Going through some of my Father’s WWII snap shots, there is one I find more evocative than the others, in which his ten man section is shown shortly after arrival in Egypt in June 1941 (see Figure 1). They were part of ‘B’ Company, 1st Battalion, The Hampshire Regiment. A group of men which, with losses and additions, he was to fight with, almost continually until mid-1944 when he was seriously wounded during the Normandy Landings.
Figure 1. One ‘section’ of B Company, 1st Battalion, Hampshire Regiment, and some locals, shortly after the soldiers arrival in Egypt, 13 June 1941. Stanley Lewis Saunders (my Father) is marked with an ‘x’. According to my Father they were issued with the ‘pith’ helmets on arrival, but it was soon realized that in the prevailing mobile and fluid conditions the infantry had to have light weight and compact kit. Having two large rigid helmets, i.e. the Mk II steel helmet and a ‘Wolseley’ was impractical. So the Wolseley’s issue to foot soldiers was short lived and they were soon replaced by the slouch hat. It can just be made out that most have puggarees.
Re-reading Stuart Bates’ excellent book ‘The Wolseley Helmet in Pictures, From Omdurman to El Alamein’ (2009) (available on this web site) it was interesting to note that the date of his probable arrival in Egypt (see Figure 2) is just after the official adoption of the aluminium foil ‘drop liner’ in Wolseley helmets. Stuart’s book includes a detailed discussion of the ‘drop liner’; basically it was a cardboard dome, lined with aluminium foil and dropped into the helmet shell and held loosely in place by the sweatband, able to ‘float’ in the dome allowing air to circulate around it. It was supposed to reflect the sun’s heat and keep the head cooler by 10-15oF relative to a basic Wolseley of the early 20th century. These quoted temperatures, however, are from the patent application, and there is some question as to how effective it actually was.
Figure 2. Stan Saunders was born 28 June 1920; like most of his generation, fate was to be unkind. Called up 14 November 1940 to become Army Service No. 5510034, his first leave (shown above on a page from his ‘Soldier’s Service & Pay Book’) was for a 7 day ‘Embarkation’ leave, starting 8 April 1941. These dates probably mean he sailed on convoy WS8A (Arnold Hague, 2007), which sailed from the Clyde on 26 April 1941, down the Atlantic via South Africa, arriving at Suez 13 June 1941.
The Experiment
The question of the drop liner’s effectiveness made me realize that I actually had a couple of Wolseleys in the house, one a standard cork spacer example with a 1917 WD date stamp and the other a 1942 (code ‘O’ stamp above a broad arrow and WD mark) drop liner version, together with a thermal imager (for taking the temperature of volcanoes – that is my occupation). Below is a simple experiment to see if the drop liner was actually effective in keeping the interior of the helmet cooler than a standard helmet.
Figure 3. Left, a standard early 20th century Wolseley helmet, simple cloth covered cork shell, with a simple leather sweatband with cork spacers. Right, a WWII felt Wolseley with aluminium foil drop liner, held in the dome by the leather headband loosely attached to the shell by four shell piercing metal loops and cotter pins (see Bates & Suciu, 2009, for more details).
Figure 4. Top, the two helmets with compressed paper fiber bowls inserted into them. This was done because a thermal imager works by converting infrared radiation (heat) emitted by an object into the visible spectrum. Basically the instrument measures the temperature as a function of the images ‘brightness’. Unfortunately aluminium foil is reflective and just like with a visible camera the image would actually show reflected light (in this case infrared) and not show the temperature of the actual foil. This would confuse any meaningful analysis. So the inserted paper bowls enable us to measure the temperature of identical material surfaces in the same plane in both of the helmets. They were left like this for an hour to both acquire the ambient temperature. The thermal images at the bottom show that after an hour, in my un-air-conditioned living room, they were a balmy 33-34oC and within 0.3oC of each other.
Figure 5. The thermally equalized helmets were then placed on a sheet of plywood on the ground in full sunlight. The standard helmet is on the left and the drop liner helmet is on the right in both images. Being around midday and only 4o south of the equator the solar radiation was ample for the purpose. After 10 minutes the helmets were quickly taken and placed on their sides in the shade and thermal images taken of their interiors. It can be seen that now the centre of the bowl in the standard Wolseley is 40.3oC (104.5oF) and the same spot in the centre of the ‘drop liner’ helmet is 35.9oC (96.6oF), with the relatively cool (blue) circular area of the foil liner clearly seen.
So it appears from Figure 5 that the drop liner does indeed help to keep the inside of the helmet cooler, in this case by 4.4oC or 7.9oF, although significant, and its effect would be welcomed by any tropical user, it is not the 10-15oF claimed by the patent holders. However, this was a very simple experiment, the helmets placed on the hot ground, if they were placed at ~6 feet (2m) above the ground on a mannequin or human head, as in actual use, the airflow around the liners may have caused a more significant difference. The results are not that surprising, however, as the Army would have done reasonably extensive trials to ascertain the veracity of the patent holder’s claims, before launching mass production and general issue.
Figure 6. A thermal image of the two helmets in full sunlight after 10 minutes. Unexpectedly the two helmets exteriors also showed significant variation, the standard helmet at left is already around 60oC at its apex, and is significantly hotter than the right hand helmet over most of its surface. It is starting to merge in with the ambient temperature of the wooden board it stands on (the blue patch in front of it is where I stupidly slid it backwards for the photo and exposed a shaded patch of wood!). The ‘drop liner’ helmet at right remains predominantly in the high 40s low 50oCs, but is starting to heat up at the top. Whether the variation between the two helmets thermal responses is due to the different liners, or whether it’s the difference in heat absorption between the cork shell and the felt shell is not known, although the heating of the front and back of the brim of the left (cork) helmet would suggest it is a factor. The wooden baseboard was exposed to the sun for a long period of time before the helmets were placed on it, so the helmets’ heating is not just solar, but also from the hot surface below. It can be assumed that the longer they stayed in the direct sun, they would probably approach parity. It can also be seen that the puggarees do tend to stay cooler than the shell itself. Traditionally of course the puggaree could be soaked in water and by evaporation help cool the helmet, whether this was done regularly in practice is a question for other researchers. I thought it best not to soak my 103 and 78 year old helmets!
A 1937 military document quoted in Bates & Suciu (2009) states that the ‘bright aluminium foil… reflect the sun’s rays’, this statement, that a foil layer in the dark confines of a thick felt dome is reflecting back some sort of penetrating solar ray, today seems strange. It probably harks back to the idea of ‘actinic rays’ a supposed component of tropical sunshine that could pass deep into European flesh, penetrating the skull and nervous system causing various deleterious effects (e.g. The Peregrinating Penguin, 2016). These health issues were almost certainly caused by dehydration and raised core body temperatures; factors which can cause collapse even in a darkened Swedish sauna! These days UV is recognized as the only common natural ‘actinic ray’, but those rays can be almost completely stopped by a light cloth hat and airy garments; even a paper parasol! Although the ‘drop liner’ foil dome wasn’t needed to block invisible deeply penetrating deleterious rays, its function was to reflect back inward radiating heat that had been absorbed by the shell due to the helmet’s outer surface being exposed to the sun. The metal foil may also have been useful in rapidly conducting body heat away from the head and into the airstream in the ventilated chamber of the helmet?
In some sections of modern society the notion of foil headwear protecting the wearer from unseen forces has again gained some traction, but ‘drop liner’ Wolseleys have yet to make a comeback.
As in all experiments once you start them, the possible ‘variables’ and questions multiply. So before an hour’s fun turns into a compulsive month, I’ll stop here.
- Steve Saunders,
- Rabaul, Papua New Guinea,
- 4.20oS, 152.16oE
- Jan. 2020
Reference
Stuart Bates and Peter Suciu (2009). ‘The Wolseley Helmet in Pictures, From Omdurman to El Alamein’. PSB Publishing
The Peregrinating Penguin (2016). ‘Pith helmets, spine pads and actinic ray’. leepenghuiblogspot.co
Arnold Hague, ‘Routes to the East’, (2007). As included in – https://www.naval-history.net/xAH-WSConvoys04-1941A.htm