Tim+ wrote:
Last year we rode a funicular railway with a single overhead wire and a
large bank of resistors on the roof that got very hot when it was
descending. I'm guessing that it was a DC motor/generator setup with the
resistors absorbing the generators output on the way down.

Today we rode a train with two overhead wires but no resistor banks. This
train apparently runs on a three phase supply. Presumably the rails
supplied the third "leg" of the supply but how safe is this with AC?
Wouldn't the rails be dangerously live relative to earth?

There were no warning signs and the track was unprotected so it must be
safe but I don't understand how. Can anyone explain? Also, how did the braking work?

https://en.m.wikipedia.org/wiki/Petit_train_de_la_Rhune

Tim


I think you mean a rack Railway using cogs on a toothed Rail between the
running rails.

Funiculars are rope hauled and purists reckon there must be an up and down
cabin/carwith one counter balancing
the other either by using water filled at the top or a motor to overcome
any weight difference, even so the term as spread to other types but they
all have a rope permanently attached to the vehicle which differentiates
them from cable trams like in San Francisco where they can be released by
a grip mechanism.

As for the 3 phase electrification there are not many examples left of this
style which was a way of using AC
at the beginning of the 20th century when motor technology was in its in
infancy and speed control crudely done by pole changing, it also allowed
for easy regeneration by using the motors as generators and feeding back
into the supply.
Frequencies were low as again motor technology was not advanced enough at
the time for higher.
The biggest user of the system was Italy where the 3600volt 16.7 Hz system
remained in use on a good proportion of the network till the mid 1970s.
Junctions were very complicated as the two overhead wires had to have long
insulated sections over pointwork and to cope with that the locomotives had
a strange look due to the collector arms reaching out or extremities to
cope with crossing the neutral sections.

https://images.app.goo.gl/3BhWnAr9suGyEfvE6

In that photo there is a water supply as used to top up steam locos, except
here it was also used to top up the
electrics as to get additional speed control liquid rheostats were used
,the liquid solution in those got got hot so was cooled by a secondary
water circuit and radiators which had to be topped up at intervals.

At one time the system was almost adopted by the Metropolitan Railway in
London to replace the original steam traction as electrical expertise for
such things existed in Eastern Europe with the Ganz company of Budapest and
not here at that time and their tender had been accepted.
Only the arrival of American finance on other parts of what would become
the London Underground network and the board of trade arbitrating in favour
of the others whose American financier prefered the DC live rail system he
knew from Chicago stopped the contract.

GH