servo motors

i'm looking at servo motors here, you know chekin prices, loookin at power, and at torque to price ratio, and just lookin around, and i noticed this servo for 10.50 bucks, and it sais:

"Torque (4.8V): 100 oz.in."

does that mena when i plug 4.8 volts, it can turn and move something that is 6 POUNDS!? i dont think that thats correct, am i just wrong? how much can this servo really sustain? heres the link to the page:

http://www.bphobbies.com/view.asp?id=A0780198&pid=A0790278

Try to read this : http://www.romanblack.com/stepper.htm

It's really about stepper motors, but the concepts should apply to servos as well.

MikMo http://www.mikmo.dk

That servo has an unusually high gearing so it has more torque than most hobby servos, the tradeoff is that is much slower. FWIW, its my experience that low cost servos like the one in your link are not comfortable operating for extended periods at the full rating.

so u guys are say that it can support six pounds?

I would say it's specified to 6 pound inches, but I wouldn't want to stand under that weight if it was supported only by that servo ;).

What do you need your servo to do?

i was thinking of making like a very large robot arm with several servo motors controlling the bending of the arm, and the rotation.

i'm guessing these guys only go 180 degress around?

and what would be the perfect lightweight material to hold it all together, wood? plastic?

yes, the servo is capable of rotating around 180 degrees.

There is a tutorial for building a sophisticated robot arm here : http://www.societyofrobots.com/robot_arm_card_dealer.shtml

A search on google should uncover some other (hopefully simpler) ideas for you.

Have fun!

can they spin more then 180 degress? becuase that seems very....... not turny in most demostrations on the tube

Servos for hobby use are designed to drive bellcrank mechanisms. These mechanisms have a limited range of motion, so a typical servo's will operate over less than 180 degrees. I am sure that some of the many websites about robots have information on getting the degree of movement you would need.

can you tell if the ones i linked spin a full 180? becuase if they are, thats good enough and ill order a couple

cna you tell me where to find relieble good servos at an affordable pirce, like if you get them, where do yo getem from?

and are ball bearing and metal gears a must for robotics? what would you reccomnd i get, and how much should i spend per servo?

thanks in advance -big93

Not sure about the max rotation of the GWS servos you are considering but I have ordered servos from the site you linked and have been happy with their prices and customer service. I usually use Hitec Servos although I have just bought a bunch of GWS micro servos for some new planes I just got. Metal gears are more robust, but more expensive and not as precise when they start to wear. Ball bearing servos are usually more robust but they are more expensive then the equivalent non ball-bearing servo.

But I don't have much experience with robotics so I am not the best person to ask. Perhaps one of the Robotics forums can give you more informed advice.