Articulation - how is load transferred between coaches?

[Martello]

The introduction of the Greater Anglia 745 / 755s prompted me to do some research into how the load is transferred between articulated coaches. I eventually found an excellent picture of the coupling between a pair of coaches, see below
https://bahnbilder.ch/picture/9850
This shows that (a) the traction load is transferred through the coupling, not the bogie (b) there is a single pivot point shared by two adjacent coaches, which has implications for the kinematic envelope. On a 755, the bogies at the ends of the train are the only powered ones, so in effect, half the power is being used to push the train from the back end, which reduces the load on the coupling. As a modeller, I have always assumed that articulated coaches share a bogie with two pivots, one for each coach (that's how models work), but that would mean the force pulling the train along has to be transferred through the bogie via the two pivots, unless there is a coupling as well.
Can anyone tell me how the NNR's QuadArts are articulated? Also, how are the original EuroStars articulated?

 

[rebmcr]

As a modeller, I have always assumed that articulated coaches share a bogie with two pivots, one for each coach (that's how models work)

Same with LEGO models, though in the only articulated one I'm aware of, the 'Horizon Express' (a first-generation TGV).

 

[delticdave]

The introduction of the Greater Anglia 745 / 755s prompted me to do some research into how the load is transferred between articulated coaches. I eventually found an excellent picture of the coupling between a pair of coaches, see below
https://bahnbilder.ch/picture/9850
This shows that (a) the traction load is transferred through the coupling, not the bogie (b) there is a single pivot point shared by two adjacent coaches, which has implications for the kinematic envelope. On a 755, the bogies at the ends of the train are the only powered ones, so in effect, half the power is being used to push the train from the back end, which reduces the load on the coupling. As a modeller, I have always assumed that articulated coaches share a bogie with two pivots, one for each coach (that's how models work), but that would mean the force pulling the train along has to be transferred through the bogie via the two pivots, unless there is a coupling as well.
Can anyone tell me how the NNR's QuadArts are articulated? Also, how are the original EuroStars articulated?

I've seen drawings for Gresley's articulated bogies, in a Model Train magazine. From memory the bogie had a dome-shaped casting on the centre of it's frame, one coach had cup & dome shaped casting that sat on the bogie, the adjacent coach had a cup casting that sat on the 1st coach's dome. Obviously the castings were designed so that the coaches were all the same height above the rails. There might have been a long vertical bolt through the castings to keep the train together after a derailment........

 

[delticdave]

Same with LEGO models, though in the only articulated one I'm aware of, the 'Horizon Express' (a first-generation TGV).

I have a few HO scale articulated trams & the bodies all share a central pivot on the articulated bogie. (Roco, Lima, Halling & Mehano products.) I've tried the two pivot concept, on my own model coaches, many decades ago, & derailments were common-place.

 

[Domh245]

I imagine the eurostars would be articulated in much the same way as TGVs, for which this page may be of interest, and particularly this diagram (the changes referred to in the diagram as explained in the text are to do with the dampers and the secondary suspension spring being replaced by a pneumatic one)

 

[Martello]

Thanks, delticdave, I hadn't come across the cup castings. My father built several 0 gauge articulated coaches, and some run well, others are temperamental!
Thanks Domh245, I agree, the Eurostars are likely to be similar to theTGVs of that period. I can't actually tell from the diagram but it seems likely that there is a link between the coach bodies to take the strain, with only the weight being directed though the pivot to the bogie.

I recently wrote an article for our local transport society journal about the 755s and predecessor articulated trains and was interested to discover that the LMS 3-car DMU of 1938 had a somewhat different system as the pivot points seem to have been carried on extensions of the bogies, to place the pivots under the coach bodies to improve the kinematic envelope. One account suggests that this didn't actually improve the ride quality and it does appear to be quite a bit different from the Stadler design (80 years later, of course).

 

[Martello]

Same with LEGO models, though in the only articulated one I'm aware of, the 'Horizon Express' (a first-generation TGV).

Thanks.