What does 2-6-6-2 mean?

[Loco-Man]

I'm a newbie and have seen that many locomotives are described using numbers sequences such as 2-6-6-2, for example. I believe it's something about the wheels, but don't know what exactly. Can someone teach me? Thanks.

[Pacific Northern]

Had you tried google

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

For basic questions try google

[ACY]

2 pilot wheels (the first, left most number 2), 2 sets of 6 drive wheels (the two 6's), 2 trailing wheels (the last or right most 2). The first number is always the number of pilot wheels it can be 0, 2, 4, or very rarely 6. The middle numbers are the number of drive wheels, there can be 4, 6, 8, 10, 12, and very rarely 2 and even numbers greater than 12. If there is more than one middle number it means it is an articulated locomotive which means multiple sets of drive wheels. The number of trailing wheels can be 0, 2, 4, 6 or very rarely 8. If there is a T at the end, it designates that it is a tank engine and does not have a tender trailing.

[bobwrgt]

www.steamlocomotive.com
Everything you want to know about steam engines.

Bob

[GN.2-6-8-0]

bachmann makes a very nice 2-6-6-2.

http://youtu.be/m6JZggW4Mac

[ebtnut]

Just to expand things a bit, the Whyte notation system was generally used in North America.  Overseas, especially in Europe, there were two notation systems.  The older system, usually used in connection with steam locos, was to count axles, not wheels.  A 4-6-2 Pacific in the U.S. would be a
2-3-1 in Europe.  In more modern times, they went to a letter system for coupled, driven wheels.  A for one driven axle, B for two coupled, driven axles, C for 3 axles, and so forth.  This is more commonly used with electrics and diesels, although I have seen steam locos referred to with this system.  Our 4-6-2 would thus be a 2-C-1. 

[mhampton]

Why not add another level of complexity?  The letter system is often used with regard to US diesels.  A GP38, for example, has a B-B wheel arrangement (two trucks, both axles on each truck powered).   An SD70 has a C-C arrangement (three powered axles per truck).  One odd one was (is?) the E8 with an A1A-A1A arrangement:  two three-axle trucks with the center axle on each truck unpowered.

[JerryB]

Ya gotta love the internet!

Ask how to turn on a TV, and get a lesson in everything from the theory of electron flow to the creation of the flat panel display microstructure! 

That lesson is then followed by posts like this one with comments from the peanut gallery! 

Happy (Very Well Informed) RRing,

Jerry