CHRONO MINER.
This is youre only unit that provide you with ore this ore is then turned into money so you can build youre great army.
If you also like to play against the computer you will discover that the ore miner is always under attack especially by the terror dromes.
The best way to keep youre trucks providing you with there serivce is to protect them well.
Or build the service depot because if the terror dromes get in the ore trucks they will eat the insides of it very quickly the only way you can remove the dromes is the service depot so if they are attacked get them to it asap.
GOOD LUCK.