Chevrolet C15A APT (Airportable)
 

CMP Design Photos - Volume 4 Self-propelled MT chassis

15-cwt based on C8A
 

Interesting! Note the modifications.

The 2 prototypes were in fact based on the C8A, which makes sense as that chassis is lighter and smaller than the C15A.

Attachment 134685

For more photos see this link https://issuu.com/mechinf/docs/ww2_t...db71066344284f in the thread http://www.mapleleafup.net/forums/sh...978#post269978

And despite being based on the C8A, it can carry 2240lbs; a whopping 20cwt!

Based on the width of frame, section modulus, kicked up profile of the frame rails over the rear axle and the length of the springs (also number of leafs to the spring) all matching the C8A I suggest a complete C8AX frame mey have been used in order to have mounts for the cab as the C8A HU seies used different body mounting system for the one piece cab and rear body compared to the sepatate components used on most other CMPs. Another similarity to the C8A is the transfer case mounted parking brake. A)lthough it could be fitted to the C15A transfer case, I don't think it was a factory fitting. The tyre size also matches C8A, which only makes sense as the profile of the C8A rims was the tapered bead seat rather than the flat bead seat of the heavier trucks (modern tires slide onto the HUP rims easily but can be a challenge on C15A).

Interestingly, the axle ratios don't match those specified for either C8A or C15A. I don't know the ratios for the C8AX.

Both the C8A and C15 (4x2) have 6.16 (or 6.17 depending on mathematical rounding) differential ratios.

I was looking at the AEDB Design Record which gives 5.42 or 5.43 for the C8A...
However, when I look at the C8A-04 parts list earlier C8A are listed as 6-37 ratio (teeth on pinion and ring gears = 6.17 ratio) and later as 7-38 ratio (matches AEDB record).

yes
 

Yes from memory the C8AX has the two ratios, one is faster . Some years ago I was following Len Schutt's C8AX down the Hume freeway coming back from Corowa, Len was getting up to a good speed, around 90kph , this with the original 216 engine fitted. I was impressed at how fast the C8AX was moving, my old XF Falcon was struggling to keep up..well may be not struggling but we were not dawdling along.

The New Zealand C8AX was reclassified as a 15-cwt truck after WW2 without any modifications. The CMP range was generally a bit over engineered for their assigned load classes.