Just wondering why people don't just scale up on designs similar to this:
Robots don't scale linearly, they scale exponentially. Thats a huge problem when it comes to weight, or cost
For example, a robot twice as big would cost 3 or 4 times as much.
(I've been promising to write a tutorial on robot scaling for a year now, I'll get to it one day . . .)
Think about it : replace each servo with a geared windshield wiper motor and encoder ( 30 dollars on ebay) .
You're forgetting motor drivers that require much more current, and feedback systems accurate/fast enough to prevent the robot from breaking itself. (basically what dunk said)
By the way my budget for this project is $5000
With that budget, you shouldn't have a problem
As for windshield wiper motors, they are known for being very power hungry (inefficient) and electrically noisy. Basically that means bigger batteries for your bot.
Anyone know ballpark values for how much torque a wheelchair motor has?
Ebay has specs:http://search.ebay.com/search/search.dll?from=R40&_trksid=m37.l1313&satitle=wheel+chair+motor&category0=
Often the torque is printed right on the motor itself, so if you email a seller, they could tell you probably.
Just remember to not get the 24V motors unless you can afford the battery weight
Anyway, keep us updated. Since I'm *sssllloooowwwwlllllyyyyy* working on my own biped, I hope to learn lots from your project.