Peumatics or Motor?!?!?!?!

[Sam2197]

our team is undecided as whether to use pneumatics or a motor to raise and lower a arm. if it is best to do a motor which one would be recommended.

[emo Sponge]

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

[Sam2197]

well i think it would be best to control the position of the arm. so from my knowledge you cant stop a pneumatic cylinder halfway through its stroke

[Joe G.]

If it needs more than 2 positions, motors are far and away the best way to go. Most motors could be used for this, but the Fisher-price motors and van door motor have been used most in the past.

sponge, I'm not really sure why you are saying that pneumatics are not safe. Certantly, precautions must be taken, but why is a pneumatic arm any more dangerous than a motor powered arm, if they are moving with the same power.

[EricH]

Kind of depends on the arm, but pneumatics have two positions. I might try two pistons for three or maybe four positions, but I'd rather use a motor for anything more than two position.

[jgannon]

Originally Posted by Sam2197

from my knowledge you cant stop a pneumatic cylinder halfway through its stroke

Multi-positioning a cylinder is very doable... team 375's bot was an excellent example of this last year. You can get sort of a "spongy" response from a piston that isn't at the end of its travel, but you can make it work.

[emo Sponge]

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

[Joe G.]

Originally Posted by emo Sponge

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

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

[Sam2197]

thanks so much to everyone. our team loves the K.I.S.S. principle. so guess motor it is. should be easy to gear it down. thanks

[GGCO]

Is your team really going to use a pnumatic catapul?? I would just stick with an arm raised by motors.

Just my $.02

[emo Sponge]

Originally Posted by rocketperson44

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

your totaly right about the precautions

[GaryVoshol]

Originally Posted by emo Sponge

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

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

Your team has posted some marvelous information about your robot, and how they are taking safety precautions. I think you'd better find out just what your team is doing before you criticize. Your posts do not present a good image for your team.

[Sam2197]

wow. i would love to know how to do that.. i do a lot with pneumatics on the side and dont know how to make it like that. the only thing about my design is that the arm at its lowest spot sits inside of the frame. so when its lowered we wouldnt reach the ball. anyone have a way to get around that so we can use pneumatics .

[jgannon]

Originally Posted by Sam2197

wow. i would love to know how to do that.

You can either buy a solenoid that has a center-off position, or you can use two of the kit valves in tandem. What you do is connect the exhausts from a double solenoid to the single solenoid. Then you use the double solenoid to choose which direction to go, and then use the single solenoid to control the position. If that doesn't make sense, I can sketch it up in Paint.

[Sam2197]

i think i get what you mean