Turntable Power

[shayfan84325]

When we build a model turntable we typically power it by turning the center shaft.  My guess is that prototypes power the wheels that ride on the ring rail.  Is that correct?  I know there were/are turntables that are powered by humans pushing poles, but most turntables I've seen in my half-century are powered by some form of mechanism.  Are they electically powered?  If they are, how does the electricity get to the motor(s) in the bridge?  I don't recall having seen wires running to the bridge, but I was never really looking for them.  Do they use internal combustion engines?  In some ways that makes the most sense, but I'm guessing that's not it.

Finally, on electric railroads do the turntables have overhead wires?  If so, how are they energized (connected to a power source)?

One more:  What is the name of the wheels that ride on the ring rail?

[tomikawaTT]

Prototype turntables are either electrically powered or air powered.  The electrical power is delivered to a rotary connector on a harp frame directly above the center of rotation.  Air power is provided by connecting a standard 'glad hand' hose connection to the brake hose and opening the angle **** (standard RR synonym for 'valve' which the technologically challenged profanity checker doesn't like.)

Can't say about a turntable for catenary motors - which are usually double-ended in any event.  (I can only think of one single-ended motor, JNR EF51 class IIRC, but others will doubtless know of others,)  I did see a transfer table with single wire on the Fukuoka streetcar system half a century ago.  The table had a goal post support structure on each end, and a slider that ran along a fixed feed wire perpendicular to the rails above the level of the normal wires.  I suspect the same electrical feed powered both the overhead and the transfer table motors.

The wheels that ride the ring rail are called carrier wheels.  I have seen them with no flange, with a single flange and with dual flanges.  Since they are fixed to the turntable, flanges aren't really necessary.  Usually, only one is powered.  If the TT is center-bearing, the heavier end of the locomotive has to be on the powered end to insure traction, since the carrier wheels at the opposite end frequently lift completely off the rails.  This is why you will sometimes see a turntable rotate 180 degrees before accepting a load.

The 19th century turntable at Jamestown, CA, is still 'people powered.'  So is the recently-constructed replica TT at Folsom, CA.

Chuck (modeling Central Japan in September, 1964 - with turntables and catenary motors)

[shayfan84325]

Chuck,

That is terrific information.  You filled in a bunch of gaps in my knowledge.  It never occurred to me that the fact that electric locos are double ended means a turntable is really not needed .

Thanks a ton!

[tomikawaTT]

Aw, shucks, Phil...  Glad I could help.

Unlike most freight motors, there are single-ended streetcars.  Since they can literally turn street corners, they are usually turned either on loops or on wyes.  Sometimes the loop runs around a city block, sometimes (as on the Shaker Heights route in Cleveland) it occupies a balloon-shaped piece of right-of-way.

OTOH, the single-ended cable cars of the San Francisco Muni are turned on turntables.  The cars coast onto the turntable, are turned manually, then pick up the cable under the turntable and depart.  There are four turntables on the system, including one inside the carbarn.

Chuck (modeling Central Japan in September, 1964)

[marknewton]

Further to Chuck's comments, - and just to show there really is a prototype for everything - there are some turntables in Europe that have overhead wiring. Avignon in France is one example.

http://www.pbase.com/raphael_e/image/55541821

As Chuck stated, powered t/ts would be run on electricity or air, but Fairbanks-Morse did advertise gasoline-powered tractors for turntables. I don't know how common they were, having only ever seen one in my travels. And while power arches were most commonly used on North American electric turntables, an alternate method of transmitting the electrical power was by slip rings on the centre bearing pedestal, just like on a model railway. That arrangement was very common elsewhere in the world - although not in Japan, as far as I know.

All the best,

Mark.

[shayfan84325]

Mark,

Cool picture.

Thanks,

[jrbernier]

  To add on to the electric trolley aspect:

• The FDD&S had trolley wires on the turntable.
• The Milwaukee Road turntable at Deer Lodge did not have wire over the turntable or the roundhouse tracks.  The Milwaukee Road used an old FM C-Liner truck with an 'extension cord' to move the massive 'Little Joe' electrics on the turntable.  The 'Little Joe' engines had dual cabs, but were operated single ended(they had electrical switch gear/steam generators in the other cab.

  Many of the 'air powered' turntables really did not have a pneumatic motors, but a piston with an arm that 'walked' the turntable around(very slow).

Jim

[marknewton]

G'day Jim,

Funny you should mention air-driven "kickers" - I saw a turntable fitted with one while I was on holidays. The crew I talked to reckoned the thing was a pain in the bum. They preferred to balance the loco and turn it by hand!

Cheers,

Mark.