question about numbers...4-4-0

[nimrod]

I have noticed numbers associated with the steam locomotives such as 4-4-0, 4-6-0..etc. Can anyone shed some light on these numbers for me?

[jonathan]

Nimrod,

The numbers, when identifying steam locomotives, refers to wheel arrangements.  For example,

a 4-4-0 means there are four leading non-driving wheels (4-), or the pilot truck in the front of the locomotive.  The second number (-4-) refers to the driving wheels; there are 4 wheels that apply force to the rails to propel the engine forward.  The last number (-0) means there are no trailing wheels behind the driving wheels.

This is a 4-4-0:


This is a 2-8-0:


Make sense?

Hope that helps.

Regards,

Jonathan

[Joe Satnik]

http://en.wikipedia.org/wiki/Whyte_notation

[nimrod]

Yes, makes sense now, thanks for the replies

[nimrod]

OK, now I seen a locomotive with 4 numbers, 2-6-6-2. Why is there 4 numbers? Thanks

[ABC]

It is an articulated locomotive with two sets of drivers. 2 leading wheels, 6 driving wheels, followed by 6 more driving wheels, and 2 trailing wheels.