I have made the start here robot(identical materials) but i have modified it with 4 motor conected in parallel.
the L293D works fine no over heatting at all.
the motors are connected in pairs right side in parallel conected to channel A,leftside in parallel connected to channel B.
On a simple test program i test each iteam seperatly
the motors go forward,turn right,turn left and reverse,reverse left,reverse right. fine
disconected motors then run test program for servo an sensor
same with the servo and sensor the detect great and pan left to right very smoothly
when all connected to gether and run on clean basic program provided (attached)
the motors run and respond to sensor but the servo moves and twitches once sometimes twice then thats it???????????