Milwaukee Rd., RMD-2 Bridge gang now at CC-344

Colleagues,The bridge gang has been hard at work at CC-344, mile 1497, and a consulting engineer, Ron Picardi, advised of some changes to reduce the poly count which have been incorporated in the right-most tower.This bridge in the real world is on an 8 degree continuous curve, but in the sim, to reduce the use of dynamic track, it is on a 10 degree curve compounding into a 500m radius piece at the west end. This somewhat complicates "bending" the bridge, so what is seen here is a trial fitting of the #s 3, 4, & 5 towers and west abutment (physically part of tower 5). Two additional, progressively shorter towers are required, and a 60ft. dpg leading east to the east abutment.J. H. Sullivan

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http://www.train-sim.com/dcforum/User_files/3f08d2161280e4c2.jpg

http://www.train-sim.com/dcforum/User_files/3f08d22312aab3ce.jpg

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RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, xlspecial261, Jul-06-03, 10:38 PM, (1) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-07-03, 04:06 PM, (2) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, xlspecial261, Jul-07-03, 05:19 PM, (3) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-07-03, 07:26 PM, (4) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, xlspecial261, Jul-11-03, 04:54 PM, (13) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-07-03, 07:27 PM, (5) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, rpicardi1, Jul-07-03, 08:35 PM, (6) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-08-03, 12:29 PM, (7) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, rpicardi1, Jul-08-03, 07:25 PM, (10) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-08-03, 12:30 PM, (8) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-08-03, 04:00 PM, (9) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, landnrailroader, Jul-10-03, 01:00 PM, (11) RE: Milwaukee Rd., RMD-2 Bridge gang now at CC-344, jonathanmlewis, Jul-10-03, 01:21 PM, (12)

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Jerry,Any chance of a tutorial on assembling these bridges in TSM? I have very little experience working with it and putting these things together on a curve with a grade is a daunting task.Any advice would be helpful.Thanks,
Todd

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I'm not the best person for doing instructions on the process, because I am a beginner too, but here is how I am doing it.First realize that real curved bridges, aren't really curved, they consist of a series of spans that form the chords of a curve. Depending on the radius of the curve, these spans may be quite long, or may have to be very short. For instance, MR used a pretty standard 40ft. girder over the tops of towers on tangent track, and 65ft. girder span between towers. However, this bridge uses 35ft. spans over the towers and 60ft. between the towers. NP used shorter spans at Bridge 63, which is on a 12 degree curve. We will get to that one shortly.First, I lay the track, following my digitized route markers as closely as possible, although if dealing with seamless data, it may be possible to tell where the track really was, and in that case, I follow the noticable path. Having done that, I note the gradient at the location, in this case 1.1 degrees. Then I note the curvature, in this case there is a compound curve with the bulk of the bridge on a 10 degree curve, 573ft. radius, and the west end on a 500m curve, or 1640ft. radius.First you must build the bridge parts, and for this I start with some of the excellent "kits" provided by Ron Picardi. With Ron's advice, I only detail the outsides of the towers, i.e. that part most visible in the various camera views of MSTS. Areas under the track, I use, at his suggestion, two-faced polygons of 4 corners, transparent, with a lattice (actually a big "X") on each. These are adjusted to fit the situation. I assemble a tower and one intermediate span.Next adjust the gradient by rotating the spans by the degree of gradient, in this case 1.1 degrees. It will require experimentation as to whether this should be a negative or positive angle.Now, the tricky part. Using the top down view, construct a disc of radius equal to that of the curve. It will not be a circle, rather it is a series of chords, I usually use 32 segments. Move/rotate, or whatever the disc until its edge is centered on the tower. Now select the intermediate dpg, and go to point mode. Select the end of the dpg, and shift it one way or the other about 1/2 way to an intersection of the disc. Delete the disk, Save the project, and export the assembly to your route.Now place the tower into position (temporarily) and eyeball the fit. You will probably have to adjust this "bend" we just did some more to get a good fit.After completing each tower until you are satisfied, save the project, join all the parts together and save the "part", but do not save the project again - this will insure that it is easier to make any further adjustments that crop up.Now create a project for the bridge, and if possible (i.e. polygon count less than about 4800) assemble the bridge into a unit. Export it to the route and try the fit.Take a whack at it.J. H. Sullivan

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Thanks for the tutorial Jerry. I get to put 5 of these things together, all on 10 or 8 degree curves so I've got some learning to do. Another question; Have you or anyone else had problems with the grades not coming out right? For some reason occasionally when I am running out either curves or tangents at the designated grade, according to the profile, they will come out too low or high on the other end.I could understand it somewhat on the curves due to how the sim handles that, even when only running them out 100 or 200 radians, but I have this problem on 500 meters straights even.This has happened a couple times on both Boylston Hill and Snoqualmie Pass. I'll be going along just fine, following the profile and checking elevations often, and all of the sudden I either start gaining or losing elevation faster than I should.The only way to adjust it is to put in a bit steeper grade than called for, which I don't want to do, but have no choice.Just curious if you have seen this phenomenon.Best,
Todd

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Yes, I have seen the problem you mention. If you are working from a profile, I suspect the profile itself may be slightly in error. Usually these elevations were determined by an altimeter, not unlike those used in airplanes, and if not properly adjusted for local pressure - which can vary several times in 24 hours, it is possible for elevation, i.e. altitude to be off by several meters. Ordinarily it was not a problem in the real world, because grade was measured by taking stadia readings off of a transit, so once it had been decided what the grade would be, they just dialed it in so to speak.Another source of error is that you cannot rapidly change the gradient in MSTS like in the real world. Hence MSTS does not compensate for curves, unless perhaps real long curves. If you have a 2.2% grade on a stretch of curvy track, this will be a compensated grade, which means that tangents will be a little steeper than 2.2% and curves less, but depending on the degree of curve.To come out reasonably close, for example on the east slope of PipeStone Pass, instead of a grade of 2%, I actually used about 1.95% throughout. Doing it this way, puts you off a few meters up or down, here and there, but the start and end is at the correct elevation. When folks start playing with the OH (with BiPolar) on PipeStone Pass, I doubt they will notice the difference - that thing will exceed the speed limit going up hill if you don't watch it.Jerry

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Ok, glad to hear that I'm not just seeing things.
I may do something like I did at Boylston, but it will entail raising the bridge (I placed the bridge several months ago). From Renslow to Boylston I ran into the same problem, except the grade was digging deeper and deeper into the hill. So, I finished laying all the track, then got the coordinates for Renslow and Boylston. Then, I downloaded the geotiff from the USGS site and redemed that portion with a -4meter elevation change.Terrain now matches the correct grade, and the correct grade gives me the correct tonnage ratings.Time to do some downloading.....Also, great work on the bridges Jerry.Todd

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The Bridge gang has completed all of the towers, and must now tweak them to fit. We may remove the guard rails, however, if left in place, they will be angular at the "joints". I shudder to think about putting curved guard rails in.J. H. Sullivan

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I agree, curved guard rails would be a nightmare and will kick up the poly count to look good.You might experiment with some to see how they look.SRV RonCurrently working on the Peavey Elevator.

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Ron,If by elevator, I assume you mean Grain Elevator, wuld you consider making it so that the name can be altered. There were elevators, rather large ones, at 3-Forks, and Deer Lodge.Jerry

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Grain elevator.Actually, the sign is very small and can either be left out, or placed as a seperate editable texture.Peavey is a compact 4x9 cell concrete elevator big enough to cover 180 x 400 feet of space. I am waiting for a chance to photograph the one by Elkton, which I can get a clear shot from 1/2 mile away. It is a huge one. There is also a huge one of the former Farm Brueau on the Saginaw River and has a dock for loading freighters. This one may be difficult finding a place to get a good photo of. Part of it was rebuilt in the early 70s after a dust explosion blew apart the concrete elevator and damaged several silos.The Auburn Feed and Grain is a sprawling complex of steel bins.I will put together a kit of parts for TSModeler as I assemble some of the above and will study the pics posted on another thread.The difficult part of those structures are the huge open tube chutes going to each silo and other places in the complex.SRV Ron

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I believe I will pass on curved ones. What I might do, if I cannot get a good looking fit with the existing ones, is use your supplied rails, shorten them to about 1/4 of 60 ft., and 1/4 of 35ft., and assemble 4 together, so there are "bend points" in between the ends of spans.Jerry

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After carefully aligning the towers & spans at CC-344, I decided it would probably be very difficult, if not impossible to fit it together as a unit in TSM and maintain alignment over to MSTS. So, I have left it has 5 units, and I have started replacing the guard rails with 3 piece guard rails, measuring 20' per section on the 60' dpg spans, and 12-11-12 ft. on the 35' spans.In addition, Ron had used a rail section for the guard rail, but I am using a square .5x.5 ft. piece. I remember seeing a number of bridges in the old days with wooden guard rails, so this is not too much of a deviation.The attached is the result at the east end of the bridge.J. H. Sullivan

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Relative to the images seen here, I found that a 3-section guard rail worked quite well. It takes some tweaking, but the result is worth the effort. In the end, I used seperate assemblies for each tower, and will probably do so on other curved bridges.J. H. Sullivan

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Looking Nice.http://groups.msn.com/MSTSNarrowGauge

Jonathan Lewis
jonathanmlewis@msn.com

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