Picking Tumblers: Part I

We are going to start with tumbler locks. They aren't the easiest lock to pick and their not the hardest - they are the most common. But in order to pick the lock, we have to understand how the lock works. It's like old school hacking: we are bypassing security by taking advantage of internal weaknesses in how the system works. Tumbler locks are made up of only a few parts: the key goes in the keyway (the keyhole) so that it can turn the cylinder which is called the plug (Right? The key turns. Got it.). The plug is housed in the main casing.

Next part, the plug has a holes drilled in it and these continue up into the casing. Each of thise holes has a spring in it. The spring pushes two little pins down into the plug. The top pins (which are between the spring and bottom pin) are called drivingpins and they are all the same length. They push the lower pins (called the keypins) down. These keypins are all different lengths. They rest on a little ledge called a ward. Pull your keys out of your pocket and look at one. It has that little canal that runs all the way from the tip to the handle of the key. The ward slides in the canal. The point of the ward is to be a ledge that the keypins rest on when there is no key in the keyway.

So that's all the pieces of the lock. Now how does it work. I said that all the keypins were different lengths. Why? Well, what else are different heights? Answer: the teeth of the key.

So here is how it works. The key goes into the keyway. The notches and teeth push the pins up to exactly the right height so that each and every one of the top drivingpins is lifted (by the keypins) to the same height (exactly to the same height as the separation between the casing and the plug). This is the most important part to understand. When the key is inserted the gap between each and every keypin and drivingpin lines up with the gap between the hull casing and the plug. This separation is called the shear line. Once they are all lined up the key can turn and unlock the door. Tada! The mechanism of a tumbler lock explained!


Check out these wikis if you want to read about the mechanism of tumbler locks again. (Let's be honest. It's where I got the images)
Wikivisual
Wikipedia
Wapedia
BambooWeb Dictionary
BookRags

Let this settle for a day or so and then I'll post a How-To tutorial for picking tumbler locks.

Rolling Hitch

Good job, Plastic Man. You'll be able to sell that tape on e-bay or maybe bring it to the JLA's monthly poker nights.

It's very easy to make the clove hitch a little more secure. By wrapping the working end around the post one more time, we have a Rolling Hitch. Because this double turn reduces slipping, this knot is useful for situations where the pull is along the same direction as the post.

1) Pass the line around the post, going over the standing end once you make it around.
2) Make a second identical turn, which follows the first turn.
3) Finish the knot in the same way we finished the Clove Hitch: with a half hitch
a) Pass the line around the post on the other side of the standing end.
b) Feed the working end underneath the third loop.
5) Cinch the knot.

Clove Hitch

Sometimes a magic lasso is just the best fashion accessory that one could ask for.

Today's knot is the Clove Hitch. This is a great and super easy way to tie a line. It's so unbelievably fast.


1) Pass the line around the post or bar or whatever.
2) Pass the line around the post on the other side of the standing end.
3) Feed the working end underneath the second loop.
4) Cinch the knot.

The things that you should keep in mind are: a) leave a bit line past the knot since it might slip a touch before catching b) if wiggling the standing part will loosen this knot.

Figure of Eight Coil

You know, I don't think that this picture is the worst one I found...

I did get one thing done for Building Batman this month: I found a use for the figure eight knot. If you have a rope that you don't use very often - like the ice-batrope that goes along with the Bat-antarctic-suit or the underwater rope that goes with the Bat-diving-bell or... well you get the idea. What you need to do is coil your Batrope. But something nice like the Alpine coil (we'll learn that one someday) is more for short term. For storage you want something like the Figure Eight Coil.


1) Make the entire rope a bight (fold it in half).
2) Coil the doubled rope (the animation only shows one coil but of course you do as many as you need).
3) Wrap the working end (the bight) around the coil.
4) Once around the coil, feed the bight through the loop.
5) Pull tight and you have a coiled rope with a nice small loop to hang your batrope from.

Figure Eight

Remember, according to Dr. Marston, she is only bound until she wants to break free.

Figure Eight
This knot sucks. I haven't figured out anything to do with it. I must have to work on my detective skills soon. I hear that the figure eight is the basis of many other knots but I don't really see any use for it by itself. I guess it could stop a rope from going through a hole or something.


In an case, this is how you tie a figure eight
1) Make a loop.
2) Bring the working end around the standing end.
3) Feed the working end through the loop.
4) Pull to tighten.

Reef Knot

I think "DEATH" must be the safety word they are using.

On to knots.
You and your sidekick are chasing a sexy villain across the roof tops. The cat-burglar is able to dash to the edge and gracefully jumps 20 stories to the distant ground. You boys are stuck and the vileness is taunting you with her stolen goods and gorgeous, criminal body. Sucks to be you, Batman. UNLESS you remember today's knot! The reef knot is used to tie two ends of line together. This is how it goes.

REEF KNOT
1) Pass the working end once around the other line.
2) Bring the ends up with the working end underthe other line.
3) Pass the working end over the other line.
4) Tighten by pulling both ropes on both sides simultaneously.

You now have a reef knot. If you tied this one with me, you can maybe see why it's often called a square knot. You can now use it to go down the side of a Gotham skyscraper. One note of warning: This knot is secure when the knot is pressed against something (like the side of a building). If, say, Catwoman had gotten to a distant building and Batman needed a longer rope to swing across on, he would not use this knot. He would use a different bend. We'll learn many more in the days to come.

What Are Knots Good For?

Why don't we start with a knot that everybody knows? And I know what you're thinking: "I don't know any knots! I'm not a sailor, batboy." But trust me, you know this one. It's called a thumb knot. It's the basis of a lot of other knots. For example, it's the first part of tying you shoes.


THUMB KNOT
1) Begin by making a crossing term (Begin with a loop).
2) By going under the loop, pull the working end through the loop (the working end is the end you are working with while the standing end is the end attached to something or just not being used).
3) Cinch it (tighten it).
4) Voila! A thumb knot.

You can make this more interesting by making the knot slipped. Slip knots are knots that can be untied in a hurry. The slipped thumb knot is tied exactly like the thumb knot except it uses a bight.


SLIPPED THUMB KNOT
1) Make a crossed loop.
2) Pull a bight through the loop. A bight is a "loop" formed by folding the rope back on itself.
3) Cinch it.

Obviously, the loop that's formed in the slip knot is not very solid. If you want to make are really simple loop out of the thumb knot, try:


THUMB KNOT LOOP
1) Make a bight out of the loop.
2) Make a regular thumb knot using the bend as the working end and the two parallel pieces of rope as the rope.

One last thing you can do with a thumb knot: you can make a very simple noose. A noose is any sliding loop.

THUMB KNOT NOOSE
1) Make a very loose thumb knot with a short working end.
2) Feed the line (the standing part, not the working end) through the hole left by the thumb knot.
3) Cinch the thumb knot around the line. You can tighten it so much because the thumb knot really sucks and so it won't catch unless you are using string, thread or fishing line or something.

Ya I know. Those are really weak knots but look at all the terms we've learned:

Crossing term - make a loop
Working end - the end of the rope being used to tie the knot
Standing end - the part of the rope fixed or not being used
Cinch - to tighten
Slip - easily undone
Bight - formed by folding the standing end back on itself
Noose - a sliding loop

Push-Ups

Four days ago I started doing push-ups following the Blog Comics, Films, Kung Fu, and Whatever the Hell Else. I'm starting easy since I've never been a particularly athletic guy but I'll try to improve fast.

The routine consists of picking a number of push-ups to do (I'm doing Elroy's gentle 100). On day one you do 100 over the course of an hour. The next day, you do 100 hundred sometime throughout the whole day. Then you repeat. You do this for ten days and then rest for two days. After the two days of rest, you try to do as many as you can in one go. Then start all over again with a larger number of push-ups.

I don't know what Batman would think about two days of rest but I think in the real world there's wisdom in giving yourself a break of some sort.

Aerodynamics of Boomerangs

I promised this a long time ago but I was too busy to write up the details and there were a couple of things that I needed to figure out how to explain better. I think I can explain how a boomerang works to absolutely anyone. That being said I may be wrong so if there is something that you don't understand in my explanation just ask.

We'll end up talking about a lot of stuff that doesn't have to do with boomerangs just so that we have all the details we need. In fact, we'll start by talking about syringes.

So you go to a doctor and they give you a needle. The fluid in the main barrel is flowing with some speed because the nurse is pushing on the end but when it gets to the needle part what happens? Because the area of the pipe has changed the fluid must move faster to get the same amount out in the same amount of time. Maybe the diagram helps a bit.

OK. Now let's talk about something seemingly completely different (and still with nothing to do with boomerangs). You're driving really fast on a highway in your Batmobile. Then you pass a semi-truck (driven by the Joker, maybe?) that is going the other way. What happens? You get sucked TOWARDS the truck not blown away from it. How come?

This has to do with Bernoulli's equation (I swear this is the only equation that we will need in order to understand boomerangs so don't get scared away, dear reader) which says that pressure plus velocity (squared) must stay constant. That means that if velocity is increased the pressure must go down and if velocity is decreased the pressure must increase to compensate and make sure that when you add them together they stay constant.

So what happened with the semi-truck? The truck and you form a short channel and just like the medicine in the syringe speeds up in the needle, as air passes between you and the truck it must speed-up too. BUT if the air speeds up that means that the pressure must go down between you and the truck (Bernoulli's equation) but the pressure on the other side of your car stays the same. That means that there is a stronger force on the other side pushing you towards the truck.

Good. Now lets talk about airplanes. Airplanes are like boomerangs, right? Forget about everything except the wing. The wing of an airplane is an aerofoil. The air that passes on the top of the wing is pushed up and has a longer path than the air below. So the air above goes faster than the air below. That means (by Bernoulli's equation) that the pressure below the wing is bigger - there is a force pushing up on the wing! This is the lift force and it's what makes airplanes fly.





Now it's time to use our imaginations. Imagine turning a wing complete sideways . Now what happens? Well for one thing there is no force counteracting gravity and it will fall but there is a force pushing it sideways. The side ways force will make the wing go forwards and sideways. It will curve but it won't quite go turn and travel in a circular path just like a boomerang.

BUT this has a bigger problem. What? Well think of a pencil that you balance on it's tip - and you laugh at me and say, "how could I balance a pencil on it's tip. The smallest bump imaginable would cause it to fall over." Right! As it tips gravity can enact more and more torque on it since as it tips the centre of gravity moves further and further away from straight over the fulcrum (like where the pencil is touching the table).

Our imaginary turning wing is even worse. If it started to tip (as it definitely will) then not only would gravity make it tip faster and faster but also soon the lift would be pointing down more and more. Our sideways wing will flip over really fast and as soon as that happens it's not going to move in a circle anymore. It will just crash downwards. Maybe the series of diagrams illustrates it.

Here's an idea. A pencil will tip because it's unstable but what if you spin the pencil really fast? Now it's like a top. As long as a top is spinning fast enough it will be stable which has to do with angular momentum. Even though gravity pulls down on the centre of mass as it starts to tip, it doesn't fall because the angular momentum which points up from the tops principle axis changes the direction of motion and causes it to have processional motion rather than falling.

So let's spin our wing. The spinning will cause the wing to be staple and it will move in a strafing path rather than tipping.

Good try but there is another problem! The wing is travelling one way at the top of the circle and the other way at the bottom! That means at the bottom the aerofoil is facing the wrong way. How do we fix this? Cut it in half and turn one arm around and glue it back together. That way the aerofoil is pointing the right way at both the top and the bottom. This is a boomerang! The wing on the top and the wing on the bottom both have a lift force pointing in the same direction causing the boomerang to turn to the left (that's why boomerangs can only be left or right handed - they have to be built differently for different hands). The two diagram shows how the aerofoil shape has the leading edge on opposite sides of each each arm of the boomerang.

The wing on top is traveling through the air faster than the bottom one because the boomerang is spinning and moving forward and the top wing moves with it while the bottom wing moves against the direction of motion. So the forward moving top wing has more sideways force than the retreating bottom wing. This unequal force is what turns the boomerang so that it goes in a circular path and not just side ways. The turning force comes from the unequal air speed of the spinning wings while the spinning is able to keep it steady.

The bend in a boomerang isn't needed at all although I've read that it makes it easier to throw. That's what I know about boomerangs.

If this was too long an explanation then you should check out

avkids
Boomerang Shop

If this was too short and you were saying to yourself, "It doesn't mean anything if it's not expressed mathematically" then the websites for you would be

Unspinning the Boomerang
Boomerangs.com

And if you still aren't satisfied check out this really in depth look at

Research Support Technologies