Bungy and Surgical tubing

[Jordan2389Diaz]

My team is trying to hook up our pneumatics system but we are wondering how power it would be? How do you hook up the surgical tubing and the bungy cords to the robot.

[Jones571]

Go to you tube and search 842 kicker and u will several great examples.

[DonRotolo]

Of course, the surgical latex tubing is not intended to be part of the pneumatic system.

The FRC Manual does explain a bit about how to connect the pneumatics. the FIRST Pneumatics Manual goes into greater detail. Both should be read before you do anything more.

As for the latex tubing, we have used it in the past as a spring to retract a mechanism, a cushion for a mechanism that hit the frame too hard, and in place of a rope or wire to kpps game pieces from falling out of the storage hopper.

This year, we tied some into a loop, and use it like a big rubber band to power the kicker. A pneumatic piston pulls the kicker back for another shot.

[Team 2811]

Originally Posted by Don Rotolo

Of course, the surgical latex tubing is not intended to be part of the pneumatic system.

The FRC Manual does explain a bit about how to connect the pneumatics. the FIRST Pneumatics Manual goes into greater detail. Both should be read before you do anything more.

As for the latex tubing, we have used it in the past as a spring to retract a mechanism, a cushion for a mechanism that hit the frame too hard, and in place of a rope or wire to kpps game pieces from falling out of the storage hopper.

This year, we tied some into a loop, and use it like a big rubber band to power the kicker. A pneumatic piston pulls the kicker back for another shot.

Yeah, I am with you on this one. The surgical tubing is not recommended or intended for the pneumatics system. It would not be a wise choice to do so, because depending on the amount of pressure that you need for your pneumatic system, the surgical tubing could expand and "pop" off of whatever you attach it to in the system.

[DonRotolo]

Not to mention it's prohibited by <R72>

[Taxi Quinn]

Originally Posted by Don Rotolo

Not to mention it's prohibited by <R72>

I dont understand what you are saying is prohibited? We are currently looking in the manual in the section you said, and we can find notheing that says anything is prohibited.

[Jones571]

Originally Posted by Taxi Quinn

We are currently looking in the manual in the section you said, and we can find notheing that says its prohibited

You may want to re read it Quinn. R72 specifically states what you are allowed to use in your pneumatic system and surgical tubing is not on there as it would be very unsafe to use in a pneumatic system. So Don is 100% correct.

[Ether]

Originally Posted by Taxi Quinn

I dont understand what you are saying is prohibited? We are currently looking in the manual in the section you said, and we can find notheing that says anything is prohibited.

Rule <R71> is quite clear:

<R71> To satisfy multiple constraints associated with safety, consistency, robot inspection, and constructive innovation, no pneumatic parts other than those explicitly permitted by the Pneumatic System Rules may be used on the ROBOT.

The "Pneumatic System Rules" mentioned in the above rule are those listed in Section 8.3.9 "Pneumatic System"


~

[boomergeek]

Originally Posted by Ether

Rule <R71> is quite clear:

<R71> To satisfy multiple constraints associated with safety, consistency, robot inspection, and constructive innovation, no pneumatic parts other than those explicitly permitted by the Pneumatic System Rules may be used on the ROBOT.

The "Pneumatic System Rules" mentioned in the above rule are those listed in Section 8.3.9 "Pneumatic System"


~

Ether-
For the engineering rule that the maximum of 20 inches per second for piston speed, can be ignored if the piston is moving in excess of that only when powered by surgical tubing as opposed to when the movement is caused by pneumatic pressure against the piston?

I am a complete novice at pneumatics and I'm taking an educated guess that it's the seals between the piston and the cylinder that are only rated for a maximum speed of 20 inches per second, and my guess continues that it causes excessive wear is independent of whether pneumatic force or elastic force is used to drive the piston to the excessive speed.

Can anyone with knowledge of pneumatic mechanisms explain?


Thanks!

[Chris is me]

Just to be clear because someone sent me an email about it and I didn't see it in the thread, you can use surgical tubing in tandem with pneumatics (i.e. a surgical tubing power kicker pulled back with a piston), but you can't use surgical tubing to store compressed air (eg, it's not pneumatic tubing). Just in case anyone was confused, sorry if it's obvious.

[Bruceb]

If you are worried about the piston breaking itself because it hits the end stop to hard to many times then Bimba does sell pistons with adjustable air cushions at one or both ends.
Bruce

[boomergeek]

Originally Posted by Bruceb

If you are worried about the piston breaking itself because it hits the end stop to hard to many times then Bimba does sell pistons with adjustable air cushions at one or both ends.
Bruce

Actually I'm worried that the 20 inches per second piston speed has been claimed (by multiple persons posting to CD) to have been given from Bimba Customer Support representatives.
As far as I know, no one with any expertise has stated equivocally under which conditions that it is SAFE to ignore 20 IPS guide on piston speed.

I typically choose to considered it likely to be deemed unsafe by thoughtful robot inspectors unless an expert vouches for the SAFETY of the configuration.

If leaving a piston attached to a "bow" when shooting an arrow is an engineering acceptable use of pneumatic piston, will someone with expertise in the failure modes of actuators please confirm?

[DonRotolo]

Originally Posted by Chris is me

Just to be clear because someone sent me an email about it and I didn't see it in the thread, you can use surgical tubing in tandem with pneumatics (i.e. a surgical tubing power kicker pulled back with a piston), but you can't use surgical tubing to store compressed air (eg, it's not pneumatic tubing). Just in case anyone was confused, sorry if it's obvious.

Back to the original post:

You know, the quote above is what I was trying to say in my previous posts. However, let me quote the first sentence of <R72>:

<R72> In addition to the items included in the KOP, pneumatic system items specifically permitted on 2010 FRC ROBOTS include the following items.

OK: Is the latex tubing NOT included in the KOP? Can anyone show me where it is NOT a Pneumatic part?

I completely agree that using it to carry air pressure would not turn out well, and I would never, ever suggest that it should even be attempted.

BUT, considering the exact wording of <R72>, there is some wiggle room here.

<R73> Items specifically PROHIBITED from use on the ROBOT include:
A. Any pneumatic part or component rated for less than 125psi.

I cannot imagine the latex tubing being rated at 125 PSI, but I'm unable to find a specification to point at.

To the original poster: Please take the safe route and have your team contact post this to the FRC Q&A forum for an official ruling.


,

[RRLedford]

Latex tubing will "blow up", like long skinny balloons do, zooming to a dramatically expanded size (8x initial diameter & 2.5x initial length) once a threshold pressure is reached (around 30 lbs for smaller sizes). Then it will only take a limited amount more pressure (or stress to the super taught expanded membrane) before it bursts.

Having used long pieces of it in water fights, with the latex tubing inflated with tap water & wrapped around my neck and body like a boa constrictor, I can tell you that when it does rupture, it does so with dramatic force. I felt like I had been hit by a strong karate chop. Not sure if it was the water or the rubber snapping me, but really stunned (and soaked) me.
-Dick Ledford

[MrForbes]

Originally Posted by Don Rotolo

I cannot imagine the latex tubing being rated at 125 PSI, but I'm unable to find a specification to point at.

go to http://www.mcmaster.com and search for "latex tubing" and read away...they say it is rated for less than 100 psi.

There might be a more authoritative spec somewhere else?

Hopefully that's internal pressure when used as a tube, and not tensile strength when used as a spring!