Telescoping Tubing Extended with Air Pressure or Springs?

[Patrick Levy]

We have been considering using 2-3 sections of PVC pipe of various sizes to build a telescoping section that would extend up to the height of the top of the tower.

1. Would it be legal to have this system extend using air pressure?
2 How about compressed springs?

Thanks!

Patrick Levy
Harding High School
Team 3202

[Nuttyman54]

A compressed spring is fine, as long as you can safely store the energy while it is compressed during the match.


If you want to use air pressure, you must do it with a legal pneumatic system (see rule <R72>). In short, you must do it with a COTS pneumatic device. You cannot hook your compressed air directly to the nested tube and blow air into it to extend it.

Hope this helps!

[Tristan Lall]

With regard to air pressure, this was asked on the Q&A—the answer was no (http://forums.usfirst.org/showthread.php?t=14194). (Consult section 8.3.9 of the manual for details.)

You could try this (http://forums.usfirst.org/showthread.php?t=14304), though.

[BryantWebb]

Keep in mind, the PVC components would have to be rated at 120psi. Our team got around this by using a fan to supply the air that is inflating *something* instead of linking it to the pneumatic systems

[vivek16]

Keep in mind, the PVC components would have to be rated at 120psi. Our team got around this by using a fan to supply the air that is inflating *something* instead of linking it to the pneumatic systems

120 psi in AIR pressure. Most pvc is rated for liquid.

-vivek

[Al Skierkiewicz]

You may find that a winch and string is more effective for nested PVC tubes.

[Bill_B]

120 psi in AIR pressure. Most pvc is rated for liquid.

-vivek
And the difference to the structure (presuming it not to be soluble in the liquid) is what? That is, I know that liquids are sometimes used in the pressure testing of gas enclosures, but I do not know of any ratio or factor as a part of that testing. 120 psi is 120 psi regardless of the fluid. However, in the liquid's case the expansion of the fluid to reach zero psi is smaller. This makes a failure in the tested device somewhat less catastrophic and also mitigates the likely trajectories of fragments. Anyone involved in such testing to determine fracture points MUST take precautions that protect them from all possible failure modes.

[Chris is me]

And the difference to the structure (presuming it not to be soluble in the liquid) is what? That is, I know that liquids are sometimes used in the pressure testing of gas enclosures, but I do not know of any ratio or factor as a part of that testing. 120 psi is 120 psi regardless of the fluid. However, in the liquid's case the expansion of the fluid to reach zero psi is smaller. This makes a failure in the tested device somewhat less catastrophic and also mitigates the likely trajectories of fragments. Anyone involved in such testing to determine fracture points MUST take precautions that protect them from all possible failure modes.

Liquid isn't compressible.

The best precaution to take against preventing failure of a PVC system is to not use it for air. It's the only one, actually.

Regardless of any safety concerns, PVC is not a pneumatic component.

[Bill_B]

Liquid isn't compressible.

...

Chris, take a little time away from your studies and check http://hyperphysics.phy-astr.gsu.edu/HBASE/Tables/compress.html concerning the compressibility of liquids.

Have you heard the riddle: which would you rather have fall on you, a ton of bricks or a ton of feathers? I'm pretty sure either load would crush you.

The question remains then what is the difference between 120 psi air and 120 psi liquid as it pertains to the structural integrity of the container.

We are in agreement about pressurizing the PVC for use in the Breakaway game - not legal.