Hi,

Not really a preservation question, Although I'm sure there are some of these trucks under preserved passenger cars, but I'm engaged in a discussion on a modeling forum about 43-EG "triple bolster" trucks, and no one seems to be able to explain how the suspension differs from other swing motion trucks. This partial drawing was presented:

https://www.flickr.com/photos/25967611@N04/52454874643/in/dateposted-public/

I see four areas where the main swing links would come through the transoms where there are four what appear to be pin seats surrounding an opening that has wear plates, so I suspect the swing hangers terminate on another four moving pieces that provide the third level of suspension, but I cannot find a drawing of the complete assembly. As it is, it appears the swing links would just hang on parts supported by other swing links. How does this work to improve riding qualities? It seems to add an awful lot of wear surfaces for not much gain. Can anyone explain, or point me to a text with an explanation? Inquiring minds want to know.

Good question. A subject which I have never clearly understood. Any responses?

A good introduction can be found in Emil Anderson's patent US 2163253. The idea is to permit a certain amount of lateral cushioning for small perturbations, like truck hunting, while more firmly snubbing any lateral motion beyond that point.

John Travilla of Swarthmore was a fertile contributor to GSC truck design in the years that this sort of concern for compliance and damping was still 'profitable'. See for example his US2419473 which describes the way these trucks can be jacked for maintenance.

Dennis, I believe you are asking about the Brill 27E1 truck, also described as a "triple suspension" truck. This truck was an ingenious example of design efforts to minimize unsprung truck weight.

I may have an article that describes this truck, which - if I can locate it - I will share.

The Shore Line Trolley Museum's (Branford CT) inspection car, Connecticut Co. #500, has these trucks. The car is well maintained and brought out for the most special occasions. The ride quality has been aptly described as "upon a cloud"!

The contrast is noticeable to me, having ridden "the worst" - i.e. the "gearless" (electric locomotives of the NYC RR whose traction motor armatures were built upon the driver axles). The S Class and T Class had the highest unsprung weight of anything I have ever ridden; they would literally "slam" their way into curves at track speed, most noticeably as overhauls were deferred in their last years of service.

The Brill triple-bolster truck is a landmark achievement of early 20th century traction engineering.

Please note my post above refers only to the Brill truck.

The so-called Pullman "triple bolster" truck is a different rarity, widely introduced in the late 1930's / early 1940's which did achieve the sought-for ride quality, however, this was at a significant cost in maintenance. IIRC, the only examples that were used in Amtrak service were the SP articulated coaches, used on a short-term lease from SP for peak travel in Amtrak's earliest years.

No sleepers with these so-called Pullman trucks were acquired by Amtrak.

Paul,
I see from your second message that you realized that I was asking about the mid-thirties cast steel passenger truck, but now that you mention it, I have never understood how the Brill truck differs from the common MCB pattern, so if you find the article please post it. Meanwhile, I'm off to search for the patents Mr. Ellsworth cited.

Tried looking for those two patents, and I couldn't get them to come up. Is there a better link that might be available? Alternately, are the patent numbers correct, or is there a good search term or phrase that would work?

EDIT: I found the patents based on the number, but neither one looks like the type of truck that's being discussed.

https://patentimages.storage.googleapis ... 163253.pdf

https://patentimages.storage.googleapis ... 419473.pdf

I agree, although the Anderson 253 patent makes it easy to see where the "triple bolster" terminology comes from; the bolster itself and the upper and lower spring planks. Now I'm not entirely sure that that terminology should even be applied to the 43-EG truck that I asked about; the person that presented the drawing is developing 3D solids to 3D print a 1:48 scale model version that will only have the primary suspension working and has no interest in how the rest works; meanwhile other modelers who tried to explain it only get to the secondary suspension, which is the basic MCB design dating to before the turn of the last century. It's obvious that the third stage occurs at the top of the swing links on this truck, but appeals for more drawings have been unanswered.

At least now I know that the design intent is to provide damping for lateral motion that is more sensitive than the main swing hangers. I suppose the next step is to look at all the subsequent patents that cite Anderson 253.

Link to the patent: https://patents.google.com/patent/US2163253A/en?oq=US2163253

Maybe try searching for Pullman Type 43 truck and see what pops up? I think there were both two axle and three axle versions with various refinements along the way. I could be full of hooey, though….

When searching for patents on google, you must prefix the letters "US" to the patent number.

Tom Hamilton

And usually append the "A" on the end.

I recommend always downloading the PDF; their OCR is often amusing. The great value in using Google Patents is that the prior art cited and the 'patents referencing' are both clickable, and if you have an idle hour or two it's surprising what turns up.

Making progress. This patent, assigned to GSC, has a mechanism that I envision is similar to what would fit at the top of the swing hangers on the 43-EG truck: https://patentimages.storage.googleapis.com/b9/b5/d8/8dbb35b87d1c8d/US2173725.pdf Figure 5 gives the best view. Its purpose is, "to absorb lateral jiggling forces as well as vertical shocks."

In the text Mr. Pflager cites another patent of his, US 2,127,93, which may give more insight, but I have yet to be able to access a copy of it.

I usually click on the inventor's name or assignee, if it is in blue.

A reference to the '725 patent including its text

https://patents.google.com/patent/US2173725A/en?oq=US2173725A

And the patent referenced in the text (which is the 4-wheel version; I think that is the type of truck referenced in the original question):

https://patents.google.com/patent/US2127934A/en?oq=US2127934A

Harry M. Pflager's patent list:

https://patents.google.com/patent/US2127934A/en?oq=US2127934A