[Donut]

Originally Posted by Kevin342

However it might be difficult to find one with enough force for under $400. Remember, we can only use 60 psi, so if you needed 150 lbs force (robot, battery, bumpers & a safety margin) you'd the need piston area to be 2.5 square inches (150/60). That's 1.78" diameter or bore. The next common size is a 2" bore, but those are very expensive, WAY over the $400 limit.

Here are a few listed on Mcmaster Carr.

If you're going to use pneumatics building your own linear actuators are a must to stay within cost. Getting normal cylinders (http://www.mcmaster.com/#standard-air-cylinders/=l2ot0l, using the PDV for Bimba works well too) and using linear slides from somewhere like Igus, 80/20, or Bosch as guides and support works well.

If you only need high force in one direction clever use of springs, surgical tubing, etc. can allow you to cut down the cylinder size. A 1.5" bore cylinder has about 105 lbs of force, loading it with 30 lbs of force from surgical tubing in one direction can give you 75 lbs extending but 135 lbs retracting.