This is my entry into the NRW robot challenge 13-18 category. This is my first instructable so constructive criticism is welcome.

It is a basic chassis that can easily be added to and expanded as necessary. It is a basic 3 wheeled 2 layer bot. I built almost the entire thing from things i had lying around, the only part i brought was the tamiya dual gearbox.

Step 1: Collect the Materials

The first step is to cut out and obtain all of the materials.

For this project you will need:

Material/parts:
Top board 130mm Dia pegboard circle
Bottom Board 130mm dia x 10mm ply with two 60 x 15 cutouts (see pics)
4x M5 x 65mm bolts threaded the entire length
12x nuts and washers to suit above
Gear box assembly and motors
2 large wheels max dia approx 60mm
Swivel wheel for rear (I made mine from mecanno)
Assorted wire
Assorted small bolts and screws
Heavy wire or guitar string
Battery holders for your micro and motors
Your Micro controller and interface components etc (I used a Picaxe 20x2 and Darlington driver in a breadboard)
Velcro or double sided tape

Tools:
Adjustable spanner
Screwdrivers
Saw (to cut the base and to plates)
Side cutters
Soldering Iron
any other tools you need to assemble/mount your controller

Step 2: Attach the Gearbox

The first step once you have all your materials is to attach the gearbox to the base plate. For this I used two screws in the screw holes but depending on your gear box it may be different.

Make sure the axle is in the middle of the cutout or you may not have enough room for your wheels, or it may tip forward if the wheels are towards the back.

Step 3: Attach the Rear Wheel

The rear wheel that I used was made from a few pieces of meccano but you could make yours from anything similar. It is just a basic wheel that spins through 360 degrees so it can go in any direction.

It is simply bolted to the base with a small bolt so that the arm can't move side to side.

Step 4: Add the Four Riser Bolts

The four bolts that support the top layer are next. They are inserted through the four holes in the corners. The placement of the holes isnt critical but they must match up on both layers and allow enough room for all of the parts to be added.

The bolts are inserted so that the heads are towards the bottom and then a washer and nut are put on the opposite side and tightened. They don't need to be super tight but tight enough so that the bolts don't wobble around.

Step 5: Motor Batteries

The next step is to add the motor batteries. I made my holder from three bits of tin but you can buy one if you want.

This step simply involves screwing or otherwise attaching you battery holder to the base plate. Nothing too hard.

Step 6: Touch Sensor (optional)

This step involves adding the touch sensor which is the most difficult step because it is so fiddly.

First we put the bolt through the a washer then the front hole and then we put a washer on and then the first nut to hold it still. Once that is secured we put another washer and then the wire with the washer on and then finally the nut loosely. Now comes the fiddly part getting the whisker to stay in between the washers while we tighten it.

Once the whisker is in place we add the sensor rings. These are simply screwed to the base plate on either side of the whisker bolt. once they are screwed down you need to move them so that the whisker doesn't touch them by bending them slightly.

Step 7: Adding the Top

The next step is to add the top. This is rather easy after adding the whisker wire.

To add the top simply put a nut and washer on each of the riser bolts roughly a cm or two down. Next put the top on and secure it with another washer and nut. undo the top nuts until they are flush with the top of the bolts and then tighten the middle ones sot that the top is as high as it will go so there is more room in the middle for more sensors or other attachments.

Step 8: Add the Brain and Let It Live!!

Attach the micro controller and batteries to the top with the velcro and hook it all up. Once it is all hooked up program your micro and watch it go.

Step 9: Final Thoughts/end Note

Thats it you should have a working robot.

This is by no means a perfect robot but it is a simple beginners robot that can easily be upgraded to accommodate more sensors or other attachments and I encourage you to do so.

If you do build one of these post some pictures of it so the world can see.