18-12-2007 21:13

T3_1565

Re: pic: Vacuum System

thats pretty sweet, any chance that can also be used for locking out pistons for say a lift of some sort???

EDIT: I just realized what I said was really dumb as the pressure in the system will keep the pistons locked out anyways DOH!

18-12-2007 21:26

ewankoff

Re: pic: Vacuum System

Wow could have really used that last year, and who know maybe this year. Think you could put up a white paper of this?

18-12-2007 21:28

Branden Ghena

Re: pic: Vacuum System

I can see if our pneumatics team would work on it.

18-12-2007 22:19

Andrew Bates

Re: pic: Vacuum System

What is the blue thing at the bottom?

19-12-2007 10:12

Peter Matteson

Re: pic: Vacuum System

When we did this back in 2004 we just bought vacuum solenids instead.

Remember vacuum is NOT pnuematics and therefore you must read the rules carefully to see what you can do each year because the wording used has changed several times in the last 3 years. The last season this would not be legal because of the way the solenoid rule was written.

I just wanted to send the caution now because we've been down that path before and avoided it the last two years due to rule ambiguity issues of how a given inspector would interpret them.

Pete

19-12-2007 14:04

Daniel Bathgate

Re: pic: Vacuum System

What are the purposes of the two closed loops? Do they do something that a simple plug wouldn't, such as act as a miniature tank?

19-12-2007 16:20

Branden Ghena

Re: pic: Vacuum System

The blue thing on the bottom is an old plastic light cover that I used to weigh down the tubing which was being finicky and twisting.

The two closed loops were our 3 second plug solution, as we couldn't seem to find one.

As to this system's in-game legality, we weren't really worried about it as we aren't planning on using the vacuum (depending of course on this year's game). Our mentors just wondered if we could do it in the first place.

19-12-2007 18:07

Daniel_LaFleur

Re: pic: Vacuum System

I've never understood this line of thinking. 0 PSI (or PSIG) is ~14.7 PSIA (absolute pressure). Why does FIRST (and most FIRSTers) choose to look at pressure and vacuum differently only because it passes an arbitrary position on the scale (chosen because that force is measured at sea level)?

The gas laws all apply whether your pressure is above or below 1 Atmosphere.

It's like saying that we should treat temperature below 0 degrees as different from temperatures above 0 degrees. While it's effects on the objects around it may change (water freezing, etc) the measurement itself does not.

19-12-2007 18:28

mizitchell

Re: pic: Vacuum System

Why are there multiple regulators and tees with plugs used where you didnt need them?

19-12-2007 18:34

Branden Ghena

Re: pic: Vacuum System

The extra T connectors are the result off a freshman build, and the reuse of this system for several different purposes. All regulators are used, however, one to limit working pressure to 60 psi and another to limit the pressure to the vacuum generator at about 30 psi, a good working pressure for it according to our pneumatics team's research.

19-12-2007 20:21

mizitchell

Re: pic: Vacuum System

why not just use one regulator set to 30 PSI instead? or is this like it would be on the robot with 60 PSI standard working pressure and 30 just for the vacuum

19-12-2007 20:28

Branden Ghena

Re: pic: Vacuum System

If you are just using the system for a vacuum 30 psi should be perfect, but the design we made was created with room for a piston, unattached in the picture, that could function while the vacuum cup was attached and stuck in place.

19-12-2007 21:52

Daniel Bathgate

Re: pic: Vacuum System

I see your point, but 1 atm pressure is hardly arbitrary (in our standard atmosphere-based game, at least). The gas laws indeed work the same, but negative signs tend to make things practically different. I can't say I personally know much about pneumatics or vacuums, though. Hey, come to think of it, could you use a standard solenoid connected backwards with a vacuum? That might be interesting (and perhaps FIRST illegal, but would it work physically? I guess it would depend on if the pressure of the vacuum was great enough to actuate the solenoids. Hmm...)

Ah. Didn't think of that since we have many extra plugs floating around but ran out of T's. Whatever works!

Good to know! I remember playing with the suction cup last year and not having it work very well; I was probably pushing all 60psi through the vacuum. I'll remember that.

I love reading about pneumatics hacks, ever since we kinda-sorta implemented mid positions to try and save our arm last year. Looping the vacuum back through the solenoid is impressively creative... though I wonder if it wouldn't be easier to just hook up a servo to that butterfly valve

20-12-2007 08:10

Daniel_LaFleur

Re: pic: Vacuum System

Yes, you can connect vacuum to a standard solenoid valve (I do in all the time at work), however you need to watch the porting. You need to make sure that air flows in the same direction that it normally would using positive pressure as the valves are generally designed with the spring force and air flow assisting closure of the valve. This means that you need to hook your vacuum source to the requirement port, your vacuum target (suction cup ... etc) to the common port and leave the supply port open to atmosphere.

The Venturi that you use will have a curve that will tell you your best inlet pressure. Generally the higher the inlet pressure the deeper vacuum the venturi will pull, however the tradeoff is that while the venturi will pull a deeper vacuum it tends to have lower flow at very high input pressures ... thus drawing down the pressure slower.

Parker makes Electronic pressure controllers and cylinders with feedback encoders that allow you to control how far the cylinder throws (infinite mid positions) ... unfortunately that are not FIRST legal . Oh how I wish FIRST would loosen up on their pneumatic rules.