Re: Weight
 

I think Dave hit it on the head (as usual). Even after 8 seasons in FIRST our team still doesn't place enough emphasis on the weight limitation. We discuss it. We think about it in the backs of our minds. But in the end we haul out the Rotozip and go to town. While it's only a few pounds it's still a glitch in the process.

I agree with everyone else in that 130 pounds is a part of the challenge. It is just one of the many design constraints that needs to be considered when developing a solution. Adding more weight doesn't make the challenge any easier, it just makes the robots heavier.

Thanks to ChrisH for the weight management tips. You can be sure we'll put those to work for us this coming season! :)

Seah

Re: Weight
 

This is the best reason yet to change (reduce) the weight restriction on FIRST robots for next year. Veteran teams have become complacent about this issue. Many of them start designing some of their subsystems in the fall, working under the assumption that the weight limit will be 130 pounds. They then have (yet another) leg up on the rookie teams and others that wait until the kick-off to really start planning out their machine.

Imagine the utter chaos that would ensue if every team really had to start from the same baseline of knowledge - or lack thereof! :) Imagine NOT being able to count on certain things to stay the same from year to year. It would do more to "level the playing field" between veteran and rookie teams than almost anything else FIRST could do.

It makes you wonder what sort of sick, twisted mind would do such a thing to all those innocent teams out there...

-dave

Re: Weight
 

Uhhh...that would be your mind Dave!!

Dropping the weight really would turn the veteran teams on their ear. We'll have to keep that in mind when considering new ideas for this coming season!

Thanks Dave!

Sean

Re: Weight
 

I don't wonder at all Dave :D . But I think it might have been more of a shock if you hadn't tipped your hand ... :yikes:

Although I'm sure it would still shake things up - I suspect anyone reading this would likely expect that it couldn't happen.

I do, however, think one change might be in order. I agree with most that the weight limit should NOT be increased, but since we are changing out batteries throughout the competitions, and we are subject to "spot" weight checks (which I think are a good thing) I think the official weight should be spec'd W/O battery. I would like to see the limit at 120 (or whatever makes sense) without battery.

Re: Weight
 

This would certainly remove all possibility of a team using a battery with the innards removed for weigh in, as some have been rumored to do in the past. Note: I have no personal knowledge of such an occurrence, but I have heard rumors about it for years. I am not picking on any particular team as I can't remember any that those particular rumors have been directed at. I think it is an urban legend myself, but it could happen ....

As an inspector, I have tried to always make sure that the robot could actually operate with the weight-in battery to minimize the chance this could occur. As a team member, we've always weighed both our batteries and marked them so we knew which one to use for weigh-in. Some years it has made a difference and others it hasn't.

Yes the scales have varied from event to event in the past. In Houston I think the difference between the scales that were there was like four pounds. I know there was one scale in particular that we directed robots that were just barely overweight to. The inspectors had no clue as to which one (if any) was "right". This year seemed to be better and I noticed that they had calibration weights in the inspection area at the events I attended. So let's not beat on a problem from past years that has been fixed.

Personally I think that robots should be weighed every time they enter the competition area. Just put a scale at the robot entrance to the arena. Before you can enter, one of the crew must verify that you meet weight. It would certainly stop complaints that "so and so put an entire new arm on after they weighed in". While it would make things a little bit more difficult for the queuing crew, it might also prompt teams to be a little more prompt for their matches. If teams knew they were going to need to weigh-in and there might be a line then maybe they would leave their pit before the very last second.

I know in LA we inspectors tried to watch out for the "morphing robots". If we recognized that a robot was sporting a new appendage, then we would send the team back to the scale. But it would probably have been pretty easy to slip several pounds of ballast past us, if it wasn't too obvious.

Re: Weight
 

While it wasn't taken to this extent, at the West Michigan regional this year, each robot that was chosen for the elimination rounds had to weigh in again. A sticker was placed on the battery they used for this weigh-in, and that battery was the one that had to be used for their first match in the elims. This helped with the issue of different battery weights in some ways (you could choose which battery to weigh with), but it also hurt you if you tried to use a lighter battery that you didn't normally use for competition.


Our team has had the same experiences, as most if not every team has. In 2001, for one example, at Great Lakes we weighed 118.5, at West Michigan we weighed 117, and at EPCOT we weighed 123.5! That's a huge difference to try to plan for. I'm in agreement with all the people who think we should weigh in without the battery and drop the weight limit to another number.

Here's a suggestion...what if, for a year or two, we changed the robot specs back to what they were in 1992? The robots were small but could still be presented with challenges that they could complete successfully. I'm not familiar with the rules and the specs from the early years, but I'm sure that parts exist that we could use. It would provide a very different challenge than what we're used to now, with the 10-foot tall bars, different zones in which to score, and ramps. Just a thought.

Re: Weight
 

In my first year (associated with FIRST), the weight was 85 pounds, the current limit was 40 amps (total) and the base constraint was a 30" diameter circle. These constraints (and others) varied from year to year until recently.

We truly anticipated the kickoff because it defined not only the game but the design constraints as well.

This is real world. Being handed "impossible" constraints forces the engineering/”sales”/manufacturing team to consider trade offs.

A few years ago, I had posted on a few threads here where the issue was the size of the main battery current limit (Then a 60 amp fuse… If it blew, you were dead.). I had stated that the Bobcat had never blown a fuse and the teams that had done so had not paid attention to their power budget.

Anyways, the total power was raised (which caused a slew of new problems) and, in retrospect, I’m still not sure that FIRST did themselves or us a favor…

Tackling “impossible” design challenges led to an amazing and unprecedented era of technological developments in the late 20th century. We put men on the moon, telescopes in orbit and robotic rovers on distant planets. The outcome of which can be symbolically represented by the enabling technologies inside the laptops most of you are using to read this message.

Another benefit of fluctuating constraints is that it levels the playing field. Designing a robot (or robot subassemblies) in pre-season becomes less profitable to veteran teams in terms of something which will be used this year. Pre-season activities become slanted more toward educating the workforce (mentor and student alike) to be able to respond to whatever twisted and devious challenges Messrs. Flowers, Lavery and Kamen (et al) might throw at us.

Also, fluctuating constraints in a very tight timetable forces a discipline on the team which is beneficial to everyone involved. We learn (or relearn) the importance of a structured timeline, (sub)system requirements and intelligent trade off analysis. Moreover, it forces the entire team to actually read the rules and approach the design as a team exercise!

Therefore, a proposal for varying constraints:

Weight: 80 to 140 lbs.
Base size: 20 to 30 inches by 30 to 48 inches.
Height: 20 to 60 inches.
Geometry: Approximately every other year, use cylinders, pyramids, trapezoids, etc.
Power: 80 to 120 amps at 12 VDC.
Cost: Between 3K and 5K (with no subsystem constraints).
Components: More variation (example: Skip using CIM motors for a year or vary the number of Drill motors from 2 to 4 for a year).

Bottom line: Some people will complain no matter what the design constraints are… I say: Let ‘em and bring it on!

Re: Weight
 

I want to second (or third or fourth) the thanks to ChrisH for his comments on how to manage weight budget. We have been bitten for the past two years by the weight constraint (despite paying attention to it and modeling all parts of our robot) and had to delete a module each year. We were planning to implement something like ChrisH's system this year, because wondering where we were in terms of weight caused a lot of stress. We didn't think of "Weight Czar" as the title for the Configuration person though!

When people talk about the "bad old days" of 80 lbs in FiRST, they do not seem to remember that we have a lot of weight allocated to required components, many of which are heavier than their equivalents back then. The battery, control system and cables, backup battery, fuse panels, blinky lights, numbers on four sides of your vehicle, etc. are all a substantial portion of a robot's weight (25 lbs). If you use pneumatics, I think you have 10-15 lbs taken in valves, compressor, tubing, regulators, etc. Also, the motors (drills and chips in particular) are more powerful but heavy.

This past year's requirement that all modules must fit into the 130 lb probably made teams with lots of design and fabrication resources have to either make design compromises in the modules or cut the number of modules on their robots.

I would say that the 130 lb constraint is "comfortable." It does limit teams that can "do everything" and make them prioritize what is important. Teams that don't pay attention to it will get bitten. However, teams that are just getting started are not likely to bump into it. It is consistent with the size constraints. I.e. a robot that is 30"x36" with all the required components will come in around 130 lb.

If FIRST knocked 5 lb off the weight requirement, it would present a challenge to most teams. I don't think adding 5 lb would be a good idea though. Knocking 10 lb off the requirement would create a significant imbalance that would probably result in less exciting competitions.

Regarding procedural changes at competitions, such as weigh in before competing, FIRST should be very careful about this. The staffs putting on competitions are clued in about the previous years' procedures. When you throw something new at them, they take some time to accommodate it. I suspect that you would have a lot of forfeits on matches in the beginning, either because of battery-to-battery variation, scale-to-scale variation, last minute repairs that result in a couple of ounces on a robot, etc. You would also have a continuous line at the weighing station throughout the competition.

What would you gain? The truly competitive teams are extremely unlikely to be gaining an unfair advantage by going over weight. They would probably reserve 1-2 lb and add an adjustable weight mechanism. At the weigh in station, they would add/subtract the few ounces necessary to get them into weight. The teams which are not so experienced would be the ones getting eliminated. And, does this really help FIRST achieve its mission?

Re: Weight
 

I think we're heading towards less weight actually...

Re: Weight
 

"level the playing field"... could this be a hint about next year's game? :D


i don't think we should worry about changing the weight limit, bu8t instead worry about makign the scales in use more accurate. my team weighs our robot with some of the most accurate scales around. i remember one time where we knew our robot was 129.4 and when we put it on the scale it read 130.7! all we did was pick it up and put it down again and the scale read 129.8! my numbers may be slightly off, but the idea is what is important - the scale was varying. the fact that it can have almost an entire pound variance of weighing the same exact thing really shows how innacurate they are.

Re: Weight
 

Make it more real world and change it a week in. Real world experience is like that - suddenly someone else can do it cheaper, lighter and better, and the requirements on the engineering team change and have to be met.

Imagine if FIRST update number three said "Due to a new customer requirement, the maximum weight is now 122.5 pounds." That would create utter chaos! :ahh:

PS - If this really happens, I must remember to delete this post.....

Re: Weight
 

I'll save a copy here to help you remember. ;)

Re: Weight
 

Having been envolved the First 1 1/2 times, got a late start the first year,
The weight issue always comes up to bite you. I'm for the reduction of weight with out the battey. As was suggested to 120ibs, or so. The
mass of the batteries varies as was stated buy as much as 1 lb. We had all ours labled with their weights at the last competion. Total differance was .8 lbs. When your parts keep breaking and the replacement ones weigh more this really pushes up the stress level. Too the point of pack it up and go home, because you can't possibly play, much less win any match. All the help in the world won't fix things if your out of time. I know you all say we are all under the same rules, but not all teams have access to the same level of resouces. I am amazed each year by the complex and amazing gearboxes, and custom machined parts that appear on teams robots. It's a game, just like in real life those with the most resources tend to come out on top. My
two cents worth. For me it's not about winning, it's being able to at least compete.

Re: Weight
 

Congrats on an accurate FIRST prediction!

Matt