Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

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

Re: Peumatics or Motor?!?!?!?!
 

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

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

What makes you think that motors are safer than pneumatics?

Both can generate a lot of force and a lot of momentum. Both can be made safe, and both can be very dangerous if used incorrectly.

To Sam2197,

both pneumatics and motors can be used equally effective. If you already have pneumatics in your design then adding a cylinder is far less weight than a gearbox and motor ... but if you dont have pneumatics already in your system then the compressor alone may weigh more than using a motor and gearbox.

In short ... it depends :P

Good luck and let us know what you used.

Re: Peumatics or Motor?!?!?!?!
 

currely i have two designs one using pneumatics and one without. i really think we will need more than just those two positions though so i think we will need a motor for this. thanks for the help everyone

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

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

Re: Peumatics or Motor?!?!?!?!
 

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 .

Re: Peumatics or Motor?!?!?!?!
 

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

Re: Peumatics or Motor?!?!?!?!
 

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

Re: Peumatics or Motor?!?!?!?!
 

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

Just my $.02

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

i think i get what you mean

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

your totaly right about the precautions

Re: Peumatics or Motor?!?!?!?!
 

go with the motors

Re: Peumatics or Motor?!?!?!?!
 

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.

Re: Peumatics or Motor?!?!?!?!
 

where did you get that number?

Re: Peumatics or Motor?!?!?!?!
 

its common knowledge

Re: Peumatics or Motor?!?!?!?!
 

We don't know it here... Go look at the books again. (Or I know who to ask, when I am at competition.)

Re: Peumatics or Motor?!?!?!?!
 

Assuming this number is true, it needs more clarification. 4% efficiency in what sense? 4% of the potential in the compressed air is converted to kinetic in a moving cylinder? 4% of the electric potential to run the compressor is converted to potential stored in the tanks? 4% of the electric potential to run the compressor is converted to kinetic in a moving cylinder?

Re: Peumatics or Motor?!?!?!?!
 

Actually, without a citation and/or verifiable reference, it is nothing but a common made-up number. Sorry, but saying"pneumatics only have a 4% efficiency " is just not credible without providing more information to back up the statement. Facts are preferred over conjecture.

-dave



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