3-Rail cars vs 2-rail cars. Couplers and stuff. Whaa?

Two-rail couplers are smaller than the three-rail equivalents:

The orange tankcar is a three-rail car and has the larger coupler. And, yes, the two can mate under some circumstances.

Typically weaver cars have a check box on the side of the box indicating if the item is 2 rail or 3 rail.  These are very easy to convert from one to the other if you have spare wheel sets and couplers.  All my 2r freight cars are weaver conversions from 3r

@Mannyrock posted:

Do swinging coupler arms as opposed to fixed coupler arms (being an integral part of the truck) have any relationship to any of this?

Thanks,

Mannyrock

Yes, they do. The trucks with articulated coupler arms/shafts will be more tolerant of curves and irregularities. These cars will track better, especially with relation to the cars coupled to them. Not that the fixed arms are bad, but they are less forgiving in close-to-tolerances situations. Most of time there will be no difference in performance.

As always, the larger the curves, the fewer the problems, and the better your trains will look.

(The Perfect Railroad has no curves, no grades and no switches, you know....)

2 rail wheels are electrically insulated from side to side, 3 rail are not. 2 rail coup[ers are mounted to the body of the car, 3 rail are mounted to the trucks. 2 rail couplers are mounted (or should be)  at a specific height determined by a coupler height gauge. The well known coupler touted by the three rail scalers is not prototypical.

ECI

@PRRMP54 posted:

Two-rail couplers are smaller than the three-rail equivalents:

The orange tankcar is a three-rail car and has the larger coupler. And, yes, the two can mate under some circumstances.

in a pinch, were you want to run both together, you can  make a conversion car , with a scale coupler on one end and lobster claw on the other.  Before the term 3 rail scale was used , it was called Hi rail, and older scale cars could be had with oversized flanges, to run with the lionel stuff