Moses,
Lots of good advice here.
If you're ever planning on being through C-U, drop me a PM and be glad to show you around the layout.
Mike Lehman
Urbana, IL
Thanks for your reply. The tips are helpful. I live down the road in Peoria.
rrebell There are two ways to cut for a curve, one is build the box sections, then cut and the other is to plan your cuts first, both work. I installed the bridge with footings and all and built the scenery up to it, could have gone the other way too. A template of your intended trackwork is a good idea as it lets you plan your cuts. One thing I found out too late while working on another bridge is that the best glue for gluing the metal shoes to the plastic bents is regular ACC, thought I had to go with an exotic to get the hold.
There are two ways to cut for a curve, one is build the box sections, then cut and the other is to plan your cuts first, both work. I installed the bridge with footings and all and built the scenery up to it, could have gone the other way too. A template of your intended trackwork is a good idea as it lets you plan your cuts. One thing I found out too late while working on another bridge is that the best glue for gluing the metal shoes to the plastic bents is regular ACC, thought I had to go with an exotic to get the hold.
Building all the nec boxed girder sections then arranging the boxes to test for miter angle and fit is by far a much better option. Trying to plan and figure the "real" angle and just which sections and how much of a cut needed would be rather difficult and also provide a greater chance of screwing up the critical angles. Remember, some of the girder cross bracing will be "chopped" off in the process, this is better done after the section is completed- difficult to guess if built for the cut. Building the "square" boxes along w/ the use of a square or wood blocks will make assy easier and allow placement on the track template. My template of the curve shows the outside of bridge ties and track centerline. By placing all the boxed sections will allow you to draw a line for the mitered angle. The 30' and 50' girders are the same height and will help in placement of the Cross beam on top of the tower. If using the taller believe 80' girder, the section over the tower will need to be kept somewhat square and the material removed from the taller girder. This longer beam/ girder is an option and not part of the standard 210' viaduct kit. This fitting is seen in the pic above.
Modeling B&O- Chessie Bob K. www.ssmrc.org
Moses45 I am a little intimidated by this bridge. First off, I built the 1st bent and it is way too tall. It will have to be altered. But more importantly if I understand correctly the three 50 ft spans are to be built completely and THEN cut to make the curve. Is this correct. What does this do to all of the struts holding the 2 bridge faces together?
I am a little intimidated by this bridge. First off, I built the 1st bent and it is way too tall. It will have to be altered. But more importantly if I understand correctly the three 50 ft spans are to be built completely and THEN cut to make the curve. Is this correct. What does this do to all of the struts holding the 2 bridge faces together?
It can be a bit intimidating at first. Do read and reread the instructions. The portion that explains how to build and/ or modify the open girders does explain most of your concerns. Make a template, you could start w/ paper and trace to something more substantial like heavier cardboard even 1/8" masonite. I will explain the reason for the heavy template later. Make the template showing the curved track and draw the line at the outside of the ties. This will allow you to place the "built" 30' and 50' open girder sections to show just wow much to "miter" for fit to the track. The 30' sections are over the tower assy, I found that it was better to cut the Span sections to fit the 30' tower beams as not to drastically interfere w/ the supporting beams on the tower tops. Once the cuts are made and you are satisfied w/ the average of the track/ tie placement and any minimal of tie overhangs, then you can cement the sections together as one length, I did all this on a flat solid surface. Now that strip of masonite or cardboard (tie width), this will allow you to bend the ME bridge flex to the exact curve to fit the bridge. I found that the extremely ridgid track wanted to bend w/ series of small kinks. The cut away "arc" of your template worked perfectly to use as a guide to bend the flextrack. Minor overbending was needed as it would tend to want to spring back somewhat. Those towers are quite tall and I only needed the top 2 sections. the base was just cut off. Footings of pine to look like concrete support the tower legs. The kit can be altered of modified if nec and ME offers all sorts of optional accesory add-on pieces and girders. If you are building this bridge to a radius under 24", 50' spans are as small as I would use as the tie overhang will be too much and it will be difficult to get the centerline of the track to keep close to the bridge centerline.
Don't be too concerned w/ cutting into the "built" girder section, there is enough bracing to still keep the assy together. Of coarse in (real life) situations the bracing would have been altered to fit the angles, but once the bridge is assembled, this discrepancy won't be seen.
If the tower assy (legs) need to be angle cut to fit the grade, the leg bracing may need some "kit-bashing" from the cuttoff bottom pieces to allow for the extended length to brace those legs. I chose to keep them even and allow scenery to follow those platforms and footings as not to deal with this.
The terrain/ scenery contours and mods to the benchwork may be nec, I placed the scenery base to accomadate the top 2 tower assy and adjusted the height of the wood footing blocks to match the rail height. Since the benchwork is L-girder, elevation changes and the bridge "sub-abutments was far easier to do. This become a bit different working w/ foam as the benchwork/ plywood and joists may need to be cut and altered to be below the joists themselves.
These pics have been posted many times, but still can prove useful
A note, the main reason for the track forming template is that the track starts from straight and eases into a superelevated decreasing radius (56- 48") I found that Pliobond rubber cement worked out great for attaching the bridge flex to the girder assy. The rails were left longer (ties removed) to allow the bridge to be anchored beyond the abutments and also allowed for feeders to be run to the rails behind those wood "sub-abutments. Later 1/4" hydrocal castings are placed as a veneer. Note the bridge shoes are barely on the notch of the shoe shelf.
gregci have no experience with bridges, but assuming the bents don't quite reach the layout base, why not embed the bottoms of the bents in plaster contoured to the surface you'd like the trestle to span? Once the plaster hardens, won't the bents be sufficiently supported to prevent the span from sagging as well as hold the bents in place without having to accurately cut the bents to length?
greg,
That could work. There are two possible drawbacks.
Scale size piers will be only a little larger than the bent's box section. There won't be much thickness to surround the embedded bent. With a little care, it might work, but that will be tricky.
Most bents actually end in some sort of shoe and pin arrangement, if some movement is anticipated, or are bolted to the pier. Having the bent embedded won't look quite right.
Moses. If you go to the following link you will see the completed bridge on the Virginian. Its on page 5 of the Virginian Build thread. If I remember correctly you are also building this.
http://cs.trains.com/mrr/f/11/t/202934.aspx?sort=ASC&pi314=5
You are correct. You build the 3 50 foot spans first. You then cut them to get the 18 inch radius curve you need. The easiest way to do this is to either solder 2 18 inch radius pieces of sectional track together and remove most of the ties or make a cardboard template as Mr Lehman recommends so you can get the cutting angle. I did it by installing the rails first over the bridge span, removing all the ties, then trimming the spans bit by bit until I had a good fit. Once I had a good fit, I glued it together. After you have done that you can measure the height for the legs of the bent. I made both Bents the same height then trimmed them to account for the grade.
This was also my first attempt at a bridge and it was a bit difficult trying to figure out what to do. If you want me to post any more photos of the bridge highlighting anything in particular, please let me know.
Thanks,
Steve
i have no experience with bridges, but assuming the bents don't quite reach the layout base, why not embed the bottoms of the bents in plaster contoured to the surface you'd like the trestle to span? Once the plaster hardens, won't the bents be sufficiently supported to prevent the span from sagging as well as hold the bents in place without having to accurately cut the bents to length?
greg - Philadelphia & Reading / Reading
Generally, the bottom legs of the bent are altered to fit the terrain. You'll want some footings for it to rest on. Once they're in place, your can size it up for cutting. If it's steep terrain, one leg may be quite a bit longer than the other. The goal is to get the top of the bent level to hold the bridge at the right height.
For the bridge spans, it's best to make up some cardboard patterns of the whole span. Presuming you're able to get the bents in place, you can set the patterns on top of them, angle them so the segments follow the track curve (which might be yet another cardboard pattern) , then mark them so that when cut they will abut properly at an angle.
Likes the bents, the bracing may need to be cut to help it fit the bent that is fitted to the site's terrain features. Try to work from both ends, ideally, but it may be easier to get proper length and fitting cutting mostly from one end.
Been a long time since I built mine, so not sure if there are plates included to help connect and fasten things. Getting some thin styrene and cutting them as needed will help hold things together.