MacGyver Season 2 Episode 1 Science Notes: DIY or DIE

I’m kicking myself. I should have been writing these MacGyver notes for each episode as they aired on TV. But no. I had to make things more complicated. Well, here I am—starting the notes for season 2.

Let’s just jump in. Note: there’s some pretty good stuff in this one.

Blade from a button.

MacGyver takes a button from his shirt and breaks it in half. From this half button he sharpens the edge so that it can cut through a rope.

I wouldn’t normally include this one in the blog since there’s not much science to talk about—but I’m just excited.

Flare-based harpoon and winch.

MacGyver takes a metal rod and puts it in an empty dip stick tube from an engine. He adds the powder from a road flare to act as a propellant. This would then launch the improvised harpoon forward.

Once the harpoon is stuck into a fleeing car, Mac wraps the cable around the horizontal axle on the sidecar to a motorcycle. As the axle spins, the cable wraps around it and pulls the motorcycle closer to the car.

Mini gun as a starter motor.

They need a car. MacGyver finds one—but it’s missing a starter motor. Really, there is nothing super special about a starter motor. It’s just a DC motor that is strong enough to turn over the engine so that it can turn itself (using gasoline).

The mini gun also uses an electric motor. In this case, the motor spins a combination of gun barrels so that the fire rate can be higher than a normal machine gun.

Could you use one motor for another application? Theoretically, yes. The only tough part might be mounting the motor (which MacGyver does with some wire—wire is often better than duck tape). The other problem is making sure the gears on the motor match up with the gears on the car to turn over the motor—but it’s still possible.

Run up a wall with a pole

Sometimes, there are hacks that look too crazy to be true—but in fact would totally work. Here is an example of such a hack.

MacGyver and friends take a long pole. MacGyver gets on one end near a wall and the other two push the pole towards the wall. This allows MacGyver to walk up the wall.

But wait! Here is a video of this trick being used in real life by a Vietnamese SWAT team.

Here is my super short explanation.

  • If you push someone against a vertical wall, there will be a frictional force pushing UP.
  • If the push is great enough, this upward frictional force can be equal to the gravitational force.
  • Boom. That means a person can walk up a wall.

Here is a force diagram of that situation.

Spring 2017 Sketches key

Oh, I also made a video to show you how this works.

Finally, here is a more detailed explanation from my WIRED blog.

Cell phone in a soccer ball.

Ok, you can put a camera in a ball and kick it through a window. Not really much of a hack, but clever.

Improvised diver propulsion vehicle.

MacGyver needs to get through a submerged passage—it’s long enough that he can’t swim the whole way. This means he needs some scuba stuff. In particular, he needs the following:

  • Some type of air supply with a regulator.
  • A mask and some type of mouthpiece to breath.
  • A light.
  • A DPV—diver propulsion vehicle.

Please forgive me, but I’m going to go over more detail in this case that you would like. I can’t help it. MacGyver is basically cave diving—this is something that I used to do quite a bit.

Just to show you what that was like, here is an older picture of me. It’s not cave diving, but it’s using all of the same gear (it was practice).

Let’s start with the scuba gear. MacGyver doesn’t have a regular scuba tank, so he uses an oxygen tank used for welding. You don’t normally want to use oxygen for scuba—you want to use air (which is only 21% oxygen). You see, oxygen is actually toxic. If you breath oxygen at high pressure, it can do bad stuff to you. Fortunately, MacGyver is going to use this at very shallow depths—he should be fine. Also, he won’t need to much gas as you consume much more at greater depths (for open circuit systems like scuba).

What is a regulator? Suppose you have a pressurized tank at 1000 psi. You can’t really breath air (or any gas) at that pressure (although there are some tricks—ask me later and I can tell you about this). That’s where the regulator comes in. It takes pressure from the tank and reduces it to the ambient pressure. That’s really important. It has to deliver the pressure at the same pressure around the human. If it was too low, you wouldn’t be able to expand your lungs and breath.

Luckily, they have regulators for welding stuff too. You need a second regulator to let air out only when you breath—but it’s possible to build one of these (they are much simpler).

Now for the DPV. These things are very useful in cave diving. How are you supposed to get 5,000 feet back in a cave if you have to swim the whole way? The early DPV (or scooters as we called them) were essentially trolling motors from a bass fishing boat connected to a battery.

Just about any electric motor with a battery could work. Ideally, the motor should be sealed so it can run underwater—but it doesn’t have to be perfect. It only has to work for a short time.

I really like the scooter in the episode. It really looks like a home built scooter.

OK, you can’t see it too well in that image—just trust me. Or better yet, watch the episode.

I also like how MacGyver side mounts his tank. Even if you have done normal scuba diving, you might be surprised at how these tanks behave underwater. Just because they are heavy out of water doesn’t mean they will pull you down underwater. Very often we would bring extra tanks (stage bottles) in a cave and carry them on our side just like MacGyver did.

Parkour Wall Jump.

MacGyver gets to run up a wall twice in this episode. Just like the wall run with the pole, this case also uses friction. It’s your classic parkour wall run-jump.

If you run towards a wall and push yourself back, there is a force between you and the wall. The faster you run, the greater the force. If this force is great enough, there will be a large enough upward frictional force so that you can get an extra upward jump.

That’s exactly what MacGyver does to get out of the tunnel. Here is a more detailed WIRED post on this wall jump.

A Cave Diving Story

I want to write about some things that happened in the past – mostly so I don’t forget.  In this case, I’m going to describe a particular cave dive that sticks in my mind.  Now, there is a warning.  This might not be exactly what happened – but it might also be true.  It’s probably the way it happened.  Let’s begin.

In case you aren’t familiar with cave diving, the main idea is to explore a cave that is completely underwater.  You start outside the cave and you are already underwater. This is not spelunking – this is cave diving.  We mostly went into springs in the panhandle of Florida – that was our roaming territory.

Just for fun, here is a picture of me with my cave diving gear.

Please don’t complain about the setup.  This was a picture from my cave diving class.  I learned quite a bit after this and changed things up – but still you can get an idea of what it was like.  That was my friend’s van that we used to drive to different caves – it was pretty sweet.

Ok – now for this one particular dive.  I am pretty sure this was at Twin Cave.  Twin Cave is in the middle of Merritt’s Mill Pond in Marianna Florida.  The only feasible way to get here is with a boat (unlike most cave diving in which you just walk into the water). It’s called “Twin Cave” because it has two entrances right next to each other (underwater).  If you have a boat, you can use a tiny little wood platform connected to two trees to set up stuff.

My dive partner (Trey) and I hitched a ride with Pat Watson.  He had a little john-boat and ferried us to the cave.  He then went back and picked up two more divers – Pat was teaching them how to cave dive and this was one of their “check out dives”.  Oh, I should add that at one point there was so much stuff in that little boat that it was barely above water.  One tiny wave and I think the thing would sink.

Now for the dive plan.  Go into Twin Caves and get into the lower levels.  In this case, we would use diver propulsion vehicles (DPV) to get through the easy part and then proceed in the lower part by swimming.  The DPVs are awesome (also called scooters).  That’s the truth.  I always wanted a scooter – but I never got one.  Fortunately, my dive buddy had just recently upgraded his DPV for a bigger one.  That meant that he still had his old one.  BOOM – scooter time,

You’ve seen these scooters.  They are basically small torpedo looking things (not exactly) with an electric motor.  You connect a line from the scooter to you so that you can “drive” with one hand.  That’s not really important, but I just wanted to say that.

Ok, so we start off on our dive.  I seem to recall that it’s sort of tricky getting into Twin Cave.  The main entrance is a vertical shaft – but then you have to turn horizontal right when you get in.  If you don’t turn correctly, you hit the the bottom of the cave.  Most cave bottoms have this silt stuff – if you hit it you change the cave water from pristine clear water to brown soup that you can’t see through.  So – don’t hit the bottom (this will be important later.  Oh, it’s even harder to get in this cave when you are trying to do with with a scooter.  We probably had a stage bottle too.

I guess I should say something about stage bottles – for completeness.  A stage bottle is an extra scuba tank that you mount on your side.  You use this stage bottle for the first part of the dive – until it gets 2/3 full.  At that point, you take the tank off and leave it on the line (there is a line running in the cave).  You then proceed on the dive using the two tanks on your back.  Using stage bottles lets you go much farther than just with double tanks.

Now back to the dive.  The first part of the cave is pretty cool.  It’s this big cylindrical cave that we called the subway.  Ok, that might not be true.  In my mind, we called it the subway.  It was super easy to get through with a scooter – just imagine a long straight circular tunnel with a diameter of about 3 to 4 meters (let’s say 10 feet for imperials).  Like I said, this is perfect for scooters.

At some point, we moved down to some small stuff and dropped off the scooters.  There are two important points here.  First, this part was deeper (can’t remember the exact depth) such that we will have more decompression time.  Second, it was low and slow down here – longer time at depth also means more deco.  I’m not going to really talk about deco time right now – but let’s just say that you don’t want to rack up a ton of deco time – it sort of sucks.

So we did our exploration of the lower part.  Now it’s time to get the hell back to the entrance and do our deco.  No more sight seeing – just hurry up.  We pick up our stage bottles and our scooters and scoot out.  Oh, quick note.  There are two things that are awesome to see in a cave.  The first is the warm glow of the Sun when you are near the cave entrance – this tells you that you are almost out.  The second is your stage bottle.  Picking up a stage just says “hey, you just got a bunch more air and a completely independent air supply – you have less chance of dying now”.  It’s awesome.

Now for the whole point of this story.  We are there on our scooters moving out of the cave while back in the subway.  Ahead we see some lights.  It was Pat and his two students.  As we start to get near, something happens.  The inflator on Pat’s buoyancy compensator (BC) just falls off for no apparent reason.  In case you have never been diving, the BC is basically a bag of air that you can fill up or empty to adjust how you float in the water.  It’s super important in cave diving because you want to stay off the bottom of the cave where all that silt is (remember I mentioned this before).

When Pat’s BC failed, so did his ability to stay off the bottom of the cave.  It was weird – he just took a dive straight down.  He sort of looked like a B-17 bomber that had just been shot out of the sky.  I saw him try to make a correction to his buoyancy, but it wasn’t going to happen.  He ended up just putting two fingers straight down to catch his fall (this is what we were taught so as to minimize the silt disturbance).  It didn’t work. His crash produced silt.  A lot of silt.

It was really amazing.  This clear water subway tunnel suddenly turned into a tunnel with a wall.  A wall of silt.  You really can’t see much in this silt – it’s effectively zero visibility (but not as bad as clay in the water).

Since we were traveling along at a good pace with the scooters – it only made sense to slow down quite a bit.  I knew there were three divers inside that wall of silt, but I didn’t know WHERE exactly they were.  So I slowed down.  Gradually clicking the throttle trigger on the scooter to maintain a slow crawl speed.

To my surprise, my dive buddy chose a different strategy – he decided to just keep going at his current speed.  I saw him head straight into that wall of silt – waiting for some type of collision.  But no, he made it though.  It was a bold move and it paid off.

For me, I went through slowly and made it to the other side of the silt wall (which wasn’t very thick).  After that we did our deco and finished the dive.  I sort of recall not taking the boat back to the van and staging area.  Instead, we used the scooters the rest of the way.  It didn’t matter at that point – you don’t have to worry about saving scooter battery or scuba air.

The end.