snap switch

[arthur0109]

what is the difference between a snap switch and a turnout?  they both seem to accomplish the same thing.  thanks

[richg]

http://tinyurl.com/3mwan3u

Rich

[Jim Banner]

A turnout is the complete appliance consisting of stock rails, closure rails, frog, guard rails and point rails complete with operating mechanism.  A switch is part of a turnout consisting of the point rails (movable rails,) and the operating mechanism.  See the diagram at this link:

http://www.tpub.com/content/armytransportation/TI-850-02/TI-850-020078.htm

Snap Switch is Atlas's name for a particular configuration of turnout.  Bachmann refers to the same turnout configuration as "basic" or "standard."  Both terms refer to a turnout with a 9" straight section and a diverging section with a near constant radius of 18" offset 1-1/2" from the end of the straight section.  Atlas makes their Snap Switch with 20^o of 18" radius which is 2/3 of a standard 30^o, 18" radius sectional track curve.  They supply a 10^o piece of 18" radius, which is 1/3 of a standard curved section, along with every Snap Turnout.  Bachmann E-Z Track turnouts have this extra piece built right in, that is, a basic E-Z track turnout is equal to one 9" straight section plus one 30^o, 18" radius curved section.

Numbered turnouts do not have a constant radius in the diverging route.  The curve through a numbered turnout is "eased," that is, it gets sharper, then less sharp as you move into and out of the diverging route.  And a numbered turnout has no curvature at all past the frog.  This gently eases the locomotive and each car into the curve and back out of it, avoiding derailments.

Snap Switches by comparison, are not eased.  The locomotive and cars are either going straight or going around a curve.  A train is not eased gently into a curve but snapped quickly into it.  Having said that, Snap Switches take up less real estate on a layout and work well as long as (a) you avoid high speeds and (b) you avoid S-curves.  An S-curve is one that turns to the right, then immediately turns to the left (or vise versa) with no intervening straight track.  This is why Snap Switches can cause problem with sidings or crossovers if you do not use a section of straight track in the middle of S-curves.

Have a look at this recent posting which shows some ways of avoiding S-curves while using Snap Switches:

http://www.bachmanntrains.com/home-usa/board/index.php/topic,18041.0.html

Jim

 

[jward]

i have never heard the operating department use the term turnout, but sometimes the engineering department will. turnouts also exist on highways and other roadways as well. my guess is that turnout is primarily a civil engineering term.

by the same token, there is no such thing as a "ground throw" by definition, all mechanisms which throw switches are on the ground. the proper railroaders term is "switchstand" and those are applied to "hand thrown" switches (as opposed to those with switch motors)

as an example of the operating department's use of the term "switch" on csx. when a train is given permission past a stop signal at an interlocking, the dispatcher must inform the train crew whether the switch motor is in "manual" (hand throw) or
"motor " mode. on norfolk southern, crews using hand throws must report the switch lined and locked for it's normal route when they are done using it.

[richg]

Generally Wikipedia has an answer. If I doubt some of the info, I do across check on the Internet. Once in a while, some find an error or two.

http://en.wikipedia.org/wiki/Railroad_switch

Rich