wanted: Chev CMP chassis views

[David Dunlop]

Tony.

One of the standard comments one finds about the CMP production during the war, when compared with other vehicles manufactured, is the very high degree of standardization of parts, not only between the various weight categories, but between the two manufacturers. They kept it as simple as possible and didn't change things unless they really had to do so.

On that basis, your evaluation of the common components between the 15 and 30cwt classes makes a lot of sense. For the 60-cwt, certain things had to be more robust and were implemented accordingly.

Regarding the 60-cwt you ran across that lacked the auxiliary springs, perhaps they were simply removed from that particular vehicle, for whatever reason, but like you noted, one vehicle is interesting, a bunch of them would make a statement.

Cheers,
David

[Hanno Spoelstra]

Interesting discussion guys. Now, concentrating on Chevrolets for the moment as I am trying to ID a C60S or C30 on 16" wheels.
I just looked up some more facts in the Chevrolet MB-C2 maintenance manual and list my findings here:

Front axle:
6” steering ends (”steering arm is a separate part and attached to the lower part of the knuckle by six cap screws”): C60S, C60L, CGT
5” steering ends: C8A, C15A, C30, ”and on some special equipped C60L vehicles”

Brakes, front drum:
15” diameter, 3.5” width lining: C60S, C60L, CGT
14” diameter, 2” width lining: C8A, C15, C15A, C30

Brakes, rear drum:
15” diameter, 3.5” width lining: C15A, C30, C60S, C60L, CGT
14” diameter, 2” width lining: C8A, C15

Brakes, booster actuated:
C60S, C60L and CGT

Wheel sizes:
16” rims: C8A, C15, C15A, C30
20” rims: C60S, C60L, CGT

Differential gear ratio:
5.43 to 1: C8A
6.17 to 1: C15
6.5 to 1: C15A
7.16 to 1: C30, C60S, C60L, CGT

Springs:
As per factory specifications.

Winch:
Standard on CGT, supplied as optional equipment on C30, C60S, C60L.

Steering gear
Ratio is 23.6 to 1, with the exception of C60L with Gun Portee or Petrol Tank which has a ratio 30.6 to 1
C8A, C15 have mounting different from all other types

[Hanno Spoelstra]

Translating the above to identifying technical specs per vehicle type (limited to C30 and C60S as this the object of our discussion):

C30:

• Front axle with 5” steering ends
• Brakes, front drum: 14” diameter, 2” width lining
• Brakes, rear drum: 15” diameter, 3.5” width lining
• Wheel size: 16” rims
• Differential gear ratio: 7.16 to 1
• Rear spring leaves: 12

C60S:

• Front axle with 6” steering ends
• Brakes, front drum: 15” diameter, 3.5” width lining
• Brakes, rear drum: 15” diameter, 3.5” width lining
• Booster actuated brakes
• Wheel size: 20” rims
• Differential gear ratio: 7.16 to 1
• Number of rear spring leaves: 12 + 6 Aux.

So the Chevrolet I am trying to ID is a C60S, by virtue of having:

• 6” steering ends - see the picture with six cap screws
• 12 + 6 Aux. rear spring leaves - see the picture showing the auxiliary springs
• True, it is fitted with 16" rims, but it is possible to fit these on 15" diameter brake drums (C15, C30 have 16" rims on 15" diameter rear drum brakes)

Now, if I check if the subject vehicle has (had) a brake booster, I am sure this is a C60S rather than a C30.

Riddle solved!

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

Translating the above to identifying technical specs per vehicle type

Excellent work Hanno. It occurs to me we've never seen the 15/30/60cwt differences specified like this before. They're always buried within tables containing other information. It's very useful to see them presented separately as you've done here.

It would appear the exact same differences apply to both Ford and Chev, although I wasn't aware of 14" & 15" brake drums. Evidently the Chev manual provides a lot more specs than the Ford manual.

All in all a very instructive discussion - I now have a much better understanding of the 30cwt CMP.