Need help transferring rotational energy

I’m trying to create a simple vehicle in which the forward momentum is created elsewhere, say on the side of the vehicle, and is then transferred down to one of the wheels to move everything forward.

Here’s a quick schematic of what I’m trying to do. I tried using both rope and elastic to try and get both wheels to spin at the same rate (similar to how a train operates), but neither worked. It either had too much slack and didn’t help or it was too tight and stopped both wheels.

Tried PHX gears?

Could you use rigid rope?

This or non-fixed hydraulic really