30-cwt vs. 3-ton Difference

[Tony Wheeler]

In the absence of any literature defining British WO load rating specs we're left to infer them from known vehicle types. In relation to CMP types they appear to be as follows:

Truck/Lorry (carried load):

8 cwt: SWB; 13" wheels
15 cwt: SWB; 16" wheels
30 cwt: SWB; 20" wheels; 2-spd transfer case (variants include Truck, 30 cwt, 4x4, AT Gun Portee; Lorry, 30 cwt, 4x4, Water) and: MWB; 16" wheels; 10.50 tyres; 2-spd transfer case (F30/C30 variants)
3-ton: LWB; 20" wheels; 2-spd transfer case


Tractor (towed load):

3-ton: 10.50 tyres; 2-spd transfer case (FAT, LAAT, F60T)

Note that for Tractors the wheelbase and wheel size are not stipulated, because they don't affect traction (towing capacity). A further spec applies to Artillery Tractors, namely winch.

As far as I'm aware the above specs hold true for all CMP variants except: F60S Bofors (Lorry, 3-ton, 40mm, Self-Propelled) which runs 16" wheels.

An apparent anomaly is the C8AX (NZ variant fitted with 16" wheels, making nominal load rating 15 cwt, and built on C15441 chassis) for which the expected designation would be C15AX. I'm inclined to suspect C8AX designation may be local misunderstanding, just like F60S designation seen on Australian F30 Ambulance.

On the question of LWB with 16" wheels, eg. F602L pictured above, I suspect these are rated for on-road use only, just like MCP vehicles. As such it would equate with the Dodge T110L5 (160" wheelbase, 16" wheels, 2-spd diff) which is rated 3-ton.

It's worth noting that design factors such as auxiliary springs, diff ratios, steering boxes, big balls v. small balls etc. do not define load rating - they simply reflect the way a particular manufacturer designs their range of 8, 15, 30, or 60 cwt. vehicles, as defined above. Which means the whole question of load rating is far simpler than it appears - once you figure out the rules!

[Grant Bowker]

Originally Posted by Tony Wheeler

An apparent anomaly is the C8AX (NZ variant fitted with 16" wheels, making nominal load rating 15 cwt, and built on C15441 chassis) for which the expected designation would be C15AX. I'm inclined to suspect C8AX designation may be local misunderstanding, just like F60S designation seen on Australian F30 Ambulance.

I don't have a C8AX parts list to confirm this, but my understanding is that the C8AX is more or less the same set of parts as the C8A Heavy Utility series from the ground up to the top of the frame rails with a C15A cab and a (probably) unique cargo box. So, if the C8AX is actually a 15 cwt, wrongly named, does that make all Heavy Utilities 15 cwt as well since they are the same structural parts and drivertrain?

[George McKenzie]

Check out my truck site that was done on 10 03 11 CMP c60l comes home .There is a bit of information about the front axel that is interesting

[Tony Wheeler]

Grant, evidently there's another factor at work in C8A/F8A load ratings which differentiates them from C15A/F15A. Something to do with the car type rear chassis perhaps...? I really don't know enough about them to speculate.

C8AX (data plate 833) Tony Smith Lithgow NSW.jpg F8A.jpg

[Tony Wheeler]

George, I'm familiar with the C60L radar trucks but I didn't bother mentioning them. Some were fitted with 16" wheels and others like yours were fitted with 20" road tyres. Either way it supports my contention that these vehicles were load rated for on-road use only.

[George McKenzie]

One of my Ford CMP has Cheve axels under it .The army had to do with what they had to work with ??

[Hanno Spoelstra]

Originally Posted by George McKenzie

One of my Ford CMP has Cheve axels under it .The army had to do with what they had to work with ??

No, it had to do with supply problems. The first batch of 4x4 Fords F15A 4x4 trucks had Chevrolet front and rear axles, the second batch of 47 F15A's trucks had a Chevrolet banjo-type rear axle and Ford split-type front unit.

PS: your thread CMP C60L comes home can be found here

[George McKenzie]

I was told that they were shipping the trucks to the UK without axels as there was a shortage of the Ford axels , so they used Cheve axels and put them under the trucks in England .Partly cause by the supply boats that were bringing axels got sunk by U boats, Have you heard this?

[Hanno Spoelstra]

Originally Posted by Tony Wheeler

It's worth noting that design factors such as auxiliary springs, diff ratios, steering boxes, big balls v. small balls etc. do not define load rating - they simply reflect the way a particular manufacturer designs their range of 8, 15, 30, or 60 cwt. vehicles, as defined above. Which means the whole question of load rating is far simpler than it appears - once you figure out the rules!

Tony,

I'm afraid this is not entirely correct. The British War Office classification was a load classification, regardless of the technical configuration of the vehicles supplied by manufacturers.

Load carrier trucks have a load rating, tractors do not - see the thread Is the FAT a 60cwt or 15cwt truck?.

To be able to carry the load and move it at convoy speed across country, manufacturers configured their trucks from existing components. As stated above, I sorted out the difference for Chevs recently, see Chev CMP chassis views. One can see clearly that the heavier the load rating, the heavier the truck's components are - so "design factors such as auxiliary springs, diff ratios, steering boxes, big balls v. small balls etc." in fact do define load rating!

Originally Posted by Hanno Spoelstra

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.

Originally Posted by Tony Wheeler

On the question of LWB with 16" wheels, eg. F602L pictured above, I suspect these are rated for on-road use only, just like MCP vehicles. As such it would equate with the Dodge T110L5 (160" wheelbase, 16" wheels, 2-spd diff) which is rated 3-ton.

The F602L has a 3-ton load rating, as has the Dodge, the fact that they had 16" wheels has noting to do with their load rating. They were fitted with 10.50-16 tyres to bear the load.

As per Vanderveen: "Truck, 3-ton, 4x2, GS (Ford F602L) V-8-cyl., 95 bhp, 4F1R, wb 158-1/4 in, 243x90x118(78) in., 7280 lb. Latest type, using many components of F60L. Tubular front axle, two-speed rear axle. Also with four-stretcher ambulance body and 134-1/4 in. wb GS with open cab."

HTH,
Hanno

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

Load carrier trucks have a load rating, tractors do not - see the thread Is the FAT a 60cwt or 15cwt truck?.

Hanno, Tractors do indeed have a load rating, despite not being load carriers. I conclude therefore it refers to towed load, not carried load (as mentioned in my post above). Pretty obvious when you think about it but we overlooked it in the thread you mention.

img008.jpg img009.jpg img007.jpg

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

One can see clearly that the heavier the load rating, the heavier the truck's components are - so "design factors such as auxiliary springs, diff ratios, steering boxes, big balls v. small balls etc." in fact do define load rating!

I suspect we're getting into semantics here Hanno! To put it another way - Load Rating determines components, not the other way around. Hence F60L with small balls is still F60L.

[Hanno Spoelstra]

Originally Posted by Tony Wheeler

An apparent anomaly is the C8AX (NZ variant fitted with 16" wheels, making nominal load rating 15 cwt, and built on C15441 chassis) for which the expected designation would be C15AX. I'm inclined to suspect C8AX designation may be local misunderstanding, just like F60S designation seen on Australian F30 Ambulance.

No, the C8AX is a chassis/cab variant of the C8A 8-cwt truck. The fact that it has 16" wheels has nothing to to with it's load rating. The Humber 8-cwt trucks have 16" wheels too.

Read Wheels & Tracks magazine issue 1 and 2, and there is little left to speculate.

[Tony Wheeler]

Originally Posted by Hanno Spoelstra

No, the C8AX is a chassis/cab variant of the C8A 8-cwt truck. The fact that it has 16"wheels has nothing to to with it's load rating. The Humber 8-cwt trucks have 16" wheels too.

Yes, I've acknowledged this already, in response to Grant's post above, where I cited F8A as a further example. But the question remains - why are these 16" wheeled vehicles only rated 8-cwt? As I suggested: "evidently there's another factor at work in C8A/F8A load ratings which differentiates them from C15A/F15A. Something to do with the car type rear chassis perhaps...?

[Rob Beale]

The C8AX has the arched rear chassis as shown in the pics, which is much lighter than the straight rear chassis of the C15A.

I did read somewhere on MLU which model Chev ute chassis was used for the C8A and C8AX, and the fact both variants were built on the car assembly line at Oshawa. Note only the C8 had 13" wheels, C8A and C8AX had 16" wheels but with 9.25 - 16 tyres as standard.

The axles and components are much lighter too. I am working on a C15A at the moment and keep finding major differences to the C8AX I have owned for over 30 years!

The C15A rear hub bearing nuts and lock washers are all Ford pattern (and as used in Universal Carriers too!) with 8 sided nuts, and Ford style inner seals.

The C8AX rear hub bearing nuts are 6 sided, and the inner seal is felt.

Always learning...
Rob