If you read my posts over at http://therobotgroup.org then you’ve already read most of what I’m posting today. If not, you’re in luck, because here’s new stuff. In October of last year I was asked to review a new robot chassis called Nomad. In November I received the kit and began the build. This is the story.
The review was for Servo Magazine and, being my first article for them I was a little nervous. What if they didn’t like my writing style and all that biz. Well, I wrote it like I write everything that’s not a technical document for work, very conversationally. I also included some photos of the build and testing. Initially I only included a couple photos, but they liked them and asked for more, which was no problem. Like I said, it was my first article for them and I photographed everything so I had plenty of photos to send them. They must have liked the photos because one of them was used for the cover.
But on to the my experience with the Nomad chassis, which was fantastic. Prior to receiving the Nomad I had purchased a Wild Thumper chassis for off-road robotics projects and was I ever disappointed with that decision. Sure it looks cool, but it performed horrendously. The motors were/are under powered and it doesn’t turn worth a crap. This is largely due to the wheel configuration and the fact that it uses differential steering; if you want to change direction you adjust the speed of one side of the bot. Works for tanks and robots with casters, not so much with 6 wheels. So, after that, my expectations were set rather low for the Nomad. After all, it uses the same steering technique but with 4 wheels instead of 6.
I was very happy to have been wrong in this assumption. The Nomad chassis performs excellently. The 12 volt motors are much more powerful than the 6 volt ones on the Wild Thumper, even when the Thumper was over powered with 12 volts. And due to the wider stance of the Nomad, the turning issue was not present. In fact, the biggest problem I have with turning of the Nomad is the fact that the channels holding tires on the wheels is too shallow and the tires keep popping off the wheel. The fix to that will be a couple of laser cut disks to increase the depth of the bead.
In addition to the chassis which included the motors, they provided me with a RoboClaw motor controller. Let me simply state that, at the moment, I have a new favorite motor controller. On top of that I was so impressed with the features I’ve already used it on another project (for a later post). In fact it’s going to take a lot to bump this one out of my number 1 slot.
Chassis assembled, controllers in place, I slapped on the RC receiver and off it went. This little chassis was so much fun to just drive around with the RC controller. It seemed unstoppable. Well, that is until the wheels fell off completely… twice. The chassis uses Servo City’s Actobotics line of parts which leverages #6-32 screws to hold everything on. Well, let’s just say it’s good to invest in Loctite or lock washers because they want to rattle out. But this is minor and easily fixed.
Having proved itself in its stock format I decided to upgrade a few things I didn’t like about the design. The chassis uses two channels with the motors and wheels at either end and connected together in the center with a shorter channel. All of it fits beautifully together. They included bearings and an axle of sorts to allow one side of the chassis to pivot which improved its versatility but the center box was rigid to one of the side channels. I didn’t like this. So, I went ahead and ordered some more bearings, rod, and spring assemblies to allow both channels to pivot while keeping the center box from spinning on the center axis. It worked brilliantly and was just as much fun to drive around.
That’s where I stopped as I had to move on to another project, the monsters mentioned in an earlier post. But I still have big plans for Nomad including a Raspberry Pi, the RoboClaw, an Android phone, and Sparkfun’s Autonomous Vehicle Challenge in June. Well, not this June, but next year. Stay tuned on more about Nomad.