Windlass mechanism

A total of 19 different types of tourniquets were used in these studies (see Figs. 5.5-5.23). The tourniquet types ranged from the simple elastic type tourniquets to a pneumatic operated tourniquet. The tourniquet types included elastic, windlass, mechanical advantage cam, block and tackle, ratchet, and pneumatic. The tourniquets tested in these studies included ... 

A capture thread of Araneus diadematus under increasing magnification. The windlass mechanism is seen in the lower picture where the core fibres after a large extension-contraction cycle have been reeled into a droplet (for details see ref. 12). 

On the basis of these requirements, a study was initiated by the United States Army Institute of Surgical Research (USAISR) to evaluate nine commercially available tourniquets for applicability to combat use. Of these nine only the seven that were within the mechanical specifications of size and weight were tested. In a report covering the study issued in 2005, Walters et al. concluded that three of the candidate tourniquets met the requirements, the Combat Applications Tourniquet (CAT), the Special Operations Forces Tactical Tourniquet (SOFTT), both are windlass type tourniquets, and the Emergency Military Tourniquet (EMT), which is a hand-operated bulb pump pneumatic type tourniquet. These three were rated as 100% effective in blood flow occlusion. Of these three, the EMT was judged as the least painful, but it was recommended only for medical personnel and not for the field... 

Another interesting silk composite, the sticky capture silks of Nephila and Araneus, are complex, albeit microscopic, mechanical windlass systems that make good use of the physics of biological micro-engineering (Fig. 8.3). In the windlass silk (which operates in the wet state) the elasticity is given by a combination of surface tension of the aqueous coat and recoil of the plasticised silk fibre [12-14] while adhesion is bestowed by a separate glycoprotein complex [12, 15]. 

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