This build started when I needed to run some wires in the ceiling of my finished basement and had no way of getting in there. So I figured I would just build a robot that could pull the wires for me. And I'm sure I could find other uses for it later. I salvaged parts from an old RC vehicle that had tracks, and I reused baby monitor cameras for the video feeds. Here are some early videos of the Rover going through the controls for the first time. If you like it please vote for me in the contests that I have entered above.
Step 1: The Build Begins
I wasn't 100% sure what the final product was going to look like at the time but I had a pretty good idea because I had laid everything out on cardboard to get a feel for size. I had to keep it low to fit between the duct work and narrow enough to just fit between the studs.
I started with a 3/32" aluminum sheet which I measured, scored, and cut out the areas where hardware would go and where I would bend the sides up for support.
Step 2: Finishing the Frame
I clamped the sheet to the workbench and used a rubber mallet to bend the flange over at a 90 degree angle. I also used some pliers to help bend and straighten the wavy sides from the mallet. You would ideally use a sheet metal bender for this but I did not have one so I had to improvise. I then drilled all of the holes for all of the hardware and components that will need to be installed.I also placed Velcro on the sides that will hold the battery packs in later.
Step 3: The Drivetrain
I am using 4 tracks that I salvaged off of an old rc tank. If you look close you can see that I have put 2 sprockets on each of these tracks which allows me to drive and rotate each track. The way it works is the inner sprocket is attached directly to the outside of the tread housing which rotates the full track around when powered, then there is the outer sprocket that is attached to a shaft that runs through the center of the inner sprocket. This is attached to the wheel that drives the treads. I hope you were able to follow all of that.
The black object in my hand with the holes drilled in them are the mounts to hold up the treads. I made these out of Delrin because I knew that parts had to rotate inside and I needed something slippery that wouldn't bind up. I added some extra speed holes to try and keep everything light.
The other object in my had with the standoffs are the rotate motor mounts. These will hold the rotating motors at the right height. I modeled these in Autodesk Inventor and printed them on a 3D printer at a local shop.
Step 4: Drivetrain Part 2
I have 4 motors that run this Rover, 2 drive motors and 2 rotate motors as I call them. In the pictures you can see the rotate motors are instilled and the track mounts are mounted. I got the rotate motors from the same RC vehicle that I got the tracks from. They are geared a lot and are pretty loud. Whats nice about them is that they have a sprocket inside that will slip intentionally when too much torque is applied so you don't strip any teeth on the gears.
In the last couple of pictures you can see the drive motors that I purchased from Pololu and I also got the motor mounts.
Step 5: Battery Packs
I wanted this robot to have plenty of battery power because I didn't want it to die on me when it was up in the ceiling. I also need the battery packs to be thin and long so they would fit along both sides of the robot. So I opted to make my own battery packs. I used C style NiCad batteries that were 1.2v and 3Ah and connected 8 of them in series to give me 9.6v at 3Ah each, and with 2 packs I would have 6Ah which is definitely overkill but then again so is this whole project.I also made a 4.8v battery pack to run the boards and you can see it installed in the robot later.
I lined the batteries up and soldered either a wire or a weld tab to each of the batteries connecting to the next. At the ends I soldered my positive and negative wires. Then I took heat shrink and shrunk the whole pack. This step is critical because you don't want the batteries to short out so every connection must be covered.
Later on I attached connectors on myself which I did on all of the hardware. This is so I can disconnect everything and swap out parts or charge batteries when needed.
Step 6: Electronics
This was the first project that I used Arduino so I have don quite a bit of research. I decided to use the Arduino Botboarduino from Lynxmotion for the processor because it has been used in a 4 wheel drive vehicle before. I then had to find a 4 channel motor controller, which I didn't find too many to choose from. I could have use 2 of the 2 channel controllers but I wanted it all in one board. So I went with the Dagu 4 channel motor controller from Robotshop. Just running the 4 motors and the remote receiver used all of my servo channels on the Botboarduino so I had to get a Pololu micro serial servo controller so I could have more channels for my servos that will control my front camera and possibly a gripper arm.
I wanted to use a PlayStation 2 controller for this build because of the top buttons are perfect for my clockwise and counter-clockwise rotation of the tracks. So I bought the Lynxmotion PS2 Controller V3 from Robotshop.
I got a toggle switch that has dual circuits in one switch so I could run 9.6v on one side and 4.8v on the other side.
I also have 4 servos that I will be using. Two for the Pan and Tilt of the front camera and two for the pinch and tilt of the gripper arm but I will show you those later.
Step 7: Wiring
Here you can see that I laid everything on the table to make sure everything worked right and motors and servos were spinning the correct direction before I mounted anything.
I had a lot of help with programming from my friend David Gitz the CEO over at FAST Robotics. I have included a copy of my program.
I have included a hand written schematic of my wire diagram. I mounted all 3 of the boards on clear lexan so the would save space and have enough space between them sot the connectors would not be smashed. I used lexan because plexiglass tends to break off when you drill close to the edges. I also crimped quick connectors on the motor board so I could easily remove a motor if I needed to.
The last picture shows all wired up. I know it looks like a mess but you should have seen it before I cleaned it all up.
Step 8: Electronics fit
Here I have most of the components in the frame to make sure everything fits. Notice the 4.8v battery pack that I made in the first picture. Also you can see all of the quick connectors I have added to the wiring.
In the second photo you can see that I added a hole for my rear mounted camera. The next picture shows it installed with 2 adhesive brackets and zip ties. I needed this to be low profile to fit, that is why I chose this mounting method.
In the next picture you can see that I have a dual sprocket on the drive motor and I will run chain form there to the front and rear track, I will do this for both sides.
Step 9: All components installed
I decided to cut some of the front off the frame so my front camera could see better and so the claw could tilt further down. The camera system that I am using is a Lorex Live Snap setup that I got off of Ebay. I like this system because it is wireless with internal battery, night vision, and I can take snap shots of what ever is on my handheld screen.I show the monitor attached to my PS2 controller with another 3D printer part that I designed. The claw is another product I got off of Ebay because everyone else sells the pinching type that only touch at the tip and I wanted a claw that had sliding teeth so the full length would contact when closed on something. I believe the claw was called a 2 DOF Arduino gripper. Then I added the tracks and chains on the sprockets. After hooking up all of the wires it was time to take it for the first test drive.
Step 10: Molding the upper body
Now I need to protect all of those nice electronics. So I built a vacuum form machine which I will be making a new Instructable later for that one. I took the tracks off for this step because they are not needed in the process. But essentially what I did was first I took cardboard and taped it on top of any electronics or sprockets that I didn't want the body to lay on (gives spacing), then I took more cardboard and taped it down to make some smoother corners when I mold it. I also added some wood spacers that will come in handy later for the claw and camera.
I then put the whole robot into a vacuum seal bag (one of the big ones that you use a vacuum cleaner to suck down). This created a a completely sealed robot and had smooth edges on everything. I then taped back all of the flaps and extra bag material. Then I use 1/8" thick ABS plastic sheet and my vacuum former to make the top mold as you can see.
Step 11: Finished Product
I drilled 4 small holes in the top of the body and ran bolts down to my tread mounts to keep the body on.
So here it is, all finished up. I havent had a chance to run any wires with it yet but it runs great and I am happy with it!!