Stiquito

Being the type of guy that has been taking things appart since I was a kid, I've always wanted to take the parts and put them back together into something more than they were before. Over the years I've been doing that on small scales but the level of complexity of the finished product was never very high. I've always wanted to build some sort of robot and this was my first attempt.

Watching Battlebots for the first time really got my motivation kicked back into gear so I started searching the web for information. I decided that I should get a book and some sort of robot kit to get me started. Which kit to buy??? While browsing through RobotBooks.com I found a few books on "muscle wire." Being a biologist as well, this really grabbed my interest. Thin wires of Nickel-Titanium Alloy can be used to mimic muscles in a robot. Heating the wire causes it to contract by 4-7% of its length. Running an electric current through it will cause it to heat up due to the resistance of the wire so it works well for robot designs.

I found a great deal ($18) on the Advanced Stiquito book, which comes with a kit to build a buglike robot that moves via "muscle wire" so I bought it. When the book arrived I quickly read the first few chapters that explained how to put the kit together and then promptly ripped open the kit and started building. In an hour or so I had my firt primative robot. It's very basic. It has six legs that are hard wired into a tripod gate. The front and back leg of one side are wired together with the middle leg on the opposite side. This produces a walking gate where two triangles of legs alternate propelling the robot forward. Locamotion is controlled manually with a "joystick" and a 9V battery. When you connect one side of the controller, one set of three legs pulls backwards and the body gets pushed forwards. When you release that connection the current stops, the "muscles" cool and the springlike legs stretch the muscles back out. Then you continue by connecting the other side.

Theoretically this is very simple and easy to use. In practice, its really difficult to get the critter to move correctly. The feet are angled so that they grab the surface when the leg is pulled backwards and they slide over the surface as the leg is pushed/pulled forwards. This only seems to work if the surface is textured just enough and the legs are all perfectly constructed so that all of feet touch the ground when on a flat surface, and so that each leg pulls backwards equally. It also helps to have a good strong 9V battery. When I first tested it out, the battery I had (pulled from my appartment complex smoke dectector) was really cheap and weak (comforting thought) so the legs didn't always contract correctly. I grabbed a good one from somewhere and the muscles responded promptly. This didn't make up for the fact that some legs pull harder than others and that its very hard to get the legs all aligned correctly so the feet are even. The kit doesn't come with enough extra supplies so you can rebuild parts that fail. The main problem is that you connect the "muscles" with aluminum crimps and if you need to recrimp a wire the aluminum breaks when you try to uncrimp and recrimp it. I recently found a hobby shop that carries aluminum crimp tubes so I'll have to pick up some extra and rebuild the legs.

As much as I was just bitching about the kit, it is fun to play with and try to tweak. Its especially good at exposing you to a new form of robot mobility and gets your imagination going. As for the book, it has a lot of interesting ideas in it but doesn't go into a lot of depth on them and isn't really organized. The first few chapters teach you about the wire and how to put the kit together. The next few tell you about more advanced projects that you can build if you buy more wire and scrounge up some other simple building materials. The rest of the book is bascially a collection of papers that people have written about robots in general or ways to make more advanced Stiquito designs.

And now for some Pictures! These were taken with my 2.1 Mpixel camera at 1600x1200 24bit resolution so they're big downloads. Where posible I cropped out the unimportant parts.

	Here is a top view of my finished Stiquito with a penny and a 6" ruler for scale. On the left side of the picture is the back end of the robot. The middle wire is the ground and the two blue wires each control different sets of legs.
	Here is the side view taken without the flash. This is one of the two pictures that I didn't crop so its 1600x1200x24bit. It may take a while to download over a modem.
	Here is the side view taken with the flash. This is the other picture that I didn't crop so its 1600x1200x24bit.
	This is a closeup of one of the legs taken with no flash. The right side (thicker wire) is the piano wire that makes up the springy part of the leg. The left side (thinner wire) is the Nickel-Titanium alloy that makes up the "muscle" of the leg. If you look closely on the larger image, you should see a hair draped across the leg for scale. This is a hair from the top of my head.