.
Any thoughts on what I have so far? I’d really like to try one of those cool
cable-stayed bridges sometime, but I’ll need to get a closer look at how the
cables are held in place.
Also, I just want to thank everyone for all the great information and
enthusiasm. All of you are helping push me to do things I never dreamed I would
do with LEGO. All of your creations are an inspiration to Stacy and I and we
are so glad we’re part of such a cool group of people. In short...AFoL’s rock.
Thanks and Play Well!
-Dave
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In lugnet.trains, Dave Sterling wrote:
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..
Any thoughts on what I have so far? I’d really like to try one of those cool
cable-stayed bridges sometime, but I’ll need to get a closer look at how the
cables are held in place.
..
-Dave
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Dave-
If you want your truss construction to actually support the bridge, you should
convert your trapezoids into triangles (i.e., break them up by adding verticals
in the middle). (Actually, the way many of us do this still makes trapezoids,
but one of the horizontal sections is so small that it’s effectively a
triangle.) The best way to make the triangles is to use length ratios 3:4:5 or
5:12:13 so they come out exactly in studs.
With regard to the “cable” in our cable stayed bridges, we just used bungee cord
(from Jo Ann Fabrics, which appears to be identical to the stuff that came with
LEGO Bungee Blasters a few years ago). In the towers, we just run through the
holes in Technic plates. At the deck, we run it through a piece of stiff LEGO
tubing, then a 1x1 cone, then a small Technic connector from the cone to an axle
hole, and wedge between the axle and axle hole and into the deck through a hole
in the side of a Technic brick.
-Ted
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In lugnet.trains, Ted Michon wrote:
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In lugnet.trains, Dave Sterling wrote:
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..
Any thoughts on what I have so far? I’d really like to try one of those
cool cable-stayed bridges sometime, but I’ll need to get a closer look at
how the cables are held in place.
..
-Dave
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Dave-
If you want your truss construction to actually support the bridge, you
should convert your trapezoids into triangles (i.e., break them up by adding
verticals in the middle). (Actually, the way many of us do this still makes
trapezoids, but one of the horizontal sections is so small that it’s
effectively a triangle.) The best way to make the triangles is to use length
ratios 3:4:5 or 5:12:13 so they come out exactly in studs.
-Ted
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Yeah, after I built this I realized that I had the technic pins at the top too
far apart and should move them each in slightly to form a triangle. Right now
the track and track bed are supporting most of the load I think. I pulled out
my old Engineering Mechanics:Statics book today and started looking at the
chapter on trusses again. Haven’t looked at that chapter in about 6 years. :-)
I’ve got a bunch of technic bricks, pins, and beams on the way from various
Bricklink stores. Once those arrive next week I am going to start again.
Thanks for the tip on triangle sizes. I’ll have to keep that in mind when
designing my new bridge.
-Dave
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In lugnet.trains, Ted Michon wrote:
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In lugnet.trains, Dave Sterling wrote:
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..
Any thoughts on what I have so far? I’d really like to try one of those
cool cable-stayed bridges sometime, but I’ll need to get a closer look at
how the cables are held in place.
..
-Dave
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Dave-
If you want your truss construction to actually support the bridge, you
should convert your trapezoids into triangles (i.e., break them up by adding
verticals in the middle). (Actually, the way many of us do this still makes
trapezoids, but one of the horizontal sections is so small that it’s
effectively a triangle.) The best way to make the triangles is to use length
ratios 3:4:5 or 5:12:13 so they come out exactly in studs.
-Ted
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Ted:
Here’s V2.0 of my 92-stud bridge. I added the vertical bracing and it made a
HUGE difference in both the stability of the deck and the lateral stability of
the actual truss structure.
More Pictures
Now I just have to wait for my load-o-technic parts to arrive and I’m off to the
races. :-) One other thing. How much clearance should I have track to top of
the bridge? I was thinking 20 studs at first, but maybe I need more? I know it
fits all my rolling stock, but what if someone shows up with a bigger train and
wants to run it on my layout? Is there a “standard” bridge height most clubs
use?
Thanks,
Dave
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In lugnet.trains, Dave Sterling wrote:
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.. • How much clearance should I have track to
top of the bridge? I was thinking 20 studs at first, but maybe I need more?
I know it fits all my rolling stock, but what if someone shows up with a
bigger train and wants to run it on my layout? Is there a “standard” bridge
height most clubs use?
Thanks,
Dave
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At work they like to quote the statement “Standards are great. That’s why we
have so many of them.”
Standard height is whatever you and whomever you interoperate with agree on. At
SCLTC, standard height is 14 bricks, measured from the top of a baseplate placed
on the table and includes the 1 plate we use to raise the track above the
baseplate (so we can use tiles under curve tracks) plus the height of the trails
themselves.)
We rarely get in trouble over lack of vertical clearance. A much bigger problem
is clearance around curves, which can bite you in unanticipated places. For
example, your bridge may offer great clearance for rolling stock that approaches
it on straight track, but not make it if it goes direct to curve track.
-Ted
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