From: romeo@niagara.Tymnet.COM (Michael Stimac)
Newsgroups: rec.railroad
Subject: Re: high-speed turnouts (points)
Date: 27 Jan 93 05:15:37 GMT
Organization: BT North America (Tymnet)

In article <1993Jan25.194010.13882@Princeton.EDU> jsm@phoenix.Princeton.EDU (John Scott McCauley Jr.) writes:
>I have a few questions about turnouts used for high-speed passenger service:

I have a Track Cyc, I'll take a stab at some of these -

>1) What are typical frog numbers? Anything above #20? Do these big switches
>   require multiple switch machines?

AREA have standards for the following switch #s: 5,6,7,8,9,10,
11,12, 14, 15, 16, 18, 20.

Some individual railroads use other #s, including both sharper than
#5, and flatter than #20. The Cyc cites #24 and #30 frogs in experimental
use. (it doesn't say where)

Ordinary turnouts do not require more than one motor, no matter the
frog angle. (slip switches, lap switches, movable point crossings
and other special track do require more than one motor)

>2) What are typical speed restrictions? Does a train have to slow down 
>   through a #8 or a #10 switch if the switch is set to the straight route
>   rather than diverging route? Are there different limits for facing-
>   point switches (train reaches points before frog) and trailing-point 
>   switches (train reaches frog before points)?

There are separate speed recommendations for straight points and
curved points (curved turnouts are *not* what is being refered to)

Also, equilateral (wye) turnouts allow faster speed than lateral
turnouts. The table's long, here are a few typical values:

frog #	straight point/lateral	straight point/equilateral
------	----------------------	--------------------------
 5	12 mph			16 mph
 6	13			19
 8	19			27
 10	20			28
 14	27			38
 20	36			52

 Here are figures for curved points

 frog #	curved point/lateral	curved point/equilateral
 ------	--------------------	------------------------
 5	12			17
 6	15			21
 8	20			28
 10	25			35
 14	34			49
 20	50			70

There is no mention of a difference for the direction of motion over
the switch in these numbers. The speed recommendations are derived
from keeping lateral acceleration low and have little to do with
worrying about the points.
 
The speed recommendations are with reference to the diverging route
(both routes in case of equilateral turnout); and in theory no
speed reduction is needed when taking the straight route. This
is reflected in the use of speed signaling for most interlockings.

>3) Does a 'swing-nose' turnout help? I think a swing-nose switch has an
>   active frog. Any other types of switches out there?

The Cyc doesn't seem to use the term "swing nose"; I'm not familiar
with the term. Some switches have "spring rail frogs" (often
called spring switches). Another type of special frog is the
self-guarding frog, which obviates the need for separate guard rails
next to the stock rails.

>4) Are wye switches frequently used to save space where large frog numbers
>   are used?

Large frog numbers imply high speed which in turn implies lots of
longitudinal space. The shortening of a wye switch is unlikely
to be a consideration. Rather, the equilateral turnout will be used
due to the great improvement in safe speed (see dramatic 20 mph
difference in last line in above charts)

Hope this helps,

Michael Stimac
-- 
Michael Stimac
(415) 355-8889
romeo@tymnet.com
These opinions are not necessarily anyone's but my own.
From: bill@nsmdserv.CND.HP.COM (Bill Kepner)
Date: Tue, 26 Jan 1993 18:03:52 GMT
Subject: Re: Unrebuilt SP SD45's
Organization: HP Network and System Management Division