From: grr@cbmvax.commodore.com (George Robbins)
Newsgroups: rec.railroad
Subject: Re: Push-Pull Service: Which Way do the Locomotives Point?
Date: 23 Jul 92 04:51:19 GMT
Reply-To: grr@cbmvax.commodore.com (George Robbins)
Organization: Commodore, West Chester, PA

In article <1992Jul20.212713.26735@s1.gov> lip@s1.gov (Loren I. Petrich) writes:
> 
> >	It varies.  Here in Boston, ferinstance, the "Green line" (essentially
> >	trolley, ex PCC Cars, has turning loops at each end & the cars are
> >	single ended.  Likewise, if memory serves, Pittsburgh (also ex(?) PCC)
> >	tends towards turning loops.
> 
> 	Well, I do recall that at least one of the Philadelphia
> trolley lines has a loop at the end of its line -- the one that goes
> to Upper Darby. I do know that this "subway-surface line" has its
> other end in a loop around City Hall.

All the Philadelphia "Streetcar" lines including the subway/surface lines
have loops, either at the end terminals or going around the block.

The Suburban trolleys to Media and Sharon Hill, ex. West Chester and Ardmore
are doubled ended and the lines end in stubs.  I'm not sure if there was
ever a loop or wye at the Llanerch (spelled right this time) carbarn or
if there is now any turning facility at 69'th street.
 
> 	More on Philadelphia: it is curious that the Market-Frankford
> subway line has a loop at one end (69th St.) but not at the other
> (Bridge-Pratt). I'm not sure about the Fern Rock end of the Broad
> Street line, but its other end, Oregon-Pattison(?), is loopless. The
> Lindenwold Line and the Norristown Trolley are also loopless.

I'm not sure that all trains use the loop when arriving/leaving 69'th
street, though some do and it is used to get the trains in and out of
the shop/storage area.

I don't think that there's any loop track at Fern Rock, many of the storage/
service tracks just cut off the side of the line (or a parallel auxillary
track) and the trains operate in stub fashion.  The area is not particularly
accessible nor are there real good view points from the street side or
station.


> 	Here in the Bay Area, BART and the Santa Clara light-rail
> systems are both loopless. I know that the SF Muni light-rail line has
> no loop in the downtown area where it runs between Market St. and
> BART, but I'm not sure about the other ends; from my maps, one of the
> lines seems to turn into another near the Balboa Park BART station. Of
> the SF cable cars, all the lines are loopless, but there are
> turntables on the ends of two of them (the Powell-Mason and the
> Powell-Hyde) for turning the cars around. The California St. line has
> no such turntables.

Note that the California Street cars can be turned on the turntable at
the carbarn.

> 	I guess the great facility of railroad locomotives and
> self-propelled passenger cars to go "backward" is not something one
> would expect from experience with flat-road vehicles (cars, buses,
> trucks, etc.). But since the vehicles are either electrically powered
> or have an electric stage (for most diesels), I guess it is easy to
> switch from forward to reverse by reversing some of the electrical
> connections to the motors. I'm not sure why there are not many
> double-ended flat-road vehicles.

Well, double-ended requires two operator stations and sets of controls,
so if there is no difficulty in turning the vehicle, then why bother?
Not to mention problems with steering geometry...  There are of course
double-ended ferries, used where turning is inconvenient or time-
consuming.

-- 
George Robbins - now working for,     uucp:   {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing:   domain: grr@cbmvax.commodore.com
Commodore, Engineering Department     phone:  215-431-9349 (only by moonlite)
Newsgroups: rec.railroad