Cutting corners (on the robot!)
 

Hi everyone,

Our current frame is about .25" over the frame perimeter limit (R3-A)

We're going to cut two of the corners at 45 degrees which will put us under the 112" perimeter limit.

My question: do those two new 45 degree angles now count as sides? R19 says "If a side is shorter than 8 in., the entire side must be protected by BUMPER" I suppose it is, since the bumper is coming from the sides and front/back.

What do you think? Any precendent of teams doing this to meet the perimeter limit?

Thanks!

-Eric

Re: Cutting corners (on the robot!)
 

Yes they count, also make sure you are able to follow all of the bumper rules with your new frame.

Re: Cutting corners (on the robot!)
 

So they need bumpers on these angles. How are we thinking that would work if the corners are really small? I'm thinking 0.5" long or so. Technically you need a piece of 3/4" wood plus noodles, etc. along that length. Except mitering in a 0.5" long piece of plywood there seems pretty difficult...

Re: Cutting corners (on the robot!)
 

That's how I currently read R26.

If that's true then if you cut the corners at all you have to have wood, pool Noodle, etc on that cut corner. The Q&A might be good for this or Al might give a ruling as well.

If it's less than a 1/4" away than that would be legal by the rest of R26.

Re: Cutting corners (on the robot!)
 

To make the example easy, if you cut a 45 degree angle (you cut off 1" from the front and 1" from the side), the length would be just over 1.4" long.

R26-A says any gap between the backing material and the frame can be no more than 1/4", so clearly something has to go there.

R19 shows the overlap of the noodle on the hexagon-shaped robot, so a vertical pool noodle attached to the new short side shouldn't be an issue.

The bumper backing could be a robust piece of wood instead of plywood. (R21-A), so perhaps you could create the small triangular piece out of solid wood and attach it to one of the existing bumpers.

The suggestion about Q&A is also a good one.

Thanks!

Re: Cutting corners (on the robot!)
 

We had to do this last year at a regional. Yes, they count as sides, the easiest thing to do is to just make curved bumpers.

Re: Cutting corners (on the robot!)
 

You can always just use your original bumper design, it's fine to have small gaps between the frame and the bumpers in the corners.

Re: Cutting corners (on the robot!)
 

We always undersize our frame by a quarter inch to prevent such possibilities. I would thing that although very small they still count as sides and therefor would need fitting bumpers

Re: Cutting corners (on the robot!)
 

Such "small gaps" at the end of the bumper segment can be no more than a half inch long.

Re: Cutting corners (on the robot!)
 

Just out of curiosity, what were the dimensions you were aiming for? Did you try to do something like 33"x23" and it ended up over? Always plan for your robot to be out of square, so make it just a little less on each side.

Re: Cutting corners (on the robot!)
 

Every year teams like to push the limits with sizing... one of the nice things about the old sizing box was that it kept teams from pushing them too much. Of course, that was also the bad thing, as every robot absolutely had to fit inside the box.

Now with the frame perimeter rule introduced last year, it's a lot easier to get people compliant if they're just a little over. For anything up to a 1/4", you don't really need to cut off a corner... simple rounding all of the corners a little bit is usually enough to get you there, which still leaving each corner as something a normal observer would call a corner and not a side.

That said, as an inspector if I had a team show up where they made a clear decision to cut off a corner (to the point where I can easily define two corners and a side where the single corner used to be) to make the size requirement but still treated it as a rectangular robot for the bumpers, I would be a little annoyed. And an annoyed inspector is a thorough inspector!

Also be aware of R26:
Emphasis mine. Clipping the corner of the frame perimeter but still using a right angle for your bumpers would leave at least part of the end of the bumper unsupported, and the way I read the rule support has to exist from the edge of the bumper inwards at least 1/2".

Re: Cutting corners (on the robot!)
 

They're only taking off a 1/4" total so I'd guess this shouldn't be an issue for them.

Re: Cutting corners (on the robot!)
 

Eric,
I have to ask what your frame is made of and perhaps you could give us a picture? There may be some other method of meeting the perimeter rule that you have not thought of. You have some very qualified and experienced LRIs answering above and they are speaking from that experience. We want you to play while meeting the rules.

Re: Cutting corners (on the robot!)
 

sounds like an opportunity to add a steel right angle iron to your bumper to reinforce your bumper. weight goes to the bumper, not the robot and it will fill the gap in the corner.

Re: Cutting corners (on the robot!)
 

Adding weight that can be seen as unnecessary to your bumpers can be a bad idea. You're allowed to put as much weight in the bumpers as is necessary to build them, but no more.

("As is necessary to build them" is a vague statement, but that's essentially what the rule is.)

Re: Cutting corners (on the robot!)
 

That's not quite what the rule says. R21 specifies how the bumpers are to be constructed and what materials you can use. For example, R21 does NOT allow you to bolt a big hunk of steel to the bumper "just to add weight". It does, however, allow you to construct your fastening system (how you attach to the robot) however you like. So if your fastening system is a big hunk of steel with some holes through it that let the bumper mount to your frame, it's fine by R21.

Bumpers do have their own weight limit (20 lbs), though, as seen in R20.

Re: Cutting corners (on the robot!)
 

That's what I was trying to get at. You're allowed to choose your own fastening system and construct it with as much (or as few) materials as required. Any weight beyond what is required to construct your bumpers (however you want) is not allowed.

Re: Cutting corners (on the robot!)
 

What rule says this? I just read through the rules on bumpers, and didn't find anything that limits parts or weight based on the intention of those parts or weight. There's a 20 pound limit total (R20).

I doubt Al will give a ruling here on CD, but he will likely give great advice, and history.

Re: Cutting corners (on the robot!)
 

R21 says how bumpers must be constructed. Plywood, pool noodles, cloth, optional angle as a cloth clamp, and a "robust fastening system". No other items are allowed to be used to construct bumpers as that would go beyond the guidelines specified in R21.

The term "robust fastening system" is vague and generally inclusive. You are allowed to design your own fastening system using any parts you wish. Once you have your fastening system, you can't add any additional materials to bumpers even if you're under the 20 lb bumper weight limit.

The bottom line is you can use steel as part of your fastening system if you can meet the weight limit. If your fastening system doesn't involve steel, you aren't allowed to add it even if you're under the weight limit.

Re: Cutting corners (on the robot!)
 

R21 says that certain materials must be used (wood, noodles, fabric). But I don't see any thing that says only these materials, or prohibits other materials.

Re: Cutting corners (on the robot!)
 

R21 says how bumpers must be constructed. Adding additional weight is not part of those guidelines.

Re: Cutting corners (on the robot!)
 

The rule doesn't say anything about reversible bumpers or velcro, yet year after year both are legal.

Outside of that, I can tell you that the ten pounds of steel I used on my "robust fastening system" are integral to it.

After three years in our pit, I have yet to see an inspector rule against added weight on the bumpers. Might just be a regional thing though...

Re: Cutting corners (on the robot!)
 

Reversible bumpers and velcro are included in the "fabric" requirement in combination with R27 which requires robots to able to display red or blue bumpers and be able to switch between them fairly quickly.

Re: Cutting corners (on the robot!)
 

If you can convince the inspector that everything on your bumper is essential, you are fine. If you screw steel plates onto your bumpers which serve no other purpose besides weight, you are in violation of bumper rules.

Re: Cutting corners (on the robot!)
 

Last year, inspectors were disallowing bumpers because teams put metal weights inside the pool noodles. Don't try that. Use the fastening system as your extra weight, as you can't add non-functional pieces and be compliant in the rules.

But, if you have a metal piece fitted to support the bumpers around the short side/cut corners, then you should be good insofar as obeying both the spirit and the letter of the rules.

Not the easiest way to do it, but it should satisfy the inspectors.

Re: Cutting corners (on the robot!)
 

I did not intend to suggest simply adding weight for the sake of weight. What I intended to say is that if you needed to fill the gap of a cut corner, you could add angle iron to reinforce the inside corner of the bumper, maintain contact with the last 1/2" of frame and that added weight would count against the bumper weight, not the robot. I have never seen bumpers that came anywhere near the 20lb limit and I would put forth that if they do, the added mass was not integrally required.

Re: Cutting corners (on the robot!)
 

While no one can "rule" on a description here, I can tell you the rule of thumb inspectors use is examining the bumper construction using the bumper rules as a reference. Those parts that are and should be part of the bumper are thought of as "bumper'. Those parts that should be robot structure are thought of as 'robot". Those things that are "robot" should be weighed and sized (Frame Perimeter determination) with the robot. Steel weights, metal rod filling the pool noodles, lead sheet, (depleted uranium?!?) etc. can be pointed at by anyone in the pit and labeled "robot". Ballast is "robot" That is not to say creative ways of bumper mounting will be automatically rejected. Our LRIs are well versed in making the determination.
Please remember that all key volunteers do not operate in a vacuum or rule from on high. They will discuss a problem as a group when needed and come to a consensus. If they can't make a ruling, each of them has a contact at HQ that is available for phone consult.

Re: Cutting corners (on the robot!)
 

Wouldn't that violate R8 (prohibition on hazardous materials)? As far as I know, depleted uranium is still toxic.

Re: Cutting corners (on the robot!)
 

And radioactive!:D

Re: Cutting corners (on the robot!)
 

R26
BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 4-10). To be considered supported, a minimum of ½ in. at each end of the BUMPER must be backed by the FRAME PERIMETER.

Al may say I am wrong but my take from the rules is that every side of the frame, in this case 8 sides, must have bumper attached. The rule states a minimum of 1/2 inch from each END of each face must be be backed by the frame. even though the corners are small they must have bumper with backing. If I were inspecting I would not allow it and I would back any inspector making the same decision where I am LRI.

Re: Cutting corners (on the robot!)
 

So Steve with what you said does that mean the KOP frame as built does NOT comply with 1/2" Frame Perimeter as there will only be the thickness of the outside plate?

Randall (2014 - 610 quick build electrical guy)

Re: Cutting corners (on the robot!)
 

You could fillet the corners instead of chamfering them. This would be more aesthetic while also maintaining the structural integrity of the corners.

Re: Cutting corners (on the robot!)
 

The kit chassis' outer structure has an upper flange. That flange extends .745 in the front and back of the robot at each corner. Therefore if the bumper is mounted to that it would be supported by more than 1/2" of material in the corner.

Re: Cutting corners (on the robot!)
 

For adding weight to our bumpers, we just use 1/8" thick 3/4" steel angle instead of the typical aluminum. We have had no issues at our regionals.


The advantage of more weight is more pushing power (for traction limited drives, because f=uN, and more weight is more N, equating to more f!)

Re: Cutting corners (on the robot!)
 

Dave,
Are you suggesting that you replaced the "optional aluminum angle" in Fig 4-8 with steel? I am sorry if you were told this was legal, I believe aluminum is the only allowed material for this part of the bumper. Please ask the Q&A.
Steve's response above is correct under the strict interpretation of the bumper rules. See Fig 4-6 for an illustration of areas of required bumper coverage and Fig 4-10 for an illustration of 1/2" support at the end of the bumpers.

Re: Cutting corners (on the robot!)
 

Thank you Dave, I totally forgot about the upper flange on top of the outer side plate which would make the frame comply with bumper rules.

Leave it AndyMark to come through again. Kudos for a job well done.:cool: