30-cwt vs. 3-ton Difference

[Bob Phillips]

There were some ambulances that were 4x2 vehicles in longer wheelbases. I have a front axle ( Ford?) and it fits right into a standard CMP 13 cab chassis as it has a hollow tube with no gears and is not a drop type axle that many standard trucks of the era would use. The ends are not drive types but have kingpins, and one version (that is now found a new home) actualy had an extended kingpin with extra support underneath the axle to provide additional support. Going down the road such a vehicle would appear to be a 30 or 60cwt depending on wheel sizes used. It is an oddball!

[Hanno Spoelstra]

Originally Posted by Bob Phillips

There were some ambulances that were 4x2 vehicles in longer wheelbases. I have a front axle ( Ford?) and it fits right into a standard CMP 13 cab chassis as it has a hollow tube with no gears and is not a drop type axle that many standard trucks of the era would use. The ends are not drive types but have kingpins, and one version (that is now found a new home) actualy had an extended kingpin with extra support underneath the axle to provide additional support. Going down the road such a vehicle would appear to be a 30 or 60cwt depending on wheel sizes used. It is an oddball!

Correct, see two pics of the Ford F602L on display at the Overloon museum attached.

imm002_31.jpg imm009_101.jpg

[super dave]

This has been very interesting and very confusing as well

[Bob Phillips]

A very interesting set of pictures Hanno! If you look at the close up photo of the axle you will see the additional lower support arm of which I wrote. The axle that I still have does not have that additional support arm and it seems probale that in rough service it would not last very long.

[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

[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...?