I wanted a robust, versatile platform that could travel at about
jogging speed, capable of climbing over anything that is too small for
the on board sensors to notice and able to survive collisions at full
It should have enough space on board to be able to take a
variety of different electronics and processor units as the project
The chassis should be able to carry a battery pack capable of supporting several hours of use between charges.
There are a few commercially available robotics platforms out there that suit most of my requirements, for example, the Lynxmotion 4WD2 Chassis or any "off the shelf" radio control buggy, but i wanted to build as much of this project as possible myself.
From the experience gained with my previous Internet controlled bot i decided to go with tank style skid steering rather than ackerman steering because it is easier for remote users to visualise what is going on.
After some experimenting with heat formed
polycarbonate i reverted to aluminium for most of the moving
components. This was largely due to the difficulties of getting
accurate results forming polycarbonate in a home oven. Some of my heat
formed polycarbonate components remain but only where essential.
Aluminium was used because it is readily available and easy to work with hand tools.
The finished result performs quite well.
had to modify my original design to make the length to width ratio of
the wheel base wider to improve turning. Also the gear
motors being on the ends of the suspension arms causes more unsprung
weight than is ideal but this was somewhat unavoidable with the tools i
had available. (Only hand tools and a power drill.)
The suspension springs were bought from ebay and are from a RC truck.
The gear motors are 12v with a speed of around 120rpm @ 12v.
The suspension performs very well. You can chuck the bot about with no damage as long as it lands on it's wheels.