Building an Arduino robot

This is part of a series of blog posts on how to build a tracked Arduino robot.

Not long ago a friend asked me for help robotizing a model tank. I found this kit online I thought could be a sensible chassis, and this kit which would make a sensible drivetrain. However, these two kits arn't meant to work together, so it requires a little bit of bodging to get it to work. Although eventually we found there was a lack of room inside the small model to fit all the components, we contined regardless.

So, a "to do" list:

• Build the kits
• Modify the kits to work together and hold the Arduino
• Wire it all up (in the next blog post)

Building the kit

I won't go through the instructions of the kits here, but I will talk about how I set up the two kits.
For the chassis, I used the big drive sprockets, the big guide wheels and the big set of road wheels and the "Type B" configuration (38.2:1 gear ratio) in the gearbox. We can use the size of the big drive sprocket and the RPM of the chosen gearbox configuration (345 rpm on the supplied datasheet) to estimate how fast our robot will go, using this equation... $$Speed = \frac{(rpm×(diameter×p))}{60}$$ Filled in, this becomes... $$0.5599\mathrm{ms^{-1}} = \frac{(345\textrm{rpm}×(0.031\textrm{m}×p))}{60}$$ Wow, thats about 1.25 miles per hour! Obviously, this doesn't take into account power lost due to friction from the tracks or drag on the robot. But just for fun, lets see how fast it would go with the "Type A" gearbox set up, which has a lower gear ratio of 12.7:1 and spins the driveshaft at 1039 RPM. $$1.6864\mathrm{ms^{-1}} = \frac{(1039\textrm{rpm}×(0.031\textrm{m}×p))}{60}$$ Thats almost 4 miles per hour, but the additional speed comes at the price of less torque. I will stick with the "Type B" set up from before for now.

Other modifications to the kit

To fit the gearbox to the chassis I cut two small notches into the wooden base. This allows the provided screws to run half embeded through the chassis into the provided receiving bar, which is mounted upside down. Potentially you could use a larger piece of wood, but it could only be about half an inch wider due to the width of the track axles, and therefore the maximum width of the track. Due to being in uni while I was making most of this, I used the saw blade on my multitool to make these notches.

To fit the Arduino to the chassis I drilled 3 holes in the chassis to match these 3 holes in the Arduino (note: I'm not sure if the holes are the same size or even in the same place on a real Arduino because I have a "DCcduino" which is a cheap alternative to a real Arduino). I then got some spare motherboard spacers (the things you put in your computer case to rise the motherboard off the back of the case) and screwed them into the chassis. I then ran some large thread PC screws through the Arduino (which might require a bit of persuading with a drill bit or a small knife to make the hole bigger) to secure the Arduino to the spacers.

Next time...

We will work out the robots wiring...