Bound to Happen, I Reckon

And a snag has been reached. I've got a simple circuit that seems to work: the battery connected to the photocell to the motor back to the battery. Simple. I soldered and hot glued the board and the battery onto the bug's back, the motor runs off the flashlight fine when I'm holding it, but when placed on a surface... nothing. So there's a problem. Perhaps the battery is too heavy? It's a pretty large 9-volt battery, after all. So I dig up those small circular batteries, similar to the ones already in the bug, but three volts each, and pile three up high to make it nine volts. I attach the wires to the fronts and backs, the bug runs fine in the air, but on the ground... nothing again. This doesn't seem to make sense. The bug runs around like a madman with only three volts, and it can't run with nine? So I up the ante: fifteen volts of power. There's SOMEWHAT of a victory here: if you place the car down just right, you can lead the car down a surface for five or six wheel rotations at best. It's always a hit or miss though. So what seems to be the trouble? Hell if I know. But it would appear that it could be only be one of two things: needs more power, or needs more light.
So, I'll be doing two more tests:
1. Add more voltage. The battery stack's getting pretty high and out of reach of the photocell leg it's got to attach to, but I'll see if I can add at least one more 3-volt to see if that makes any difference.
2. A stronger light source. I plan to go to Lowe's tomorrow and pick up the strongest light source they've got (with guarantee I can return it later this week), and see if it will move differently with more light.

If neither of those two options does me any good, then what can I do. I've got to work with what I have. I'll set up a mini-arena with a start line, and make it like I'd holding a competition: who can get this rinky dink car to go the farthest using the flashlight as a guide? It'd be somewhat interesting. Not really much of a concept, but at least it's something.
More to come. Jeezum crow...