Elementary Electrics for New Railway Modellers

Elementary Electrics for New Railway Modellers.

Smokey Joe

An Introduction to Electricity for Model Trains

This information is aimed at people with little, or no, prior knowledge of electrical theory to help them grasp the basic priciples.

Historically model trains have been powered by:
(a) clockwork.
(b) on-board batteries,
(c) steam.
(d) electricity supplied via the rails;
Which is the most popular method in use.

Model trains have been operating using electricity since the 1920s.
Quite early on, the use of mains voltage was replaced with lower (safer) voltages within a few years. (After a few people had been electrocuted presumably).

Keep Off Live Rails          Does not apply to model electric trains anymore.  Fortunately.
These days, mains voltage electricity is reduced to a safer voltage, usually between 0 and 12 volts.
This is achieved by using either a combined transformer/controller, or a separate transformer and speed controller.

 Hammant and Morgan Clipper
Transformer and Controller Combined

Hornby R8250 and Plugtop Transformer
Separate Transformer and Controller

By varying the voltage, the speed of the train is increased/decreased.
By reversing the polarity (direction) of the current, the the train will change direction

Two rail, three rail, or pantograph ?

Actually, lets disregard pantograph.
Cantenary Apparatus
Cantenary apparatus hanging in the air providing power for the locomotives -
Nothing wrong with it; It has followers but it is not the simplest system.

If you have the patience of Job and the steady hand of a brain surgeon, this could be for you.

The Two Rail System

From 1958 Mecanno (or Hornby Dublo) took the decision to sell the two rail system, and phase out the three rail. (see three rail system, next section).

Two rail is, by far, the most popular method of getting power to the trains.
And it's simple:
Conductive pickups on the locomotives collect the power from one (or several) wheels on either side, and pass the current to the motor.Pickups on a Hornby Loco

You have  two rails, to provide the electricity: one for negative and one for positive.
To change the direction of travel, just reverse the polarity.
This is effortlessly acheived by your controller - either by turning the speed knob in the other direction, or by using a switch on the controller to reverse the current.

You should be careful to not reverse the direction while the train is still moving , there is a small risk of causing damage to the locomotive.
Certainly it is not a good way to treat a motor.
This is why the reversable speed knob has many supporters.

The volts vary from zero to 12v but in actuality that 12 volts can be several volts higher.
Some lower price controllers struggle to put out even12 volts when driving a heavier engine.

You may like to think about Amps.
A small model locomotive needs about 250 mA (a quarter of an amp).
Larger heavier engines pulling many wagons will need more but very rarely need a full amp.

You cannot do any serious damage with 12v
(unless you get very creative).

Hornby Dublo Three Rail.

Hornby Dublo Three Rail
Launched in 1938. When Hornby was part of Mecanno, and no longer manufactured, but there are many layouts still in use and used track is readily available.

On the three-rail system the left and right rail are connected (common) and the return electric current flows through the centre/middle rail.
The locomotives have a 'skate' which conducts electricity back to the centre rail.

Hornby Dublo 3-rail centre pick up                                                     Centre rail pickup

Three-rail layouts may not look 'realistic' by todays standards, but (to me anyway) they have a certain charm.
They also have many enthusiastic followers.

If you operate a three rail system you will never be able to run modern two rail working locomotives on the track. Unless they have been converted.

Pre-war Hornby and Lionel 0-gauge electric trains use this system.
A similar third-rail system was developed by Marklin for its H0 models before World War 2 and emulated (in principle) by Hornby when they released their Dublo system.

Marklin later improved the appearance of their tracks by replacing the third rail with “studs” which were located between the main rails, appearing every 5mm or so. Hornby continued to use a third rail until they introduced a more modern 2-rail system in 1964.

A bit about Scales

Z scale – 1:1220.  Ridiculously Small
N scale – 1:160.    Very Fiddly
TT scale - 1:120    You could ask the question "WHY BOTHER?" Neither here nor there
HO scale – 1:87.   You would be hard pushed to spot the difference from OO
OO scale - 1:76     The most popular size (in the UK anyway) Highly managable.
S scale – 1:64.
O Gauge - 1:43   Nice and big, but you need plenty of space.

A guide to British scales