The assembly I've outlined below is experimental. Pipe fittings weren't meant to be used for this purpose, so please take caution when pumping pressurized air into these assemblies. The muscles I made were used for my Soft Pneumatic Exoskeleton. Air muscles work and are easy to build.
max air pressure: 120 psi
suggested lengths: 6"-30"
Materials (prices as of 6/29/2008) (materials listed below can be purchased at mcmaster.com)
High-Temperature Silicone Rubber Tubing Soft, 3/8" ID, 1/2" OD, 1/16" Wall
mcmaster.com # 5236K15 | $1.31 per foot
Heavy Duty Polyester Expandable Mesh Sleeving 1-1/2" ID, 3/4" to 2" Bundle Dia, 3'L, Black
mcmaster.com # 9142K34 | $5.83 each
Standard Brass Compression Tube Fitting Adapter for 1/2" Tube OD X 1/4" NPTF Female Pipe
mcmaster.com # 50915K226 | $3.86 each
Standard Brass Compression Tube Fitting Long Nut for 1/2" Tube OD
mcmaster.com # 50915K106 | $2.36 each
Moisture-Resistant Acetal Push-to-Connect Adapter for 5/32" Tube OD X 1/4" NPTF Male Pipe
mcmaster.com # 51055K8 | $1.45each
Standard Brass Compression Tube Fitting Tube Support for 1/2" Tube OD
mcmaster.com # 50915K246 | $7.37 for a pack of 10
Low-Pressure Brass Threaded Pipe Fitting 3/8" Male X 1/4" Female Pipe Sz, Reducing Bushing
mcmaster.com # 4429K522 | $1.78 each
Brass Yor-Lok Tube Fitting Cap for Tubing, 3/4" Tube OD
mcmaster.com # 5272K146 | $8.70 each
Choose-A-Color Flexible Nylon 11 Tubing .106" ID, 5/32" OD, .025" Wall Thickness, Red
mcmaster.com #5635K62 | $0.21 per foot
For each muscle you want to assemble you need:
(1) Silicon tubing cut to length (ex. 12")
(1) Braided sleeving cut to length -1/2" ( ex. 11.5")
(2) Tube Supports (1 pack comes with 10)
(1) Tube Fitting Cap
(1) Tube Fitting Long Nut
(1) Reducing Brushing
(1) Brass Compression Tube Fitting Adapter
Average price per muscle: ~$30
Note: The Tube Fitting Long Nut replaces the Hex nut that the Compression Tube Fitting Adapter comes with.
Pneumatic power and control parts
Valves (mechanical or solenoid)
Pressurized air source ( air reservoir or air compressor)
For pneumatic controls, vexrobotics has a nice starter kit. http://www.vexrobotics.com/vex-robotics-pneumatic-parts.shtml
Step 1: Place silicon tube into braided sleeve
Cut the braided sleeve to the same length minus 1/2 inch.
Burn the ends of the braided sleeve with a lighter to prevent it from fraying and to give it a lip in the compression sleeve assembly.
Shove the silicon tube into the braided sleeve.