# What do the locomotive numbers mean?



## AdRockTrains

I see each locomotive has numbers and dashes, like 2-6-6-2, etc.

What do they mean?

Thanks!


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## johnfl68

That is a Whyte Notation.

In your 2-6-6-2 example, is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels, and one pair of trailing wheels.

(2) wheels (six) wheels (six) wheels (2) wheels










You can find out more about the Whyte Notation here:

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

John


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## CTValleyRR

That is known as Whyte Classification, and denotes the wheel arrangement on steam locomotives. Picture a locomotive with it's front facing to your left. The numbers, in order, then represent the number of leading (unpowered), the number of drivers, and the trailing number of unpowered wheels.

In your example, 2 leading wheels, 6 drivers, a second, independent set of 6 drivers, and 2 trailing wheels. A loco with no wheels in that position uses a zero as a placeholder: 4-4-0, or 0-8-0. A T is often used to denote a tank engine (no tender), thus 0-4-0T. Each wheel arrangement is typically associated with a name as well: your 2-6-6-2 was called a Mallet (pronounced like they French, mal-lay or mal-ley); a 2-6-2 was a Prairie, 4-6-2 Pacific, 2-8-2 Mikado (or "Mike" for short), and so on.


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## AdRockTrains

Thanks!


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## MtRR75

This website has lots of good info on the different types of steam locomotives -- probably more than you want to know.

http://www.steamlocomotive.com/


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## Cycleops

On Diesel locos in the U.S. I believe you have either a six or four axle arrangement on one 'truck'. In the UK we call a four axle truck (or bogie as we call them) a Bo, and a six axle truck a Co. So a loco with two four axle trucks is a Bo-Bo and a loco with two six axle trucks is a Co-Co. Otherwise the wheel designations for steam are the same as in the US. Just for a bit of balance.


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## DonR

I was surprised to learn that the famed EMD E series locos came with 6 wheel
trucks, but on some the middle axle was not powered.

Don


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## Fire21

Cycleops said:


> On Diesel locos in the U.S. I believe you have either a six or four axle arrangement on one 'truck'. In the UK we call a four axle truck (or bogie as we call them) a Bo, and a six axle truck a Co. So a loco with two four axle trucks is a Bo-Bo and a loco with two six axle trucks is a Co-Co. Otherwise the wheel designations for steam are the same as in the US. Just for a bit of balance.


I think I understand what you're saying, but I believe we count the axles differently in the US. Here a B-truck has two axles...4 wheels. A C-truck has three axles and six wheels. The Union Pacific DDA40X loco had D-trucks...4 axles and 8 wheels. I know there are some other wheel arrangements on some American locos, but each has their own designation, I think, like the Doodlebug and the Centipede.


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## microbuss

about the Wheel Arrangement on a diesel?
I seen it as 0-6-6-0 or 0-4-4-0 On the builders plate lol


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## Cycleops

microbuss said:


> about the Wheel Arrangement on a diesel?
> I seen it as 0-6-6-0 or 0-4-4-0 On the builders plate lol


Harking back to old steam loco designations perhaps?

Thank you Fire21.


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## DonR

The Doodlebug, the real one and the Bachmann HO model, has only
one 4 wheel powered truck. The rear truck has no motors. I've actually
rode in one of these things on the Missouri Pacific line through my
home town. The Gasoline or Diesel powered generator sits between
the cab and the passenger section.

Don


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