HTCR trucks

[trainiac]

How many HTCR truck types are there? I thought there was just the HTCR-I (uneven axle spacing, 40-42" wheels) and HTCR-II (even axle spacing, 45" wheels), but there appears to be more.

standard HTCR-I (BN SD70MAC)
http://www.railimages.com/gallery/dougandreasen/abh

Even axle spacing, 40" wheels--HTCR-II? (BNSF SD70MAC)
http://www.railimages.com/gallery/dougandreasen/abe

Uneven axle spacing, 42" wheels, but new shock struts--late HTCR-I? (UP SD70M)
http://www.railpictures.net/viewphoto.php?id=4244

[nickleinonen]

i've never really noticed any difference between the trucks other than the newer ones have the split journal box making it easier to change out traction motors... i don't think i've ever seen 45" wheels... [all i see at work is 42" & fat 40"]

[trainiac]

The differences are minor--The wheelbase is one of them (evenly spaced on the HTCR II, offset center axle on the HTCR I). The 45" wheels are only on the SD80MAC and SD90MAC and were the reason for the wheelbase change, if I'm not mistaken. That's why I was confused when I saw a photo of a truck with the even wheelbase but 40" wheels.

The reason I was wondering was that I'm in the process of making drawings of the SD70 series, and I'm trying to include these truck differences. I guess I'll call any truck with the offset center axle an HTCR I and any with even axle spacing an HTCR II...