Cantilever Wheel Bumpers

[Richard Wallace]

From a related thread:

Originally Posted by dlavery

I hate to "break" it to you, ...

I highly recommend reading Dave's full comments on this topic, in the thread linked above.

[Molten]

1/8 inch is not enough. Look at lavery's math. If I was a ref, I'd tell you to go back to the drawing board. Sorry, just my opinion. Not an actual official.

Why is everyone determined on having cantilevered wheels? Can someone give me a bit of info? Is there really much of an advantage?

Originally Posted by Molten

Why is everyone determined on having cantilevered wheels? Can someone give me a bit of info? Is there really much of an advantage?

Weight. That's two less full length chassis members. That boils down to less materials, less fabrication time for the chassis, and so on.

[Molten]

I'm sorry but I'm not seeing it. Anyone got some good pics to describe how this works? Sorry, but its pretty clear I'm not on the west coast.

Originally Posted by Molten

I'm sorry but I'm not seeing it. Anyone got some good pics to describe how this works? Sorry, but its pretty clear I'm not on the west coast.

Search CD media for any of 254/968's drive trains, that's a Cantilevered "West Coast" Drive base.

[JesseK]

Dave's math assumes several underlying principles, and the debate parallels that of traction vs wheel width on carpet. The 'ideal case' can always be argued against in one way or another. Unless you're sending something into space or 7 miles under the sea, the 'worst case' can always be engineered around with protections or tolerances such that the worst case becomes negligible.

In Dave's scenario, extra bumper support would spread the energy of the impact across more surface area, therefore increasing local structure integrity. Those of us who do cantilevered wheels simply need to do the same. What Dave doesn't tell you is that the impact energy has gone through the bumpers it then enters the 'equal and opposite' clause of Newton's laws. Due to the full extent of <R08>, I believe there will be many a pinball robot...now that will be fun to watch....

[GaryVoshol]

Originally Posted by Molten

I'm sorry but I'm not seeing it. Anyone got some good pics to describe how this works? Sorry, but its pretty clear I'm not on the west coast.

http://www.chiefdelphi.com/media/photos/32160 (Not that this really needs more promotion, sorry)

Originally Posted by Madison

Please refrain from making "personal judgements," about rules. If there is a question about how a rule may be interpreted or enforced, bring your concern to the GDC through the proper channels and await their remarks.

Our best guess about what satisfies the criteria of these rules can be detrimental the progress and success of other teams -- especially younger teams that haven't yet learned the ropes.

I thought that was the intent of CD, to thrash out ideas amongst teams and give warnings where we thought them due.

[Madison]

Originally Posted by GaryVoshol

I thought that was the intent of CD, to thrash out ideas amongst teams and give warnings where we thought them due.

We need to be careful about the language we use, however. There are differences between working through problems and writing hypothetically and declarative statements like, "1/8 inch is not enough... If I was a ref, I'd tell you to go back to the drawing board."

I understand that Jason disclaimed his role as an official in his post, but it's a behavior that happens frequently here and I just wanted to call some attention to it so that we all remember that we are not, generally, the arbiters of these decisions and, more importantly, that new teams understand that the things they read here are meaningless when they come to competition.

[EricH]

The GDC has answered... Don't shoot the messenger!

[JHSmentor]

Originally Posted by Molten

1/8 inch is not enough. Look at lavery's math. If I was a ref, I'd tell you to go back to the drawing board. Sorry, just my opinion. Not an actual official.

Why is everyone determined on having cantilevered wheels? Can someone give me a bit of info? Is there really much of an advantage?

I've seen plenty of people throwing up designs on CD or describing their past robots using 1/8" thick aluminum for their chassis.

Is this truely not the case or are you just referring to the original post saying that it would just be a strip of 1/8" without any angle or channel or gussetting?

Just currious because our robot last year was completely built out of 3/16 sheet - outer wheel plates just held on with standoffs - and, while this was totally bomb proof, it seemed way overkill to me (and heavy to boot).

[Molten]

Originally Posted by JHSmentor

I've seen plenty of people throwing up designs on CD or describing their past robots using 1/8" thick aluminum for their chassis.

Is this truely not the case or are you just referring to the original post saying that it would just be a strip of 1/8" without any angle or channel or gussetting?

Just currious because our robot last year was completely built out of 3/16 sheet - outer wheel plates just held on with standoffs - and, while this was totally bomb proof, it seemed way overkill to me (and heavy to boot).

The form of the aluminum has as much effect on its integrity as the thickness. 1766 has always built its bots out of aluminum tubing. It really isn't that much thicker then 1/8" however given that it is a square tube, it absorbs forces much nicer then a 1/8" plate as the original post suggests.

Understand from my original post, that I was making my personal judgment based on the way the vamfun described the set up. Withoout at least a picture, I can't say with any confidence which way I would side in an actual ruling. Wow, I'm starting to sound a bit like the GDC on this one. I guess I've heard them respond on this topic way too many times.

[Madison]

Originally Posted by Molten

The form of the aluminum has as much effect on its integrity as the thickness. 1766 has always built its bots out of aluminum tubing. It really isn't that much thicker then 1/8" however given that it is a square tube, it absorbs forces much nicer then a 1/8" plate as the original post suggests.

Understand from my original post, that I was making my personal judgment based on the way the vamfun described the set up. Withoout at least a picture, I can't say with any confidence which way I would side in an actual ruling. Wow, I'm starting to sound a bit like the GDC on this one. I guess I've heard them respond on this topic way too many times.

Please refrain from making "personal judgements," about rules. If there is a question about how a rule may be interpreted or enforced, bring your concern to the GDC through the proper channels and await their remarks.

Our best guess about what satisfies the criteria of these rules can be detrimental the progress and success of other teams -- especially younger teams that haven't yet learned the ropes.