Hello everyone.
I am working on creating a mobile platform. Below are listed some of the design requirements.
-It needs to carry a load of 300 lbs (300 Lbs doesn’t include the weight of the frame, batteries, motors, tires, etc)
-Top speed of 15-20 MPH
-Traction needed. It needs to be able to get through mud, rough terrain, etc.
-Torque. Again, it needs to be able to get through mud, rough terrain, etc.
-The battery life needs to last as long as possible.
Attached is an image of the basic design. As you can see, it has 6 wheels. The way that this platform will turn is by activating the left set of 6 wheels, to turn right. To turn left, it activates the right set of 3 wheels. To turn in place, it will activate the left set of wheels forward, and the right set of wheels, backwards. The wheels are 25 inch ATV wheels.
Now, my question is this. What motors shall I use? 
There are many options, and im not sure which would be best.
Option 1: I could put a small scooter motor (Or other motor), on each wheel.
Potential motors for Option 1:
36 Volt 500 Watt Electric Motor with #25 Chain Sprocket (MY1020)
This motor would provide .67 hp to each wheel, resulting in 4 hp for the entire platform. However, it would require a 36v system.
Another option, slightly lower power output. However, it is a 24v motor.
This is a pretty high power output motor for a relatively low price.
For all of these options, I worry about them breaking. Hooking that small of a motor up to a 25 inch atv tire via #25 chain… I dont know if it would work. Would it even turn the tire? Does anyone have experience with something like this? lol
Pro’s of Option 1: Reduced cost, from less powerful motors.
Option 2: I could link all of the wheels together on each side with a motorcycle chain, and put one motor on each side.
Potential:
4 HP 24V DC VEHICLE ELECTRIC MOTOR - eBay (item 230415376902 end time Feb-20-10 07:05:41 PST)
So, what are some of your ideas here. What motors would you go with? And finally, What batteries would you use? So far Ive mostly considered 12v car batteries. Please remember, that budget is a huge concern here.
Thanks!