Some are identified in degrees, some in numbers, and some in diameter. Is there some place, video, book, etc. where I can find out what it all means, and how they are properly used? (Which switch should be use in what situation).
tia
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I'm interested in this as well. Particularly as some of my locomotives require 72 inch curves. Can they negotiate a #4 or #7 switch or do I need 72inch?
Railroad track turnouts* are not really measured by an arch. A switch is what you throw. 
Lionel called them switches to complicate it unnecessarily 
(I called them "switch-tracks" and got some backlash once 
An angle is more prototypical, and that's what the numbers are supposed to correspond with, the angels of deviations from the through track. Normally the angle used is listed too. I never learned them.
Laying track outside of sectional tubular can be an exercise in math and geometry... or a good eye and some flex-track to wing it
*please your webmaster Rich; "turnouts",& M.U., not lash-up, unless your talking command control ops
Yeah, that's why the RRs all employed "turmoutmen" and not "switchmen" . . . .
Oh, wait . . . .
Turnouts it is.
I was going to ask the question turnouts or switches originally but figured I would be better off asking one question at a time.
Worked as a machinist so math and geometry aren't foreign to me, and I bought a lot of flex track.
I'm not sure M.U. would be the proper terminology for the time frame I want to model, but if it makes webmaster Rich happy I will try to remember it. 
I don't care if you call them Bartholomew .
I think the nmra uses "switches" too . That's a good place start for a better guide than I'd be.
..and switchman throw the switches and levers that operate turnouts 
I like this for putting it in perspective .
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I once asked a professional railroader and he said he never heard the term "turnout" but it has been my understanding, and I certainly could be wrong, but the entire assembly is called a turnout and the parts that move are called the switch or the points.
palallin posted:Yeah, that's why the RRs all employed "turmoutmen" and not "switchmen" . . . .
Oh, wait . . . .
In the real railroad world, they are indeed referred to as "switches", because there are NO "electrical switches" involved with changing from one track to another (remember that there is NO electricity in the two steel rails that the trains operate on). However, in model railroading, there are both "turnouts" to be thrown 9so that trains can change tracks) as well as electrical "switches" to be thrown (to control power to the tracks).
Let me try to answer a part of your question not yet addressed. When you see a turnout/switch for sale that is labeled "O72," the seller is identifying an item that diverges from the straight-through portion of the track into a curve that could be substituted for a portion of a plain section of O72 curve track. This is essentially the only difference between a #4 or #6 switch described above and an "O72" or "O31" switch. Which type you use depends more on your choice of equipment and geometric limitations of your layout.
You will quickly learn that the "Oxx" switches use less space in layout design, but may cause operational problems if trying to crossover between two parallel lines of track or if trying to enter a yard area with longer equipment (18-22 inches for cars and 24-36 inches for engines). You also will not find "Oxx" switches in special trackwork like slip switches (single or double).
Chuck
?? at one time "turnout" was suggested to be the proper term . I don't recall it all verbatim, but I'm sure on "turnout". It was my mention of the use of "switch track" by my family that caused it to be pointed out. But, point taken HW; you speak from experience as well. ...I added lever in there
I realize that away from a yard/station, that switches would be manual/mechanical. But what about yards?, towers?. Never electric? Hydraulic? ...Subway/El ?
Using Ross #4 turnouts, I created a half-circle of turnouts (using my track planning software) connecting the diverging path through each turnout. The diameter of the circle measures 117" or O-117, substantially more gradual or wider diameter than O-72. Numbered turnouts diverge from the straight (tangent) at an angle, and the diverging track is straight. Whereas an O-72 turnout is a curve of O-72 (approximately) through the diverging track.
In both cases, there are short straight sections of track ahead of the points. So an O-72 turnout curve may be sharper than O-72 (a bit, depending on the manufacturers design) to compensate (when the turnout is designed to literally "drop-in" to replace a curve).
As others have mentioned, numbered turnouts are superior to O-XX turnouts for cross-overs, as there is no reverse curve created across the joined diverging routes.
Using Ross #6 turnouts to create a semi-circle, resulted in a diameter of 237" (O-237).
[I would love to have Lionel Fastrack numbered turnouts (perhaps a #5) and a curved turnout (perhaps O-96/O-72)]
billyb posted:I'm interested in this as well. Particularly as some of my locomotives require 72 inch curves. Can they negotiate a #4 or #7 switch or do I need 72inch?
Doesn't look like your question has been answered. On numbered switches, the switched path is straight rather than curved (as on an 072 switch).
Your locomotive w/ an 072 requirement should work and look even better on numbered switches. If you use Ross switches, they offer Transition track that is used in conjunction with the switch to return the path to parallel to the adjacent track.
A Ross 204 three way switch mated to a couple of I believe Ross 100 switches. Note that the diverge on the three way, a #4 switch, is more abrupt than the 100 switch, which is probably a #5. Larger the number, the more gradual the transition to diverge.
It's starting to make more sense. Let me see if I have it correctly. Numbered switches diverge from the path in a straight line, where switches identified with a diameter diverge from the path in an arc. Numbered switches are expressed as a ratio, #4 being 4/1, #6 being 6/1, etc.
So what makes a turnout "hi-speed"? I've seen that term used with 7.5 turnouts in advertisements. Is it just that the transition is so gradual that trains can take them at hi speeds without issues?
Thanks everyone for your input
RadCam posted:It's starting to make more sense. Let me see if I have it correctly. Numbered switches diverge from the path in a straight line, where switches identified with a diameter diverge from the path in an arc. Numbered switches are expressed as a ratio, #4 being 4/1, #6 being 6/1, etc.
So what makes a turnout "hi-speed"? I've seen that term used with 7.5 turnouts in advertisements. Is it just that the transition is so gradual that trains can take them at hi speeds without issues?
Yes, just like the real railroad "high speed switches", although in the real world those huge big long switches must have moveable-point frogs.
Thanks everyone for your input
Hot Water: "In the real railroad world, they are indeed referred to as "switches", because there are NO "electrical switches" involved with changing from one track to another (remember that there is NO electricity in the two steel rails that the trains operate on). However, in model railroading, there are both "turnouts" to be thrown 9so that trains can change tracks) as well as electrical "switches" to be thrown (to control power to the tracks)."
Well... on the other hand, low voltage current sent through the rails (1:1 railroads) make possible ABS (Automatic Block Signaling) when trains short the rails and this is detected by the signals.
Also, the points of a turnout or switch-track are frequently operated by electric motors, and these do have switches (limit switches) within them that detect their position.
Alex
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