lol, This robot is going to be sooo huge, and heavy, you’ll need to operate it with HUge servos like 500$$ 
worth…or I dont know what im talking about 
Yup… I was beginning to get a little worried there. 
Whered you get 116 from?
(12 servos * 8 legs) + (10 servos * 2 grabbers) = 116 servos total.
[size=75]Where “grabbers” are the little leg-like appendages near the spider’s mouth.[/size]
Ohh, thought you guys ment 8 legs total. Well, 116… Good luck mate. As Jim said, may the force be with you.
Uh… cutting through the mockery (shame on you guys! ) yes, servo control by the hundreds is a possible feat.
If I were you, though, I’d build a simple controller to do it.
The easiest way to do that would be through shift registers as the SSC-32 does it.
That way, you don’t have to go hunting for a 100+ I/O microcontroller.
With 12 8-channel shift registers, you’ll have 96 servo outputs.
That would either mean that you’d need to control each of the 12 shift registers via an I/O, or via a a single I2C bus line.
I’d go with the first option, as it allows you to operate at the microcontroller’s instruction speed (somewhere around 10Mhz, but that depends on the micro) rather than the I2C speed (maximum 1Mhz).
Since servos need a pulse update only 20 times per second, you can give the shift register all it’s needed instructions in a miniscule amount of time and still have a huge portion of that to do other tasks.
If DIY electronics isn’t your thing, though you could indeed just buy 4 SSC-32’s.
That would necessitate the need for a micro with at least four TTL TX pins, but with a micro like the Atom, that isn’t a problem.
The control is relatively simple.
Now… the mechanics, that’s an entirely different story.
When you conquer this feat and come back to rub it in our face, we’ll all pretend we supported you the whole way.
Until then, we’ll laugh at this poor Christopher Columbus who’s daft fancy tells him that this world is round!
HAH!
This is why I need the SolidWorks files saved as STEP files so I can use them in AutoDesk Inventor.
it would be alot easier to show a picture, then discribe it in words.
I might be confused on the DOF but heres how I view it
Up = 1DOF
Down = 1DOF
Left = 1DOF
Right = 1DOF
Up/Down = 2DOF
Left/Right = 2DOF
Up/Down/Left = 3DOF
Just correct me if I’m wrong.
My understanding of the 3DOF leg. With Images from my project.
3DOF leg
http://www.malatorymods.com/spider/spider-17.jpg
Knee able to do 2 motions up / down
Hip1 able to do 2 motions up / down
Hip2 able to do 2 motions Right / left.
http://www.malatorymods.com/spider/spider-25.jpg
Hip2 is the location attached to the body
hip1 is attached to Hip2 and 1st leg bone.
I though with the extra bone pieces in the legs I was able to vizualize the movement a little better. But removed them as I was seeing when it was making the legs weaker.
http://www.malatorymods.com/spider/spider-61.jpg with out the extra bone
Ok, that explains everything. opps, then it’s only 6DOF in the 8 main legs, and 5 in the grabs. oops. ahahahahah 
That would make a bit more sense. Though 6DOF legs, damn what you gunna make 'em do? Thats 58 servos total then. Seems a bit more possible. 2 SSC-32s will do a good job then.
Still makes it a little on the large and heavy side of thigns … Glade to help clean something up.
/me cleans the mud off his shoes…
While that still will be difficult to manage, it’s definitely possible.
Try to minimize the distance between the legs by minimizing the radius of the body.
A tight bundle of sticks is a lot stronger than a loosely-bundled one.
Well, I have the dimensions of the spider I’m modeling this after.
I like it, I’m saving up to buy one, aren’t they cute.
Looking at those pictures, it looks like this could be done with a 5DOF leg instead of 6DOF. I haven’t studied spiders much, as I’m a bit arachnophobic, so I may be wrong here. It looks like I can see a total of 6 joints on the spider’s legs, but at least one of them looks like it would never move, so you could probably get away with making that a solid section in the leg. Of course, if you’re going for prototypical, then you would need every DOF that the real spider has.
I think it oughta look cool as hell when you get it done.
On a side note, would it be feasible to do something like this with pneumatics or hydraulics? This would theoretically eliminate the problems of weight in the legs, but would probably make the whole thing a lot more complex, and I have no idea how you would go about controlling the cylinders.
if he had hydraulics or pneamatics, it would make it alot harder, he would need a big rolling pump on board to provide power to the pneamatics, and idk if hydraulics would work
Pneumatics and hydralics would require 7209384723892394 more amps of power. I dont want to be running a 240 volt connection from the fuse box just to be able to play with it.
carefull with making spiders … they can get out of hand…
here is the 1st one I did last year at this time … thinking getting the body down and then move to motion. I also was trying to fit a larger computer into the body at this time as well
Out side using it as a holloween deceration.
http://www.malatorymods.com/helloween/spider-61.jpg
size look next to a 4’ store bought spider.
http://www.malatorymods.com/helloween/spider-55.jpg
Daughter trying to poke its eyes out
http://www.malatorymods.com/helloween/spider-44.jpg
One with a 6 year old laying infront of it.
http://www.malatorymods.com/helloween/spider-54.jpg
as you make your spider I will be intrested in following along… not that I like them and it is close to what I am doing as well.
Well after 38 hrs of banging my head, slamming the keypad, large quantities of caffinee, and many pages of dimension’s, I have completed the Trochanter and Femur joints.
I’ll post some pictures later, it’s lunch time. Mmmmm grilled cheese.
Picutre!!! This is just a concept assembly of the leg. I am working on modeling light brackets to use.
http://i105.photobucket.com/albums/m208/The_Captain_2006/Robotics/Concept%20Pictures/SpiderWalkingLeg.jpg
Is has a 31.75" reach 
, I might shrink that. It is modeled 4x as big as the spider’s leg just to give you an idea of why it is so big.
sure looks cool man
i hope you are ready to drop some money on the servos fro this beast