I have just got a UPS update that my kit will reach on 26 Dec 18, right after Christmas. So i still can enjoy the Christmas holiday now. Anyway, the only update i have is i have decided to go for somewhat fail safe chain track chasis. It does comes with 2x of gear motor (DC 6V-12V with 320mA no load current, 446rpm, 4.5A stall current). Well, these pair of motor should work on my playground. If they don't i have another pair of 6W Maxon DC geared motor which i salvage from an old factory automation machine. The Maxon has 420mA no load current, and 1.1A stall current, but its operating voltage is at 24V, making power supply slightly more complicated than sticking with the chasis kit motor, hence i will try not to touch it yet. It is also very encouraging to know that a single of this Maxon motor cost more than the chasis with motors 
Maxon motor is best known as the chosen motor for use in a number of NASA MARS rover, starting in 1997. My weed cutting robot is operating in an environment much simpler than the Red Planet, hence i guess the Maxon will be the best backup i have. Now that i think, i am located in a tropical region where it rains a lot, and this makes me think that my garden is probably more challenging than Mars. It makes me ponder how would i make my weeder to be IP66 https://en.wikipedia.org/wiki/IP_Code , which means protection from dust and protection water projected in powerful jets from a nozzle with a 12.5mm diameter opening in any direction (a.k.a rain)
The only thing i am unsure, since it is a salvaged unit, is its RPM. i try look at https://www.youtube.com/watch?v=tgJUasdvfMA that provide some explanation, but i guess it is best to just power it up and see how it fares.
The other motor that i am preparing is this RC servo with 1 axis bracket like the picture below. this will serve to hold my cutter in various angle. i try to do away with 2 axis as i think i can turn my rover instead.
for now, Merry Christmas ...until i get the kit and try power up just the motors
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