The Barrier Thread

[lemiant]

To everyone who thinks you can cross the bump unaided (that video shows what lifting the robot before the wheels hit can do) with 6" wheel, I'm fairly sure that is wrong. The center of your wheel is 3" off the ground and as such you would ram flat into the metal. MY guess is that you'd break the wheels or send your robot hurtling head over heels before it would go over the bump. Even a 8" wheel would be sketchy, because it is level with the top of the metal. To be certain you would need 10" wheels.

[mdiradoorian]

or you can have pneumatic wheels

[slijin]

Originally Posted by Grim Tuesday

Breakaway was a much higher drop, though.

EDIT: How would we do the math for this?

I believe what you're looking for is shear stress analysis.

Originally Posted by lemiant

To everyone who thinks you can cross the bump unaided (that video shows what lifting the robot before the wheels hit can do) with 6" wheel, I'm fairly sure that is wrong.

If the side-profile of your robot is trapezoidal-esque - that is, you have powered wheels elevated above the ground - you'd be able to do so with 6" wheels.

I don't personally believe that people will break their wheels by anything, including driving into the rail (which is steel, as can be confirmed by the CAD) - if they do, it'll be because the wheels will have already experienced heavy damage - but I do expect to see wheels damaged by collisions and impacts. Plactions will crack very easily if you abuse them enough.

[Grim Tuesday]

My question on math was how we would calculate if a wheel can climb a surface, my bad.

[slijin]

Originally Posted by Grim Tuesday

My question on math was how we would calculate if a wheel can climb a surface, my bad.

Then you'd be comparing the net upwards force (acceleration and friction) to gravity.

[R.C.]

Originally Posted by lemiant

To everyone who thinks you can cross the bump unaided (that video shows what lifting the robot before the wheels hit can do) with 6" wheel, I'm fairly sure that is wrong. The center of your wheel is 3" off the ground and as such you would ram flat into the metal. MY guess is that you'd break the wheels or send your robot hurtling head over heels before it would go over the bump. Even a 8" wheel would be sketchy, because it is level with the top of the metal. To be certain you would need 10" wheels.

Alex,

If you actually do the math and check your geometry, you will come to the conclusion that a 8wd 6" wheel will definitely clear the 4" "Bump". Also there are a lot of ways with 4"-6" wheels you can clear it. 10" wheels would be a bit overkill.

-RC

[Ankit S.]

Originally Posted by mdiradoorian

or you can have pneumatic wheels

I was thinking about this too, the 8 inchers from AndyMark are lookin' especially nice right about now...

[Gray Adams]

Originally Posted by R.C.

Alex,

If you actually do the math and check your geometry, you will come to the conclusion that a 8wd 6" wheel will definitely clear the 4" "Bump". Also there are a lot of ways with 4"-6" wheels you can clear it. 10" wheels would be a bit overkill.

-RC

Yeah, our feeling is that just throwing more wheels at the problem would be more effective than massive wheels.

[Bill_B]

FRC gamers are so used to nice flat surfaces (for the most part) we hardly ever think of a standard vehicular feature ---- suspensions. I'm looking forward to see what the 6WD fans do for this year.

[DonRotolo]

Originally Posted by lemiant

To everyone who thinks you can cross the bump unaided <> with 6" wheel, I'm fairly sure that is wrong.

Sorry, but I have to disagree. I can even do it with 4" wheels.

As a trivial example, imagine a wooden 'ramp' at the front end of the robot (inside the bumper perimeter), starting at 5" and ending at 2". Hitting the barrier at speed will launch the bot over.
As for high-centering, if you use Gates Belt instead of chain, it can act as a tank tread for between the wheels.

[Ninja_Bait]

Originally Posted by DonRotolo

Sorry, but I have to disagree. I can even do it with 4" wheels.

As a trivial example, imagine a wooden 'ramp' at the front end of the robot (inside the bumper perimeter), starting at 5" and ending at 2". Hitting the barrier at speed will launch the bot over.
As for high-centering, if you use Gates Belt instead of chain, it can act as a tank tread for between the wheels.

Key word in the post you quoted was "unaided". Take away the wedge and try again.

[Bjenks548]

I bet our 2010 robot could make it over with no problems!
http://www.chiefdelphi.com/media/photos/35272Some nice 10in pneumatic tires!

We're planning on using the slants in front of our robot along with the 8" pneumatics from Andymark. Deflate the wheels a tiny bit, and they become instant shock absorbers.

[PayneTrain]

Originally Posted by mdiradoorian

come on we have not thought of everything yet just wait in the next couple days we will have something.

No one was dragging you down for not considering the entirety of a design; they were just pointing out the possible flaws before you found them later on...

[the man]

I think he was being slightly sarcastic.