Since I’ve never built a train track, I’m sure that I’ll learn more than I’ll ever wanted to know about train tracks by the time I have it completed. I’m also sure that I’ll eventually look back and realize that I would have done some things differently once I’ve gone through the process.
That said, I plan to research as much as I can to reduce the risk that I’ll have to scrap major pieces of work after the fact because I didn’t have the knowledge to do it right the first time.
So, from my reading, here’s some things to be considered when I design and build the track:
The width between the rails is critical. If the distance between the wheel flanges is 14.5″, then there needs to be another quarter inch added for the distance between the rails so the wheels don’t bind.
The width between the rails in the curved sections needs to be about one eighth of an inch larger to keep the wheels from climbing the rails and derailing.
The curved sections can’t be too tight. The degree of curve is expressed as the distance of the radius that would scribe the curve. From reading, it seems that the tightest curve that the train will be able to handle is about a thirty foot radius. If you think about the geometry, the minimum radius of the curve would have to be increased if the wheelbase of the engine increases or as the track width increases. I’m going with the thirty-foot radius and hoping it works out.
The grade of the track can’t be too steep. It seems from reading that a three or four percent grade is pretty much the maximum that a train should encounter. Because of the slope on the property where the track will go, I may have as much as a twelve or fourteen percent grade. Based on the hill-climbing tests I’ve already conducted, I know the motors have enough power to handle a fifteen percent grade, assuming I can get enough traction to keep the wheels from slipping.
So my general approach to building the track will be to create track sections that can be attached to each other on the track bed. The curve sections will need to reflect a thirty foot radius, so I’ll build some sort of template for those. In addition, I need to ensure that the distance between the two rails is consistent. So I’ll need some sort of template to ensure that the distance between the two rails doesn’t vary as I assemble the track sections.
Once I get some curve sections of track completed, I’ll want to run a test to make sure the engine can handle the curve without derailing. Assuming that test works well, then I can use this approach for the remainder of the curve sections.
I’ll also need to figure out how I want to set the track on the ground. The simplest way would be to just lay the sections on the ground. There may be several problems with this approach, however. The ground is uneven, so the track would be uneven as well. If the track tilts to the side, then the engine will also tilt on that section of the track. Too much tilt and it may fall over. That would be a train wreck. Not good. Also, the grass and weeds will grow between the cross-ties and will be a nuisance to control.
The best approach would be to set the track on a bed of ballast (gravel) to give it the best support and enable me to make leveling adjustments. I don’t want to have to deal with removing tons of gravel at some point in the future, so I’ll start with no gravel and see how it goes. Maybe later, if necessary…
Track construction can be divided into making the rails and making the cross-ties. The rails are made by ripping a 5/4″ decking board into three strips that are equal in width. Deckboard is used, as it is easy to work with, readily available, and comes pressure-treated.
Cutting the deckboard into strips leaves two rails that have the rounded edges, and a center strip that has square edges. I used a router with a quarter-inch rounding bit to round the edges of the center strip. This way, I can get three rails from one deckboard.
The cross ties are made from pressure-treated 2x4s that are cut into two-foot lengths. To ensure that the rails keep the proper distance between them and are firmly anchored to the cross ties, I cut grooves into the cross ties to hold the rails. Since the 5/4″ deckboards are actually one inch in thickness, I needed grooves that were one inch wide and that were spaced the proper distance apart.
My first thought about cutting the groves was to put a dado blade on the table saw. But a little research showed that there are no dado blades for a ten-inch table saw that are one inch wide. This would have necessitated at least two passes per groove, and it would have been difficult to ensure that the groves maintained the proper widths and distances between each other.
My first attempt at actually cutting the grooves was to just make multiple passes over the table saw blade with each pass cutting just the width of the saw kerf. I made enough cross ties to construct an eight-foot section of straight track. But the process was labor-intensive and prone to error. Not a good solution for cutting hundreds of ties.
I abandoned the approach of using a table saw for cutting the grooves in favor of using a router. I found a router bit that cuts a one-inch wide groove with a single pass. This approach looked much more promising.
What I finally ended up doing was to attach several ties with bar clamps so I could cut all of them with a single pass of the router. I also cut a piece of plywood with a width such that it could be used as a router guide and ensure that the grooves for each side of the tie maintained the proper spacing. Here’s what the setup looked like:
Using this approach to making straight sections of rail, I constructed several sections and connected them so I could run an engine test. The test was just to make sure that the engine would track along the rails without jumping the tracks.
The side rod (or connecting rod) of a real steam engine connects the piston to the engine’s drive wheels. It works like the connecting rods of a standard gasoline engine that connects the piston to the crankshaft. The steam pressure pushes the piston, which is connected to the side rod. The other end of the side rod is attached to the drive wheel and causes it to rotate.
Since this engine is driven by electric DC motors with a chain drive, the side rods are entirely superfluous and decorative. But it makes a nice visual to help complete the effect.
Front End of Side Rod
For the piston rod, I have a half-inch steel rod that sits in five-eights inch diameter holes drilled into the wooden end caps of the cylinder. The rod can slide freely. I threaded the rear end of the rod with a die cutter so that I can attach some sort of fitting to attach to the side rod. My original plan was to fabricate a bracket by bending and drilling steel bar stock and attach to the piston rod with nuts. But when browsing the hardware store for something to use I found a galvanized pipe fitting Tee that I thought I might be able to use.
The inside of the pipe fitting was already threaded. But it turns out that the thread pitch of the pipe fitting was not the same as the thread of the steel rod that I cut. Not a problem – I just re-threaded the pipe fitting to match my steel rod with a thread cutting die. I screwed the rod into the fitting and locked it with a nut.
The fittings were also threaded on the sides, so I drilled them out. I found some clevis pins at the hardware store of the proper diameter and length and used those to create the wrist pins that attach the side rod to the piston rod. Here is a picture of the final assembly of the front end of the side rod. Note that the pipe fitting is just a little too wide for the side rod, which was cut weeks ago. I added a second layer of bar stock to the back side of the side rod to use as a spacer to prevent binding.
Back END OF SIDE ROD
The back end of the side rod attaches to the drive wheel. The drive wheel has a half-inch steel bolt protruding from the side of the wheel, to which the rod is attached. I drilled a hole in the rod and inserted a bronze bushing that I lubricated with a little axle grease.
A real steam engine also has additional rods that are used to control the valves that allow steam into the cylinders at the proper time. The control of these valves is determined by the position of the wheel during the rotation cycle. So the wheel typically will have additional linkages for this purpose. These linkages are included in this design and create another nice visual effect.
The fittings for the linkages were fabricated from steel bar stock that I cut with a jigsaw. Then I drilled and ground the pieces to get the desired shapes. The fabricated pieces are attached to the steel bolt with locking nuts. The other end includes a bolt to hold the actuating rod that gets pushed and pulled during the wheel rotation. You can see a picture of the assembly here.
Here’s what the final side rod assembly looks like in operation: