MacGyver Science: Banh Bao + Sterno + Drill + Burner + Mason

Image: Rhett Allain. A cordless drill used as a microphone.

Season 5 Episode 4

A quick comment. I really liked this episode. It has:

  • Peter Weller as Mason — great.

Now for the science.

Breaking Glass With a Temperature Difference

Image: CBS MacGyver

In order to break through a glass window, MacGyver first smears some sterno (that heating stuff for food trays) onto the window. He lights it on fire and then throws ice water on it. After that, he hits the window with a sparkling wine (we don’t know if it’s from the Champagne region in northern France) which breaks the window.

So, can you break glass with a temperature difference? Yes. In fact, here is a paper looking at the breakage of glass in fires.

Experimental Study On The Breakage Of Toughened Glass In Enclosure Fires. Xie, Q., Zhang, H., Wan, Y. T., Zhang, Q. W. and Cheng, X. D., 2007. Experimental Study On The Breakage Of Toughened Glass In Enclosure Fires. AOFST 7

See. It’s legit. But wait! There’s also this fairly awesome trick you can use to cleanly cut a bottle with fire and ice.

OK, but what about shooting the cork? Although it looks cool, the cork is probably not moving fast enough or with enough mass to break the glass. A better option would be for Desi to try the chair again.

Hydrogen Fuel Cell Car

This is not a MacGyver hack, but it’s still science. Matty and Russ are trying to recruit this science fair kid (Eli). He converted a car to run on fuel cells. Since it’s not really part of the plot, I don’t want to go into all the details of fuel cells — let me just give the short version.

A hydrogen fuel cell use hydrogen and oxygen. When these two elements are combined, they form H2O — water. This process creates an electrical current that can power the car.

Check it out. Here are some students from Swarthmore that built a fuel cell motorcycle.


Using a Drill as a Microphone

Image: CBS MacGyer

Mac and Desi need to hear what’s going on in the next room. Angus takes a cordless drill, removes the battery and connects the the contact points (where the battery would connect) to the wires going to a speaker (it doesn’t have to be Bluetooth). Then he connects a plastic plate to the drill bit and presses it against the door to hear.

I’m really happy with the way this hack turned out. At first, the goal was just to have MacGyver create some type of listening device from stuff in a morgue (that’s how a lot of these hacks start out). There are a lot of ways to make a microphone, but I wanted to do something different. In my physics class, I often show that you can use a small motor as a speaker. The idea is that an electric audio signal will make the motor shaft rotate back and forth with the same frequency as the sound. So, you can hook up a motor to an audio output and then touch the motor to something that a student holds in the mouth. The vibrations allow you to hear the stuff through the motor. It’s pretty awesome.

But if you can use a motor as a speaker, couldn’t you also have it work in the opposite way? Could you use the motor as a microphone? That was the plan. It’s at least theoretically possible.

For fun, I decided to try this out with a cordless drill. Guess what? It works? Check it out.

Sometimes, I surprise myself. Here is a more detailed explanation.

OK, one more video. Here is how you can use a cordless drill as a hand crank generator (not part of this episode, but it has to do with electric motors).

Remind me later that this is one of my favorite MacGyver hacks.

Electrostatic Hair

They are trying to find evidence from a bad guy. There could be hair that went into the air vent. In order to get this hair, Mac adds a wire to the end of a plastic broom handle. He rubs the broom so that it is electrically charged. When he puts the broom handle into the vent, it attracts the hair so he can pull it out.

Here is an awesome Minute Physics video that shows how an N95 face mask works. It’s basically the same thing as the electrostatic filter.

But back to the hack in the show. There are really two things to consider here — first, the charging of the broom. When two different materials are rubbed together, you can get electrons to transfer from one object to the other. This makes one of the objects positive (when it loses electrons) and one of them negative (gains electrons). This is called the triboelectric effect.

The second physics thing is to look at why an uncharged piece of hair would be attracted to an electrically charged broom handle? The answer is that the hair becomes polarized. Let’s say the broom is negatively charged. This negative charge will attract the positive charges in the hair and repel the negative charges — that is called induced polarization.

Now that the positive charges are a little bit closer to the negatively charged balloon, they will have a slightly greater attractive force than the repulsive force between the two negative charges. This leads to an overall attractive force and shows how a charged object can attract a neutral object.

Mini-Vac Taser

Image: CBS MacGyver

You can’t really see this build, but this basically makes a high voltage output using the motor. This is essentially the same idea as the spark gap generator. If you have a spinning motor, you can use that to create alternating electrical contacts to make a high frequency alternating current. An alternating current running through a loop of wire (and inductor) produces a high voltage.

Here is a very basic spark gap generator (an early form of a radio) that uses a buzzer instead of motor — but it’s the same idea.

And yes, MacGyver could probably put everything back together so the vacuum worked again.

Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. Former WIRED blogger.

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