and IMPROVISED BARRIERS
The traditional Caltrop is a four pointed device that was originally scattered on roads in ancient times to injure the hooves of horses being ridden by the opposing army. These devices are equally effective against today's automobile tires.The four points are arranged in a manner that guarantees that one point will stick straight up no matter how the caltrop is placed on the ground. This allows the devices to be scattered from a fleeing auto, thrown by hand or dropped from the air.The road can be opened only after the caltrops are picked up one at a time by hand. The cleanup personnel are susceptible to sniper fire during this cleanup period. A pileup of several disabled ve hicles will of course add to the problem of reopening the roadway, especially if all available tow trucks have received multiple flat tires,as there is usually only one spare tire per truck. Imagine several hundred of these devices on a major freeway during rush hour traffic. A.A simple caltrop can be made as Tollows. They are easier to make than describe. If the following does not make sense, try it first with a couple of pieces of coat hanger or welding rod, and play with the design until you come up with the right shape. A dimestore protractor is useful in determining the correct number of degrees for each bend.
The completed units should be painted flat black or dark gray.They will blend in with the color of the roadway and will be almost impossible for drivers to spot and avoid, even if they are on the lookout for them.
1. Cut two pieces of iron or steel rod, V to h" diameter, to a length of 3V.
2. Sharpen all four ends to a sharp point with a file or grinder.
3. Weld or braze the pieces into and 'X' shape.
4. With the 'X' lying flat on the behch, bend one leg until it is straight up in the air, i.e. at a right angle to the bench.
5. The remaining three legs are now bent until they are at 120 deg. angles to one another. If placed on a circle, the legs would divide that circle into three equal parts. All 3 legs should still be flat on the bench.
6. Each of the three legs is now bent until they rest at a 30 deg. angle from the surface of the bench. The fourth leg should still be vertical .
Each of the four legs should now be 120 deg. from its, two adjacient legs. The caltrop should now rest solidly on any combination of three legs, with the fourth pointing straight up.
Several variations of the caltrop design exist. The following are the most useful and easily improvised. B. The spike board (see PMA Vol An).
The spiked hazard used at drivein movies. These allow normal traffic to exit, but cars trying to make an unauthorized entry are Impailed on the spikes, which protrude at about
45 deg. from the ground. Those spikes are mounted on a weighted axle which pivots flush with the roadway on exit but locks solidly in place during an attempted entry.
The borders between European countries are equipped with movable road blocks that resemble the foldr ing gates often used to prevent toddlers from falling down stairs or from entering 'off-limits' rooms.The device has a sharpened spike at each pivot point and is anchored at one side of the road. A guard extends the obstacle into one or both lanes to block the road, and folds it out of the way to allow authorized vehicles to pass.
E. A Caltrop like device that requires no welding or bending can be constructed from short sections of pipe and six bolts and nuts. If welding equipment is available,the same "device can be constructed using six large nails. The advantage of this type of caltrop is that several of the units can be strung onto a chain or cable. This a'ssembly can be stretched across a roadway and anchored to solid material,i.e.boulders, trees, wrecked vehicles,etc, at each end. The road can be reopened only by cutting the chain or cable with a torch or bolt cutters. The personnel attempting to remove the obstacle are again open to sniper fire.
The pipe caltrop is constructed follows. The measurements can be altered to suit the materials on hand Each individual caltrop is made from a six inch long section of 1-1V meter pipe, and six 3" bolts w/nuts." a. Orill 6 sets of holes through the pipe, in 3 rows of 2 holes each.Pipe will contain total of 12 holes.IE., six sets of holes, one set for each bolt (See drawing), b. Use a grinder or file to sharpen tfie ends of the bolts, c^ Pass the bolts through the holes and Install and tighten the nuts, d. If welding equipment is available, large nails may be installed in the holes and welded in place.
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