Chevrolet 1533X2 30-cwt trucks

[Charlie Down]

Hi Andrew and Grant,
That could be an airline on Post 114, but a bit vague to be confirmed. Adds to the mystery. Attached photo shows what could be an airline behind the driver's seat near the rifle mount, not sure if that helps or not, although it focuses the area of the cab for its location. 6" of pipe not much to work on though.
The parts sheet only shows one airline connector from the pump, so only one connector makes sense.
Looking at the problem from another angle. If it was my truck, where would I want the connector located for easy access and connection, centrally on the truck? In the cab, obviously, not on the floor where it could be stepped on and kicked/pick up dirt and be a trip hazard. Not under a flap that could be damaged, knocked off or jammed. Not too low down so that I have to move stowage to get to it. Most likely I would mount it on the inside of the side panel of the cab on the LHS. I most likely wouldn't mount it under a flap on the side of the cab below the door.
MCP and CMP trucks were simple practical designs. the flap is out of character. It was a standard kit to fit MCP trucks, most of which had doors fitted, so access would require the door open and you would need to hold the door open to stop it slamming onto the hose and connector and damaging them.
But in that case what was the flap for? Have I mis-interpreted the original photo of the flap? Are there photos of CMP airline connectors fitted to trucks?
Are there specific panels to fit under the door with a flap on them? Sounds a complicated way to fit the kit if you have to remove a panel and weld/bolt a new one in to fit the connector.
More questions than answers! If pushed I would go for the flap arrangement purely because there is evidence for it, but I'm not convinced yet.

[Tony Smith]

Originally Posted by Charlie Down

MCP and CMP trucks were simple practical designs. the flap is out of character.

But in that case what was the flap for? Have I mis-interpreted the original photo of the flap?

Are there photos of CMP airline connectors fitted to trucks?
Are there specific panels to fit under the door with a flap on them? Sounds a complicated way to fit the kit if you have to remove a panel and weld/bolt a new one in to fit the connector.

More questions than answers! If pushed I would go for the flap arrangement purely because there is evidence for it, but I'm not convinced yet.

There is no evidence for any flap, either in a manual or a photo.

The airline fitting on CMP trucks just bolts through the chassis rail with no additional panels or fixtures. The MCP just passes through a hole drilled in the running board.

[Tony Smith]

Originally Posted by Charlie Down

Are there photos of CMP airline connectors fitted to trucks?

This is the Left side chassis rail of a 12 Cab Chev.

You can see the PTO port on the side of the transmission (Dark grey, no pump fitted), and the pre-drilled holes in the frame. A short copper pipe runs from the pump to the inside of the frame rail. The airline fitting bolts through the lowest of the 3 holes, connecting directly to the copper pipe.

[Tony Smith]

Originally Posted by Charlie Down

Are there photos of CMP airline connectors fitted to trucks?

Originally Posted by Tony Smith

This is the Left side chassis rail of a 12 Cab Chev.

You can see the PTO port on the side of the transmission (Dark grey, no pump fitted), and the pre-drilled holes in the frame.

Jaap De Wit has posted some good pics of his 12 Cab Chev which clearly illustrates the relationship between the position of the Transmission gear lever, the Air Compressor engagement shaft, and the Air Fitting hole on the Chassis in THIS THREAD

[Hanno Spoelstra]

Next topic on Chevrolet 1533X2 configuration: the rear axle. The requirements document of the LRDG posted by John J. Valenti specfies a 6.17:1 differential ratio.

From the “Desert Chevrolets” article in Wheels & Tracks magazine no.8 I copied the technical details of the 1940 Chevrolet WA. This had a differential ratio of 5.43:1, or 6.17:1 as an option.

I’ve read the 1533X2 was fitted with a 2-speed Eaton axle. Can anyone show the technical documentation to underpin this?

2B188792-D663-4F75-A854-7F96B31ADE73.jpeg

[Charlie Down]

My research has led to a website http://chevy.oldcarmanualproject.com/index.htm
which has lots of old manuals on it.
I have attached illustrations showing exploded diagrams and parts lists of a 2 speed differential, a standard axle for comparison and diagram of the linkage to the cab although it doesn't show the cable connector to the speedo adapter.
Its not clear to me whether the 2 speed unit bolted on to replace the conventional axle differential casing at the front of the axle, or it came as a complete replacement axle. I haven't yet found a good clear photographs of either axle for comparison.
The front axle was 100mm wider than the normal axle to allow for the extended fenders and sand tyres. I presume the rear axle would also be extended. Would this be a new axle, or would they just have extensions to the standard axle?

[Hanno Spoelstra]

There’s a lot of info to be found on the Eaton conversion. But where do we find documented proof of the assumption/fact that the 1533X2 was fitted with a 2-speed Eaton axle? Is it only the handle in the cab?

Would there be a need for a 2-speed axle? Or would the LRDG have more benefit from a limited slip differential as fitted to the CMP C15?

[Charlie Down]

From what I've gathered from reading around, the 2 speed axle gave alternate 'half gears' so the 4 speed box became effectively an 8 speed box offering a lower crawler gear and better economy over a range of terrain as a more suitable gear ratio was often available, both very useful to LRDG Patrols.
However I would have expected it to be detailed in the specification, with the only possible reference being the 'Speedo adapter' which would be necessary for more accurate navigation during the day, until a star fix could provide accurate co-ordinates at night.
Looking at period photos of LRDG trucks the 2 speed handle shows up whenever there is a suitable angle of the cab, which admittedly isn't often!
So until proved wrong, with the photographic evidence, and the obvious advantages of having this feature on the trucks, a reference to speedo adapter (which could admittedly be to do with the larger sand tyres) in the specification, Tony Smiths very positive identification of the feature ( and other features!) I am happy that 2 Speed Axles were a standard and beneficial feature of 1533X2 trucks.

[Charlie Down]

Hi Tony,
I was wondering about that piece. It wasn't painted, meaning it was fitted after the paint job or it was masked to stop paint clogging up machining on the fitting. It makes sense. Simple, effective and quick to mount/repair/use. Very MCP/CMP in character.
However, initially I looked at period photo's of the trucks, and later stowage setups which often involve large wooden or metal ammo chests bolted to the step. It didn't make sense that they would have to unbolt these boxes to get to the airline, then remount the boxes when they were finished.
I then put myself in their position and thought about the problem. What if they drilled a hole in the stowage/ammo box, fed the airline through the hole and attached to the connector and then bolted the box in place. They would then only have to open the box, take the airline out and engage the PTO to use it. It would be quicker and simpler, they would have the airline stowed where they need it (freeing up space else where), the airline would only take up a small area of the box allowing it to be filled with ammunition or other stowage.
The first photo show S1 Patrol in September 1942 ready to go. They all have a chest for 10 x 100round Vickers K gun drum magazines fitted on the step. So a fairly standard fit for this Patrol. If you did the above, drilled and fitted the airline in the box you would still have plenty of room for 9 drums of ammunition.
I really like that idea and have absolutely no evidence for it, apart from that it's easy to do and makes sense! Its exactly what I would do.
The other photo's show (when magnified) the fitting on trucks in the field and at the factory. The rhs is shown to show it wasn't fitted on both sides.

So I have a new theory/idea.

And what the hell is that flap all about!

[Tony Smith]

None of the stowage pics show the airline fitting blocked or covered, the boxes are at the rear of the step, the airline is at the front of the left side step.

You are in a flap about this so-called flap! What on earth are you talking about, what flap?

[Charlie Down]

This photo shows what looks like a flap, which is what I'm trying to sort out. It has generated lots of conversations on here and the LRDG preservation society facebook page. Initially I thought it was the airline connection and started looking for evidence to prove this, which has by a convoluted path led me here where I am sure its not, but don't know what its is. So yes I'm 'flapping' about a flap, but what I really want to work out is how the airline was set up from the pump because it's never really been discussed in LRDG circles, but apparently MCP/CMP forums are much better informed!

[Hanno Spoelstra]

Originally Posted by Charlie Down

This photo shows what looks like a flap, which is what I'm trying to sort out. It has generated lots of conversations on here and the LRDG preservation society facebook page. Initially I thought it was the airline connection and started looking for evidence to prove this, which has by a convoluted path led me here where I am sure its not, but don't know what its is. So yes I'm 'flapping' about a flap, but what I really want to work out is how the airline was set up from the pump because it's never really been discussed in LRDG circles, but apparently MCP/CMP forums are much better informed!

Charlie, that "flap" may be something else? A small tin with cigarettes, spare tyre valves, or ???

[Charlie Down]

I thought maybe a note book. Its something though, and whatever it is, it has led us to the right answer. Thanks Tony for solving this. I'm putting this one to bed now, job done.

[Tony Smith]

Originally Posted by Charlie Down

This photo shows what looks like a flap, which is what I'm trying to sort out.

What I see in that pic is the truck has got a flat tyre, and the crew have delegated the Sikh Trooper to be the one to change it. Meanwhile, the rest of the crew have taken the opportunity for a Smoko break, and the Trooper nearest the door has decided to help himself to a tin of Bully Beef.

[Charlie Down]

Hi Tony

Hopefully last question.

In this compilation view, are these levers for the PTO, or for something else such as a 2 Speed axle , as has been suggested elsewhere? (no mention of a 2 speed axle in the LRDG specification, but it does have details such as the rear axle ratio, so would have thought it would be mentioned if fitted)
Earlier you said that a slot was cut in the floor (photo attached of a floor for a LRDG conversion project) that allowed a screwdriver to be inserted to engage the PTO, but the drawings of the parts diagram shows a lever as part of the PTO compressor kit. Did the screwdriver fit into the end of this lever or was there an extension lever up into the cab?

Just seeking clarification.

Thank you for clearing this all up

[Tony Smith]

Originally Posted by Charlie Down

Hi Tony

Earlier you said that a slot was cut in the floor (photo attached of a floor for a LRDG conversion project) that allowed a screwdriver to be inserted to engage the PTO, but the drawings of the parts diagram shows a lever as part of the PTO compressor kit. Did the screwdriver fit into the end of this lever or was there an extension lever up into the cab?

Thank you for clearing this all up

Those levers are for the Eaton 2 speed rear axle.

There is no "lever" in that parts diagram. The pump has a fixed vertical shaft with a screwdriver slot in the top, and the lower end has a fork. This fork engages a sliding gear. When the shaft is rotated with a screwdriver, the fork pushes the gear rearwards to mesh with both the countershaft in the gearbox, and the crankshaft of the pump.

[Hanno Spoelstra]

Some original documents referring to the Chevrolet 133" wheelbase trucks. The "W.B." in these documents caused some confusion, but these are in fact Chevrolet WA trucks.

132748462_1920195304795016_3756009213865161287_n.jpg 132188790_10157782435993148_5042062919135481054_o.jpg
(via Brendan O'Carroll and John Valenti)


From the “Desert Chevrolets” article in Wheels & Tracks magazine no.8 I copied the technical details of the 1940 Chevrolet WA.
117798106_1207321656271707_7590470014854090807_o.jpg


Edited to add: the above information refers to the Chevrolet WA 30-cwt truck used by the LRDG before the 1533X2 was taken into service

88EF1CF5-79B2-4F11-B833-2C37E3F02D96.jpeg

[Bob Carriere]

Hi Hanno

The "W.B." refers to wheelbase and not to "series WB.....by coincidence the 1940 WA series is the 133 inches and the WB series the 158 1/2 inches wheel base.....

On the first memo they refer to 113 wheelbase which applies to cars or at 113 1/2 for the 1/2 ton trucks.

Precious documents ........ and the magazine documents makes mention of either 900x13 ot 10.50x16 .........

Any idea which Heavy duty front axle they were requesting from General Motors....? GM did list a std front axle for the 3/4 ton Commercial KD with 11 inch brakes and the Heavy duty axle for the 3/4 ton Commercial KE with 14 inch brakes .......BUT with 123 3/4 wheel base........

Frame wise all 113 and 1/2 ton trucks had a curved frame above the rear axle......
.....all larger trucks 123 and larger the rear frame was flat from the rear of the cab to the end of the frame.

.....and GM also had the HD Maple Leaf front axle same as the HD Cab Over Front axle.

TONY........ I have a 1543X2 parts list, issued November 1940 ( no 167) and it does list the Eaton 2 speed axle....... but blank luck on the 1533!!!!!!

Two front axles are listed for the 1941 model....... one with ball bearings and one with cones and bearings for the "X" HD front axle using 10.50x16 tires. To me cone race /bearings denotes a model similar to the Maple Leaf HD or the COE......... The front wheel hub on HD is unique in having a small domed bolted cover instead of the recessed screw on cap ......

So much to learn........ so little time.

Cheers

[Hanno Spoelstra]

From Clive Law’s “Drive to Victory”:

56CCFF60-D1A7-49A6-95A6-2FACB1BD6067.jpeg

[Simon Theobald]

Dear Hanno, I wanted to thank you and everyone else who contributed to the information I asked for about the truck in my Father's WW2 photo. All of the great information helped me model a version of the picture I showed you. I don't think it will be the most accurate but gives a flavour of the right truck..... and likely the last I ever attempt! Thanks again and stay safe from a "locked down" England!!

[Tony Smith]

Well done!

[Bob Carriere]

Very well done indeed.

Bob C

[Charlie Down]

Hi Bob,
I'm trying to get details of the bumper brackets. It looks like the 1533 and 1543 had solid brackets that raised the bumper to allow the starting handle to pass through the bumper, not the lower spring style civilian brackets. Is there any information in your 1543 parts list about these brackets or is the 1940 edition too early for this detail.
It also appears that there were supporting bumper rods outboard of the brackets that attached to the bracket on the chassis end and went through separate holes in the panel below the grill, before attaching to the bumper.
Trying to clear up this detail.

Many thanks

[David Herbert]

I would have thought that the reason for raising the bumper was to get it further from the ground as the vehicle was to be used cross country. That would have required the starting handle hole to be in in the bumper rather than above it. There would have been no motivation to have the starting handle go through the bumper otherwise.

David

[Charlie Down]

Sorry, that was badly worded on my part, the bumper was raised to give greater ground clearance, which resulted in the starting handle hole now locating in the top of the front face of the bumper.
Apart from the 1500 series of Chevrolet trucks these bumper brackets don't seem to have been used on other trucks.

[Bob Carriere]

Although the part book No 167 does list front bumper (7.825) in the index it is NOT shown either as a picture or a listing in the parts section...... lowest number in the bumper listing is 7.831 ...... bar, front bumper than goes on o the various brackets an rivets/bolts.

The 1940 book no 154 also has a bumper section but starts at 7.831....no diagram and 7.831 is Bar, bumper 2 required...... the rest is all brackets info

Engine crank is 0.239 is listed by itself with no additional info......

The books are like bibles written by different apostles....more or less the same but not good enough by themselves to get you to heaven!!!!!!!

Stay healthy

Bob C

[Tony Smith]

Originally Posted by Bob Carriere

TONY........ I have a 1543X2 parts list, issued November 1940 ( no 167) and it does list the Eaton 2 speed axle....... but blank luck on the 1533!!!!!!

Cheers

The Major Assemblies manual shows that it it the same rear axle assembly (and subsequent superceding numbers) used on both trucks. Very heavy duty for the 1533! This might help someone seeking to scrounge parts from a donor truck to make a 1533 replica.

I see that the model code for both 1533 and 1543 are the only trucks with the two speed specified. I wonder if the xxx3 indicates "two speed" axle?

[Grant Bowker]

Originally Posted by Tony Smith

The Major Assemblies manual shows that it it the same rear axle assembly (and subsequent superceding numbers) used on both trucks. Very heavy duty for the 1533! This might help someone seeking to scrounge parts from a donor truck to make a 1533 replica.

I see that the model code for both 1533 and 1543 are the only trucks with the two speed specified. I wonder if the xxx3 indicates "two speed" axle?

It might be like the use of the same parts being used throughout the CMP range. Only one part to inventory and not enough weight or cost saving to justify the added trouble/cost of having two sets of parts.

Statistically, the number of spares/truck required to keep a fleet serviceable goes down the larger the fleet size of identical trucks (or airplanes, ships or widgets) you are maintaining since the odds of them all failing at once get smaller as the fleet gets larger. Put another way 1 failure is 100% of a single vehicle fleet but the same failure is only 1% of a 100 vehicle fleet.

[Tony Smith]

Originally Posted by Grant Bowker

It might be like the use of the same parts being used throughout the CMP range. Only one part to inventory and not enough weight or cost saving to justify the added trouble/cost of having two sets of parts.

Exactly. And for the same reason, I would hazard a guess that the Chev parts 5806664 and 5824253 have precisely identical equivalent parts with Ford part numbers used in the FC60L. Same Eaton diff centre, same track and spring centres and same 8 lug hubs for WD wheels.

[Grant Bowker]

Again by parallel to CMP, Ford and Chevrolet may have used different rear axles. The ones shown appear to match Chevrolet casting style (not a Ford split axle). I don't know how Ford handled 2 speed axles - whether with a split housing, a GM style banjo or a pure "supplier" axle (Eaton, Timken, Spicer etc.). I will try to dig into this more later.