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Wooden Truck Bolster

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Wooden Truck Bolster
Posted by staybolt on Wednesday, March 17, 2021 1:33 PM

I'm assembling a 1900-era wooden box car from a kit. The truck bolsters simulate what apparently were single heavy, square cross section wooden beams on the prototype car. What isn't provided for or mentioned in the kit instructions and drawing is clearance between the truck frame and the bolster to allow for pivoting/turning of the truck. I assume in the prototype of such a car that there was either a heavy wooden or iron block containing the truck kingpin (correct term?) bolted to the center of the bolster which maintained the necessary clearance. Depending on the material used on the prototype I could use basswood (for wood) or brass or plastic (for iron) to model the part. I've searched the web for a diagram and/or description of the construction of such a bolster, but haven't yet found anything.

Anybody know about this construction or could point me to a reference to it on the web? 

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Posted by gmpullman on Wednesday, March 17, 2021 3:13 PM

Hello,

There are several volumes of the Car Builders Cyclopedia available at Google books.

https://books.google.com/books/about/Car_Builders_Cyclopedia_of_American_Prac.html?id=0UJttWHSwNYC

You can search for bolster and scroll to the area where construction details are covered and perhaps find drawings suited to your car.

We had a thread about truss rods here a while back and I accessed some of the scanned images for a reference.

Hope that helps, Ed

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Posted by staybolt on Wednesday, March 17, 2021 5:50 PM

Ed,

Thanks much for the link. I have a few issues of "Trainshed Cyclopedia", but none showing any 1900-era cars, and anyway, those don't provide the detail of the "Car Builders' Cyclopedia of American Practice" you cited. I knew about that publication, but I didn't know of its availability via Google. 

 

After looking at the bolster figures and definitions, I found that the construction I was seeking was part of the body bolster and not the truck bolster I had named in my posting. Evidently, iron castings and straps, as well as wood, or a combination thereof, was used to build that part of the bolster to provide the clearance needed for truck movement.

 

                    -Chuck  

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Posted by BN7150 on Wednesday, March 17, 2021 6:14 PM

I have studied the trucks of this era. I extracted photos and drawings from seven volumes of the Car Builders' Dictionary from the 1879 edition to the 1912 edition and posted them in my blog. Maybe some of them are what you want. Although it is written in Japanese, there should be no obstacle because it is composed of images.

This photo is the Roaring Camp Railroads I visited in 2008.

Kotaro Kuriu

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Posted by staybolt on Thursday, March 18, 2021 12:43 AM

Thanks, Kotaro....I'll take a look. There evidently were various approaches to mating the truck bolster with the body bolster (via the king pin), all of which had in common the need to provide clearance between the two so the truck could swing/pivot freely. I model in HO in the 1920s when wooden freight cars, although becoming "old" technology, were still in revenue service. I try to incorporate as much prototype detail as is practical in the 1:87 scale (!).  

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Posted by BN7150 on Thursday, March 18, 2021 2:59 AM

The followings are parts of the 1903 edition. Freight cars generally don't have center pins or king bolts. The car body is just on the trucks. In Japan, the center plate is expressed as the center "dish".

Kotaro Kuriu

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Posted by dehusman on Thursday, March 18, 2021 9:15 AM

Freight cars do have a center pin , but its a drop fit, not bolted on.  On a freight car if you jack up the body, the trucks stay on the tracks, what keeps the body on the trucks is gravity.

The underside of the car has a male casting that fits in a female casting on top of the truck.  The bowl is about 8-12 inches in diameter (depending on capacity and era) and a couple inches deep.  Those castings are what transmits the lateral forces between the car and the trucks, not the king pin.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by Overmod on Thursday, March 18, 2021 1:57 PM

No one has apparently brought up the issue of side-bearings or their clearance.  This takes on a certain degree of importance in modeling as those are generally not modeled as load-bearing or indeed to run in contact.  You can see the lower part of the side-bearings in the enlarged Cambria diamond arch-bar drawing.  To my knowledge these were not intended to be constant-contact bearings in the modern sense, although almost certainly a loaded car would tend to touch on one or the other side as it ran...

To my knowledge, trucks of this early era did not have a formal bowl center bearing (which incidentally also vastly increases time between center-bearing greasing or lubrication); the upper plate of the center-bearing ('malleable iron' in the Cambria truck) was screwed into the center-plate block going to the center sill, and the lower plate to the truck bolster.  Where this construction could start to get interesting was in the "Ohio" high-speed tender truck design, where the side bearings are far outboard, as fulcra of long arched leaf springs with their ends bearing on the axle boxes, and the braking effort, etc. taken through the center pin sometimes using a multiple telescoping section center-pin arrangement to give the necessary very long excursion between loaded and empty ride height.  

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Posted by staybolt on Friday, March 19, 2021 12:59 PM

Indeed, there's motion in many directions to account for in the design of a truck and its interface with the car or tender body. When you think about it, if the huge forces of the moving mass of a car body, loaded or not, weren't dissipated to some degree, those relatively small wheel flanges wouldn't be able to keep the car on the rails.

Re side bearings...they're modeled as castings on the Kadee #501 arch-bar trucks I'll be using on my wooden box car. 

Interesting description of the "Ohio" tender truck design and necessary accounting for changing height as fuel and water weight rises and falls....reminds me of how that affected adhesion of the driving wheels under the triplex tenders on the Virginian and Erie.

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Posted by Overmod on Friday, March 19, 2021 5:24 PM

staybolt
When you think about it, if the huge forces of the moving mass of a car body, loaded or not, weren't dissipated to some degree, those relatively small wheel flanges wouldn't be able to keep the car on the rails.

Which brings up what is probably the most important echaracteristic of the three-piece truck -- and by careful extension, the use of the principle in Buckeye-style three-axle trucks -- that as much as possible of the accommodation and equalization take place between the bolster end and the wheelset axles.  And not at all at the center bearing or by extension via side-bearing contact merely as a limiting stop.

One interesting adaptation of this understanding is the Taylor truck (as seen on the Reading).  This design made the pivoting of the sideframe an actual bearing, rather than relying on differential compression of the spring packs to allow it, and also allowed pedestal-like motion of the bolster end in the sideframe for better secondary suspension.  There is one picture of a wooden-bolster archbar truck showing what happens when the sideframe 'equalizes' -- you can imagine the maintenance and safety considerations when that has happened!

If you are interested in prototype development, I encourage you to look first at the development of high-speed freight trucks at Chrysler and then Symington-Gould, and then at the progressive evolution of constant-contact side-bearings (and what that idea implies in practice).

If I recall correctly, one of the great early adoptions of vulcanized rubber in car springing -- which was a revolution in the years after 1834 -- was as side bearings, and it is instructive to work through the reasons this did not prosper at the time... or indeed later with the advent of the Fabreeka spring, up to the point that EMD and other engineers made the idea valuable.

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Posted by staybolt on Saturday, March 20, 2021 12:04 AM

Hmmm....you note some interesting subjects, Overmod: the Buckeye 3-axle truck, the Taylor truck and vulcanized rubber use in springing. The Buckeye name is familiar....I'm thinking a post-1920s truck design (?). The Taylor name is new to me, and I didn't know vulcanized rubber even existed as early as the 1830s.

I've enjoyed the discussion, and I'll take a look at those subjects, but for now...back to modeling my favorite years of U.S. railroading...the 1920s.   

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Posted by Overmod on Sunday, March 21, 2021 7:07 PM

The Buckeye truck goes back to 1910, although ... like the Delta trailing truck a decade later ... it went through a couple of revisions by the time it became popular.  Google "battleship gondola" to see early versions; the pre-WWI N&W had hoppers with similar three-piece-derived sideframes...

Likewise, according to John White (of the Smithsonian) in his book on the American Passenger Car (in volume 2 if you have the two-volume set) the use of rubber in car springs was notable only a couple of years after the discovery of vulcanization (sulfur-bridge crosslinking) in 1834.  This was almost as fast as the discovery and utilization of X-rays in dentistry, another under-researched thing.  Where the trouble came in was that the new material was seen as a complete replacement for helical or leaf springs, which it was admirably suited to be... except for one little thing: they didn'd design and test for winter conditions.  Or for long-term UV degradation.  

And then came the rise, and fascinating fall, of gutta-percha, a bit like the English version of the French experience with fax machines in the late 1860s.  Latex was a poor material by comparison... and by the time the gutta-percha revolution ended, the United States was in the throes of Jacksonianism, and railroading was to take very different turns thereafter.

It does turn out that the Taylor flexible truck postdates your era, by about a decade.  I'd thought it was introduced in the mid-to-late Twenties.

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