Wheel Size?

[Apeace]

I just noticed that the rule book has no mention of the wheel size constraints. Any thoughts?

[the man]

I think it may be possible to get over the 4" bump with no restrictions, besides I guess a 38" wheel...

[davidthefat]

You can make your robot have two bike wheels and it will be fine assuming that you can program your robot to stay balanced at a flat angle.

[the man]

Did some one say segway bot?

[Andrew Lawrence]

As long as none of your wheels are above 60 inches in diameter, I'm sure everything will be just fine.

I so want to use 60" wheels now!

[davidthefat]

As long as none of your wheels are above 60 inches in diameter, I'm sure everything will be just fine.

I so want to use 60" wheels now!

But the wheel needs to be contained in the bumper perimeter... Or did that change this year?

[PayneTrain]

I don't want to rain on your parade, but they couldn't possibly be any larger than 36 inches in diameter if you plan on building a 28x38 inch frame around them.

[the man]

That why I said 38" the maximum no height dimension.

[Apeace]

So it sounds like you could use larger wheels to get over the barrier much easier?

[davidthefat]

So it sounds like you could use larger wheels to get over the barrier much easier?

Other than design constraints, nothing is stopping you from doing it.

[Flimsor]

I think we should use a custom sized tank drive system that is the exact maximum dimensions allowed. That way, if the robot gets flipped over it can still drive, and we can get over the bump.:cool:

[ThaineP]

You should totally make adaptive-geometry wheels to get over the bump in the middle. :D

[Ernst]

You should totally make adaptive-geometry wheels to get over the bump in the middle. :D

How about a Tweel (http://en.wikipedia.org/wiki/Tweel)?
They might be used in future lunar rovers, so they should be good enough for FIRST.

[couvillion]

Along the lines of cool and not really helpful.

http://upload.wikimedia.org/wikipedia/en/thumb/a/ab/Tri-star.gif/320px-Tri-star.gif

I have not been able to come up with a engineering reason as to why tri-star wheel is better than a regular wheel of the same over all size. But like the design all the same. For those that aren't sure what is going on here it is the same setup as a planetary gear system with the ground acting as the ring gear.

[ratdude747]

Along the lines of cool and not really helpful.

http://upload.wikimedia.org/wikipedia/en/thumb/a/ab/Tri-star.gif/320px-Tri-star.gif

I have not been able to come up with a engineering reason as to why tri-star wheel is better than a regular wheel of the same over all size. But like the design all the same. For those that aren't sure what is going on here it is the same setup as a planetary gear system with the ground acting as the ring gear.

I remember seeing an old 2004 clip on youtube with a bot that used them to climb the stairs...

[MrForbes]

Did some one say segway bot?

Yeah, there was a segway bot sketch made by one of the younger mentors during the kickoff....

Of course the discussion deteriorated to a unicycle robot.

There should be no limit to the size of wheels you can use besides the 38" limit, but think about how tippy the robot would be with larger wheels.

[I LOVE ROBOTS!]

I don't want to rain on your parade, but they couldn't possibly be any larger than 36 inches in diameter if you plan on building a 28x38 inch frame around them.

someone forgot about putting the wheels in diagonal. so find the hypotenuse, then that's accurate.

[the man]

44.407in with a frame made of 1in on a side.

[Ninja_Bait]

someone forgot about putting the wheels in diagonal. so find the hypotenuse, then that's accurate.

We have successfully gone from the realm of intelligent engineering to the realm of infeasible, useless number mashing.

[the man]

Oh come on now. Impractical at worst. :o

[The Lucas]

I remember seeing an old 2004 clip on youtube with a bot that used them to climb the stairs...

That was 1218 The ChaBots. They made it all the way to the Einstein Final that year. They were pretty hard to stop, even if you dropped a robot on them (http://www.chiefdelphi.com/media/photos/19332).

[PAR_WIG1350]

44.407in with a frame made of 1in on a side.

I don't want to rain on your parade, but they couldn't possibly be any larger than 36 inches in diameter if you plan on building a 28x38 inch frame around them.

The frame perimeter would be at ~2-10 inches. the largest part of the wheel will be at .5*wheel diameter. In other words, the frame itself has no effect on your maximum wheel size, the vertical projection of your frame perimeter is the limiting factor. that means that a wheel with a tapered tread (allowing it to extend into the corners of the frame perimeter) could be up to 47.2 inches in diameter if it were placed on a diagonal, despite the ridiculousness of such a configuration. Assuming a frame 10 inches off the ground, the wheel, at frame level would measure only 29.1 inches. by lowering the frame to 2 inches from the ground, that number drops to 13.6 inches.

In a far more conventional long setup. 38" wheels would measure only 25.7 inches at a height of ten inches and 12.2 inches at a height of two inches.

We have successfully gone from the realm of intelligent engineering to the realm of infeasible, useless number mashing.

If engineers can't say what if, then the world would be a much more boring place. That being said, once wheel diameter gets a little higher than ten inches, making them any bigger would yield a negligible advantage. And that is ignoring the added weight of the larger wheels and the extra gearing needed to bring the motors back into an operating envelope which the electrical system can cope with (without browning out every time you try to turn).

[the man]

Slightly irrelevant, but I remember a team that had a large gear dropped on their robot during shipping. That would suck.

[Alex Cormier]

That was 1218 The ChaBots. They made it all the way to the Einstein Final that year. They were pretty hard to stop, even if you dropped a robot on them (http://www.chiefdelphi.com/media/photos/19332).

340 also had them on Einstein in 2004. ;)

[Cem8301]

I just noticed that the rule book has no mention of the wheel size constraints. Any thoughts?

Wheel size constrains how easy it is for your robot to turn. I was a little surprised, but with these wheels on our off-season robot we could do nothing but move backwards and forwards on tile/ carpet.

http://i.imgur.com/XmPZv.gif

[MrForbes]

Wheel size constrains how easy it is for your robot to turn. I was a little surprised, but with these wheels on our off-season robot we could do nothing but move backwards and forwards on tile/ carpet.

It's not the size of the wheels, it's the layout....they are spaced far apart front-back, not far apart side-side, and they have good traction.

[ratdude747]

That was 1218 The ChaBots. They made it all the way to the Einstein Final that year. They were pretty hard to stop, even if you dropped a robot on them (http://www.chiefdelphi.com/media/photos/19332).

that wasn't it.

340 also had them on Einstein in 2004. ;)

maybe.

IIRC the clip was from a regional, may have been a qualification...

[scree0114]

would omni wheels be better than the wheels they give you in the kit?

[Apeace]

I think it all depends on how you lay them out. You could do a skid drive, which is where you have 6 wheels, and the center two are the KOP wheels while the outer four are omni wheels. That way, you could spin on a dime.