Chain contacting BUMP
 

I have posted to Q&A. Opinions: Chain dragging on BUMP while crossing. Not supporting the weight of the robot, just dragging on the corners of the
BUMP. Violation of <R08> or not.

Re: Chain contacting BUMP
 

IMHO Violation of <R08> & <R36>

If the chain is not supporting, why not just design a guard to protect the field?

Re: Chain contacting BUMP
 

I know you referenced the rule so its not like you haven't read it. Simply showing it for visual purposes.
I also see you say it isn't to gain traction so it is slightly in conflict with the rule. Even with that in mind I don't think it would permitted. Simply because there is too high a chance of it possibly getting caught in the rug as your moving over it and ripping the rug or simply because it will dirty the rug with the grease/oil transmitted from the chain to carpet. Last year we had to cover up a chain system that was a foot above the floor just because it was splashing too much grease/oil supposdly. It also violates the general rule that metal should not be in contact with the carpet. So I would have to say no, the GDC would not permit it, and also your inspector at your regional would not allow it.
Is there that much if an issue you cant bring your chain system higher to avoid contact with the bump while moving over it?

Re: Chain contacting BUMP
 

We will probably either guard the chain or re-route it. Would rather leave it alone if you know what I mean.:rolleyes:

Re: Chain contacting BUMP
 

Better to be safe then sorry. Wouldn't want to show up to a regional and have to redesign your drive system because an inspector won't allow your robot on the field! Good luck.

Re: Chain contacting BUMP
 

The main reason I posted this was for others to check their design before it is too late and hard to make the correction. We usually do not have to worry about this happening.

Re: Chain contacting BUMP
 

Q&A has answered: http://forums.usfirst.org/showthread.php?t=14011

Short version: Drag a chain, you've just violated <R08>. Plan accordingly.

Re: Chain contacting BUMP
 

this would have been a good "don't ask, don't tell".

Oh well.

I guess if we oil the chain to make it not a traction device, then it has oil, which is a different no-no

Re: Chain contacting BUMP
 

we had the same issue
some Aluminum skids with 1/16 polycarb extended under/around the chain did the trick. I'll see if we have a good pic somewhere

Re: Chain contacting BUMP
 

Gates is donating sprockets and belts this year... a belt in contact with the field would likely be less of a problem.

That said, we'll probably stick with good ol' #35 chain... we're familiar with it, and the sprockets are easily accessible.

Jason

Re: Chain contacting BUMP
 

There are some advantages to a belt drive. While you have to calculate exact distances, it never stretches, so you don't have to break and tension it ever. The ability for it to touch the floor, with some traction, may be beneficial for some, though I'd recommend for most people you try to ensure noncontact unless you know what you're doing...

Re: Chain contacting BUMP
 

Chris,

Even if you do exact Center to Center distances. It would be a smart move to build/design in a way to tension them. Better to be safe than sorry.

-RC

Re: Chain contacting BUMP
 

Thanks. I've only played with belting in prototypes and word of mouth, so I'll keep this in mind in the future.

Re: Chain contacting BUMP
 

This is a related question.

Consider an aluminum chassis that rubs against the carpet for <1 second as it climbs over the bump. Is that legal? How does <R08> apply?

Re: Chain contacting BUMP
 

IMO, the frame can touch, as long as it is smooth. It's not attempting to gain traction, and it's not a moving part, which is the most likely way to cause damage to the field.

You may want to avoid it anyway, since the touching means your wheels may not be touching any more, and if you take a kit with the weight of your robot on the frame instead of the wheels, you may get a bent frame out of the deal.

Re: Chain contacting BUMP
 

More than just R08 is this...

G26> ARENA Damage - ROBOTS may not damage any part of the ARENA or BALLS. For ROBOTS that violate this rule, the TEAM may be required to take corrective action (such as eliminating sharp edges, removing the damaging MECHANISM, and/or re-inspection) before the ROBOT will be allowed to compete in subsequent MATCHES. Violation: Potential Disablement if the Head Referee determines that further damage is likely to occur

Lubricants left on the field, damage to the carpet, etc., comes under this rule.

Re: Chain contacting BUMP
 

Whether you have a chain or a belt, a tensioning idler scheme is HIGHLY advised, so why not place this in the middle underside of the chain/belt wrap, pulling upward there to help clear bump corners? This way it handles two issues for you - carpet protection and keeping chain/belt taught, yet yielding to overloads.
BTW, the EXTREME linear tension stress levels developed when a taught, no-idler chain/belt gets bashed in the middle by the bump corners at high speed is a great way to break them, and/or some other weaker component in your drive system. We are talking as much 100-fold type of leverage here when a 90 degree force hits a chain/belt under full tension with no elasticity provided by an idler mechanism.

-RRLedford

Re: Chain contacting BUMP
 

Where do you suggest we can buy industrial grade roller chain

Re: Chain contacting BUMP
 

you already have an industrial grade .#35 roller chain. McMaster-Carr has more

Re: Chain contacting BUMP
 

easiest thing to do is to cut a piece of delren (plastic that is self lubricating) rod and use it as a tensioner to lift the chain up. We attached this to the inner and outer rails of our chassis under our chain runs and it did the trick.

Re: Chain contacting BUMP
 

Josh! Stop giving away our secrets! :D . You left off that we drilled the hole off center on the delrin so we use it as a a type of cam (turn the delrin a little to tighten the chain).