Just noticed last night that I have one HO car with this unusual arrangement. I also remember seeing this in 1:1 scale in the late 60s or early 70s when I worked for NYC>PC although I don't recall the car type.
Any ideas of how common this was or why it might have been done?
ChuckAllen, TX
You colud spend a great deal of time studying the effects of railroad car suspension and everything that goes on between the rail head and the car bolster.
This interesting look at the basics will explain much of the theories:
https://www.wheel-rail-seminars.com/archives/2018/pc-papers/presentations/PC03.pdf
Railroads were continually looking for solutions to balance car suspensions especially considering the job the spring package needed to do given the difference in weights of a loaded car and the empty weight.
Coil (helical) springs alone could introduce too much "bounce" and lead to commodity damage, track damage and poor tracking qualities. Often there were more than one spring nested inside the visible outer coils.
Before designs of successful "snubbers" there were attempts at using leaf (or elliptical) springs in order to help dampen this bounce. The friction between the leaves of an elliptic spring provide for some dampening.
There's only one "sweet spot" for a given weight for a spring to bear. Railroads and carbuilders were always in search of ways to economically expand this ideal spring action when designing for loaded vs. empty car performance.
There were dozens, if not hundreds of designs attempted to design a good, working snubber/spring/suspension "package" that met all of the criteria and still had to be economical, durable and easy to repair in the field.
Passenger cars and some freight cars used hydraulic snubbers similar to automobile shock absorbers. There were also many styles of bolster-to-sideframe mechanisms to attempt to dampen vertical travel using various springs, rubber pads and wedges.
Short answer, to reduce bounce and attempt to improve ride quality.
Good Luck, Ed
Leaf springs are also non-linear. In the normal position, they give a softer ride. In the heavily loaded version, they are stiffer and less likely to bottom out (a VERY not-soft ride). They are usually seen under cars carrying people, cabooses included.
But. They also show up a lot under steam locomotive tenders.
Ed
The major user of the coil-elliptical spring arrangement that I saw most often was, the Pennsy, on its X-29 boxcars used in passenger service.
I remember seeing a pre-1920s Pullman passenger car (with open vestibules) at the Essex Steam Train and River Boat museum in Essex CT. It has leaf springs on one truck and blocks of wood on the other. They were 8x8 beams that spanned the whole truck. The guy at the museum said they were made that way! Now I thought that was interesting.
-Matt
I didn't notice this when I was there, but I saw it while sorting some pictures.
The DURANGO AND SILVERTON has both leaf and coil springs on the passenger gondolas.
-Kevin
Living the dream.