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Why do shunters have coupling rods?
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Yes, that was my assumption…
Peter Sarf
Established Member
I think most shunters hark back to the steam era where most/all motive power had coupling rods (and one motor) for several axles so would be odd otherwise.
Of course the newest shunter on BR the class 18 has two bogies and no coupling rods.
Indigo Soup
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Also because the shunters in use in the UK were a pretty early design, and at that time coupling rods were what locomotive designers knew and understood.
Big Jumby 74
Established Member
Except Sentinal of Shrewsbury, who produced a mix of rod driven and chain driven diesels. Most of their 6 wheel locos were rod driven, but a good proportion of their 4 wheel locos were chain driven, so no rods. After the amalgamation with Rolls Royce one of the last designs was the Steelman 6 wheel loco, another rod less design.
Peter Sarf
Established Member
This reminds me there is another connecting rod arrangement I have seen. Two axles with wheels with a third "axle"/shaft with no wheels but all three connected by the connecting rods. The wheel-less "axle"/shaft has counterweights on it and is presumably the "axle"/shaft connected to the engine/traction-motor.Countershaft drive shunter.
(From memory) The drive from the gearbox drops to a longitudinal shaft and the axles are geared off that like a heavy truck.www.facebook.com
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Countershaft drive shunter.
(From memory) The drive from the gearbox drops to a longitudinal shaft and the axles are geared off that like a heavy truck.
Jack shaft.
norbitonflyer
Established Member
Most Diesel mechanical shunters had a jack-shaft, connected to the gearbox, which drove the wheels through coupling rods. Classes 01, and 03 to 06 all had this arrangement.
The use of a jackshaft means that the size of the final drive gearbox is not constrained by the size of the wheels, and also reduces the unsprung weight, as there is some freedom of movement in the connecting rod (the connection between the jackshaft and the driving wheels) Here's a Class 06
Early diesel-electrics also used jackshafts - in this case between the middle and rear axles, and driving the front one
In more recent designs (starting with the 1946-vintage LMS and SR designs which became Classes 11 and 12) traction motors had became small enough to mount directly on the axles, removing the need for a jackshaft (and thus reducing the overall length of the locomotive) but unless each axle had its own traction motor the power was still distributed by coupling rods. The standard shunters - Classes 08-12 - have two traction motors but three axles.
Some Diesel hydraulics have a single transmission which drives one axle and the other is coupled to it, so no jackshaft - as seen on this Class 02.
But Class 14 uses a jackshaft (under the cab, behind the steps)
Or they may have both axles driven direct from the transmission (which is also the arrangment used in larger DH locomotives like the Warships)
The use of a jackshaft means that the size of the final drive gearbox is not constrained by the size of the wheels, and also reduces the unsprung weight, as there is some freedom of movement in the connecting rod (the connection between the jackshaft and the driving wheels) Here's a Class 06
Early diesel-electrics also used jackshafts - in this case between the middle and rear axles, and driving the front one
In more recent designs (starting with the 1946-vintage LMS and SR designs which became Classes 11 and 12) traction motors had became small enough to mount directly on the axles, removing the need for a jackshaft (and thus reducing the overall length of the locomotive) but unless each axle had its own traction motor the power was still distributed by coupling rods. The standard shunters - Classes 08-12 - have two traction motors but three axles.
Some Diesel hydraulics have a single transmission which drives one axle and the other is coupled to it, so no jackshaft - as seen on this Class 02.
But Class 14 uses a jackshaft (under the cab, behind the steps)
Or they may have both axles driven direct from the transmission (which is also the arrangment used in larger DH locomotives like the Warships)
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contrex
Established Member
Very usual in earlier electric locos like this wonderful Swiss beast, and if people have the time or inclination, the Wikipedia page for 'Jackshaft' has plentiful descriptions and pictures of some astonishing locos. Some very intricate linkages were invented, and I really like the Ganz type, as seen on the French PO Belles hongroises.
Jackshaft (locomotive) - Wikipedia
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ac6000cw
Established Member
Very usual in earlier electric locos like this wonderful Swiss beast, and if people have the time or inclination, the Wikipedia page for 'Jackshaft' has plentiful descriptions and pictures of some astonishing locos. Some very intricate linkages were invented, and I really like the Ganz type, as seen on the French PO Belles hongroises.
Jackshaft (locomotive) - Wikipedia
en.wikipedia.org
View attachment 173362
I was lucky enough to see one of those Swiss 'crocodiles' still in normal service on my first visit to Switzerland in 1979 - wonderfully charismatic machines!
The three preserved locos strutting their stuff on the 100th anniversary of the class in 2019 (not my video):
contrex
Established Member
I love the sound that 16 2/3 Hz AC motors make!
Peter Sarf
Established Member
Thanks for that. I knew the Crocodiles existed but I had never seen them in motion. Or even their motion in motion.
I will never be able to look at a class 08 in the same light again
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GRALISTAIR
Established Member
Interesting that a magazine produced by the shunters society ( forget its actual name) is called “Coupling Rods”
Great video. I vaguely recall Dad pointing one out to me in regular service, on a family holiday in the early/mid 70s, but I was very young and it's not a strong visual memory. Unfortunately, it appeared unexpectedly and passed too quickly for him to get a photo. In more recent years I've seen the metre gauge RhB baby crocs in action on several occasions. These combine the fascinating jack shaft and rod drive mechanisms with added cuteness.
Landquart RhB - Krokodil 415
The historic Ge 6/6 I stands in the rain on track 7 in Landquart. In operation since July 2, 1929 and still running. Friday was not a good day for photos. I had just come back from lunch and it was pouring with rain. Switzerland, June 21, 2024.
flic.kr
norbitonflyer
Established Member
On the contrary - shifted cranks could damage the couplng rods. Explained in tghis thread
Class 08 shifted cranks
I have heard about this defect on 08 shunters and wondered what and how this happens? Is there an explanation or better still a picture somewhere of this failure?
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12LDA28C
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Of note is that one of the Class 08s at the Cholsey & Wallingford Railway has operated without its coupling rods for many years. I imagine this makes for an interesting drive with a decent load on a slippery rail.
norbitonflyer
Established Member
Assuming both traction motors are working that makes it an A1A (or, in Whyte notation an 0-2-2-2-0)
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