Question on ENGINES

[Anonymous]

this might be a dumb question.. But i was wondering what does the 4-8-4 and 0-8-4 and 4-6-4 means when you see them on sites for sale? is there a meaning to each one of those numbers? Thanks Rick

[jrbarney]

Rick,
If I understand your question correctly, what you're asking about is what is known as the Whyte classification system for steam locomotive wheel arrangements. Here's one explanation:
http://www.scsra.org/library/whyte.html
If you enter Whyte classification at Google, you'll find other sites that also explain the system. There are no dumb questions, what is dumb is to not ask them - most of us have learned everything we know by asking questions either out loud or mentally.
Bob
NMRA Life 0543

[cwclark]

in laymen's terms: the first number is the number of small front wheels in front of the drive wheels. the second number is the number of the large steam driven wheels and the third number is the number of the small rear wheels on any given steam engine..if there are any....(if not the number "0" will denote that there are none in either the front or back small wheel sets......diesels on the other hand are usually GP's or SD's (4 wheels per truck (general purpose) or 6 wheels per truck six drive axle) and the numbers refer to the horsepower..ie a GP 35 is a four wheel per truck with a horse power rating of 3500 ponies....steam engines also were measured in traction power while diesels were measured in horsepower......

[BentnoseWillie]

A "GP-5" is a diesel-era modeller picking up a freight car by hand. [:o)]

GP and SD are designations used by one builder only (EMD); the GP series started with the GP7. There is, however, a universal wheel-arrangement system for diesels:

• Sets of powered axles are denoted by the letter A (1 powered axle); B (2 powered axles together); or C (three powered axles trogether)
• Unpowered axles are denoted by the number of them between powered axles.
• These designations are grouped to describe each truck.
• Trucks tied together on a common bolster are grouped together with the number of unpowered axles between them, with a "0" if there are no axles between the coupled trucks.

Most North American diesels fall into three categories under this classification system:

• B-B: 4 axles, all powered. Examples: EMD's GP series and Alco's RS-Series.
C-C: 6 axles, all powered. Examples: EMD's SD Series and Alco's C and RSD series.
• A1A-A1A: Six axles, center axle in each truck unpowered. Examples: EMD's E series and Alco's RSC series.

There was also one lonely C-BoBo locomotive in North America (Seven axles, all powered, one truck with 3 axles and one pair of two-axle trucks on a common bolster) - Burlington Northern briefly operated an SD45 that had been modified with this configuration to test the EMD HT-BB truck.

GE includes the wheel arrangement in the model number: B for 4-axle and C for 6-axle. I don't think they've done any other wheel arrangement under a diesel in North America.

[AltonFan]

Some railroads and diesel locomotive builders used to (maybe still do) classify B-B diesels as 0-4-0+0-4-0.

[nfmisso]

QUOTE: Originally posted by cwclark

the numbers refer to the horsepower..ie a GP 35 is a four wheel per truck with a horse power rating of 3500 ponies....

NOT EMD has had exactly three GP and two SD models where the number cooresponded to the hoursepower: GP15, GP18, GP20, SD18 and SD24.

The GP35 and SD35 were 2500 hp.

Alco Century series, General Electric, Baldwins and Fairbanks Morse have/had horsepower base designations on some models.

Both Diesels and Steam locomotive are rated in both tractive effort (force) and horsepower.

Tractive effort and horsepower are not totally related. For example, the SD40 and GP40 are both rated at 3000 hp, but the SD unit is rated at around 90,000 to 100,000 lbs continuous tractive effort (depending on ballasting) while the GP is rated at around 60,000 to 65,000lbs continuous tractive effort. A steam example is the N&W Y6b 2-8-8-2 and J 4-8-4. Both are 6000 hp steam locomotives. The Y6b could excert 170,000lbs of starting tractive effort. The J 80,000lbs. The Y6b developed peak horsepower around 20 mph. The J around 45 mph. The Y6b could reach 50 mph, the J over 110 mph.

[nfmisso]

QUOTE: Originally posted by BentnoseWillie

There was also one lonely C-BoBo locomotive in North America (Seven axles, all powered, one truck with 3 axles and one pair of two-axle trucks on a common bolster) - Burlington Northern briefly operated an SD45 that had been modified with this configuration to test the EMD HT-BB truck.

It was actually an A1A-BoBo. The center traction motor on the lead truck was removed because the SD45 control system handled only six traction motors.

Both the EMD FL9 and some models of the F-M C-liner had Bo-A1A arrangements.

[Anonymous]

Thanks alot everyone for explaining all of this to me...By what i read i take it that i have two good engines and they are both 4-8-4 engines..thanks again Rick

[BentnoseWillie]

QUOTE: It was actually an A1A-BoBo. The center traction motor on the lead truck was removed because the SD45 control system handled only six traction motors.

Both the EMD FL9 and some models of the F-M C-liner had Bo-A1A arrangements.

Hey, I learned sumpin' today! It's a good day [:)]

Thanks for the extra fill-in, Nigel!

[AltonFan]

The Whyte Classification can also give other clues about an engine's use. A loco with no pilot wheels is not suitable for speeds above 20 mph, and indicates that the engine was likely used as a switcher. A 2-wheel pilot truck indicated an engine capable of freight train speeds (40-60 mph), and a 4-wheel truck, passenger train speeds (60+ mph). A 4-wheel trailing truck indicates modern (1925 or later) steam power, capable of pulling power at speed.

Of course, there are exceptions to the statements given above, and are based on North American practice. (English railroads adopted the pilot truck late; the better track conditions in 19th century England permitted locomotives without pilot trucks to run a very high speeds.)