Model Railroad, Covered Bridge

thingiverse

This is a model of a covered bridge for model railroads. This design is based on pictures on the internet and does not model a specific bridge. This bridge is roughly scaled for O27-scale trains (e.g. Lionel). The design was as big as I could make it for a Makerbot Replicator2 with a build volume of 11.2"L x 6.0"W x 6.1"H (284-mm L x 152.4-mm W x 154.9-mm H) As built, the bridge can handle an O27 scale train but it is a very tight fit. You'll have to have at least one straight track outside of the bridge. At full scale, the bridge opening is 65-mm wide by 102-mm high. When printing the bridge for other scales... for O27, scale by 105% to 110% if your printer has a bigger build volume (an O-scale probably won't fit at 100%) for S, 100% is a good size for HO, scale by 65% to 70% for N, scale by 40% to 50% for Z, scale by 40% to 45% A full-size bridge took me over 20 hours to print. Instructions The dimensions of the stl files are: overall height, 150 mm (5.91") width 140 mm (5.51") length ~ 260-mm (10.24") opening: 65-mm wide by 102-mm high. Special features of this bridge: boards along the sides, tin roof. The fullsize version of the final design was printed. Smaller bridges of earlier designs were also printed. The bridge was printed on a Makerbor Replicator2 printed vertically, separate builds for the body and roof scaled by 100% (see recommendations above for scaling) PLA (Makerbot filament) Printed: Low(faster) resolution, 8% infill, 2 shells, 0.30 mm layer height, 230C a raft was not used on 1 occasion, the filament clogged and the roof didn't fully print. It printed fine the second time. the design includes some supports for the roof. no need to add more. you'll need to remove most of the supports in order for the roof to fit on the building. the roof warped a little. i carefully used a heat gun to warm the plastic enough to bend it back into shape. because it is so long, adhesion to the build surface is a problem (more for the roof than the main body). The boards above the opening printed very well and I did not need to clean it up. However, depending on your printer and control parameters, you may have to clean up the top of the opening. At full scale, the bridge opening is 65-mm wide by 102-mm high. When printing the bridge for other scales... for O27, scale by 105% to 110% if your printer has a bigger build volume (an O-scale probably won't fit at 100%) for S, 100% is a good size for HO, scale by 65% to 70% for N, scale by 40% to 50% for Z, scale by 40% to 45% If you can, make your own measurements of the opening that you need and scale appropriately. Some best practices for printing: optimize print parameters for your printer, filament, etc (only you can determine the best parameters) use good filament level your build plate prior to printing complex parts. it's worth the few minutes it takes. always level after removing tape, or if pulling hard to remove a part. make sure the build plate is clean. if using blue tape, stretch it tight when applying it to the build plate. if you have small holes in the blue tape, the bridge should still print without any problems. pre-feed the filament 30 to 60-s before printing (i.e., run load for 30-60s) do not print several complicated parts in one build (do complex parts by themselves) I find that printing faster is better (probably so the filament can't ball up in one spot) when the filament spool gets low, the filament can be tightly wound on the spool and the filament may not feed properly... take special care... when a new spool is used, it is easy for the filament to jump outside the spool and then it will bind up later around the spool holder ruining your build make sure it is easy for the filament to enter the filament feed tube. others have designed spools, mounts, etc. for that purpose. i use a small rope that forces the filament away from the spool before entering the filament feed tube. if you hear clicking when printing, that may be a result of the filament wrapped around the spool and not feeding make sure that there aren't any obstructions on the spool, such as some filament used to hold it in place during shipping for the replicaor2, look at the blob a filament in the left front part of the build plate and then the trail of filament to the biuild location. there should be a glob, and the line of filament should be continuous and smooth one way to remove parts when using blue tape is to use a very thin spatula bought in craft-art stores (advice from youtube). get one with a wide, blunt front end (not long and thin). mine is 11 mils thick (0.011") and 20-mm wide at the front. a painting spatula/scraper in hardware stores won't work and may damage the build plate. (I use blue tape so I don't have any best practices for bare plates, heated plates or for other tapes like mylar) perform regular maintenance (grease, etc). when I continued to have problems printing even after performing maintenance, following troublshooting instructions, changing filaments, cleaning gears, cleaning everything, optimizing print parameters, changing temperatures, etc., I bought a new extruder assembly from Makerbot and it solved all of my problems (sounds like a poor quality print head to me...went bad after 3 months) Parts list: glue or epoxy. Assembly instructions: Glue the roof if you want to. Can leave unglued. Special instructions for model trains: If it's a tight fit, you'll need staight tracks leading into and out of the bridge. Nail down the track and bridge so that they can't move. Make sure cars have good trucks so they don't wobble. Still, a very tight fit for O27 and won't handle a standard O-scale unless it is made bigger. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, LGPL version 2.1, or (at your option) any later version of the GPL. Woverine Boat LLC is providing this document and its contents on an "as is" basis and makes no representations or warranties of any kind with respect to this communication or its contents. Woverine Boat LLC disclaims all such representations and warranties, including for example warranties of merchantability and fitness for a particular purpose. You should have received a copy of the GNU General Public License along with this program; if not, see http://www.gnu.org/licenses/gpl-2.0.html or write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Version number 9.A (first distributed version) Author : Wolverine Boat, LCC - wolverineboat@flash.net Copyright © 2014 by Wolverine Boat, LCC Created Feb. 14, 2014 Modification: Feb. 14, 2014 ... original version Special instructions: User feedback: Limitations: Designed with OpenSCAD 2013.06 Model train info (approximate values and may depend on manufacturer (1" equals 25.4 mm) O27 scale 1:48, track ~50.0-mm W x 10.3-mm H, typical car ~54.8-mm W x 79.3-mm H, car+track ~ 89.6 mm H, 1-ft = 6.4 mm S scale 1:64, track ~47.0-mm W x 13.6-mm H, typical box car 51.2-mm W x 67.8-mm H, car+track ~ 81.4-mm H, 1 ft=4.8 mm HO 1:87, track ~28.5-mm W x 4.6-mm H, typical box car 36.0-mm W x 55.8-mm H, car+track ~60.4-mm H, 1 ft=3.6 mm N 1:160, track ~16.0-mm W x 3.8-mm H, typical box car 20.3-mm W x 31.5-mm H, car+track ~ 35.3-mm H, 1 ft=1.9 mm Z 1:220, track ~16.0-mm W x 4.7-mm H, typical box car 15.6-mm W x 21.9-mm H, car+track ~ 26.6-mm H, 1 ft=1.4 mm (Lionel O track is 4.4-mm higher than O27 track). I have not listed G scale because it's too big for my designed parts. Disclaimer: This bridge was not based on a specific prototype and there isn't a true scale for this item. The design is based loosely on Google images of covered bridges and not on anyone's design.