This is a design for a small robot chassis that is very mobile.  It navigates by dead reckoning, but has I/O pins available for a variety of sensors and actuators.  It is small enough to run indoors, yet robust enough for most lawns and patios.

     One constraint I had to deal with was keeping costs to a minimum, preferably nothing out of pocket.  Fortunately my junkbox has some high quality parts and a BOE BOT I could "borrow" from.  All the parts used are still available today. this will be nice when it's time to build the second and third copies.  (a swarm of one leaves a lot to be desired)

Please vote for this instructable in the over 18 category.

Step 1: Materials

Materials I used:

Board Of Education microcontroller board from Parallax.com
battery case (4AA cells)
4 AA battery cells
Tamyia track and wheel kit  ( I got mine from Amazon)
2 RC servos modified for full rotation (mine came from my BOE Bot,  Parallax.com sells them separately)
1 standard (unmodified) servo  -- (optional)
5 bolts 1/4" x 3" with nuts
4 bolts #6 x 1"  washers and 3 nuts each
1/8" (3mm) plywood 18" x 24"

Tools used:

PC and serial cable (for programming)
screwdriver / wrenches
Lasercutter - You could get by with a fretsaw, or scrollsaw, and a drill press,  but a lasercutter is great to have access to.

Step 2: Cut Out the Structural Parts

Cut out the drive gears and structural parts.  I user 1/8" plywood, but plastic would be more weather resistant.  If you are cutting with a fret saw, or a scroll saw, look closely at the template and instructions as some of the cuts are not essential.

Step 3: Mount the Drive Gears on the Servos

Mount the cut drive gears on the servo horns.  The servo horns that came with the BOE Bot kit fit nicely through the hole in the center of the cut drive gear.  The overhang needs to be trimmed before gluing in place.

Step 4: Mount Bogies

Mount the bogies, Drive wheel and bogie wheels to the bottom level.  This level is 2 pieces thick and the screws (from the Tamyia tread kit) will go through 1 3/4 pieces, holding them together.

Step 5: Install Drive Servos

Place the drive servos with the drive gear in the cutout for them on layer 1.  Add the standoff spacers and the bottom half of deck 2 on top.
Shown here with tracks already in place as I didn't take pictures until I had finished putting it all together ...well a few times.

Step 6: Add Circuit Standoffs to Layer Three

Bolt the two pieces of layer three together using the #6 bolts through the holes that line up with the controller board's holes.  Bolt it from the bottom leaving the end of the bolt sticking up to mount the controller board to later.

Step 7: Install the Lift Servo (optional)

Step 8: Bolt Together Assemble and Install Track

Now using the (5)   1/4" x 3" bolts and nuts, bolt together all three layers of the chassis.

Then assemble and install track.  The track just snaps together.  Instructions came with my kit.   It is easier if the tracks are installed on the drive gear 1st then the bogies and guide wheel.

Step 9: Mount Microcontroller Board

The bolts installed in step 6 should be sticking out of the top of the bot.  Place a nut on each bolt down far enough to place the BOE board on the bolts and secure with another nut.  Plug the servos in.

Step 10: Mount Battery Box - Program

Mount the battery box.  I just used Velcro to secure it.  install battery cells and plug battery bot into the microcontroller Board.  using the serial cable and a PC program as you wish.  I found the code, examples, and lessons for the BOEbot from parallax.com are thorough, easy to understand, and have provided the code I have used so far.  They also filled my head with great ideas for future applications.

Step 11: Going Further

above is a photo hint of where I'm hoping to take this project. 

It would be easy to substitute a different microcontroller board, or make custom attachments. 

Build a copy for yourself, then add to it, change it, make it better.  It would be great if you wrote up an instructable of your hacks so the rest of us could gain from your insights and hard work.

Thanks for reading.
<p>Actually we made a simular design for a robotic tournament, but of course it was driven by 12V motor and it was made out of aluminium, but the same concept.</p>
<p>Cool, Have you posted any pictures or info about it anywhere on the interwebs?</p>
<p>We participate in a tournament so there are pictures.</p><p>But I have found this one, you can see how the &quot;tank&quot; part looks like.</p>
<p>It is a really fast machine, fastest one at the tournament</p>
<p>It looks like you put a lot more engineering into the mechanical system than I did. It looks great!</p>
Nice idea, great job!
<br> Thanks for the compliment. If you are going to build a copy, or a similar Bot, PM me for the latest files.&nbsp; The design is not yet to the next plateau where I plan to make several of them, but I does have improvements from the model posted here.&nbsp; When I do get there it will probably be different to justify it's own instructable.&nbsp; If you, or anyone else, can't wait, I'm glad to share what I got.&nbsp; This machine could use some control.&nbsp; Maybe <a href="https://www.instructables.com/id/Cellphone-Operated-Robot-1/">DTMF via cell phone</a>?<br>
The robotic base can be used with my robot I'ble. Very cool! 5/5*
Awesome I'ble.... What is that paddle thing on the end?
Thanks for the encouragement.<br> The paddles are from the 1st draft of an attempt to get this thing to cut grass. I would like to have a swarm of them. If they can be be built it is just a matter of making it work ;&lt;)<br> I posted at just the chassis stage because of the contest deadline. Attachments were not ready (still are not ready) for prime time. The cutter pushes the grass away as much as it cuts. The paddles are an attempt to keep the grass in place long enough to be cut.<br> Ya gotta love Google Patent Search! This sort of problem was solved, and well documented by the 1950's<br> I plan on making an updated instructable about it someday. In the mean time, I sometimes post updates on this project page at<br> <br> http://twichel.com/projects/plowboy/plowbot.asp<br> <br> Whenever I have time, I am faced with the build/post what I have already built, decision. Build almost always wins. The contests are great if only to give me a deadline for getting some of what I did out there for others to improve.<br> Thanks again,<br> LaserLine
By<br> <strong><em>&quot;If they can be be built</em></strong> &quot;<br> <br> I meant to say <strong>&quot;If they can be built cheaply enough&quot;</strong><br> <br> LaserLine<br>
Wow you're very resourceful. Nice idea, great job!
Did I miss something? I do not see any code listing. I would be interested in how you did your dead reckoning routine. Are you using back emf for speed feedback?
No, you didn't miss it. I have not been able to edit my Instructable since I published and entered the contest. The issue may be on my end I'll try another machine. The code is all from parallax. a direct drop in from the boe bot.<br> <br> http://www.parallax.com/Portals/0/Downloads/docs/books/edu/Roboticsv2_2.pdf<br> <br> &nbsp; At the moment the bot is just a dumb chassis. It moves for a set time, turns, and reverses for the set time hard programed. One could do this for as long as you have memory for the program, but it gets boring fast. I ran into the contest just as I finished the milestone of a programable, operable, chassis, so I published that component. unfortunately all my sensors from the boe bot have been &quot;borrowed&quot; for other projects. I have several being shipped to me now. When I get to another milestone, I might publish another instructable. Who knows, maybe even have someone edit my grammer before hitting the publish button!!<br> <br> I am trying to post a play by play on my website at:<br> <br> http://twichel.com/projects/plowboy/plowbot.asp<br> <br> Much of what goes there is pre 1st draft, occasionally stuff drawn up that has not even been built or tested yet, but I do try to distinguish between what is tested and not tested. I am always trying to decide, build the next gismo, or post about the last gismo. Anyway the Parallax tutorial I linked to above Is where I got the code (and a lot more that once lived in my Boe Bot)
Cool! Any chance of a video of it working! Voted and rated :)
Thanks for the vote and rating. The video is a great idea. I'll see if I can persuade my son to create, and post, one for me to embed here.
If you have any questions, or want more detail, let me know. I usually check my email and comments at least daily.

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