I got another cheap RC model car that I am currently converting into a rover:

The RC car costs less than 20,-€ including shipping and it's hard to get a chassis with wheels, motors, batteries with charger and power electronics cheaper when buying single parts and build it all from scratch. With a Raspberry Pi zero WLAN and a camera module, this would be a base for a world tour robot for less than 50,-€.

The gears of drive motor and steering don't look too bad and test drives will show how many miles the mechanics can do:

I connected a Raspberry Pi 3 to the h bridges of the car:

The model car came with 4 NiCd cells and I have added a voltage divider as battery sensor to avoid deep discharge. I will add a holder for 4 AA batteries. With those commonly available NiMH cells you can operate the rover almost continuously if you replace the batteries with freshly charged ones each 2h.

All details of the conversion will be published in a video about my latest rover that is currently in the process of editing.

The software is nearly identical to the version I used with my previous rover R6 that is today (October 15, 2017) out for another test run:

http://homofaciens.de/robospatium-controlstation-R6_en.htm

I will also bring my first outdoor rover R5 into the playground, however this robot is powered by lead acid batteries that allow no more than 2h of operation, thus it wont be online the whole day:

http://homofaciens.de/robospatium-controlstation-R5_en.htm

Hope to bring R7 online for a couple of hours before the deadline of this year's Hackaday prize that ends tomorrow. Have a look at my RoboSpatium to see if R7 is up and running:

http://www.homofaciens.de/robospatium_en.htm

It's almost all done to put a first earth explorer into a tiny parcel - some price money would speed it up ;-)

Come together in exploring our planet!