Originally Posted by emo Sponge (Post 690406)

if your arm sticks out you should use peumatics
if it does not use a motor
peumatics are not realy safe

Originally Posted by emo Sponge (Post 690423)

our team has a peumatic catapult and it is very dangerous
if the air compresor became faulty it could set off the catapult and injure someone

Originally Posted by rocketperson44 (Post 690427)

Yes, but it would be just as dangerous if it was motor powered. Anyways, either way, proper precautions to limit the risk of injury should be taken.



Back to the arm, it sounds like you are not completely sure over whether it needs more than 2 positions. In this case, motors would probably be advantageous. If you are not sure, than that (correct me if I'm wrong) means that you are probably not sure what the third position would be. As others have said, using sensors/mechanical stops/multiple cylinders, it is definatly possible to have 3 or more pneumatic positions. However, it is much harder to make these positions variable. Motors will allow you to put the arm in any positon needed, with no tricky mechanical work.

If you are sure, then the simplest way to do it would probably be what EricH suggested:

http://www.putfile.com/pic.php?img=7596589

Originally Posted by M'gnad-knockah (Post 690515)

the other downfall to pneumatics is the efficiency, pneumatics only have a 4% efficiency, which sucks because the compressor has to run, and waste battery power.

Originally Posted by M'gnad-knockah (Post 690791)

its common knowledge

Originally Posted by M'gnad-knockah (Post 690515)

the other downfall to pneumatics is the efficiency, pneumatics only have a 4% efficiency, which sucks because the compressor has to run, and waste battery power.

Originally Posted by M'gnad-knockah (Post 690791)

its common knowledge