Sideways Hanging - Yes or No

[Swampdude]

Pretend he's a robot... This was our first thought on how to hang (due to it's efficiency), so I assume many of you are thinking the same thing. But we're preemptively ditching the idea as I'm sure it will knock the tower over and also point load the vertical member beyond yield. Not to mention if your hanging like this and a couple more bots climb aboard. Actually I haven't studied the footing of the tower but it seems like 3 bots piled up on each others back could get pretty far from center on the tower. Seems like it could go over pretty easy. Perhaps the GDC didn't see this coming, but I recommend a ruling on it soon.

FYI - I'm not planning on asking if this is acceptable on the GDC forum thing.

[thefro526]

There was a team in the 2007 FVC game that did the exact same thing. It was a really efficient way to hang, and I thought of applying it to this year's game...

I'd like to think that the GDC designed the tower with this in mind but, I guess if they haven't we'll know soon enough.

[karatekid]

I think you definately need to consider the balance problem-maybe 2 on 1 side and 1 on the opposite side?

[Brandon Holley]

Originally Posted by Swampdude

Pretend he's a robot... This was our first thought on how to hang (due to it's efficiency), so I assume many of you are thinking the same thing. But we're preemptively ditching the idea as I'm sure it will knock the tower over and also point load the vertical member beyond yield. Not to mention if your hanging like this and a couple more bots climb aboard. Actually I haven't studied the footing of the tower but it seems like 3 bots piled up on each others back could get pretty far from center on the tower. Seems like it could go over pretty easy. Perhaps the GDC didn't see this coming, but I recommend a ruling on it soon.

FYI - I'm not planning on asking if this is acceptable on the GDC forum thing.

Have you interacted with the actual field elements? The tower is pretty rigid in my opinion. The steel piping that is used is very rigid. I would make sure you fully explore this option before determining the vertical member will be stressed beyond yield.

-Brando

[Kims Robot]

The tower is very rigid. At one point at the NH kickoff there were three kids hanging on it, and not gingerly.

Its really hard to tell from the photos/drawings, but there are solid metal plates below the tower & the bumps that help keep them solidly in place. They are mentioned in the rules:

The BUMPS are fixed to base plates that are secured to the carpet of the FIELD to keep them from moving. The base plates are covered with the same carpet as the FIELD. Note that this forms a small (approximately ½-inch tall) transition from the FIELD surface onto the base plates.

I dont see it mentioned, but the same style plate is underneath the Tower. You can sort of see it here.

[Swampdude]

I guess my big concern is the column in compression and then a bot hanging sideways as mentioned shock loading that column in bending. Plus if the bot is hanging out like that and maybe sticking out 4', then another bot climbs on the back of bot 1, or even 2 bots. That could put the bots collective cg as much as 4'-6' away from the side of the tower. That's a lot of force on that 1 column that's now in compression and bending. bad.... And if the collective cg gets out past the edge of the floor plate in any direction it could pull it over.

[Brandon Holley]

Originally Posted by Swampdude

I guess my big concern is the column in compression and then a bot hanging sideways as mentioned shock loading that column in bending. Plus if the bot is hanging out like that and maybe sticking out 4', then another bot climbs on the back of bot 1, or even 2 bots. That could put the bots collective cg as much as 4'-6' away from the side of the tower. That's a lot of force on that 1 column that's now in compression and bending. bad.... And if the collective cg gets out past the edge of the floor plate in any direction it could pull it over.

I totally agree that its a valid concern, however there may be ways to avoid that. I think its a creative idea, and I didnt want you to dismiss it quickly thinking the tower was not robust enough to handle the load.

-Brando

[GaryVoshol]

Is whatever mechanism you will use to grab able to be released without power?

[SuperBK]

I don't see why it wouldn't be legal. It doesn't have to lift that high, only enough to get the wheels off the gound, so it won't put that much side stress on the tower.
Brian

[Chris is me]

While there doesn't seem to be anything wrong with it... Why would you hang this way other than the "normal" way? Or other non-normal ways?

[Jeff Rodriguez]

Originally Posted by SuperBK

I don't see why it wouldn't be legal. It doesn't have to lift that high, only enough to get the wheels off the gound, so it won't put that much side stress on the tower.
Brian

It has to go above the plane of the platform.
From the definitions in 7.2:
ELEVATED: A ROBOT that is completely above the plane of the PLATFORM and in contact with the TOWER shall be considered ELEVATED.

Either way, once you are off the ground its the same amount of force no matter how high you go.

[Swampdude]

Originally Posted by Chris is me

While there doesn't seem to be anything wrong with it... Why would you hang this way other than the "normal" way? Or other non-normal ways?

Instead of making an extending arm that goes 7+ feet up to the hang bar you only need to go up 3'. and if you do it right it takes less force to get your bot up in the air. Not to mention you don't have to share the hang bar with anyone. And you could help other bots up easier from this position. And you could in theory get connected faster and elevated faster than extending 7' and pulling the full distance... so lots of reasons. I just don't want the field breaking so I threw it out there before it became a problem later on, or to verify if it's ok (not that this is the place to do that - but I don't have a tims login and I can't ask team questions, plus the answers traditionally take too long).

And yes you could design a gripper that could let go easy enough.

[Kevin Sevcik]

Originally Posted by SuperBK

I don't see why it wouldn't be legal. It doesn't have to lift that high, only enough to get the wheels off the gound, so it won't put that much side stress on the tower.
Brian

Inaccurate, sir. You have to lift your wheels above the platform to be ELEVATED.

As to why do this.... Well this way, you don't have to reach 7 ft in the air to lift. And you can just as easily lift from under the ball return.

The towers shouldn't flip unless you're doing something very wrong. The base plate is an 80" piece of aluminum plate, so it'd extend about 18" out from the tower on each side. A single robot should have difficulty tipping the tower. Front to back, anyways.

As far a strength.... A 150lb robot with an 18" CoG will put a bending load on a tube of about 50% yield, if you only grab one pole. I don't have a convenient calculator at hand for point load crushing force on tubes, but you can reduce the crushing force significantly by simply spreading your "hands" out father.

Finally... It's dirt simple to make a grasping mechanism for this that releases without power. The dude in the video could have managed just as well with a hook for a left hand and a bunch of friction tape.

[Ken Leung]

The Team Drawings in the document section: http://www.usfirst.org/roboticsprogr....aspx?id=16097, specifically TE-10012.pdf within 2010 Team Field Elements.zip, show a version of the tower using 4X4's as the vertical posts.

If these drawings are official, then it seem the GDC did not intend for robots to attach to the towers using the vertical posts. If they did, then these drawings are invalid for the official game.

Someone need to post a clarifying question in Q&A about this.

[Daniel_LaFleur]

Originally Posted by Ken Leung

The Team Drawings in the document section: http://www.usfirst.org/roboticsprogr....aspx?id=16097, specifically TE-10012.pdf within 2010 Team Field Elements.zip, show a version of the tower using 4X4's as the vertical posts.

If these drawings are official, then it seem the GDC did not intend for robots to attach to the towers using the vertical posts. If they did, then these drawings are invalid for the official game.

Someone need to post a clarifying question in Q&A about this.

Ken,

That drawing is for the low-cost field for teams to practice on and in this case does not accurately portray the official field due to different material (1-1/2" steel tubing vs 4x4) .