Wouldn't it end up behaving like the skid steering anyway? It's just that they rotate freely instead of being powered.
I'll explain my issue and let me know what you think.
Right now, I have the rover on differential FWD drive with 2 rear castor wheels. It's a big rover that's suppose to carry a heavy load (100kg) and this has been accounted for by the motor and the design. This has been achieved nicely indoors. The issues I'm facing are these:
- The front wheels (driven) are air pumped and offer some absorption/suspension, casters are rubber and don't offer that. So this rougher terrain it gets all bumpy and shaky.
- Since the casters are not the same size as the driven wheels, I have them at different levels, it's extremely hard to assembly them properly, so at a given time, one of the casters doesn't have good contact with the group and will spin randomly. This is really obvious with rough terrain, but also sometimes on a smooth flat surface (without the load onto it)
- Given that all wheels aren't connected on the same height on the chassis, I end up not using the available space of the rover for components and I'm stuck with only have the chassis, since the casters are quite big. I'll attach a picture of the current rover.
So by having two passive wheels, I'll have the suspension from the air pumped tires, they'll all be on the same level - increasing the compartment space and allowing better traction with the ground.
The reason I'm trying to avoid the skid steering mechanism is it needs more space for the chain/gears on each side. Heavier load, and more things that could mechanically fail.