Pneumatics for joints? How about cheap ones?

[S. Karim]

Anyone know where to buy small (2-3" tube) and cheap pneumatics? My lego one pushes out 1" but its plenty for rotation. 2" might be awesome for a biped, and would require a tiny amount of servos (ankles, head). However, pneumatics are VERY smooth, like oil smooth (well thats hydraulics, so lets say air smooth lol). Pneumatics are also, VERY strong.

Ideas? thoughts?

[rgcustodio]

How about these:
http://www.vexlabs.com/vex-robotics-pneumatic-parts.shtml

[S. Karim]

Saw that link a long time ago while purchasing the vex starter kit. It looks awesome but its kinda expensive...

[Nyx]

Check out the electronic goldmine... They have inexpensive air cylinders...

http://www.goldmine-elec-products.com/products.asp?dept=1345

[sotu]

How does they work exactly? Do you add power and they starts?

[S. Karim]

you're talking about pneumatics?

you run air through one hole using a pump/compressor, and the cylinder goes out, you flip the switch and itll release the air out of the other hole, pulling the cylinder.

air is super f'ing strong, pneumatics are extremely powerful, more torque than servos if you have the correct pneumatics. my lego pneumatics can lift the entire car off 1 cylinder. hydraulics are the same,except you're running psi of oil, so its damn near impossible for something to resist it.

[sotu]

Oh yes thats right, they dont use liquid like haudralic!

[Admin]

Pneumatics are bad because:

Requires high pressure air supply
Sags
Very inaccurate

(there is a post somewhere in the forum that discribes the issue really well but I cant seem to find it)

[sotu]

In some other post i have posted a picture of an idea i had, i can try to explain the picture, u guys think this wil work:
A walking robot or biped robot as someone will say using no servos at all. Just a Pneumatic pump going from the upper tie to the lower leg, when the pump pushes out the leg stretch and when the pump is going back into the pump holder the leg bends. Sounds reseneble to me!

[S. Karim]

You'd need a small piston for every joint. It'll be a mechanical challenge to place them properly, because the piston bending the knee will have to be attached to the thigh. It'll be pretty awesome but a huge one because each joint requires a separate switch since you cant control them in unison for a biped.

[NestorClassFour]

Pneumatics for use on androids are generally flawed because the way the human moves is via pulling muscles, not expanding ones. I am working on a similar project and instead I am using cable and servos in order to move limbs.

However, if you are experienced with pneumatics, you should stick to it, but use some stretchy rubber to ensure the pistons do not bend!

"I see the logic of your plan, it just seems too.......heartless," (Sonny, I, robot 2004)

[guyfrom7up]

Why not use air muscle, that's what I'm going to use, search it on google, there's even a website of how to make them.  Air muscles are extremely strong and light.  Air muscles contract, like real human muscles, so it's even better for making a humanoid robot!