Couplers and bogies on articulated cars

[Overmod]

Erik_Mag

With the trucks on a standard lightweight passenger car easily account for a third of the weight, articulation was a reasonable way of shaving weight off of a train.

There were other reasons, principally that the guiding of one car by another was much better at high speed (and still is).  One other interesting reason was that there need be no bulkhead or vestibule restricting the inside passage between cars, something now being re-introduced (or at least promised) on the New York subway system.  You might find a carpeted 'turntable' similar to the joint in a jetway over the truck, and rotating with it, to accommodate curves without tripping the passengers...

[Erik_Mag]

tree68

They are hinged on the truck (bogie).  Hence, articulated.  The principle was used occasionally on passenger cars, notably diner/kitchen sets.

Articulated passenger cars were very common in the first couple of years in the "streamline" era, with many trains being a single articulated unit. By the beginning of WW2, the diner/kitchen sets (notably the Espee's 3 unit set) were about the only articulated cars being produced.

With the trucks on a standard lightweight passenger car easily account for a third of the weight, articulation was a reasonable way of shaving weight off of a train. Back in the days when the largest engines (referring to prime movers not locomotives) were 1200HP, cutting weight by 15% was important.

[Overmod]

The wells are hinged (IIRC with a ball-and-socket type joint on extensions of the well sections, to allow for a little 'twist' when running) and the joint bears on the truck bolster, with a pin on which the truck pivots.  I don't believe there is any draft gear at all between wells.  Extensions provide side bearing.  A traditional name for this type of articulation is 'Jacobs bogie'

Much of the construction of the three-piece truck between articulated units is common in design to an 'ordinary' one.  Naturally the spring nest has more 'stiffness' over the range of travel to accommodate the higher load on the truck when the wells are fully 'stacked', and most importantly the wheels are larger in diameter to handle the greater weight.  This is very clear once you know what to look for.

Back in the 'good old days' it was not uncommon to see some of the articulated trucks braced against lozenging -- this involved little clevises welded onto the bottom of the sideframes, with a generally X-shaped structure pinned to them so the sideframes could move in suspension, but could not take up a 'parallelogram' resonance if the truck developed play at the bolster ends.  These were quickly removed in practice, but at least until recently you could still spot the occasional sideframe with the clevises.

[tree68]

Perry Babin

Are the car bodies connected to each other or are they connected to (hinged on) the bogie?

They are hinged on the truck (bogie).  Hence, articulated.  The principle was used occasionally on passenger cars, notably diner/kitchen sets.

It's possible to determine whether it's a single car, a three well, or a five well car just by listening to the train passing over a joint/switch/whatever.

You can kind of see it here:  

 

 

[Perry Babin]

I haven't been able to find information on the coupling and trucks/bogies on articulated well and spine cars. This is for the points where there are no standard knuckle couplers.

Are the bogies special?

Are the car bodies connected to each other or are they connected to (hinged on) the bogie?