Tuesday, October 19, 2010

DIY: Demolition Derby

The guys in the above video used a fuse to ignite an explosive in the RC car.

Crude, but effective.

However, one can take this one step further and build a remotely piloted bomb that will detonate on command.

Inexpensive RC (radio controlled) cars, planes and helicopters have proliferated. They can be purchased everywhere from kiosks in malls, on-line, to stores like Radio Shack. A very good time to shop for RC cars is after Christmas, especially at Radio Shack.

By inexpensive, I'm referring to those under $40.00. Check out Hobbytron for examples. Sure, you can spend much more, but why? You won't be competing in a race against anyone (except maybe the poor schmuck who is sprinting for his or her life). While this can be an anti-personnel device, it is primarily to be a destructive device designed to harass and deny your opponent cover.

How smart is it to hide behind a car when someone can essentially drive a bomb under the gas tank?

An RC car will not always be useful, even if it is a 4X4. The terrain may make its use uncertain at best, and for optimum effectiveness, you need line of sight. Unless you're willing to spend the money for wireless camera equipment, which can get pricey, other potential solutions should be examined. This tactic would probably be best utilized in an urban or suburban environment.

Back in the early 80's, I remember hearing a story of an assassination that had been carried out using a LARGE remote controlled plane that was carrying a block of C4. I looked around on the web to see if I could find the story, but wasn't able to. If memory serves me correctly, the operation was carried out in Africa and the target was an executive with some company. No one had been able to get close enough to target him in a conventional manner.

An enterprising individual wired the landing gear servo to flip a trigger switch. The plane was then flown into the target's office window, and the rest is, uh....history.

So, there's the first thing you're going to look for on your donor vehicle. A function you will not need. Some of these cars come with lights and horns that you can trigger from the remote. Some have brakes. The "brake" essentially reverses the current in the motor to cause it to stop turning. It isn't a braking system in the conventional sense, but it can be used as a trigger with a proper diode setup.

The inexpensive RC cars usually have a single circuit board that combines the receiver and switching circuitry for auxiliary functions. If you obtain an assembled, ready to run car, it will be fairly easy to determine which wires run what function. Just follow them from the lights or whatever, back to the circuit board. If you're building it yourself, lucky you, you have the instructions that should tell you what is what.

Now, generally these circuits will not be able to supply power enough to be able to activate an electrical trigger for an explosive. You will need to install a relay. Measure the output, when the source is on, and select an appropriate relay. So, for example if you measure 7vdc out, you may want to select a 6vdc relay maybe like this one.

Why? Because as the car runs, there will be a voltage drop. You want to make sure you have enough power to drive the relay, and if it fails because of over voltage, hey ... we're only using it once.

So, wire the output from your controller to the coil on the relay. Below is a diagram from Radio And Electronics School to help you visualize what we're doing.

The bottom battery is your source from the on board controller module. The top battery is another battery that you place on board to trigger your electrical detonator. The lightbulb represents your detonator. The box in the middle is your relay. The switch (broken line) to the left of the bottom battery is the control in your hand.

For example, if you're using the headlight function, when you trip that function the switch closes.

Strip your donor car down to bare minimum. You want it small and neutral in color. No point in making it an easier target for potentially disabling gunfire. By discarding the unnecessary parts, you make room for the weight of your payload.

You're after function, not form.

If any of you remember the 1988 movie, starring Clint Eastwood, The Dead Pool you will remember the clip below. It's in French. It was the best quality clip I could find on YouTube.

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