Your approach will work fine Rob. Although not necessary, MicroMark makes a specific tool called a "Rotape" which is a modified tape measure that basically replaces the string. It's sort of handy to have.
Also, if you are laying flex track you need to plan how you'll handle the joints. Laid loosely, you'll have a kink in the curve which will cause derailments. To avoid that, take two pieces of track, connect them in a straight line, solder the joints and THEN bend them. These are the only railjoiners that I solder.
Lance
Visit Miami's Downtown Spur at www.lancemindheim.com
LION of course has his own way of doing things. Since him does not bother with roadbed (it costs money, you know) him uses whatever material he can find in the barn to make a table top. Him cuts the board to a minimum 24" diameter inside curve, and uses a small block of wood to measure an offset to the ties.
In theory each track (LION has a four track mane line) should be of larger diameters. I have found that this is not always the case, so a good case can be made for scribing the curves as described above. The LION tried that, but his pivot moved on him, and so he came up with some weird lines on his table. Mostly the LION just slaps the tracks down so that they will fit, and then tests his biggest cars or locomotives on them to see if they work. If they work, fine, who cares what the radius is. If they do not work pull them up again and rebuild the curves until it will both work AND fit on the table. If that does not work then you have to rebuild the table.
Some say planning is the key to success. LION says: slap down the tracks and eat the planners for lunch.
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
Rob, as long as you keep your central pivot from moving, just decide earlier what radius you want, pinch the string between your fingers and a pencil at that distance, and draw an arc longer on each end so that it goes past the point where the tangents (straights) start again. Let the flex track form natural easements at the point of tangency as they naturally will, slowly going from curved to straight.
It would help to have this all figured out in a plan so that you won't be faced with a really tight curve when you try to close up your loop, if you are going to have a looped main.
I have what is called a trammel. I cut a length of cedar lath, or stapping, and drilled a small hole near one end into which I drove a screw. That is my pivot. Then starting at 18". and in inch increments from there outward, I drilled countersunk holes into which I could insert the tip of a pencil. Note that you could make the pivot hole large enough to fit over the mounting screw on a camera tripod head for times when you need both hands free and when your curve is on a table top already supported by legs of a height. Just find your place for the curve, situate the tripod so that the head is near the eventual center of the circle for that radius, and then fiddle with the tripod's location until you can draw an arc that fits nicely with your plan.
Note that you are the one who must answer your question about which curve is better. Obviously, if your engines are long, or you have long autoracks or heavyweight passenger cars, curves much under 25" are likely to leave you with problems. Many HO items are fine with 18" curves, and maybe they're all you have room to make. What is the situation with you...do you have room for 26" curves?
Crandell
String and pencil, or a thin strip of wood with a pivot hole at one end and holes for the pencil at the various radii. A wooden yardstick works well for this. Just rememebr if you drill the pivot hole at the 1" mark, you have to put the pencil at 19" for an 18" radius curve. I used a scrap piece of 1x2 and drilled a hole for it to pivot ont he mounting screw of my tripod, sinc emy layotu is around the walls and most curve centers are in the middle of the floor somewhere. The tripod allows me to place the pivot at the currect location and get it up to a height where the stick pivots smoothly at table level.
Depending on which brand of track you use, smooth curves following your centerline are pretty eacy - Atlas track is fairly springy and will form smooth curves very easily, while ME needs to be 'walked' into position. Something that can help are products like the Ribbonrail gauges, avaiilable in varios radii. They fit between the rails of the flex track and hold a set curve. If you have easy access to look down from above, standing on a ladder ot something, you might not need them, as you can generally eyeball the curve and make sure you are following your centerlien with no bulges in or out. Likewise for straight areas, if you can get down at the edge and sight along the straight it's pretty obvious to see if you have the track straight or if it wiggles back and forth.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Hi everyone, This is going to be my first time laying flextrack (H.O. ) and I was wondering what method is the best and most used for making radius bends whether it is 18" ,22" , 24" , or better. the only thing I could think of was a piece of string attached to a pencil and nail and measure the string half of whatever the desired measurement and mark the radius that way? I wanted to see if there was a better method out there, jig, or tool before I start.Youre help will be greatly appreciated. Thanks guys !
ROB