The TCWs for these were first created in TC V10.5, then updated to V11.2 a few months later. Today, two PCs later, I opened the files in TC 17.2, and did "Skip All" on all the materials, etc. After changing the material on the outer case for "Bill's pump" to a nearly transparent one, the attached render was "first shot", taking about a minute to complete. The render of the 'exploded' drawing required me to re-locate a .jpg for one material before completing, and also took less than a minute.
There's a story behind this that I've attached as pump story.txt for anyone interested.