[sapper740]

OK all my Engineer loving friends, here's some of what you can expect should the exalted one bestow an Engineer Forum upon us. (Have I told you what a great, great guy you are lately, Jefe?)

Tonight's episode:

Expedient Surfaces:

A subject dear to any Engineer's heart and critically important to the war effort: how to allow heavy vehicles and aircraft to traverse or land on soil, sand, or mud that would otherwise be excluded from operational use. We didn't always have the choice of where we were to engage the enemy and the need for close air support and air superiority necessitated the building of air strips close on the heels of the advance. There was no time for building elaborate concrete runways, taxiways, and ramps. The British system of "Chevron" planking was stout but tended to tear up the tyres of landing aircraft. American PSP (Perforated Steel Planking) and the lighter PAP (Perforated Aluminum Planking) proved an ideal surface, though it was heavy and required sufficient logistics for timely delivery and relatively large crews to install. A simpler, quicker system of expedient surface for runways was needed. This need was amply met by PBS (Prefabricated Bituminous Surfaces). PBS was invented in Canada, improved by the Brits, and perfected by the Americans at the U.S. Army Waterways Experiment Station (WES) in Vicksburg Mississippi. PBS consisted simply of cloth impregnated and coated with bitumen. Army duck, Osnaburg (Muslin), burlap, and Hessian cloth were used as fabrics, and asphalt as the bituminous coating. When used by American construction engineers, the Army distributed PBS in rolls approximately 3 feet wide and 300 feet long, the average roll weighing 350 pounds. A coat of mica powder on its top surface prevented adhesion during transportation and storage. As a flexible surface, PBS had the unusual advantages of being waterproof, dustproof, and inexpensive, and it could be laid rapidly by a machine called a "stamp-licker," which applied a solvent (usually diesel fuel) to the underside of the strip as it was unwound. The strips were half-lapped, which resulted in a more watertight surface. PBS also proved to be exceptionally easy to repair as two men with some of the cloth and a bucket of tar could quickly repair any small holes. Site preparation involved clearing the area of any vegetation after the Engineers removed any mines and unexploded ordnance. After leveling, the ground was compacted and a "Penetrometer" was used to test for sufficient compaction. I've uploaded four pictures, one shows the PBS being pre-staged, another the "Stamp licker" laying the PBS, thirdly; PBS and PSP in a side-by-side test, and lastly; aircraft tires mounted on equipment to test the both the durability of the surface and wear on aircraft tires.

CHIMO! Derek.


(P.S. next episode, self-powered towed sand shite spreaders!)