Diesel Wheel Arrangements

[43106]

I think we're all familiar with wheel arrangements for diesels and electric locos - Co-Co meant that there were 3 axles on each bogie, and each axle had its own traction motor. On a B-B, there was 1 motor driving both bogie axles. OK, that's fair enough.

What about Class 31's?

They have the wheel arrangement A1A-A1A, meaning that the front & back axles of each bogie was powered, and the middle axle wasn't. But was there 1 motor driving BOTH the powered axles, or did each axle have its own motor. How do you distinguish one from the other?

 

[truckman060473]

there's 4 motors driving a class 31, but maybe someone in the know can go into detail as to how the A1A A1A arrangement decription is meant to mean it has 4. It is a bit like thinking that a Bo-Bo could also be described as AA - AA

 

[EM2]

If it had a single motor per bogie, it'd still be A1A wouldn't it?
A single axle *has* to have a single motor!

 

[Mvann]

A1A-A1A means that each bogie has 3 wheel sets, of which the middle set is non motored and is there just to spread the axle weight. A 1 just means it's a load bearing axle. The system is based on the French wheel system, e.g a pacific steam loco is a 21C. The 2 and the 1 denoting the non driving axles and the C denoting three driving axles. Hence why channel packet was numbered 21C1 in southern days and the bluebells Q1 is called Charlie 1.

 

[4SRKT]

AFAIK all diesel electrics have each powered axle driven by its own traction motor. Only diesel hydraulics have B-B or C-C wheel arrangements. The o denotes that axles are individually powered rather than coupled.

However, since it must be theoretically possible to have a hydraulic loco with an A1A-A1A wheel arrangement with the two powered axles on each bogie driven by the same torque converter, how would such an arrangement be differentiated from a class 31? Surely to be strictly accurate a 31 should be called Ao1Ao-Ao1Ao.

 

[route:oxford]

What about Class 31's?

They have the wheel arrangement A1A-A1A, meaning that the front & back axles of each bogie was powered, and the middle axle wasn't. But was there 1 motor driving BOTH the powered axles, or did each axle have its own motor. How do you distinguish one from the other?

Would the A1A-A1A arrangement have significantly improved the RA rating of the class 67?

I'm sure I read somewhere that there was an issue with squeezing it all in for a Co-Co arrangement, which is why it is a Bo-Bo. Could well be the same position with space for a A1A-A1A.

 

[6S83]

AFAIK all diesel electrics have each powered axle driven by its own traction motor. Only diesel hydraulics have B-B or C-C wheel arrangements.

The EMD GA-8 has frame mounted motors with the wheels driven through carden shafts, I'm pretty sure they only have one motor per bogie, making them B-Bs. They have some in Argentina which came into their own during the El Nino floods by being able to work through water up to frame height.
The SNCF 72000s are C-Cs with monomotor bogies too, some other French diesels could well be similar.

Hope this helps.

 

[ungreat]

there's 4 motors driving a class 31, but maybe someone in the know can go into detail as to how the A1A A1A arrangement decription is meant to mean it has 4. It is a bit like thinking that a Bo-Bo could also be described as AA - AA

"1" in a diesel wheel arrangement means an unpowered axle.Since the 31 is a six axled loco,the "1" is simply denoting the unpowered axle

A1A A1A translates as "powered axle,unpowered axle,powered axle" etc

BO BO means two powered bogies of 2 axles to each bogie with no unpowered axles

Class 40,44,45 and 46 were 1 CO-CO 1. Leading axle unpowered,then 3 powered axles etc

The old class 28 was a CO-BO

In a nutshell,if there is only one powered axle followed by an unpowered axle,it is given the "A" prefix,two powered axles with no unpowered ones between,BO or B for the old hydraulics(due to both axles being powered by the same final drive from one source),and CO or C for the hydraulics again

 

[train bore]

I think we're all familiar with wheel arrangements for diesels and electric locos - Co-Co meant that there were 3 axles on each bogie, and each axle had its own traction motor. On a B-B, there was 1 motor driving both bogie axles. OK, that's fair enough.

What about Class 31's?

They have the wheel arrangement A1A-A1A, meaning that the front & back axles of each bogie was powered, and the middle axle wasn't. But was there 1 motor driving BOTH the powered axles, or did each axle have its own motor. How do you distinguish one from the other?

Does it have toilets?

 

[At_traction]

The system is based on the French wheel system, e.g a pacific steam loco is a 21C. The 2 and the 1 denoting the non driving axles and the C denoting three driving axles.

Or rather a British version of the original French designation which would have been the "2C1". More logical IMO, but the Brit version is of course decipherable too.

 

[starrymarkb]

Does it have toilets?

Not for passenger use, but then again it doesn't have any seats for passengers (being a locomotive)

Hopefully the stock it pulls would have...

 

[Teaboy1]

Happened upon several BO-BO-BO electric loco's on my recent rambles around Verona-Venice-Bolzano, Italy. Do we have similar wheeled arrangements here in blighty?

 

[starrymarkb]

Yes, The Shuttle Locomotives... Bo-Bo-Bo is generally used where the curves are too sharp for a Co-Co

 

[43106]

"1" in a diesel wheel arrangement means an unpowered axle.Since the 31 is a six axled loco,the "1" is simply denoting the unpowered axle

A1A A1A translates as "powered axle,unpowered axle,powered axle" etc

Correct, but it doesn't tell the full story

BO BO means two powered bogies of 2 axles to each bogie with no unpowered axles

Again, correct, but Bo-Bo actually means that each axle has its own traction motor, whereas B-B had 1 traction motor driving both axles

Class 40,44,45 and 46 were 1 CO-CO 1. Leading axle unpowered,then 3 powered axles etc

The old class 28 was a CO-BO

In a nutshell,if there is only one powered axle followed by an unpowered axle,it is given the "A" prefix,two powered axles with no unpowered ones between,BO or B for the old hydraulics(due to both axles being powered by the same final drive from one source),and CO or C for the hydraulics again

You are missing my point/query, or I haven't made myself clear, so I'll repeat.
In a B-B or C-C arrangement, each bogie has only 1 traction motor driving all the axles, whereas on a Bo-Bo or Co-Co, each & every axle has its own motor.
The query I'm trying to raise is...on the A1A-A1A, is there a motor for each axle, OR is there 1 motor driving both axles? How do you differentiate between both arrangements - is it possible?