Why can't hexapods walk faster?

Hello! Im new to arduino but all its possibillities is just awesome! Right now I'm curious about hexapods because I will probably build one myself in the future.
What i wonder is, how come hexapods don't walk faster? What kind of factors are holding it back?
Like in this video http://www.youtube.com/watch?v=O3ovrT8pWww&feature=youtube_gdata_player.
I know this question is based on sci-fi but is it possible to make a hexapod walk as fast as a human, like 5 km/h?
thanks in advance!
/A

Buy the fastest servos and write efficient code. You need to find the most optimal "walking gait" for your hexapod depending on mechanical construction/servos. I'm quite sure the hexapod in the video can walk a lot faster then is shown in the video.

The speed is limited by the length of the legs and how fast you can move them. To move at human speeds you may need to use human-sized legs (about 30 inches) or VERY fast and powerful servos.

It must be just the power to weight ratio not absolute size, ever seen a spider or a crab run? They can really motor.


Rob

The speed of that robot and similar beasties is mainly limited by the speed of the
servos. Typical servo speed is 60-degrees in 0.15-0.2 sec or so, but that probably
doesn't count startup and stop times. The following guys use pneumatics and claim
5 body-lengths/sec.

http://www-cdr.stanford.edu/biomimetics/documents/sprawl/
http://www-cdr.stanford.edu/biomimetics/

There's also the fact that most walking robots out there use static walking ("easy") vs dynamic walking ("hard") - note that I am not trying to imply that static methods are easy to implement, but relative to dynamic walking - they technically are. Then there's "passive dynamic walking"...

Right now I'm curious about hexapods because I will probably build one myself in the future.

If you are going to build a robot, I suggest building a car-like (two motors in back, two wheels in back) one instead. It's cheaper, faster, easier to program, easier to build, and less can go wrong. But if you really want to eventually build a hexapod robot, make the legs longer (sort of like johnwasser said), and probably use stronger servos to compensate for the the extra weight of the larger legs.