C-21 drawing

Howdy,



Just getting started, the DeGolyer drawings*, C-21 (Colorado Fuel & Iron 101-102) are pretty good but by no means complete (no domes, no tender, etc). The C-25 (Crystal River 103) drawing is a little better (domes!) and quite useful as there are a lot of similarities between the two classes. Need to figure out the front end of the frame and how the foot plate attaches, what the back firebox bearers look like, etc. Anything new (Grande) will have to be measured from photos.

One issue I'd like to throw out to the forum: driver diameter and tolerances. Online sources and the folio sheet call for 38 7/8" drivers for the C-21s (38" for the C-25) while the original Baldwin spec sheet (from DeGolyer, available online: [digitalcollections.smu.edu]) call for 38" diameter. That's what I'm going with for now. As a matter of driver maintenance, the tires would get turned down a bit to clean up the tread, right? What would the tolerance be before tires have to be replaced? I think that's where the extra 7/8" came from, or just a wrong measurement, not sure.

*By the way, the Maxwell tracing of the C-21 erecting card which appears in Dorman's "Gunnison" book is pretty spot on, any dimensional irregularities are from the original.

Not easy doing an accurate drawing of locomotives gone for sixty years, so as I go along I'd appreciate any contrary thoughts, confirmations, rivet counting, opinions, useful information, etc. It's all good.

More-to-come.

Mike