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Leav
01-15-2005, 05:46 AM
I build spudguns for fun, and i have learned many things along the way, one of them is that sch40 pvc is pretty strong stuff.

let's say that your robot needs lots of air power: would a pvc air tank be better than a metal tank (like the one from the KOP) in terms of [volume]/[weight of tank] ratio?

and even more important: are we even allowed to use pressure rated sch40 pvc pipes and fittings for the pneumatic modules?

Thanks!
-Leav

Cory
01-15-2005, 06:24 AM
Absolutely not. You cannot use anything but the kit provided pneumatics tanks, fittings, etc.

Making your own would be equivalent to strapping a bomb onto your robot. It's all about safety

Leav
01-15-2005, 07:40 AM
Absolutely not. You cannot use anything but the kit provided pneumatics tanks, fittings, etc.

Making your own would be equivalent to strapping a bomb onto your robot. It's all about safety

what do you meqn strapping a bomb? it is perfectly safe!
maybe you ment to add "in the eyes of the officials" or something, because if not, i must tell you that you have much to learn about pressure rated PVC. :)

-Leav

Aignam
01-15-2005, 08:00 AM
what do you meqn strapping a bomb? it is perfectly safe!
maybe you ment to add "in the eyes of the officials" or something, because if not, i must tell you that you have much to learn about pressure rated PVC. :)

-Leav
Well, you get what he meant. Bottom line: Illegal.

Andy Baker
01-15-2005, 08:08 AM
what do you meqn strapping a bomb? it is perfectly safe!
maybe you ment to add "in the eyes of the officials" or something, because if not, i must tell you that you have much to learn about pressure rated PVC. :)

-Leav

First of all, as Anthony and Cory said, it is illegal. Use the Clippard accumulator tanks to store pressurized air on your robot.

Secondly, in my opinion, *IF* PVC tanks were legal, they would not be a very robust source for an air accumulator on a FIRST robot. These robots see a high degree of twisting, load, and shock. If PVC was used, then it would likely crack under competition conditions if it was used on a robot that did more than sit in the corner.

Many FIRST teams use PVC on their robots for structural members. Many teams have had this same PVC crack under odd situations. There are good and bad aspects of this material. Having them hold pressurized air on a FIRST robot is not one of them.

Andy B.

Leav
01-15-2005, 09:09 AM
thanks for the comments guys :)

i dont understand why you all attacked me for asking a simple question, but i guess thats how things go here.... :/

as a spudgunner i must say that PVC is superior to all your fragile earth metals!!!!
:D :rolleyes: ;)

Stephen P
01-15-2005, 09:42 AM
As a spudgunner I must say
PVC SHRAPNEL HURTS
(as do hairspray burns)
And metal is much tougher than sch40- My friend made a metal pneumatic cannon that operates at 4000 PSI and shoots ball bearings through 4 feet of wood.

Leav
01-15-2005, 09:52 AM
I wouldnt know :rolleyes:

Stu Bloom
01-15-2005, 10:21 AM
... i dont understand why you all attacked me for asking a simple question, but i guess thats how things go here.... :/

as a spudgunner i must say that PVC is superior to all your fragile earth metals!!!!
:D :rolleyes: ;)Sorry you feel that you were attacked, but I don't see any harsh responses. What I do see is that you asked a question, then challenged the answer that you got. How do you expect people to react? Besides, the rules CLEARLY state that you can only use pneumatic parts included in the kit (except this year you can use a second identical air tank).

<sarcasm ON>
I guess most 16-year-olds probably do know more about strength of materials and pressure vessel design than professional engineers.
<sarcasm OFF>

Good luck this year ... and don't hurt yourself ;)

Leo M
01-15-2005, 10:32 AM
This message is not intended for Mr. Leav - I know there is no way I can reach a person who is so sure of himself, whose mind is closed to the possibility that he may be in error. But for the rest of you, read on:

Please, do not, under any circumstances, pressurize PVC pipe with air. Anyone who has ever been around exploding plastic pipe knows the terrible consequences - the energy released creates shrapnel moving at high velocity. This occurs suddenly; the brittle fracture mechanism of PVC gives no warning.

No PVC pipe manufacturer will recommend even low-pressure air testing. All, without exception, warn against it, and for good reason.

First is putting heavy emphasis on safety this year. I would be avoiding my responsibilities as a mentor and professional engineer if I let this one go by. As I said, I know Mr. Leav will not listen to me. I hope that he never has to learn by awful experience the danger of what he is doing.

Will any of the other engineers reading this please back me up. Maybe, if enough of us say the same thing.....

Cory
01-15-2005, 01:10 PM
Please, do not, under any circumstances, pressurize PVC pipe with air. Anyone who has ever been around exploding plastic pipe knows the terrible consequences - the energy released creates shrapnel moving at high velocity. This occurs suddenly; the brittle fracture mechanism of PVC gives no warning.

Like I said, you are strapping a bomb on your robot.

I have no doubts that you may have used PVC successfully in your spudgun applications, but FIRST can't just let any hack with a supply of PVC and pipe cement make their own air tanks. I would imagine there is a very high amount of quality control and inspection done on those Clippard accumulators to make sure they meet stringent standards. That's not something that will happen with your homemade tanks.

Leav
01-15-2005, 02:27 PM
This message is not intended for Mr. Leav - I know there is no way I can reach a person who is so sure of himself, whose mind is closed to the possibility that he may be in error.

.......

As I said, I know Mr. Leav will not listen to me. I hope that he never has to learn by awful experience the danger of what he is doing.


Sorry you feel that way, but i'm afraid you are wrong.
my post may have been childish, but it was ment to be because i was "accepting defeat" .
i understood that there is no way to use a pvc air tank in FIRST, and continued to make a little joke (please note smiley faces after the "pvc is superior" text).

I would imagine there is a very high amount of quality control and inspection done on those Clippard accumulators to make sure they meet stringent standards. That's not something that will happen with your homemade tanks.

agreed....



and in short:
I will not use PVC pipes and tanks in FIRST, and when i build spudguns, i will hope that i never feel the effects of pvc shrapnel.

Happy build season,
-Leav
:)

Steve W
01-15-2005, 03:11 PM
People please be more sensitive on your posts. The people reading these posts do not hear sarcasm or always see smilies. I had to go back to notice, sorry Leav. Let's make this thread an example of what can go wrong if we don't watch what and how we write.

Joe Johnson
01-15-2005, 03:21 PM
Not going anywhere good. Closing the thread...

Joe J.