Suction Cups: How?

The manual allows for a team to use suction cups and to create a vacuum using the pump. How does one do this? Revese the electrical connections to the pump? Is there a “in” port of the pump where it’ll create a vaccuum when running forward?

-Kai Zhao

DO NOT reverse the input to the pump! As for the in port, my team hasn’t gotten our kit yet, so I haven’t looked at an actual pump yet.

Anybody else?

–Rob

Doesn’t accelerating air over a hole creat a vacuum. That’s how air planes fly. They accelerate air over the top of the wing which lowers the air pressure and creates lift. I know that if you take an air gun and blow arcoss the top of tub you can suck water up thru it so it should work with air as well. You can try it by taking a small piece of tubing and plug one end with your finger and the other end use an air gun to blow over the top NOT inside and see what happens:)

Unfortunately, a system like that would be a “custom pneumatics component”, making it illegal.

I see only two ways to generate vacuum legally:

  1. Use a cylinder to create a vacuum in the air tube and suction cup by driving the cylinder with another actuator (motor, etc.).

  2. Use the suction cup itself. If you would use a bellows-style cup, you can press it down, seal it, and then pull up on the cup a bit and there would be a vacuum in the cup.

Neither of these uses would not give you very good vacuum, but vacuum none the less.

Andy B.

I just read the part in the manual that states you can only use a cylinder to create a vacuum. Opps I guess that’s what I get for being a slow reader.

My team also has had some trouble with the idea of suction cups. I belive you must use some kind of device to flatten the cup and the peel it up later. :cool:

As stated above all you would have to do is take an air cylinder and don’t hook it up to the air. use one of the port and hook it to your suction cup and pull or push the shaft and it will create a vacuum on the port.

*Originally posted by jrgrim12 *
**Doesn’t accelerating air over a hole creat a vacuum. That’s how air planes fly. They accelerate air over the top of the wing which lowers the air pressure and creates lift. **

Very little of a plane’s lift comes from this, almost all of it comes from the angle of attack. Stick your hand out the window of your car, directly into the wind. Curve it, notice any difference? Now angle it up. :slight_smile:

The only way I can think of to leagally create suction (good suction) is to use pnumatics to move a plunger inside a tube. If done right you shouldn’t lose any pressure.

Greg

i thought suction cups were illegal.

*Originally posted by GregT *
**Very little of a plane’s lift comes from this, almost all of it comes from the angle of attack. Stick your hand out the window of your car, directly into the wind. Curve it, notice any difference? Now angle it up. :slight_smile:

The only way I can think of to leagally create suction (good suction) is to use pnumatics to move a plunger inside a tube. If done right you shouldn’t lose any pressure.

Greg **

What you’re talking about is the Bernoulli Effect. Basically, it means that as the speed of air increases, the density of the air decreases. In the case of an airplane, the curve of upper section of the wing causes the air to travel more quickly over the top than the bottom. This creates a lower air pressure on the top so the airplane lifts up.

Now, many modern planes use an “angle of attack.” What this means is, that as you fly, depending on how much lift you want, you change the angle of the wing, which causes the curve “seen” by the air to change. This gives a change in the amount of lift.

Matt

The reason why you would use a suction cup is because with no air between the cup and your surface, there’s no air pressure, and you get 14 pounds/square inch pressing down on your cup, increasing the force of friction. All you need is a large suction cup and use a pneumatic cylinder to press the air out. As for why airplanes fly, it’s mostly conservation of momentum with a little Bernoulli, according to my competent physics teacher. I’d use ansi art to illustrate but I suck at it. Basically, air flows into the turned wing and exerts a force on it up. As air travels down the back of a curved wing, again, conservation of momentum the wing must move up to have no momentum gain.

I’m fairly sure using the bernoulli principle would fall under the ‘custom pneumatic components’ section, anyway. I think the only way to make a vacuum legally involves actuating one pneumatic cylinder with another, creating a vacuum air connection of the cylinder being moved. If you attach this to a decent suction cup, you should be able to form a vacuum between that and any surface.

Tyson

think of how a plunger works / for a couple of bucks you have an inexpensive suction cup you could prototype with.

It shouldn’t take that much pressure to make a suction cup go down. It all depends on the material of the cup itself. I would think a normal automotive suction cup from msc would be the way to go. Those don’t look like they were designed to be used by a vacuum pump. Plus if what I’m guessing is true these suction cups can have 170pounds of suction.

Most of the tops of the containers i saw at FIRST were cracked and some of ours are as well…so dont count on sucking on the top of the container …it really sucks.
Jim:rolleyes:

*Originally posted by Matt Leese *
**What you’re talking about is the Bernoulli Effect. Basically, it means that as the speed of air increases, the density of the air decreases. In the case of an airplane, the curve of upper section of the wing causes the air to travel more quickly over the top than the bottom. This creates a lower air pressure on the top so the airplane lifts up.

Now, many modern planes use an “angle of attack.” What this means is, that as you fly, depending on how much lift you want, you change the angle of the wing, which causes the curve “seen” by the air to change. This gives a change in the amount of lift.

Matt **

Very little of any planes lift actually comes from the Bernoulli Effect, this is just a widespread mis-conception. Yes, it does contribute, but it is not the largest lift component.

All planes change their AOA (angle of attack) not just modern planes. To climb a plane lowers it’s tail and points up, increasing the angle of attack and gaining more lift.

Greg

*Originally posted by frumious *
**I’m fairly sure using the bernoulli principle would fall under the ‘custom pneumatic components’ section, anyway. I think the only way to make a vacuum legally involves actuating one pneumatic cylinder with another, creating a vacuum air connection of the cylinder being moved. If you attach this to a decent suction cup, you should be able to form a vacuum between that and any surface.

Tyson **

There are at least two other legal ways of creating a vacuum, though one only applies to suction cups. The first is simply hooking tubing up to the compressor inlet. Of course this makes it difficult to pressurize our pneumatic system at the same time, but it works and is legal. The pneumatics guy at the LA Kickoff said you should get about 24 inches of mercury vacuum from the compressor.

The other way is to push down on a suction cup until it’s flat. Push down on the cup with a ring and then pull up on the center. How hard a vacuum you get depends on how hard you pull. But there isn’t much volume so a slight leak could be trouble.

*Originally posted by GregT *
**Very little of any planes lift actually comes from the Bernoulli Effect, this is just a widespread mis-conception. Yes, it does contribute, but it is not the largest lift component.
**

If you want to start an argument, go to one of the aero newsgroups and ask “what creates lift?”. Even the aero guys can’t agree on an explanation that other people can understand, even other engineers. But they sure can calculate it.

While we are all aware of the top secret “Magic Smoke” factories that produce that crucial component installed in every electrical and electronic device; few people are aware of the small “Homesick Angel” installed in every type of aircraft.

Unfortunately (for aircraft designers) they have no say in which angel they get and some are more “homesick” than others. Early attempts a flight were often thwarted by the fact that most of the angels found here on earth were in no hurry to get back home. However, as time has passed and more and more aircraft take to the skies, more angels have been lured to earth.

By the way - I’d consider this thread officially Hi-Jacked <G>