This page contains a Flash digital edition of a book.
Curved One of the challenges with this project was the necessity to make the tunnel curved. Adding a radius to any project is a challenge. Note the space between the bores and the more prominent tunnel portals on the other end.


Cast Satin is available from Brag- don Enterprises and was used in the creation of the tunnel liners. Bragdon sells the liquid mixture in several differ- ent sizes, allowing you to match your purchase with your project.


then glued the pipe together with PVC cement and filled in the gaps with various strips of styrene. Af- ter cutting off excess styrene with a sprue trimmer, I filled in the re- maining gaps with plastic model- er’s putty and sanded the pattern smooth. Next, I removed the roof pat- tern from the plywood track foot- print and attached two 0.250 by 0.750-inch styrene strips to the bottom of the roof pattern to form the pattern for the perpendicular side walls. Gaps were again filled with modeler’s putty and sanded smooth. Railroad tunnels include safety bays built into the side walls every 50 feet or so to give work- ers in the tunnels a place to avoid moving trains. I created forms for these enclosures from styrene strip and tubing and glued them to the outside of the tun- nel liner pattern in the appropriate locations.


The bottom of the pattern was leveled and at- tached to a flat


62 RAILROAD MODEL CRAFTSMAN


base. I considered using sheet sty- rene as a base but ended up using a scrap piece of Melamine shelv- ing that I had in the shop since it was cheaper. I used a piece of vi- nyl house siding to build a dam around the pattern, and various scraps of sheet styrene were used to fill in the ends of the pattern. After I had filled all the gaps in the dam with vinyl bathtub caulk, I was ready for the casting process. I used “Cast Satin” resin from Bragdon Enterprises, although similar products are available from a number of suppliers. I did not make a rubber mold since I was casting on an original pat- tern. I applied a mold release agent to the pattern and the dam. I mixed the resin in small batches and applied it to the mold with my hands (wearing rubber gloves). It took nine batches to fill up the dam and make a thick enough coating on top of the pattern. Af- ter the second coat, I embedded strips of fiberglass screen in the casting to strengthen the roof and give the resin a rough surface to which it adhered. I poured each coat of resin shortly after the pri- or coat had solidified to allow the nine coats to adhere to each other. When the resin had cured, I stripped off the styrene and vinyl dams and used a chisel to dis-


lodge the casting from the pat- tern. I had been a bit sloppy with the mold release and had not wor- ried much about air bubbles in the resin. After a thorough wash- ing to remove the mold release, I filled the voids created by the air bubbles with putty and sanded the area smooth.


The next step was to construct tunnel portals to match the pro- totype. I used double-track por- tals and concrete walls from Pre- Size Model Specialties, which are cast in resin. These castings have a texture to simulate the marks left on concrete by the joints in the forms used during construc- tion. The Oscawana tunnels had a semi-circular roof, so I modified the portal castings on my band- saw and spindle sander to match photographs. I trimmed the ends of the tunnel liner castings to the appropriate angles using my chop saw, and the portals were screwed and epoxied in place. I thinned pieces of the concrete wall cast- ings and cut them to match the shape of the concrete slabs on the prototype tunnels. Careful fitting of the concrete wall pieces was required to match the angles of the various walls on the East end portals. I fabricated the wall caps from strips of 0.250 and 0.188 styrene. The curved piece of the


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100