Chevrolet MCP 3 Ton Lorries G.S. (Australian)

[Mike K]

Lionel

I have the 1940 GMH NASCO parts book . The front cover of the book states "SPECIALLY COMPILED FOR THE AUSTRALIAN COMMONWEALTH MILITARY FORCES" . The book is for sedans and trucks

The 1940 Chevrolet truck was series 13, 14, 15.

1940 Maple Leaf was series 16 - diff ratio was 7.16 to 1

1940 CHEVROLET

Basically, the model 14 had a 133" wheelbase

The model 15 was 158 1/2" wheelbase ( yours ? )

15-40 ES Chassis and cab with special 12 X 7 GS Wagon with canopy top - Standard truck chassis fitted single rear wheels 5.20 X 6 pierced disc wheels . rear axle ratio 6.166 to 1

15-40 E2 Chassis and cab with special 10ft. 6ins x 7ft GS Wagon with canopy top- Standard truck chassis Dual wheel with 7.20 X 6 pierced disc wheels rear axle ratio 6.166 to 1

Effective with overseas 18 x 8 wheels , the wheel equipment for these units will be changed to 5.18 X 8 3/4 offset

1940 MAPLE LEAF

The Maple leaf model 16-40/E12 Chassis cab 157 3/4" wheelbase with special Office Lorry body

..............................16-40/E8 ...............................................wit h special stores lorry body

..............................16-40 /E6 ................................................wi th special breakdown vehicle body

The AWM have that pic incorrectly captioned, its actually a Maple Leaf office lorry , not Chevrolet .

[Lionelgee]

Originally Posted by Mike Kelly

Lionel

I have the 1940 GMH NASCO parts book . The front cover of the book states "SPECIALLY COMPILED FOR THE AUSTRALIAN COMMONWEALTH MILITARY FORCES" . The book is for sedans and trucks

The 1940 Chevrolet truck was series 13, 14, 15.

1940 Maple Leaf was series 16 - diff ratio was 7.16 to 1

1940 CHEVROLET

Basically, the model 14 had a 133" wheelbase

The model 15 was 158 1/2" wheelbase ( yours ? )

15-40 ES Chassis and cab with special 12 X 7 GS Wagon with canopy top - Standard truck chassis fitted single rear wheels 5.20 X 6 pierced disc wheels . rear axle ratio 6.166 to 1

15-40 E2 Chassis and cab with special 10ft. 6ins x 7ft GS Wagon with canopy top- Standard truck chassis Dual wheel with 7.20 X 6 pierced disc wheels rear axle ratio 6.166 to 1

Effective with overseas 18 x 8 wheels , the wheel equipment for these units will be changed to 5.18 X 8 3/4 offset

1940 MAPLE LEAF

The Maple leaf model 16-40/E12 Chassis cab 157 3/4" wheelbase with special Office Lorry body

..............................16-40/E8 ...............................................wit h special stores lorry body

..............................16-40 /E6 ................................................wi th special breakdown vehicle body

The AWM have that pic incorrectly captioned, its actually a Maple Leaf office lorry , not Chevrolet .

Hello Mike,

Thank you for the reply - going off the information that you sent ....

The model 15 was 158 1/2" wheelbase ( yours ? ) I would say "yes" and

15-40 E2 Chassis and cab with special 10ft. 6ins x 7ft GS Wagon with canopy top- Standard truck chassis Dual wheel with 7.20 X 6 pierced disc wheels rear axle ratio 6.166 to 1.

I was just directed towards another forum where a restorer suggests that "The military trucks had many heavier components, as compared to the civilian trucks. They had bigger axles, heavier wheel bearings, heavier brakes, heavier chassis with frame reinforcements, and heavier springing." Accessed April 4th 2016 from, http://www.hcvc.com.au/forum/restore...rucks?start=10 Posted on 12 Nov 2011.

Perhaps these upgraded specifications brought them up to 3 Ton Lorries?

Kind Regards
Lionel

[Mike K]

Originally Posted by Lionelgee

"The military trucks had many heavier components, as compared to the civilian trucks. They had bigger axles, heavier wheel bearings, heavier brakes, heavier chassis with frame reinforcements, and heavier springing."

Perhaps these upgraded specifications brought them up to 3 Ton Lorries?

Kind Regards
Lionel

No that's not correct . The 1940 models issued to the army were mechanically no different to the civilian specifications. Bigger axles , heavier brakes - makes no sense at all . We are talking about 1940, who was making special heavy axles or brakes ?

The standard series 14 models were 30 cwt and the series 15 was 3 Ton , there was no special " heavy duty " model in the Chevrolet range in 1940 . The Indian pattern Ambulances were built on the 30 cwt or series 14 chassis.

20 cwt = 1 long Ton

[Grant Bowker]

One source described part of the design philosophy for CMP trucks as being "use one size heavier than normal practice". I.E. use higher capacity (but still off the shelf) parts than might be expected for the carrying capacity of the truck to allow for the "abusive" loading and operation the Army subjected their trucks to. Other sources have described the Maple Leaf trucks as being "Heavy Duty Chevrolets made in Canada". I'm not saying these statements are 100% accurate but they might explain the disagreement seen in the posts above concerning component sizing.

On the topic of split rims - they can be perfectly safe if in good shape and treated with respect. Worn, rusted, mismatched (rim to ring) or otherwise abused wheels won't properly engage and may separate as they are being inflated. So yes, a cage or other restraint is very strongly suggested for safety. The real nasty split rims are the Firestone (and others?) RH-5 rims produced long ago that separated near the center of the rim (as opposed to at one side), have less bearing area along the joint and can't be visually inspected for engagement. A group of reference charts on servicing one piece and multi-piece rims can be found at http://www.kentool.com/index.php/new...safety-posters The content originates in the USA but should be basically the same worldwide.
This link from a rim manufacturer describes safe tire mounting processes http://www.accuridecorp.com/files/20...4-06-22-12.pdf It specifically describes treatment of multi piece rims. If these rims had been banned for safety reasons I strongly doubt that a manufacturer would want to get into the liability arena of describing how to use an outlawed product. The document has a 2012 copyright so isn't badly outdated - nothing like our beloved MB-C2 or MB-F1 that were published 70+ years ago. The publication also refers to a multi piece rim for tubeless applications. I hadn't realized they existed, thinking the joint in the rim would let air escape. Apparently the inner edge of the bead seals on the main part of the rim and the side/lock rings are narrow enough they don't interfere with the seal.

[motto]

Lionel, if the wheels on your truck are the stock, standard Chev 20" type of that era with a lock ring that is full circle, (not split like a cir clip) and they are in good shape then they are quite safe to use.
As I posted on another forum recently, GM and Studebaker between them built around 800,000 6x6 trucks during WW2 (These used the same lock ring arrangement as the Chev 20" wheels we are discussing). This gives a total of 8,000,000 wheels. Add another 800,000 spares and those produced for other trucks such as the Yankee Joe and we must be up around 10,000,000. Yes that's 10 million 20" wheels.
I have yet to hear of one failing.That doesn't mean that it hasn't happened in the intervening 70 years but if so it would be an exceedingly rare event.
As regards the question of what license is needed to drive this class of truck it would quite likely vary from state to state. In Victoria you can drive a vehicle up to 4.5 ton Gross Vehicle Mass on a car license. Strangely enough you can also tow a trailer up to 9 ton GVM subject to the capacity of the tow vehicle.
I have a friend that was pulled over by an RTA official whilst driving his Studebaker 6x6 and asked for his license. The RTA bloke said that the truck could not be driven on a car licence as it exceeded 4.5 ton gross and the friend tried to tell him it was only a 2-1/2 ton truck and pointed out that it said so on the dash plate. The limb of the law didn't agree with that explanation.

David

[Lionelgee]

Hello Grant and David,

thank you both for your extensive information about my rims. I will take a couple of photographs - once the camera's batteries charge. Then I will post them up.

How readily available in Australia are the 7 x 20 tyres - 8 ply?

Kind Regards
Lionel

[Lionelgee]

Hello All,

I have just loaded up three photographs of the wheel rim - a couple of which are close-ups. It looks like the ring is in a single piece and it seems like an over-sized circlip.

The rims have a patina on them which will hopefully come good once they get sandblasted and painted again.

I circled the lock part of the rings - luckily it was at the top of the tyre so they were easy to photograph. BTW this tyre is one of the better ones I have .

Kind Regards
Lionel

[motto]

7.50 - 20 tyres are more common than 7.00 - 20 but they are still not common. If you started looking you would probably turn some up.
That type of wheel lock ring I am not familiar with and I have not seen them on a Chev. The L/L Chev lock ring was a complete circle. These wheels must pre date that style. As stated earlier, I am not familiar with what was around before the '42 model or after for that matter.

David

[Grant Bowker]

Sitting here in Canada, I have to admit ignorance of the Australian vintage tyre market.
Based on a quick search, there seem to be some sellers in Australia, see
http://www.hcvc.com.au/forum/salewan...es-or-7-00-x20
http://www.antiquetyres.com.au/20700-0
http://www.oldworldlamps.net/tyres_20_inch_16.html

They certainly exist in USA at Coker Tire among others
https://www.cokertire.com/tires/styl...m_diameter=120

Keep in mind that you may not need to limit your search to 8 ply or PR (ply rated as opposed to real plies) tyres, you might get away with 6PR provided they have enough weight capacity and you should be able to use 10PR (or more). If using 10 PR, see if you can get hold of load/inflation tables for the tires. You should be able to run a lower than "rated" pressure as you are also likely carrying a lower than rated load per tyre but without the manufacturer's tables it is hard to guess how much the pressure can be reduced safely. It would likely also work to go up to 750-20 size if that's more readily available. There is a chance the extra width might rub somewhere but my guess is that the chance is small and I doubt the extra 7% width would be obvious.

Looking at your photos, unless there is an illusion happening, I would want to check the condition of the ring in the photo with both red and white circles as it looks as if it might be bent enough to not seat as well as desired. But - if the tyre is just pushed away from the ring, all might be OK.