Chevrolet 1533X2 30-cwt trucks

[Hanno Spoelstra]

On a LRDG research FB page, John J. Valenti posted the specs drawn up by the LRDG for what became the Chevrolet 1533X2. It mentions all kinds of interesting details, like an “engine driven air pump”.

B9C54D76-2819-4383-853C-DF5EECEF2157.jpeg

[Grant Bowker]

Yes, very interesting.
Given the stated objection to WD pattern was weight, complexity and gear noise of the 4WD drive, I wonder why a C30 modified to use a commercial pattern Timkin (their spelling) front axle wasn't considered. It would have provided many of the features they asked to include on the modified commercial chassis. Hatred of the cramped cab 11/12 (document dated 1941 so before cab 13)?

The phrase "engine driven air pump" could describe the CMP standard pump mounted on the transmission but powered by the engine.

[Hanno Spoelstra]

Grant,

I think the previous experience with civilian GM trucks from “Local Purchase” in North Africa influenced these specs. See the attached document from 1940 listing the types of trucks in use by the LRDG.

Apart from the purpose built body by Gotfredson, the rest of the 1533X2’s configuration seems to be made up from off the shelf components already used for MCP and CMP trucks.

The tyre pump would indeed be the gearbox mounted compressor which was an option on MCP and CMP trucks.

Noteworthy is the specification of the rear axle with 6.17 ratio. This would be the same axle as on the C15, which has a type of differential lock. Thus, the 1533X2 was ideally equipped for the desert, whereas the extra weight, noise and fuel consumption of an all wheel drive system apparently did not give enough advantage.

FCC42046-1E20-4BD8-8AD0-596D04CBC275.jpeg

[Charlie Down]

Hi, this is my first venture into MLU, just joined today as advised by Hanno. I am currently trying to get a set of drawings of the floor and cab area including the dashboard completed for the LRDG Chevrolet 1533X2 truck on the basis that we don't know much specific detail about it. On the spec above it stated that the trucks would have a PTO air pump, but have never seen one being used. I have so far got details of the actual pump and its location, I know what the airline looks like and the connector, but have no idea where the airline runs to from the pump and whether it comes out in the cab or somewhere else. The cab makes sense as it's central to all 4 wheels, but there is no photo evidence of it's location on the LRDG trucks. I know the pump and airline were a standard accessory, was its fitting and location also standard?

[Grant Bowker]

This doesn't apply directly to the 1533x2:
When fitted to a Chevrolet CMP, the pump is driven by PTO attached to the left side of the transmission, engaged by twisting a rod with slot in the end using a screwdriver or similar tool through a hole in the floor. On CMP, the air output line ran to a fitting mounted on the frame rail adjacent to the pump. Based on the photos of the trucks, the frame rail isn't readily accessible so either an extension to the airline, relocation of the line or an access door would be needed. One of the photos in post #19 above shows a couple of projections on the filler panel between running board and cab (at the forward edge) that might be an air fitting. I hope someone with more knowledge can give you a better answer.

[Charlie Down]

Thanks for the reply Grant. Based on the information you gave I had a good look at my 200 odd LRDG truck photo's. I looked at the area below and around the door frame, as you suggested. The running board on most LRDG trucks was loaded with stowage, quite often running its length, with extra boxes, spare wheel on the Breda gun trucks and cans stowed in front of the standard rack containing 3 x 2 gallon POW cans. This means that if the airline came out in this area on a vertical surface the stowage would block access, which doesn't make sense. This left the horizontal steps, which don't show up well in photos, due to the canvas door at the front, stowage at the rear, troopers in the way etc. However I did find this intriguing photo of a 20mm Breda gun truck having a tyre change. A trooper seems to be lifting a flap on the step, which ties in with your comments, would give the crew access when the running board was heavily stowed, is central to the vehicle and explains why its not visible in the other photos. Would this be a possible solution to the question? Does it make sense considering standard fitting on other vehicles? Also would there be one on the other side too? Are there any photos of this arrangement on other MCP Chevrolets?
Annoyingly I've looked at this photo a hundred times and never noticed that detail!

[Hanno Spoelstra]

I think you have cracked the nut, Charlie!

Please post that other photo of the tyre inflation too.