pneumatic usage question
 

Were planning on having an arm and tube gripper powered by pneumatics. The arm design depends on the claw/grabber we make, so were were waiting on exact measurements on it until the claw is done. The arm design uses 2 pneumatic cylinders, but if it needs to extend longer then it may use 4. We are torn between two designs for a gripper/claw, both of which use one pneumatic cylinder.

My question is:
If we were to lock onto a tube with our claw, whatever design it is (Both of our choices have one pnuematic cylinder) and then go to lift the arm and then extend it, will the system have enough air to keep a good grip on the tube? How far would the pressure drop if we used two on the arm? four?

Re: pneumatic usage question
 

To answer this question we will need to know the size of each cylinder (length and diameter) and the size and number of storage tanks you plan to use.

Re: pneumatic usage question
 

I would suggest trying to find the specs, test strain, etc. The power of your compressor (which must be A, the one they gave you, B, one of equal strength, or C of lesser strength) may be able to cope if you get a large enough tank or set of tanks.

Re: pneumatic usage question
 

none if it is exactly planned out. Some one brought up the problem so I figured I'd post it. We have the storage tank from the kit this year and 4 smaller ones, plus whatever we got last year (we didn't use pneumatics last year). Is it the more the better?

Re: pneumatic usage question
 

The amount of air storage increases, and therefore, as long as you stay within the safety limits regarding psi, more is most certainly better. Be careful about the weight though.

Re: pneumatic usage question
 

Find the volume of your storage (small storage tanks from the past were 18.85)
Multiply by the amount of air pressure. 18.85 x 120 psi = 2262 working units. Find the volume of your cylinder (2"dia with 4" stroke = 12.56)
Multiply by working pressure of 60psi = 753 units

So one extension and retraction would use 1506 of you 2262 working units.

You can see from this simple example figuring pneumatics isn't too difficult.

Make yourself a spread sheet and go to work. You should also figure out how fast your compressor of choice can replace your working units.

Re: pneumatic usage question
 

Two notes: In this case, without the compressor, you will not actually reach 60 psi in the cylinder on the retraction. Instead, it will be about 48 psi - across the entire system).

Note, that the working pressure IndySam is the maximum allowed. If a lower pressure can be used, you will get more extensions and retractions of you pneumatic for the same amount of air.

Like IndySam said, make a spreadsheet and see what your numbers are.

Re: pneumatic usage question
 

Absolutely correct, just remember to know the minimum psi that your valve will work with, you can only drop the pressure so far.

You can even do different pressures for the open and retract if you use multiple regulators and solenoids.

Re: pneumatic usage question
 

We are looking to use pneumatics for the first time this year. We want to use it to extend and retract an arm with a gripping device. I don't anticipate the arm weighing a lot as the rings it will lift are very light. Does anyone know if the 3/4" bore and the 12" stroke Bimba cylinders will do the trick (or do we need to go to a bigger bore?

Re: pneumatic usage question
 

Im not an expert but from experience, any bore would have the same power, its just a matter of how far. no matter if its 12" or 6" its still 60psi

But I could be wrong, thus why I made this topic lol.

Re: pneumatic usage question
 

3/4" bore will give you about 26lbs of force.

Re: pneumatic usage question
 

Yup you're wrong :)

the 60psi is pushing against the piston so the more surface area you have the more force you have.

A 2" cylinder will have seven times more surface area than a 3/4 cylinder, seven times more force.

Re: pneumatic usage question
 

How do you calculate the working units an actuator needs to move?

Re: pneumatic usage question
 

Bimba is a great company, particularly for their support of FIRST. However, Clippard has a fun and useful online calculator for bore diameters. The strokes depend upon the geometry of your mechanism. the working units mentioned previously can be calculated from all that design done first.