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Coil springs AND Leaf springs in one truck

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  • Member since
    October 2004
  • From: Allen, TX
  • 1,279 posts
Coil springs AND Leaf springs in one truck
Posted by cefinkjr on Wednesday, July 28, 2021 9:48 AM

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?

Chuck
Allen, TX

  • Member since
    August 2003
  • From: Collinwood, Ohio, USA
  • 12,989 posts
Posted by gmpullman on Wednesday, July 28, 2021 1:42 PM

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

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Posted by 7j43k on Wednesday, July 28, 2021 3:25 PM

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

  • Member since
    February 2015
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Posted by NHTX on Wednesday, July 28, 2021 4:47 PM

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. 

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    February 2012
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Posted by mthobbies on Thursday, July 29, 2021 8:02 AM

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

  • Member since
    June 2020
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Posted by Lastspikemike on Thursday, July 29, 2021 8:53 AM

Only one truck actually needs much suspension travel on reasonably built railways. Wooden beams would twist under loads, probably by enough to accommodate track irregularities. For cars and before unibodies owed very stiff chassis construction the flexing characteristics of steel frames had to be allowed for in suspension design, stiffer springs were required than would have been ideal.  When 1920's sportscar drivers enthused about how their cars cornered as if on rails they weren't kidding. Lighter modern passenger cars needed much more sophisticated suspension systems than those older designs.

I was very interested to see the mass damper system described in the linked publication. When those were banned in F1 racing everyone was all excited about banning up to the minute sophisticated suspension technology....apparently not!

Damping requirements for freight cars would be minimal because the ratio of spring to unsprung weight would be very high anyway and the spring rates could be very high also. On passenger cars the problem is quite different. There was a good reason for those heavyweights which seems counterintuitive unless you understand how spring rates are affected by weights they suspend.

Friction damping should be more than adequate for most freight cars. I noticed express boxcars used more complex trucks than regular boxcars and possibly that was required to ensure more accurate tracking at the high speeds. 

Alyth Yard

Canada

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    January 2017
  • From: Southern Florida Gulf Coast
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Posted by SeeYou190 on Tuesday, August 3, 2021 10:00 AM

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

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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