Re: SWING-MOTION TRUCKS (1 detailed & 2 simple dwgs.)

Hi, Rich -

Ron's explanation is way better than what I was going to write - which was an over-
simplification of how it all fits together - so refer to his description when looking at
the drawings below.

It might help to think of the leaf springs as part of a multi-layered bolster that slips
down between the cross-members at the center of the truck - labeled 'truck frame'
in the following revision of your drawing to tie them in with my two drawings below:



The heavy top piece of the truck bolster rests on the tops of the two leaf springs, which in turn rest on the spring plank, and this plank hangs from the truck frame cross members, which also help keep everything from shifting forward or backward. (The drawings have been revised to better show that the hangers are attached to the bottom of the frame cross-members):



As Ron described, the hangers are suspended at a bit of an angle (exaggerated in my drawings) so that they tend to keep the bolster centered in the truck. There is the additional advantage that when the car enters a curve, its inertia ("centrifugal force") tends to shift the car to the outside of the curve. This causes a greater angle in the outside hanger, lifting the outside of the car slightly, and a lesser angle of the inner hanger dropping the inside slightly. This is exaggerated in the following drawing of a car going around a right-hand turn on level (unbanked) track:



Note how the leaf springs essentially move with - or as part of - the bolster assembly, giving additional cushioning to the coach.

In order to focus on the leaf springs and hangers, I've deliberately left out dozens of little parts, including details of how the hangers are attached, and the coil springs, pedestals, bearings and wheels, etc., which are all part of the truck itself, with each coil spring reacting separately to the bouncing of its adjacent wheel.

- Russo



Edited 4 time(s). Last edit at 07/01/2010 12:56PM by Russo Loco.