Bachmann Online Forum

For example, I don't understand why a track is called 22" radius instead of in degrees.

Radius of a circle = distance from center of circle to edge = 1/2 of the diameter of the circle. In the case of model train track, measured to the center of the track.

Degrees of circle = measurement of sements = complete circle = 360 degrees, 1/2 circle = 180 degrees, 1/4 circle = 90 degrees

The two have nothing to do with each other.

Model train track is not measured using the civil engineering method of degrees of change in direction - it is measured in radius.

Typical section track that comes with sets is 18" or 22" radius - making 36" or 44" diameter circles respectively. Typically 12 pieces of 18" radius to a circle and 16 22" radius to a circle - making each 18"R piece 30 degrees of the circle and each 22" radius piece 22.5 degrees of the circle.

Most more advanced modelers use flex track and larger curves in the 30" - 40" radius range.

Large/long locomotives and cars cannot negotiate tight curves like 18 and 22 inch radius.

Scaled down from real life, even a 36" radius curve in HO is very tight compared to what real trains run on.

Sheldon

Succinct!  Thank you.

In addition, most people wouldn't understand a turn measured in degrees.  And then I'd complain about degrees instead of the far more logical mils.   :D
Gene

Sheldon
The radius of the curves used  on the layout has more to do with available space than it has to do with the sophistication of the modeler.Some of us even use EZ track and don't even count the rivets.

grumpy,

I did use the adjective "most" and I will admit I was raised to be an over acheaver who does not "settle" for mediocrity. So I made enough money to build a big enough garage to have a large enough room above it to have an 800 square foot layout with 36" plus radius curves.

But looking at many others I know in this hobby, my layout, its size and its cost is rather modest. Its all a matter of perspective.

Keep this in mind, scaled down to HO, the minimum radius of an EMD F7 would be 34". Our curves tend to border on rediculous - I do what I can to build model trains, not toy trains.

Sheldon

Maybe getting overly technical, but the measurement of degrees of curvature is as follows:  It is the number of degrees formed by a 100 foot long chord touching at either end of a circle.  The formula for computing radius from degrees is:  5730 divided by degrees of curve = radius in feet.  Most main line steam locos were limited to about a 15 degree curve, at low speeds.  This equates to a radius of 382 feet.  In HO, this would be about 52" radius. 

 ???but, I've still got the question:
                           How do you know if the piece of track you are holding in your hand is 22" radius, or 15"? Perhaps the section that you need filled requires a 12"!!
                                                                             THANX!!
                                           :-\                                     Ernie

If you don't have the package it came in, try comparing it to a known piece.  If you know you have an 18" and the unknown is not as curved, you have a 22", if more curved, it's a 15".  If you need a 12" curve in HO you need to fall back and regroup, or take up street cars.
Gene

Gene;
Circular Mils is not always the better way to express angle.

In my trade, we use degrees.  For example, three-phase power is measured one phase as 120 degrees out of phase in relation to the other two; thus the three legs will geometrically equal 360 degrees, or one revolution.

Circular mils is used in determining the area of a conductor, such as 200MCM would be 200,000 circular mils.  this aspect is essential component in determining a conductors rated ampacity.

I had always thought that somewhere in turnout computation that degrees was a computing component. 

Something that puzzles me, that maybe you do know.  In the movie, "The Enemy Below", the graphic expression on the u-boat's sonar screen puzzled me.  Every scope I have ever seen, it was expressed as a circle, with the respective boat as the centre, and everything radiating outward from it.  How was that German equipment set up?

Rich

Rich,
I have not seen, or do not remember the movie.  Hollywood can mess up the military something fierce.   All my real use of mils was in laying and firing artillery, and for that the mil is very useful.   Using mils for electricity is beyond me. 
Gene

The radar scope on the U-boat in "The Enemy Below" was an accurate rendition of a German (I forget exactly what they called it !) scope.  If I remember correctly, the early British radar units, circa Battle of Britain time frame,  had a similar display.  Basically, if you took a round scope screen and cut it from the center to the top (although some may have been from bottom to center) , and then 'unwrapped it' counterclockwise to where it then ran straight out to the right, you would have the linear scope display.  You could adjust the range setting and the blip showed intensity and direction if I remember right.  All the old sets took a whole lot more skill to read them than (most of) todays computer readouts.
It's all in what you get used to using.  I had an early Loran with no graphical display, but I got so used to looking at latitude and longitude numbers and course tracks that I could look at the numbers and my brain did the math and I knew exactly which way to go to get somewhere.  A couple of friends had the graphical display style units on their boats and they were totally lost with my stuff.
Thaks for the reminder.  "The Enemy Below" is one of my favorite flicks.  One of Mitchum's best efforts.  Up there with "Thunder Road" for entertainment value. ;D
Oh Gene, once upon a time a Va. Nat'l Guard battery, newly converted from a Nike missle battery to artillery, dropped a WP round in a motor pool because of the military's liking for zero to 3200 mils twice, rather than zero to 6400 mils.  It was not my battery, because at the exact same time I was arguing about the basic geometry of the situation with two lieutenants.  I believed some people learned something about turning people loose with artillery, live rounds, and a bunch of instruction books that day.  Just lucky they were 'only' 105s instead of the 155s they went to two months later.

Oh yah.... Thunder was his engine and white lightin' was his load. 8)

I haven't played with HO sectional track for a long time, now, but aren't most of them marked somewhere with their radius?  I know the old Atlas sectional track had it cast into the bottoms of the ties. 

Quote from: ebtnut on January 10, 2008, 11:11:32 AM
I haven't played with HO sectional track for a long time, now, but aren't most of them marked somewhere with their radius?  I know the old Atlas sectional track had it cast into the bottoms of the ties. 

I haven't had occasion to buy any Atlas for quite a few years now. I can't seem to locate the radius designation on the bottom of the my sections of EZ-track.

Virginian,  I think I know the battalion.  Laid 3200 out.  Did you know Richard Dechert?  Dead Eye Dick?  If you do, drop me an e-mail. 
Gene

BACK TO THE TOPIC, what you can do is measure the length of the area you need to fit. So if you have to fit half of a complete loop in an area that is only 30 inches wide, then divide by two, which = 15 inches. Thus, you would need a 15'' radius curve.

to figure out what you're holding, find other peices that are exactly the same as the one you have and make at least one half of a circle.  Measure the diameter (from one end of the track to the other) and then divide by two again, and that's what radius of that particular section of track.

I hope I could be of any assistance to you.

Hi all,
Bottom of E-Z track. 

And you can do a patent search on Google!

http://www.google.com/patents?id=KfoaAAAAEBAJ&printsec=abstract&zoom=4&dq=4953785#PPP1,M1 (http://www.google.com/patents?id=KfoaAAAAEBAJ&printsec=abstract&zoom=4&dq=4953785#PPP1,M1)

Gene;
As I said, circular mils are used to measure the cross-section of a conductor.  Each conductor has a circular mil rating, and that is how it is rated for ampacity.

Example:  generally speaking, 500MCM Copper, would be rated for about 400 amps.

Hollywood does have it's BS papers, I'll agree; however, that sonar (echo plotting  the Germans used) was the genuine article.  I just couldn't figure it out.  OK, just about time for "Numbers".  Adieu...
Rich

I got a bad idea! clean the kitchen floor. Take a nail, pound it in the middle someplace, tie a string to it, measure the string, at the lengths you are wondering about, tie on a black non washable magic marker, draw an arc of each radius you want to hold those pieces to. Or, if you are laying out flex track, do it outside, draw the arcs on pieces of stiff cardboard, has to be big, like the side of a big ol' box, cut a good quarter round- or 90 degree chunk. Keep both pieces, to manuever in tight corners, draw the lines for your track radiuses or rad-e-i huh? OR trim the cardboard another half the width of the track and use it to butt up against when you are laying track down.....I guess this is called a template?  and whatever anyone says about the kitchen floor, you didn't hear it from me ...btw, I always heard of degrees in a curve, someone explained it to me once, I forgot, then it was all detailed again for the wold to learn...I feel I am in the company of geniuses..... steam geniuses? keep up the good work gentlemen, stay healthy!!! the world needs your brains......

What I did to get my radius, I took a yard stick, drilled a hole on the 1 inch mark. Make the hole big enough to put a nail in. This will be your axis. Now, take your radius (say, 22") and add an inch to it. Now, it's 23". So, drill another hole at the 23" mark. Because you drilled a hole at the one, it became the 0 point. which means the 23" is still a 22". So, now you've got a hole at the 1 and the 23, your nail is in the 1, so put a pencil in the 23. Hold the nail and drag the pencil forward in the yard stick to get an arc. There's you're radius guide line.

Sounds complex, but it's a lot easier than it sounds...if you want to explain it better, tell me.

Train Brain,
That is a very good solution which works well on a platform layout - that is one built on a flat 4x8 or 5x9 or something like that.  It will not work on a open grid layout by and large.   However, one can achieve the same thing by using the drilled out yardstick to mark out a pattern on a piece of plywood or similar material and then cutting out the pattern to use as a boiler plate.  Just remember that track radius is measured to the center of the track, not to the inner or outer rail.
Gene