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Co-Co vs Bo-Bo-Bo


rodent279
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Question for the traction engineers amongst the RMWeb community. Why would you choose a Co-Co instead of a Bo-Bo-Bo wheel arrangement for a diesel or electric locomotive, or v.v.? Each type must have it's own advantages & disadvantages.

Please discuss, genuinely interested to know!

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1 hour ago, rodent279 said:

Question for the traction engineers amongst the RMWeb community. Why would you choose a Co-Co instead of a Bo-Bo-Bo wheel arrangement for a diesel or electric locomotive, or v.v.? Each type must have it's own advantages & disadvantages.

Please discuss, genuinely interested to know!

Bo-Bo-Bo can take tighter curves than Co-Co while still offering the same improved adhesion characteristics of six driven axles over two.

 

Co-Co is less complicated to apply to a locomotive as Bo-Bo-Bo requires either an articulated locomotive or the centre bogie to have some degree of 'side-play' or elastic joint to accommodate curves.

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8 hours ago, hexagon789 said:

Bo-Bo-Bo can take tighter curves than Co-Co while still offering the same improved adhesion characteristics of six driven axles over two.

 

Co-Co is less complicated to apply to a locomotive as Bo-Bo-Bo requires either an articulated locomotive or the centre bogie to have some degree of 'side-play' or elastic joint to accommodate curves.

Ah, so tri-Bo's can take tighter curves? That explains why the Eurotunnel shuttle locos are tri-Bo's then, because of the tight curvature in the terminals.

Can a tri-Bo be a high speed machine, like a Co-Co?

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Hi there,

 

I would be interested in this too.   AFAIK the only countries using Bo-Bo-Bo arrangements in any great number are Italy and Japan.   I don't know about Japan, but I suspect the Italians used them because of their many coastal railways with tight curves.

 

The Italian E656 has a max speed quoted as 150km/h.

 

But most high speed train bogies are Bo configuration, or at least two axles not three.

 

cheers

 

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1 hour ago, rodent279 said:

Ah, so tri-Bo's can take tighter curves? That explains why the Eurotunnel shuttle locos are tri-Bo's then, because of the tight curvature in the terminals.

Can a tri-Bo be a high speed machine, like a Co-Co?

Essentially yes, tighter permissible curves. They tend to be more for curvy and hilly routes, for high speed you may as well design a more powerful Bo-Bo or Co-Co as generally higher speed routes are straighter and flatter.

 

1 hour ago, Revolution Ben said:

 

Hi there,

 

I would be interested in this too.   AFAIK the only countries using Bo-Bo-Bo arrangements in any great number are Italy and Japan.   I don't know about Japan, but I suspect the Italians used them because of their many coastal railways with tight curves.

 

The Italian E656 has a max speed quoted as 150km/h.

 

But most high speed train bogies are Bo configuration, or at least two axles not three.

 

cheers

 

New Zealand has a good few Bo-Bo-Bo diesels. There are also Chinese, Russian, Swedish and Swiss "Tri"-Bos but only one or two such types mostly.

 

57 minutes ago, Caley739 said:

The earlier Italian classes seem to be listed as B-B-B rather than Bo-Bo-Bo. I'm unsure of the difference but think it means 3 traction motors v 6 traction motors.

The early Italian six-axle/three bogie machines E625 and E626 are Bo-Bo-Bo.

 

B-B-B would indeed be each bogie having jointly powered axles (the 'o' denotes each axles is individually powered) but as far as I'm aware the Italians did not adopt monomotor bogies, only really the French did to any significant degree.

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You need a bigger loading gauge for a Bo-Bo-Bo design to work, with a Co-Co there is space between the bogies to drop an engine sump or transformer into, otherwise such equipment has to be smaller or crammed in around inter bogie articulation or the extra pivot point.

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1 hour ago, hexagon789 said:

Essentially yes, tighter permissible curves. They tend to be more for curvy and hilly routes, for high speed you may as well design a more powerful Bo-Bo or Co-Co as generally higher speed routes are straighter and flatter.

 

New Zealand has a good few Bo-Bo-Bo diesels. There are also Chinese, Russian, Swedish and Swiss "Tri"-Bos but only one or two such types mostly.

 

The early Italian six-axle/three bogie machines E625 and E626 are Bo-Bo-Bo.

 

B-B-B would indeed be each bogie having jointly powered axles (the 'o' denotes each axles is individually powered) but as far as I'm aware the Italians did not adopt monomotor bogies, only really the French did to any significant degree.

B'B' is the UIC designation, it's the same as Bo-Bo in that it means 2 bogies each with 2 independently powered axles. The French monomotor electric locos, BB 7400's etc, have a single motor driving two axles, hence they are C-C.

The FS E656's actually have 2 motors per axle, but are still Bo-Bo-Bo (or B'B'B), as they are independently powered.

Edited by rodent279
Correction to first para.
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2 hours ago, Revolution Ben said:

 

Hi there,

 

I would be interested in this too.   AFAIK the only countries using Bo-Bo-Bo arrangements in any great number are Italy and Japan.   I don't know about Japan, but I suspect the Italians used them because of their many coastal railways with tight curves.

 

The Italian E656 has a max speed quoted as 150km/h.

 

But most high speed train bogies are Bo configuration, or at least two axles not three.

 

cheers

 

 

Isn't there a Swiss Class Re6/6 , which despite the name actually has a Bo-Bo-Bo configuration . I think they are now class 620 and are with SBB Cargo . Quite a big class I think 

 

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Yes, the Swiss Re6/6 were BoBoBo locomotives and very successful too. Used mainly on freight duties on lines with plenty of curves. 
 

The Rhb also had/has metre gauge BoBoBo locos too. At first sight they look as if they are articulated with the centre bogie linking the two bodyshells, but the two halves of the body only move vertically to cope with gradient changes.

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7 hours ago, ColinK said:

Yes, the Swiss Re6/6 were BoBoBo locomotives and very successful too. Used mainly on freight duties on lines with plenty of curves. 
 

The Rhb also had/has metre gauge BoBoBo locos too. At first sight they look as if they are articulated with the centre bogie linking the two bodyshells, but the two halves of the body only move vertically to cope with gradient changes.

Here you go -

 

1769345884_DSCF0019copy.jpg.3c1d1ef8a4acdda5f711ad9209afdefb.jpg

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10 hours ago, rodent279 said:

Ah, so tri-Bo's can take tighter curves? That explains why the Eurotunnel shuttle locos are tri-Bo's then, because of the tight curvature in the terminals.

Can a tri-Bo be a high speed machine, like a Co-Co?

Exactly that, and as the person who argued the case for them when the Eurotunnel locomotive tenders were being assessed, I had to do all the work that not only showed that they did have a history of high speed use, ie they weren't just for freight locomotives coping with twisty steeply graded track) but that their wheel/rail forces were significantly lower, ie they were more track friendly, particularly on the tight curves of the loop at the Cheriton terminal.

 

 

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4 hours ago, jim.snowdon said:

Exactly that, and as the person who argued the case for them when the Eurotunnel locomotive tenders were being assessed, I had to do all the work that not only showed that they did have a history of high speed use, ie they weren't just for freight locomotives coping with twisty steeply graded track) but that their wheel/rail forces were significantly lower, ie they were more track friendly, particularly on the tight curves of the loop at the Cheriton terminal.

 

 

Thanks for a job well-done, Jim. Out of interest, who were you working for?

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4 hours ago, burgundy said:

The Kiwi version (made in Japan). 

DSC02561.JPG.23bd9375d8a1058421515ef1e8c9e78c.JPG

Best wishes

Eric 

The Japanese Railways, being a 3' 6" gauge system, made something of a speciality of tri-Bo locomotives. With the length, and thus the power, of the traction motors being limited by the reduced space between the wheels, the result is a need for more motors, and wheelsets to carry them. The three bogie arrangement not only behaves better on curves, but avoids the complications of having the bogie pivot right where a traction motor wants to be on a the three-axle bogie. The problem of power limitation would have been particularly acute with DC traction motors as the commutator and armature end windings, along with the width of the drive pinion and gearcase consume a large part of the motor's length without contributing anything to the creation of tractive effort.

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Bo-Bo-Bo is relatively common in Japan and to a lesser extent in New Zealand and Australia on narrow gauge to take tight curves.  A few examples:

 

New Zealand EF class built by Brush Traction with the same thyristor control system trialled in 87101. The Eurotunnel 9 is based on this design.

1024px-KiwiRail_train_from_Feilding_to_H

 

Japan EF60

1024px-JRE-EF60-19.JPG

 

Queensland 3100 class. Queensland's first electric locos of the 1980s were largely copies of contemporary Japanese locos, locally built bodies full of Hitachi systems.

1024px-QR_electric_locos_3102_&_3255_on_

Edited by DavidB-AU
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Beaten to it by David: I was going to mention the Queensland Railways tri-Bo electrics myself. There were a few variations from different manufacturers, some for the coal lines between Blackwater and Gladstone, and some for more general use on the main north-south line. My photos below show members from all three main batches, although there were actually five number series with sort of master and slave versions of the coal locos using their locotrol units, visible behind the middle pair of locos. This was on the Blackwater line.

They were quite ugly locomotives, in my opinion, with almost no style whatsoever. The patchy paint schemes didn't help, possibly emphasising the lack of any sort of coordination in their shapes.

1211390672_QRCentralQldElectricCoalTrain1991-1.jpg.7a3dba9f3b9aad8eca505a55782bfc7c.jpg

1736115623_QRCentralQldElectricCoalTrain1991-2cropped.jpg.ad1e82443973c66ac8aa2583a4c4427d.jpg

And for the record, 11637 is a model of one of the Swiss Re6/6 locos from Lima. This has a central can motor wth flywheels driving the outer bogies only, with the centre bogie being fully floating.

P_20200226_150214_vHDR_On.jpg.069cdaf69053889184dbb8f73dd52cfd.jpg

 

Edited by SRman
typo fixed
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