How can I be sure that my curves are accurate when using flex track?
Dr. Anatomy
Hi Doc, and [#welcome] to the Forums. I hope that people don’t think we’ve got a medical convention going here. [swg]
If by “accurate” you mean following a specific radius, the usual practice is to draw a track centre-line at the required radius. This will work on any tabletop-style layout of wood or foam construction. If you’re using wood subroadbed on open grid or L-girder benchwork, the usual practice is to cut, or, for spline, curve, the roadbed to the specified radius, then lay the flextrack either to a centreline or other constant marker.
You can use a yardstick or similar piece of light wood as a compass, driving a small nail 1" from one end for a pivot, and drilling holes at distances from the pivot point equal to the radii you wish to use - the holes should be sized to accommodate a pencil, and should be marked as to the particular radius they represent.
Of course, you don’t have to limit your curves to set values - one of the advantages of flextrack is the ability to introduce curves anywhere you wish, provided, of course, that you don’t make them sharper than what your locos and rolling stock can handle. I built my layout with no trackplan, simply by cutting 3/4" plywood subroadbed curves of various radii (all greater than my desired minimum of 30") and placing them wherever I needed a curve to get the layout’s track around the room. I then connected all of the curves, introducing small, gradual curves of unknown radii wherever they were needed in order to get the track to line-up. After that, running trains showed where any changes needed to be made.
Wayne
I use homemade trammel - it’s a yardstick with a couple of pins. I use it to lay out the arc’s and then line up the flex track along those arcs. Since I use Atlas flex track, I will tack it down using the holes in the middle of the tie until the adhesive caulk is set then I remove the tacks. . If you are using easements those should be drawn as part of he geometry as well. This may not be most efficient way but it works for me.
Hi Doc.
I also made a trammel out of an old wooden yardstick. It works well for initial planning on your benchwork especially on larger more sweeping curves. However it can become a bit cumbersome to use as you progress and things get in the way.
What I did was use the trammel on the bench at first and then used it to draw out different radiuses on a large appliance box and cut them out. In the photo below is a example. The cardboard is an inch wide so the inside curve is 30" and the outside is 31". I drew a huge arc on the cardboard and then cut it into sections so I could use just one or join them together if I needed a longer template. I eyeballed most of my track laying and mostly used the cardboard templates to make sure I didn’t go under my minimum radius. I also found them useful in drawing parts of my trackplan on to my foam. Good luck and[#welcome]
Brent
As other posters have indicated, a trammel or similar device is usually necessary. If you have a situation where you can’t put the center point on the benchwork/plywood, as in building a shelf-type layout, it is relatively easy to use a camera tripod as a center. I took a piece of wood about an inch wide and about 4 feet long and drilled a hole big enough for a Sharpie marker near one end. I then measured out from the center of the hole the various distances for my radii and marked them. I then epoxied 1/4x20 nuts (with the threads drilled out) at the various points I had marked. By placing the nuts over the camera mounting screw on the tripod (which you have placed at the center point of the radius) and then strike the arc.
Once you have marked the center line, you can lay the cork roadbed to the centerline, then lay your track down on the roadbed, keeping the center of the track over the center line of the roadbed.
One feature of the flex track is that it almost automatically creates a transition curve between the tangent and the curved. track, with the resulting smooth operation over the track.
Good luck…
Dr A,
All good suggestions.
My problem with flex track curves weren’t the curves themselves but the tranistion from the straight track. Where I began the curve connecting the flex track to a piece of straight track some times caused a problem. The flex track exerts pressure at that point affecting the beginning of the curve. The problem showed up with larger diesel and steam engines which can be picky,and also longer cars. It is a good idea to check all of your track by running the longest car you ever expect to run even if you have to buy one for testing purposes. I learned this the hard way.
Bob
I used a similar method for my around-the-room layout, simply clamping a board of suitable length to the top of the benchwork, then using it to support the pivot end of the trammel/compass.
That’s why, if possible, it’s better to lay-out and install the curves first, allowing the free end at the start and finish of the curve find its own position. Of course, this works best with easily curved track, such as Atlas.
Wayne
I used the trammel to make cardboard templates of various radii too, but I also use a piece of 1/8" masonite about 1/4" wide and 8 feet long (it was cut from a full sheet of masonite) and lay it on the subroadbed and make long sweeping curves to any (I don’t know what radius they are but they are over 30") situation I need. It also helps blend or transition the curve into the straight. I now use this rather than any specific radius as it looks much more prototypical. I just cut my plywood to fit the area and lay the curve out to fit. The cork roadbed follows the line and the flex track follows the center of the cork. Very easy and fast. You could also use a shorter length, like 4 feet. Good luck with your layout. Any of the posted methods work, I just happened to find a good use for the ‘scrap’ of masonite I had from another project.
Bob
Dr. A,
Simple as falling off a log. A pencil or a sharpie tied to a piece of string. Lets say you want a 34" curve at one end of the bench work. place the sharpie or what ever in the center of the curve and stretch the string out the desired radius in this case 34" secure the center point or of the arc with a push pin clamp tape what ever works. Keeping tension on the string now just move it in the shape of the arc. Same as using a trammel but as others have said once you start building the trammel can get int he way. If you prefer the trammel method just cut some strips of wood to desired radius lengths 24", 34" etc. and you have a set that didn’t cost you anythng
I’ve used Ribbonrail Track Gauges in the past for my flex curves in n-scale.
Walther’s carries them in a variety of scales: