wanted: Chev CMP chassis views

[Hanno Spoelstra]

Originally Posted by Tony Wheeler

I find the best way to think about CMP frames in general, be they Ford or Chev, is to consider the siderail as 3 separate sections: front section, rear section, midsection - the latter being straight channel. All front sections are identical, and all rear sections are identical - it's only the midsection that varies, and only in length, according to wheelbase. No doubt this greatly simplified production, and may have been standard industry practice in truck manufacture.

Niels was so kind to measure up the chassis of his CGT and C30 trucks - please refer to the attached drawing from the Chevrolet manual to which I added red lines at datum points "C", "D", "E" and "F".

Chevrolet CMP Frame dimensions_redlined.jpg

He reported the following frame height dimensions on the outside of the C30 frame rail:
C: 20 cm
D: 20,5 cm
E: 18 cm
F: 14,5 cm
On the CGT it was bit hard to get the measurements, but from what Niels could tell they where the same as on the C30.

As the distance between "C" and "D" is the same on all chassis (transfer case is fitted to cross member "D"), this means the difference in chassis length is in the mid-section "D"-"E" as follows:
C30: 150 cm
CGT: 73 cm

The difference between the two is 77 cm. I would expect it to be equal to the difference between the wheelbases: 134" - 101" = 33" = 83,8 cm, so there may be some more measuring up needed.

Tomorrow I will post some of the pictures Niels made.

Hanno

[Hanno Spoelstra]

Pictures of chassis at datum points "C" and "D", plus dimensions:

Datum point "C" (at tip of pen), right hand external view (left) and right hand internal view (right).
Frame height is 20 cm at this point:
IMG_3515.jpg IMG_3517.jpg

Datum point "D" - the transfer case cross member - left hand external view (left) and left hand internal view (right).
Frame height is 20,5 cm at this point:

IMG_3519.jpg IMG_3520.jpg

H.

[Hanno Spoelstra]

Pictures of chassis at datum points "E" and "F", plus dimensions:

Datum point "E" left hand internal views; view from the front of frame member (left) and view from the rear of the frame member (right).
Frame height is 18 cm at this point. Note the frame reinforcement (inner frame rail) in the left hand picture:
IMG_3521.jpg IMG_3522.jpg

Datum point "F" at the rear frame cross member.
Frame height is 14,5 cm at this point.
IMG_3525.jpg IMG_3526.jpg

H.

[Eduard Sorokin]

Originally Posted by Hanno Spoelstra

Niels was so kind to measure up the chassis of his CGT and C30 trucks - please refer to the attached drawing from the Chevrolet manual to which I added red lines at datum points "C", "D", "E" and "F".

He reported the following frame height dimensions on the outside of the C30 frame rail:
C: 20 cm
D: 20,5 cm
E: 18 cm
F: 14,5 cm
On the CGT it was bit hard to get the measurements, but from what Niels could tell they where the same as on the C30.

Well, one more enigma is here.
I always thought, all images in technical manuals, handbooks and spare parts catalogues have the factory blueprints as their base. And looking on CMP frame drawing in Manual, I was glad, because of this drawing could to be very useful (for example, in scale modelling of any CMP truck).

Now dear Hanno and Niels provided us with exact dimensions of frame side member heights.
Having those dimensions, I tried to measure those heights on that image from Manual to compare them. Using rear spring length (49 1/2 in.) as basic dimension, I have found the scale of Manual drawing and measured and calculated the remaining dimensions.

My results are below:
C: 15,03 cm,
D: 14,4 cm,
E: 13,28 cm,
F: 10,28 cm.

Thus, the results are very different from the actual dimensions. And my conclusions are:

1) The Manual's authors used some random "drawing" (based of factory plans of frame), which is similar to all frames of all CMP models (for the purpose not to give different drawing each time, in each Manual on each other model). The author's intention was to give general view (overall arrangement) of CMP frame, without too many particular detailing.

2) Possibly, the authors used frame drawing from lighter models - from C15 or even from C8. Only measuring of frames of those exact models could to confirm or to refute this assumption.

3) Finally, the Manual authors could made simple sketch drawing of frame - "by eye", and without use of any factory drawing, to show only general shape of frame.

This is big, big enigma...