Thursday, November 17, 2016

Vehicle Recovery Part 1: Attachment Points

So, you're escaping the zombie uprising by driving in a convoy of your tribe to your super-secure BOL when you run over an especially squishy crawler and your vehicle slides into the ditch. Can you get back out of the ditch before the zombie horde catches up to you? Since AAA isn't likely to be running on time (or at all) during an emergency, you may have to be your own tow-truck. Part 1 will cover the vehicles and Part 2 will cover the methods and equipment. There may be a Part 3 if I receive feedback requesting specific information.

Front-Wheel Drive Vehicles
If you're driving any front-wheel drive (FWD) vehicle made in the last 30 years, it is likely an unibody and doesn't have a frame that the body is attached to. Rear-wheel drive (RWD), all-wheel drive (AWD) and 4-wheel drive (4WD) vehicles are more likely to have a sturdy frame underneath to accommodate the transfer of power from the engine to the rear wheels. A sturdy frame will provide plenty of places to hook up to, but a unibody style vehicle will be trickier.

The majority of cars on the road today are FWD, and thus present a challenge when trying to tow them or pull them out of a ditch. Without a solid frame, there are few places sturdy enough to attach a hook without damaging the car. I have seen newer cars with tow hooks or loops welded onto the underside by the factory; this makes life a bit easier if you ever need to hook up your car for a tow or recovery. Older FWD cars need to be studied a bit, with a healthy dose of common sense applied, to find a good place to place a hook for pulling the weight of the car:
  • Don't attach a tow line to anything that is designed to move. Axles, steering components, and suspension parts (shocks/struts, coil springs, etc.) are not going to be strong enough to withstand the force needed to drag a car, and once any of them are bent or broken, your car is out of service until you can find the right parts or shop to replace them. Trying to drive a FWD car with a bent half-shaft is a good way to shred a transmission.
  • It is unlikely that you will find anything to hook to near the center of your vehicle. Most tow points are about mid-way between center and either tire. This means that any force applied will tend to pull the vehicle to the side as well as forward. Keep this in mind when planning your path!
  • The metal you hook to should be at least half the thickness of your chain or cable. Find the beefiest place you can to hook to -- there will be some serious force applied to it.
  • Look for where the engine bolts to the car. That may be as close to a frame member as you're going to find on a FWD car.
  • Rear axles on most FWD cars are only there to keep the vehicle's rear end off the ground. They have no structural strength to speak of. This is why you see fewer of the old-style tow trucks on the road and more of the flat-bed style. lifting the front end of a FWD car shifts the weight to the rear axle, and most of them aren't sturdy enough to handle it.
Rear and 4 Wheel-Drive
These vehicles have their own peculiarities:
  • A lot of RWD/4WD vehicles have trailer hitches installed on the rear. I will detail the types and limits of hitches in part 2, but they generally make good tow points since they are bolted to the frame. 
  • Axle housings are usually castings and may not survive a narrow cable pulling on them. They kind of fall into the "parts that move" category, but are stiffer that a bare half-shaft that you'll find on a FWD car. Use a tow strap if you have to pull by the axle housing, as it'll spread out the force and be less likely to cause a crack in the casting.
  • There are usually holes in the frame of a RWD/4WD vehicle for attaching accessories. These will make for good places to attach a tow line, especially if you add an eye or clevis before you need it.
Some General Rules
 These apply to all vehicles:
  • The towing or recovery vehicle will need to have enough power and traction to pull the weight of itself and the towed vehicle, as well as overcome any slope or suction involving the towed vehicle.  Power is the size of the engine and the type of transmission; traction is the weight over the drive tires and the surface the tires are sitting on. Do what you can to improve the traction (increase the weight over the tires or modify the surface under them) if you have to.
  • Pull gently. Jerking or "snatching" a car out of a ditch without the proper gear will only break things. If you're lucky you'll only break the chain or cable; otherwise you're going to do damage to one or the other vehicle. Automatic transmissions should be set to low gear; manual transmissions should be in the highest gear you can pull forward in.
  • Snow and sand aren't bad for "sticking" a car, but mud will cause suction and make it much harder to pull a car. 
  • Lighten the towed vehicle as much as you can before trying to pull it. Common sense should tell you to make it as easy on the towing vehicle as possible. The exception to this rule is if you are using the towed vehicle drive wheels to assist the towing vehicle. If traction is a problem, shift weight so that it is over the drive wheels. 
  • No vehicle made after about 1975 has a real bumper. Old cars had steel bumpers rigidly mounted to the frame, but now they are all a part of the energy-absorbing crash protection engineered into the car. Bumpers are not a good place to try to hook onto anymore.

As with any prepping idea, it is a good idea to look under your car now while the weather is good and you're not dodging zombies. Figure out where you can hook a tow chain before you need to, so you'll be prepped for it if the need ever occurs.

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