--- In STMFC@..., Richard Hendrickson <rhendrickson@...> wrote:
Except the Simplex bolster wasn't cast, it was fabricated, but using few rivets. It's selling point was the structural steel cross members, for those who didn't trust castings not to crack in service. Very strange, then, to order them for use with cast steel sideframes, which leads me to believe that when CPR re-trucked their cars to comply with the AAR mandate to eliminate archbar trucks, the bought new sideframes, but retained the Simplex bolsters that had been used in the original archbar trucks.While I can't disagree with this I looked at a RedA completely different animal, Jon. The Simplex cast steel bolster
I looked through the 1922 CBC. It appears that at that time the Simplex bolster design was owned by American Steel Foundries. Here is the sum total of what they have to say about it:
"The Simplex bolster is a trussed construction and, although of a built-up type, it is not dependent upon rivets for strength, due to its lapped end construction."
The Simplex bolster was composed of three castings, a length of rolled steel channel, and a length of appx 1" x 12" (not dimensioned in the illustration) steel flat stock. The channel, laid flat, flanges down, formed the top chord of a truss. This was fitted between two end castings that incorporated the spring seats. A casting was riveted to the middle that acted as a king post. The flat stock passed under this kingpost, was threaded through slots in each end casting, and was forged back upon itself, thereby holding the whole assembly together. The design was similar to the Huntoon bolster, marketed by the Republic Railway Supply Co., except in the Huntoon design, the flat stock was simply riveted to the end casting, it's obvious weak point.
Since the design intent of both these bolsters was to avoid the use of a casting to span between support points, which was exactly what the ARA / AAR mandated cast steel sideframes did, it is obvious that the thinking behind the design was at least one generation behind current practice, and the design simply faded away.
That, of course, left the Simplex name available to be applied to something new and different.