Re: The Barrier Thread
 

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.

Re: The Barrier Thread
 

or you can have pneumatic wheels

Re: The Barrier Thread
 

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

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.

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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.

Re: The Barrier Thread
 

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.

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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

Re: The Barrier Thread
 

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.

Re: The Barrier Thread
 

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...

Re: The Barrier Thread
 

I think he was being slightly sarcastic.