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Originally Posted by Betty_Krocker
well from concept everything is in the front anyway, but in this situation pushing power doesn't matter. I you want control you want pulling power.
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Pushing other robots around isn't going to be viable this year, but you still need to be able to use all your traction effectively to navigate the field quickly. The problem with FWD and front wheel steering is that you're using up all the traction in the front and wasting the traction in the rear, and you're just going to understeer all over the place and not be able to do anything about it. Rear wheel steering wouldn't be the way to go this year because you'd pivot around the front wheels, which would make steering with the trailer much harder. Since you want to have your COG and pivot point towards the rear to be able to turn with the trailer easier, the optimal 2WD setup would be RWD with front wheel steering.
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The same reason drift cars are rear wheel drive is the same principal rear wheel drive results in loss of control,
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Drifting isn't losing control. In fact, it's being able to control the car with the throttle even when you're breaking traction. Watch the sport at at competitive level, and tell me those drivers don't have control of their vehicles.
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and 4wd is going to work too hard to steer sicne the wheels would rather slip inline than transverse (which makes skid steer out of the question)
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Actually, testing has shown that the wheels are so rigid that they don't much care if they're sliding inline or transverse. Skid steer can work perfectly fine this year. And if you're comparing AWD with car-style steering to 2WD with car-style steering, the AWD system is going to destroy the 2WD one. Watch some World Rally Championship, and you'll see the advantages in car control that AWD gives you on low-traction surfaces. Being able to four-wheel drift through corners would be a huge advantage this year, as it would let teams maneuver while maintaining speed to avoid being scored on.
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i will admit that 4wd is a valid point, but all drive systems of this year have MAJOR tradeoffs, thus making not one type (except for rear wheel drive) the best, it will be interesting to see at competition....
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Like I said, as far as 2WD car-style drivelines go, RWD with front wheel steering is going to be optimal. The ability to control the rear of the robot with the throttle in a RWD setup would give you better control than in a FWD setup which can understeer much more easily than it can oversteer.
And by the way, the whole "pushing is better than pulling" thing is more or less a myth. RWD makes more efficient use of it's traction than FWD, no matter what surface they're on. The reason why FWD is better in the winter is that when they're varying levels of traction on different parts of it road, it's easier to control, and understeer is safer than oversteer. Manufacturers don't like selling cars that oversteer, is because the majority of people don't understand vehicle dynamics, and don't have the experience to correct oversteer instinctively. If a RWD car starts to slide out, most people are going to slam on the brakes. This transfers weight to the front of the car, increasing the grip on the front wheels, and decreasing the grip in the rear, causing the car to pivot further. To correct a slide in a RWD car, you need to use steering input and throttle modulation, not panic braking. In the context of Lunacy, where the traction on the regolith is entirely uniform, and it doesn't matter if you slide into other robots, RWD would be far superior.
Just because traction is reduced this year doesn't mean that the laws of physics went out the window. FWD still sucks. In fact, it sucks even more this year, because the robots are going to be driving at the limit of their grip all the time.
This is one case where I really wish Andymark didn't listen to their customers so well. - ASD20 [more] 
06-01-2009, 09:49
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