I wrote:

The roller bearing was indeed not really applied to railroad
practice until the 1920s but was a known principle much earlier in
mechanical design, as Paul has discovered. There was a roller bearing
arch-bar truck introduced in the 1920s (for a photo, see Hendrickson's
article in RP CYC 4).

I forgot to mention that by the 1928 Cyclopedia, there were passenger roller bearing trucks shown (for PRR and SP) but at that time, no freight trucks with such bearings.

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