increasing flow rate to pnuematic cylinder

[windell747]

Hi, you guys probably already know about this, but we're pretty disappointed at the velocity of the pnuematic cylinders. I've heard that this is partially due to the diameter of the tubes.

Does anyone have any suggestions as to how to increase the flow rate to the cylinders?
Are we allowed to use tubing with a larger ID?
I've also read that some teams are using T fittings at the inlet of their cylinders. Is this legal?

Much appreciated!
Windell

[laxcompute]

We're a rookie team, and in the process of designing our pneumatic system. So I've ran across some of this stuff.

1. Flow rate to the cylinders is limited both by the diameter of the provided tubing (either .106" or .160", I can't remember which at the moment) and the maximum legal cV on the valves used, which is 0.32 (unitless). Basically, that means that air moves slowly. You could use cylinders with the smallest diameter, but that of course limits your force.

2. No. The provided tubing is already the maximum dimensions.

3. Yes, but from what I've read, you cancel out anything you gain by having theoretically increased flow, because of the currents when the two channels of air come back together.

[Ether]

Hi, you guys probably already know about this, but we're pretty disappointed at the velocity of the pnuematic cylinders. I've heard that this is partially due to the diameter of the tubes.

Does anyone have any suggestions as to how to increase the flow rate to the cylinders?
Are we allowed to use tubing with a larger ID?
I've also read that some teams are using T fittings at the inlet of their cylinders. Is this legal?

Much appreciated!
Windell


consider other design options:

http://www.chiefdelphi.com/forums/showpost.php?p=910176


some answers to pneumatics "legality" questions:

http://forums.usfirst.org/showthread.php?t=13976

http://forums.usfirst.org/showthread.php?t=14227

http://forums.usfirst.org/showthread.php?t=14218

http://forums.usfirst.org/showthread.php?t=14196

http://forums.usfirst.org/showthread.php?t=13957



~

[Peter Matteson]

Read through the First Q&A forum. Several methods that have recieved GDC approval there.

http://forums.usfirst.org/forumdisplay.php?f=1398

[dtengineering]

Here's my thoughts on the situation:

http://www.chiefdelphi.com/forums/showthread.php?p=907839#post907839

[Matt H.]

1. Flow rate to the cylinders is limited both by the diameter of the provided tubing (either .106" or .160", I can't remember which at the moment) and the maximum legal cV on the valves used, which is 0.32 (unitless). Basically, that means that air moves slowly. You could use cylinders with the smallest diameter, but that of course limits your force.


Cv is not unitless. The Cv of a valve is the "flow rate in US Gallons per minute [gpm] of water at a temperature of 60 Fahrenheit with a pressure drop across the valve of 1 psi."

Source: http://www.valvias.com/flow-coefficient.php

Also see:
http://en.wikipedia.org/wiki/Flow_coefficient

[Ether]

Cv is not unitless. The Cv of a valve is the "flow rate in US Gallons per minute [gpm] of water at a temperature of 60 Fahrenheit with a pressure drop across the valve of 1 psi."

Source: http://www.valvias.com/flow-coefficient.php

Also see:
http://en.wikipedia.org/wiki/Flow_coefficient


Great teaching stuff Matt. Thanks. I was looking for some nice graphs to show my team of airflow (either mass airflow or scfm) versus pressure drop for various Cv values, but was unsuccessful.

Just wondering if maybe you had found some and could share the links.


~

[laxcompute]

Cool. I stand corrected. But hey, a week ago I didn't even know what cV meant at all, so I can live with that =p

Nice to learn (yet something else) new.