empty toothpaste tubes for air bladders ?

I have seen air muscles made out of the neoprene surgical tubing inside
a fine mesh/netting material. A prof at Arizona State University was
using them for prosthetic development.

Bob

    --Festo Pneumatics makes these sort of things but I gotta say
they're energy-intensive, expensive and provide very little movement. Maybe
it's better to keep working on something that's not off-the-shelf. What's
your application? The toothpast tube idea sounds innnnnteresting!

--
        "Steamboat Ed" Haas         :  "Hold on! we're passing                
        Hacking the Trailing Edge!  :  through the moronosphere!"
                          www.nmpproducts.com
                   ---Decks a-wash in a sea of words---

Yeah - that's the idea I have, as well. Although I must admint that for now it
is a *very vague* idea !
JCD

anything like that ?

Are you deliberately wanting trash?  If not, perhaps a dollar-store
could be a cheap source of actuators.

The air-pump water rockets have air pumps that might be hackable into
pneumatic pistons.  Also, balloon pumps.  I've seen halloween haunted
house makers write article's on making your own pistons from PVC pipe.

Printer ink refill kits have a plastic bellows device to hold the
replacement ink.

I've always wanted to make something that used dryer vent hose as an
actuator.  It is available in various sizes, but the smallest I've
seen in 3" diameter.  4" and 6" are more common....

Well, now you've got me thinking about this again, and I feel the need
to elaborate;

The idea is a pneumatic giant octopus tentacle. Take 3 of the dryer
vent hoses, and place them around a core made from plastic pool vacuum
hose. The 3 vent hoses around the perimeter should be about twice the
length of the core. Fasten the outer hoses by either wrapping with
wire or tape.

As air is pumped in, or sucked out of one or the other of the 3 outer
hoses, the arm will respond by curling.

The air source would need to be something like a shop vacuum. However,
I've also considered making a giant joystick by cutting a 30" diameter
disk of 1/2" plywood. Put a 6" long piece of 2x2 wood in the center to
act as a pivot. PUt a longer stick on the center going up to act as a
handle.  Then place 3 pieces of 12" diameter vent hose, perhaps 12"
long each, under the plywood in 3 spots around the perimeter. As you
stand on the disk, you shift your weight from side-to-side and cause
the bellows underneath to push out or suck in air which you can pipe
to the tentacle.

For further refinement, you might use that hose down the center to
pump in air that gets used on another set of vent hoses further down
the tentacle. Then, where the 2nd stage gets used, you would need 3
butterfly valves (presumably actuated by R/C type servos) to control
the air flow into the end of the tentacle.

Part of the purpose of the vacuum hose down the center is to prevent
the tentacle from twisting.  But, it may also be possible to omit it.
Then it would be possible to extend or contract the entire length of
the tentacle by blowing in or sucking out from all 3 chambers at the
same time.

Please let me know if you try this idea!

Joe Dunfee

anything like that ?

Naaaaaw. I just like to see how I can recycle things. I was thinking along the
line of 2 toothpaste tubes connected with plastic
hose. One is inflated and the other is deflated. To actuate the empty one it
would be squeezed with a accentrically mounted
cyclinder or something like that. When the other one inflates it pushes apart
some gripper fingers; shortens a "bicep"; or
whatever.

After considering all of that, I started questioning when would it even be worth
using air/hydraulic actuators versus electrical.
The more I think about it, the more I can not come up with a decent reason.
Anyone else ?

JCD

Some guy named McKibben will be happy (is he still alive?).

If you can afford to use precompressed air (e.g. cartridges for
bb/paintball guns), then pneumatics can beat electrical.  I built a
CO2-powered car that outraced the competition in a robotics course...
also annoyed the professor.

If you first need an actuator to compress the air, then its a harder sale.

Pneumatics are naturally springy and compliant, and they can store
energy for quick bursts.  Both effects might also be achieved with
traditional spring-damper systems, but pneumatics might provide a
better shape or actuation profile than a normal mechanical system.

Like hydraulics, pneumatics allow for isolation of the (heavy)
compressor from the (light) actuator.

There is a possible energetic advantage of using a storage tank;
generally leaving the compressor off, and only running it at the
optimal level.  However this is offset by leakage and friction in the
valves and actuators.

- Daniel

    Bad idea.  They'd wear out too fast.  Sections of bicycle
inner tube, though...

                John Nagle

Why would they wear out faster than inner tube ?

On Fri, 1 Aug 2008 01:15:06 -0400, "pogo"


   Toothpaste tubes are made of thin metal, just strong enough to be
filled up at the factory and emptied out by hand one time. Repeated
filling and emptying, even with air, would quickly cause it to fail
due to metal fatique.

   Using an nner tube sounds like a good idea. Speaking of which, I'd
like to find an automotive tire inner tube (excellent for making a
very-low-vibration platform), but it appears they quit making those
many years ago when tubeless tires became common.

Erm, maybe in the 20th century, but mine are made of some sort of plastic.

On Mon, 8 Sep 2008 19:44:30 +0100, "Deep Reset"


   Oh, geez. Maybe I don't brush my teeth often enough.

On Mon, 08 Sep 2008 01:44:08 -0400, Ben Bradley wrote:


You still see the occasional person floating down a river with their head
and shoulders stuck through an inner tube, so they must still be
manufactured (although it is possible that they are now manufactured only
for recreational use).

--
John F. Eldredge -- john@jfeldredge.com
PGP key available from http://pgp.mit.edu
"Reserve your right to think, for even to think wrongly is better
than not to think at all." -- Hypatia of Alexandria

wrote:


   I suppose I could ask the ballbot guy, it looks like one in this
video: