pic: ~850 PSI Robot

[Jnadke]

For people lacking knowledge in physics, here's what this picture is saying:

Let's assume STP conditions, so the air pressure outside is 14.7PSI. Now, I'm also assuming that plate is 1 square foot. This is 144 square inches. Lastly, I'm assuming the table weigh 50lbs.

144 ( 14.7PSI - X ) = 50 lbs
X = 14.3PSI

All this picture says is that they are providing enough suction to reduce the pressure between the plate and the table to less than 14.3PSI. Nothing more, nothing less.

I'm not trying to bash your team or anything, all I'm saying is you're running the wrong test. Robots aren't going to lift upward, they'll push sideways. It doesn't matter if your robot can suck all the air out until it is a near-perfect vacuum, if your plate is just aluminum making contact with the polyethylene, with a coefficient of 0.1, any robot with 120lbs of torque can push you off the ramp. Now, if you had, say, rubber with a coefficient of friction of 2, and you created a vacuum, it would take a metric ton of lateral force to push you off. Big difference.

Unfortunately this isn't possible because the rubber would fracture long before a metic ton of lateral force was imposed on your robot.


I'm very impressed by the mechanism itself though. It looks very well engineered. What size cylinder are you using to suck the air out? Also, did you use a motor to actuate the cylinder or did you use another cylinder to do it? It seems to me that using another cylinder (in combination with the compressor) would allow you to suck out a far greater volume of air. Although it would weigh more, it would probabaly be less complex because you'd only have to draw the cylinder once to remove a sufficient volume of air.

Did you hook up a pressure guage to determine how much air it is sucking out?

[purplehaze357]

guys...its a joke ok...this is the off-season and there is no need to get into the legistics of a suction cup....nor is there ever a need to stifle a team's accomplishments...this picture was obviosly created out of sheer fun and youre all turning this into a physics lesson....which i dont think it was ever inteded to be...chill out have fun

[Raven_Writer]

Originally posted by Jnadke
For people lacking knowledge in physics, here's what this picture is saying:

Let's assume STP conditions, so the air pressure outside is 14.7PSI. Now, I'm also assuming that plate is 1 square foot. This is 144 square inches. Lastly, I'm assuming the table weigh 50lbs.

144 ( 14.7PSI - X ) = 50 lbs
X = 14.3PSI

All this picture says is that they are providing enough suction to reduce the pressure between the plate and the table to less than 14.3PSI. Nothing more, nothing less.

I'm not trying to bash your team or anything, all I'm saying is you're running the wrong test. Robots aren't going to lift upward, they'll push sideways. It doesn't matter if your robot can suck all the air out until it is a near-perfect vacuum, if your plate is just aluminum making contact with the polyethylene, with a coefficient of 0.1, any robot with 120lbs of torque can push you off the ramp.

I'm very impressed by the mechanism itself though. It looks very well engineered. What size cylinder are you using to suck the air out?

ARRRRRRGGGGHH!!!!!!!!!!!!!!

This wasn't really a test, this was just showing stuff. The robot isn't ment to push upwards, the robot goes up so that the plate can come down to the ground.

The pneumatics I'm unsure of right now [I'm sick, so my memory is "bleh"]. Matt should know though.

[EDIT]

guys...its a joke ok...this is the off-season and there is no need to get into the legistics of a suction cup....nor is there ever a need to stifle a team's accomplishments...this picture was obviosly created out of sheer fun and youre all turning this into a physics lesson....which i dont think it was ever inteded to be...chill out have fun

Thank you, and he's correct.

I'm not a genius in physics, so I might be wrong.

[Matt Attallah]

Wow - did this thread get out of hand.

1st off - That table didn't weigh any where near 500 lbs. No way - no how. (comon Eric - even if the engineers did say that, use some common sense. Even if that whole table was made out of lead, I don't know if it would weigh 500 lbs.)

2. Please, everyone, don't argue. Eric just thought wrong. People make mistakes. Back off him. The engineers may of said 500 lbs, but they meant something else. (Comon - we ALL have had those moments...)

3rd - The co-frict (like my nick name?) was pretty high when the "plastic" was not dirty. At Pittsburgh, a robot ramming us at full force (~130 lbs at about 10 fps) could not move us. At Nats - there was sssssoooo much dirt that the co-frict went down. The foam we used was very-very soft to compensate for some of that - but it just over-loaded the foam.

Jnadke -

To throw a little monkey in your theory - what is the trajectory of a robot coming UP a ramp? (it's not straight up, when you are at the edge of the plastic - you gotta take that into account)

Now enough with the arguments - just everything be. Eric just wanted to show what we created b/c he is proud of it.

Remember - FIRST is not about bashing people even when they are stubborn...

Never argue with an idiot - he may be doing the same.

Now back to the fun - Thank you for all of your praises on our vacuum plate. We had fun trying to think of ways to attach our selves at the top of the ramp - and we thought this would be great. (We did account for some dirt at the top of the ramp - but dang, how much dirt was up there? Maybe we should of hired some Tonka Trucks to clean it up? )

As for the pnumatic stuff - we used the largest cylinder to draw about 6 psi of vacuum over 144 in sq. (1 square foot!)

[Raven_Writer]

Originally posted by Matt Attallah
Wow - did this thread get out of hand.

1st off - That table didn't weigh any where near 500 lbs. No way - no how. (comon Eric - even if the engineers did say that, use some common sense. Even if that whole table was made out of lead, I don't know if it would weigh 500 lbs.)

2. Please, everyone, don't argue. Eric just thought wrong. People make mistakes. Back off him. The engineers may of said 500 lbs, but they meant something else. (Comon - we ALL have had those moments...)

3rd - The co-frict (like my nick name?) was pretty high when the "plastic" was not dirty. At Pittsburgh, a robot ramming us at full force (~130 lbs at about 10 fps) could not move us. At Nats - there was sssssoooo much dirt that the co-frict went down. The foam we used was very-very soft to compensate for some of that - but it just over-loaded the foam.

Jnadke -

To throw a little monkey in your theory - what is the trajectory of a robot coming UP a ramp? (it's not straight up, when you are at the edge of the plastic - you gotta take that into account)

Now enough with the arguments - just everything be. Eric just wanted to show what we created b/c he is proud of it.

Remember - FIRST is not about bashing people even when they are stubborn...

Never argue with an idiot - he may be doing the same.

Now back to the fun - Thank you for all of your praises on our vacuum plate. We had fun trying to think of ways to attach our selves at the top of the ramp - and we thought this would be great. (We did account for some dirt at the top of the ramp - but dang, how much dirt was up there? Maybe we should of hired some Tonka Trucks to clean it up? )

As for the pnumatic stuff - we used the largest cylinder to draw about 6 psi of vacuum over 144 in sq. (1 square foot!)

Thank you Matt.

Yes, I am proud of it.

I might be wrong, maybe they said around 150 and I just heard wrong. I also stated that I was sick, and it messes up my memory.

Maybe we should of hired soem Tonka Trucks to clean it up?

That'd be so freakin' sweet! lol

[GregTheGreat]

Hey, lets not get out of hand now. No robot bashing. LOL. Let's remain civilized. Remember we are all robot dorks at heart.

Good Luck to everyone at the invitationals.

[Raven_Writer]

Originally posted by GregTheGreat
Hey, lets not get out of hand now. No robot bashing. LOL. Let's remain civilized. Remember we are all robot dorks at heart.

Good Luck to everyone at the invitationals.

True, true. We all rock!

Thanks, and you to.

[GregTheGreat]

Thats Right, we all rock, robots rule!!!

Go DORKS! lol

Good luck to everyone at the invitationals

Originally posted by Raven_Writer
True, true. We all rock!

Thanks, and you to.

[Madison]

Are you all going to break out into a big group hug or something now?

Contrary to popular opinion, learning doesn't need to end with the season. There's no harm in seeing how or why things work, even if it's just for fun.

[Jnadke]

Raven_Writer:

I would like to start of by saying I'm sorry if I caused you any anguish. As said above, there's never a time not to learn. I was merely trying to explain to you the physics behind it.

There are too many misconceptions between what I actually said and what people think I said. If you read, I actually praised what they built. I believe that it a very quality piece of engineering, and that it would be very useful in competition. What I was trying to do is explain how it would not be useful if you didn't understand the physics behind it.

FIRST is about inspiration. It's hard to be inspired if you don't understand what you are trying to be inspired about. Science and Technology have one thing in common: Physics. You'll take it if you ever get into a science/engineering-related field.

Originally posted by Matt Attallah
Jnadke -

To throw a little monkey in your theory - what is the trajectory of a robot coming UP a ramp? (it's not straight up, when you are at the edge of the plastic - you gotta take that into account)

The ramp is 14.5 degrees, right?

The sine of 14.5 is 0.25. On the other hand, the cosine of 14.5 is 0.97. What does this mean? 97% of the force exerted by a robot going up the ramp will be exerted in the horizontal direction. Only 25% of that force will be exerted upwards. For all practical puposes, 97% is very close to 100%. Given that the 25% upward force will actually decrease your ramp traction, 100% horizontal force is a very generous estimate.


Did you guys use a motor to suck the air out of the cylinder? What kind of valve system did you use? Pressure valves? What size bore did you use? I'm just curious about the design. It might be of use in the future...

[Raven_Writer]

Originally posted by Jnadke
Raven_Writer:

I would like to start of by saying I'm sorry if I caused you any anguish. As said above, there's never a time not to learn. I was merely trying to explain to you the physics behind it.

There are too many misconceptions between what I actually said and what people think I said. If you read, I actually praised what they built. I believe that it a very quality piece of engineering, and that it would be very useful in competition. What I was trying to do is explain how it would not be useful if you didn't understand the physics behind it.

FIRST is about inspiration. It's hard to be inspired if you don't understand what you are trying to be inspired about. Science and Technology have one thing in common: Physics. You'll take it if you ever get into a science/engineering-related field.



The ramp is 14.5 degrees, right?

The sine of 14.5 is 0.25. On the other hand, the cosine of 14.5 is 0.97. What does this mean? 97% of the force exerted by a robot going up the ramp will be exerted in the horizontal direction. Only 25% of that force will be exerted upwards. For all practical puposes, 97% is very close to 100%. Given that the 25% upward force will actually decrease your ramp traction, 100% horizontal force is a very generous estimate.


Did you guys use a motor to suck the air out of the cylinder? What kind of valve system did you use? Pressure valves? What size bore did you use? I'm just curious about the design. It might be of use in the future...

I'm also sorry, if I got an attitude yesterday. Today I'm refreshed [w00t].

I'm aware of the physics though, but thank you for correcting me. Matt said yesterday it was prob. about 50 lbs., and he's probably right.

We used 2 cylinders, and a air compressor for the vacuum effect. I dunno if we used a bore, I don't think so though. Later on I'll grab the specs of it, and post it. I do know we had 60 psi regulated. And it doesn't work out well when the platform is dirty.

[Matt Attallah]

Originally posted by Jnadke
Did you guys use a motor to suck the air out of the cylinder? What kind of valve system did you use? Pressure valves? What size bore did you use? I'm just curious about the design. It might be of use in the future... [/b]

Well, we just used the 2" dia. w/ a 12" (why does that sound wrong to me) stroke. We just used 2 of them. One to do all the pushing/pulling power, and a nother to actucally do the vacuum. I'll get some detailed pics up soon.

[Jnadke]

Originally posted by Matt Attallah
Well, we just used the 2" dia. w/ a 12" (why does that sound wrong to me) stroke. We just used 2 of them. One to do all the pushing/pulling power, and a nother to actucally do the vacuum. I'll get some detailed pics up soon.

Oh, so you used one cylinder attached to the compressor to actuate another cylinder that's attached to the suction mechanism?

I remember seeing another team with a vacuum mechanism in Newton (on the webcast). It was pretty neat. They had a motor driving the cylinder like a piston. I'd imagine they had some pressure valves so the air can only flow in one direction.

[Raven_Writer]

Originally posted by Jnadke
Oh, so you used one cylinder attached to the compressor to actuate another cylinder that's attached to the suction mechanism?

I remember seeing another team with a vacuum mechanism in Newton (on the webcast). It was pretty neat. They had a motor driving the cylinder like a piston. I'd imagine they had some pressure valves so the air can only flow in one direction.

[EDIT]
Yes, we did.

I saw that team to, it wasn't as good as ours, but it was still really cool. It helped them out a lot of times to, it sucks I forgot the team # / and name.
[/EDIT]