Ok here the deal;
750lbs of dead weight
I'm building a car style robot
I need 2 motors and controllers
The reason I need 2 is because each one needs to be driven independently of each other like a tank set-up would be.
It will be Rc controlled.
Please keep it kinda simple please.
A few more details would be useful. How will you power this behemoth? What kind of speed/acceleration are you looking for?
Prefer 24v ,and speed does matter too much. I just don't want it crawl along. Any more details just ask.
How much $$$ do you have to spend?
You want to do it right? Study this "design", the CMU Terragator:
http://www.ri.cmu.edu/publication_view.html?pub_id=293
This sounds like essentially what you are trying to build. I hope this isn't your first robotics project, and I hope your prior projects had a fair degree of complexity to them, because this project won't be easy, nor will it be cheap.
Your best bet is to build a steel or aluminum box frame (welded construction would be best, but you could potentially use steel gridbeam construction), then use inexpensive all-terrain tires with chain drives to surplus electric mobility chair motors. Hopefully you will be able to salvage the motors from a working wheelchair, because motor controllers for such motors don't come cheap, either. Power should come from large deep-cycle or SLA batteries, with a small on-board generator providing re-charge and peak-load handling.
For such a large robot, Arduinos (or more likely embedded ATMega328s) become peripheral devices (for sensor and control processing) to a larger, on-board PC-based system. With the load handling capability you want to design for, you could probably create a small parallel cluster PC system if you wanted to.
I did mention this wasn't going to be a cheap project, didn't I?
I am in the process myself of building a similar robot, but I am taking it slower, using a Power Wheels H2 as my initial development platform; total amount spent so far for the project (though I am not really tracking it as well as I should; such is the case with these projects) has been somewhere around $1k US. I've been doing a bit of research here and there for what a robot like the CMU device would cost to homebrew; depending on what you are planning to use as the load carrying platform, its somewhere between $1k US on the low end (very optimistic on that, too), to somewhere north of $10k US on the high end (and can go much higher if you want; a Polaris isn't cheap).
Fortunately, what I described above (which is basically what the CMU machine was/is), falls on the lower end of that scale - if you really scrounged the parts - say by making heavy use of Craigslist, Ebay, online surplus dealers, auto-salvage and/or metal salvage places, digging in bulk-trash pickups around town (if you have them), swap meets, etc - you could probably keep it under 5 grand.
Whatever you ultimately do, though - think about this FIRST: How will you stop it, should it "run amok" - because it can, and likely will. Before you so much as begin a design like this, you need to come up with a safety override system, to shut the machine down immediately. It needs to incorporate a multiple redundant system, such that should anything go wrong, it can be commanded to stop in some manner where it -will- stop; you need to come up with a control system that has redundant "heartbeats" to bring the system to a halt should one fail, or should other spurious/conflicting signals be intercepted. You also need to think about security - for instance, even in my simple design, I will be using a mac-address locked 802.11g AP for communications interface to the on-board PC; I will also be using a custom generated SSL cert over HTTPS to encrypt all communications - the on-board PC will have a LAMP-based web-server for the command/control interface - such a system, provided that all security updates to the system are implemented, should prove to be secure to all but the most determined attackers (there is a limit to what you can do, and since this machine won't be moving that fast, it doesn't make sense to go beyond that).
Good luck, and don't bite off more than you can chew...
Back to the subject of driving motors, the below sabertooth motor controller can be operated from an RC receiver.
Motor and controllers cost?? Like to spend about $1000 to $1500 for both
I've built different robot before but not to this scale.