Whaaaaat? Another Cheap Robots tutorial? That's right I'm back! And I've got an idea that I think you kiddies are really going to like, but you'll have to bear with me for a bit. This is a particularly simple 'ible, but it's going places. I promise.

"But Jay!" I can hear you exclaiming, excited and confused, "You've already got a bottlecap wheel tutorial! Why make another?" Well, my inquisitive reader, this here is a metal wheel tutorial! Why is that particularly important? Metal conducts, you see, and that will be a very useful feature as this project nears completion. This is going to be awesome and I cannot wait!

But before we get started, I've gotta make sure one thing is perfectly clear. This 'ible will involve hammering things into other things. It'll also involve some sharp metal bits, so if you're under... let's say 16 (that sounds like a nice, legally safe number) make sure you get your parent's permission, and maybe their supervision for this project. Honestly, the more the merrier, so don't hesitate to ask for help!

Let's get started!

~~~~~
For more Instructables on building cheap robots, please check out the For Cheap Robots collection!

For more things that I've done, you can check out my profile page!

For more info from Digilent on the Digilent Makerspace, check out the Digilent blog!

Step 1: What You'll Need

For this project you'll need:

Some metal bottlecaps. I'm using a soda cap and a Snapple cap here, but you can use pretty much any metal cap.
A geared motor. It's very important that the motor have a gear-box, otherwise your motor won't have the torque to move your robot. If you want to know more about this, check out my Motors and Wheels for Cheap Robots 'ible.
A sturdy Phillips screwdriver. It's important that it's Phillips, and it's important that you don't mind hitting it with your hammer a little (possibly a lot).
A hammer. It doesn't need to be overly large.
A thumb-tack.
A pair of pliers. These will keep your thumb intact later on.
A hot-glue gun. All day erry day
MOST IMPORTANTLY: A piece of scrap wood. You'll be hammering things into other things, and this scrap wood will keep your counters un-marred. Trust me, you'll need this.

Step 2: Make a Tiny Hole

Get your thumb-tack, hammer, pliers, bottle cap, and scrap wood.

Place the bottle cap face-down on the wood (so the side that would be inside the bottle faces up). We want to puncture out from inside, so the motor can rest inside the cap when we add it.

Use the pliers to hold the thumb-tack so the point is as close to the center of the cap as possible. Do your best to eyeball it. You want to use pliers to hold the tack, otherwise your fingers are likely to get smashed even if you do use the hammer correctly.

As you can see in the third picture, a few good strikes with the hammer make a neat little hole in your bottle cap. Unfortunately, in picture four you can see that it'll make a neat little hole in whatever surface you're hammering against too. That's why we use scrap wood!

Step 3: Embiggen the Hole!

Place your bottle cap face down so the puncture pushes out from inside the cap. That'll let us push our motor through in the same direction, so it can rest inside the cap instead of outside, which makes for a better alignment of forces when the wheel is holding your robot up.

You have to use a Phillips screwdriver so it'll make that neat cross-shaped hole. The little metal bits that poke out will help grip the shaft of the motor, and can even hold it better than the hot-glue!

You also want to take this carefully. Tap the hammer a bit to widen the hole, and check to see how it compares to the shaft of your motor. You want the motor shaft to just fit inside the hole, and if you make it too big, your fit will be looser. Keep in mind, though, that you're hammering a screwdriver into wood. You may have to tap pretty hard.

Once again, we're hammering on scrap wood so the little cross-shaped hole doesn't end up in your nice counters!

Step 4: Assemble

It may take several tries to get your cross-hole to just the right size, but when you do, those little metal leaves will grab hold of your motor shaft firmly and hold it in place! Really, the hot-glue is just for good measure.

Once you've got your motor and wheel together, you're ready to go!

Like I said at the beginning of this tutorial, this is just the first part of a couple of tutorials that's going to end with something really cool! That said, because of how well the wheel can grip a motor shaft, these really are a fantastic set of wheels on their own.

I hope you enjoyed this tutorial and I hope it helped you make a neat robot! As always, I'd love to see how you use this tutorial, so let me know if you do! Good luck!