Latest update: 2 November 2015
General Design Philosophy:
A locomotive usually picks up power from the track via the wheels and a set of pick-up shoes. Inside the motorblock, wheel contacts or carbon brushes pick up power directly from the axle(s) or wheel(s). This power is fed to the motor, which in return will power the geared axles.
The numbered of powered axles depends on the type of locomotive. In a 0-6-0 steam locomotive, all three axles may pick up track power but only the two outer axles may be powered by the motor.
Motor Block Components:
Every manufacturer has its own approach on how to build a motor block for their motive rolling stock. There’s no ‘right’ way to do it, but some designs are better than others. The list below highlights the different design approaches and components:
An ideal motor would have these characteristics:
- capable of delivering smooth running even at low speeds
- low current draw
PIKO uses 5-pole motors in most of their models, while for instance LGB and Train Line use 7-pole ‘Bühler’ motors. These are considered to be the best in the business, and are known for their smooth running and low current draw.
With or without ball bearings. Ball bearing equipped motors deliver smoother running (especially at lower speeds) and improve pulling power [This statement needs verification!].
The perfect locomotive wheel provides good power pickup from the track, smooth running and a high durability for a lifetime of running. Also, the wheels shouldn’t pick up dirt too easily, so they don’t need cleaning often.
LGB and Train Line use stainless steel wheel treads, while for instance PIKO equips their locomotives with chrome-plated wheels.
Track Power Pickup (Direct):
Pretty much any G scale locomotive features a set of ‘power pick-up shoes’ (pictured below), which slide on top of the rails to provide direct power pick-up to the motor. These pick-up shoes (also called ‘skates’) have springs, to ensure they make contact with the track at all times. Advantages? Reliable power pick-up. Disadvantages? They are ugly, and they don’t pick up power from the track when the loco travels over the plastic frog of a switch. Short locomotives (0-4-0’s for example) may come to a standstill on a switch as a result.
Track Power Pickup (Wheels & Axles):
In addition to the pick- up skates, power is picked up from the wheels as well. The first method is the use of brass power pickup strips (left picture), which are pushed against the axles for reliable pickup. This is used by PIKO for example. Another solution is the use of carbon or metal brushes which push against the inside of the wheels (right picture), which is used by LGB, Train Line and others. The brushes provide reliable pick-up, but create a fair amount of drag, and they may squeek without sufficient lubrication.
Axles can be placed directly into the motorblock housing (left). The use of ball bearings lowers the rolling resistance and minimizes wear (right).