LRDG Wireless set up

[Charlie Down]

Yesterday I got Brendan O'Carroll's new LRDG book, 'Fighting with the Long Range Desert Group' (which is excellent) and found a photo of a Wireless Chevrolet WA with panel on the side that could be a charging switch panel. I have now found 2 other WA photos with the same panel fitted. I have grouped a close up of the panel with the panel partially seen on a 1533X truck for comparison.
The panel has at least one knife switch and I assume based on other charging panels it would need 3-4 to make it work (see attached MKV Panel).
Hanno has suggested that the panel could be a main on off switch and posted the image attached. It doesn't match the original photo but has opened up more questions about the set up.
I've been working on the assumption, based on feedback from various wireless forums that the trucks would need a charging switch panel to manage the power and charging of the batteries. There are so far no known charging panels that fit the photo of the 1533X2 panel, so it has been presumed that it would be relatively easy to make one in a base workshop with a few suitable components that would fit onto a truck. I don't know why they didn't use a standard panel, they weren't the only wireless trucks in service in the Desert at that time. And I imagine they would have access to any if they were available. The early British Wireless trucks normally operated with 4 6 Volt batteries, and a separate battery for the vehicle. 2 batteries would provide the necessary 12 volts and the other 2 would be charged, usually by a chore horse or later on, a PTO driven generator. There is no evidence that the LRDG had that many batteries, although the spares could have been stored in a locker or in a box, ( I need to check the battery inventory) which would make sense as the Patrol was really about escorting the Wireless truck to a position to transmit intelligence back to base, and not having back up batteries would seem like a stupid idea, and the LRDG weren't stupid. It was suggested that the 1533X2 panel used knife switches on the charging panel based on the photos, and that they could be commercial not military. The LRDG did have some Chore horses on their inventory, but not it seems enough to equip all the Patrols and they seem to have been retained by HQ. Sorry for the random ramblings and thoughts. Its a serious test of my limited Wireless knowledge. I also need to stop calling the battery on the side step a spare battery, when it was clearly a Wireless battery in series!

[David Dunlop]

My guess on the knife switch, Charlie, is that it is the selector switch between two distinct aerial setups for the wireless set so the operator can change quickly from one operating frequency to another.

Another factor to consider. Vehicle starting batteries are a very different design from wireless batteries. They are meant to provide a huge starting current quickly and then have very little to do other than sit and get recharged.

Wireless batteries, on the other hand, are designed for deep discharge where a few amps are needed over as long a time as possible. In fact, you will often find operating ratio data provided in wireless manuals advising operators of the best possible combinations of receiver time (low amp draw) and transmitter time (high amp draw) to enable the wireless batteries to last on a full charge as long as possible. Wireless batteries are quite happy under a float charge, most vehicle batteries do not like it. Vehicle batteries will experience increased failure under high deep discharge conditions as well.

The LRDG would have been aware of all the limitations of the two sets of batteries on patrol. Just another set of supply considerations each time they set out.

One other thought. What is known of the fuel supplies for the LRDG? Did they have access to fuel depots placed in the desert while on patrols, or did they have to carry all they needed from start to return? If fuel was not an issue, having a chorehorse as part of your kit would make sense. If fuel was critical, maybe they deleted a chorehorse from patrols and used PTO driven generators for charging the wireless batteries. Either way, you would still need the switchboard seen tucked behind the drivers arm.

David

[Bruce MacMillan]

In the photo from Charlie it shows a 4pdt switch on the side of the vehicle. It's in a convenient place on the side where batteries would be kept. My thoughts are this is for charging batteries. Here are some diagrams of the battery system from my M152 sigs van. You can see there is a 4pdt switch to select battery banks and each bank has a pair of wires connecting to the switch. This allows one set to be used and the other to be charged. The knife switch is not rated for radio frequencies so you wouldn't want to attenuate the already low power output.

[Bruce Parker (RIP)]

My 2 cents. Almost every British radio truck and even carriers used a 12 volt electrical system for the wireless completely independent of the 6 volt vehicle system. The 12 volt wireless system included either replacement batteries delivered every morning (along with your rations I presume) or two sets of batteries so one could charge while the other was operating the radio. This arrangement would be modified for setups working away from 'base' as the LRDG did, so a self contained system with a generator is the most likely. Jumper cables to pairs of 6 volt wireless batteries to charge then put in series for 12 volts?? That would be about the only way using the truck generator if a chorehorse wasn't available.

As to the type of radio, it seems 11 sets were first used, but did they ever change over to 19 sets? The electrical system above would have accommodated either.

[Mike Cecil]

Hi Bruce,

Interesting comments, so I'll chuck this into the mix as well: the Australian Cruiser Tank used three different voltages (6V, 12V and 40V), with the 6 & 12 volt systems reliant on the same design/amp-hour 6 V batteries as the 6V system. The 6V system was grounded to the hull.

The 12V system used 2 x 6V batteries and was wired independently and 'sealed' from the vehicle. A 12V generator was included, run by a connection to one of the transfer case lay shafts.

My point here is that the same 6V battery type was used for both, so could be changed over in the field (with some considerable difficulty) between systems if needed. While a single 12V battery would have reduced the stowage problems a little, battery commonality made interchange between systems possible and also simplified the supply stream.

Mike

[Bruce MacMillan]

Originally Posted by Bruce Parker

As to the type of radio, it seems 11 sets were first used, but did they ever change over to 19 sets?

Good question, I know there were issues with the 19 set in North Africa due to the heat. I just watched Sea of Sand on youtube and wonder if the trucks used were ex LRDG? Here's a clip showing a WS19 but as the movie was filmed in 1958 it may not be period correct for WW2

[Charlie Down]

Gentlemen, thank you for your input, that has given me much to ponder.
To quickly answer some questions
WS11 was used throughout the campaign, it worked they could mend it and it met their needs..
Supply dumps were established throughout the desert. Petrol, water, food and medical supplies seem to be the main items. No mention of batteries, let alone different types/spec.
Batteries. The truck battery and the wireless battery on the driver sidestep are the one known about. Whether the wireless battery was 12 volts? I'll see what I can find about any other batteries, but currently looks like too few batteries for the job. I need to look into this.
Chore horses are mentioned but the inventory (late 1942) suggests there were only enough for HQ. However at other times the situation could be different.
The photo suggests to me that there was one large knife switch and 3 other smaller (knife?) switches, as opposed to 4 ganged together. however I understand the concept of the ganged 4 switches, just trying to work out how that idea could be accommodated by the truck 's wireless set up.
I presume the trucks were supressed for wireless use, maybe all the trucks at the factory, but there is no mention of it.
The trucks in the film 'Sea of Sand' were mostly Dodge trucks, but there was at least one (ex RAF?) Chevrolet 1543 long wheel based truck modified to look like a 1533X2.

I think I need a lie down for a few days to take on board all the information and then cross reference it to any documents!

Attached is the best view of the wireless battery on the sidestep. I don't know if that helps in any way. 12 Volt maybe?

[Mike Cecil]

Charlie,

As far as I'm aware, only the top view of the battery will tell you the voltage (by the number of cells visible).

Mike