I am looking for a general time line concerning log cars specifically built for that purpose. Specifically, the changes in their bunks, from low chocks, to tall stakes. When did the stakes begin to grow in height? I remember building the new stakes, when the Milwaukee Road upgraded their log cars. This was the winter of 1974-75. But such tall bunks had already been in use for many years. Was this development in the early to mid-1950's? Or sooner? Anyone have some ideas?
When I think of purpose-built log car, I think of the skeleton/spine cars used by many of the canadian railroads. This site gives a build date of 1968 for a batch of NSC cars: http://www.readytrain.com/catalog/cpr_logcar/cata/index.html so the design had to be in use since then. What type of log car are you talking about? The spine style or the one with bulkheads and side stakes? http://vanderheide.ca/blog/wp-content/uploads/2017/07/IMG_7715.jpg
Hopefully these links will work. Spine type or skeleton with simple chocks: https://www.pwrs.ca/new_announcement_images/products/Rivarossi/att__3.png A next type of evolution. Then came: https://www.trovestar.com/generic/gallery.php?idGallery=65926&id=147572 This one I can recall seeing as a youth. The downward pressure of a log causes a chain or lever (depends upon who built it) to pull the stake inward and pinch logs to help hold them in place.