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Michael Leicht 21-08-2004 23:20

Weight
 
Who want a little more weight for there robot instead of 130lbs? I mean at the last couple days you have more weight then you need or should have. I think they should add 5 more pound to the weight limit. with this 5 pounds you could open the possibles with 5 more pounds. What could you add to your robot that is 5 pounds that could really help you? so who likes the idea.

Heretic121 21-08-2004 23:46

Re: Weight
 
honestly... i think it all depends on what the game is, and how many diffrent complexitys it has next year... but i also think it depends on how many motors there are, and thier wieghts if they are heavier than this year...

sanddrag 21-08-2004 23:48

Re: Weight
 
This has been discussed numerous times before. While nearly everyone except who's lifting it weould enjoy the extra weight-space, the problem is if the limit was 135 lb, why not increase it to 140, aw heck, how about making it 145 lb, and so on and so forth. I think the goal of sticking with the 130 lb limit consistently, is seeing how much you can pack within that restriction, rather than how much you can expand with extra weight. The challenge is not how many ideas can you fit on your robot, it is how can you even fit the ideas you have.

ZACH P. 22-08-2004 00:09

Re: Weight
 
It need not be increased. It is part of the design challenge.

Arefin Bari 22-08-2004 00:11

Re: Weight
 
The whole point of making the weight limit to 130 lbs is because teams need challenge. This is one way a team can prove how good they are mechanically and how complex can they make their robot... :)


p.s - i was a little late to post this one... Zach P. beat me to it...

Cory 22-08-2004 00:40

Re: Weight
 
If the weight limit is raised 5 pounds, people will find 10 pounds more crap to put on their robot.

No matter what the weight limit is, a large number of teams will *ALWAYS* have trouble making it

$0.02 Cory

Bharat Nain 22-08-2004 01:23

Re: Weight
 
I don't think I'd like carrying a 140 lb. robot on the field.

OR

have it slip and fall on my feet, or something.

From a designing and robot performance standpoint, this is an excellent suggestion. I could do a lot with some extra pounds to play with. But otherwise, I think its good as a challenge and also for safety reasons.

Mike AA 22-08-2004 01:32

Re: Weight
 
Quote:

Originally Posted by Bharat Nain
I don't think I'd like carrying a 140 lb. robot on the field.

OR

have it slip and fall on my feet, or something.

From a designing and robot performance standpoint, this is an excellent suggestion. I could do a lot with some extra pounds to play with. But otherwise, I think its good as a challenge and also for safety reasons.

I second the carrying that weight, its bad enough to work with 130 pounds.

Get steel toed shoes, they make tennis-shoes made with steel toes, I have a pair, sure they're a few pounds heavier but its protected my feet MANY times.

The weight limit is just another part of the challenge along with everything else.

Steve W 22-08-2004 02:05

Re: Weight
 
I personally would like to see 120 -125 lbs without the battery. One of the problems is that battery weight varies as much as a pound from 1 battery to another.

Joshua May 22-08-2004 02:10

Re: Weight
 
Just really seconding what has been mentioned previously, the weight is all part of the challenge. It is another design obstacle that you must overcome. In real engineering situations, there will be limitations that FIRST also employs, including suppliers, prices, weight, size, etc.

Quote:

Originally Posted by Bharat Nain
I don't think I'd like carrying a 140 lb. robot on the field.

OR

have it slip and fall on my feet, or something.

I second that, I've already thrown my back out carrying around the robot as is, 130 lbs. is definitely enough. :)

Kyle Love 22-08-2004 10:56

Re: Weight
 
Quote:

Originally Posted by ZACH P.
It need not be increased. It is part of the design challenge.

I totally agree. We were like 129.99999999999(repeatingHAHA) and we did weight reduction before we added things, such as our goal grabber we added at MWR.(I think it was MWR.) It is something that is a challenge outside the game itself. We all need to just deal with it. (meant nicely)

Quote:

Originally Posted by Heretic121
honestly... i think it all depends on what the game is, and how many diffrent complexitys it has next year... but i also think it depends on how many motors there are, and thier wieghts if they are heavier than this year...

I also agree with that...I mean come on if the game has like 10 different things to do there will be teams that want to do it all. And if there are more motors that would take away weight to use for stuff to play the game. If the game doesn't really require that much "extra" parts, but more motors I think it should stay the same, just to make things more challenging. :rolleyes:

-Kyle

Michael Leicht 22-08-2004 11:35

Re: Weight
 
i see what you mean now and i think that they should stick with the weight limit of 130 because that makes you think more then just we can do it we have the extra weight. so they should keep the weight limit the same.

Matt Adams 22-08-2004 11:40

Re: Weight
 
I guess I'd like to throw in a few comments on this...

When you look at the weight of a FIRST robot, much of the weight is non-negotiable. Things like the drive motors, battery, chain, wheels, controller, speed controllers and wiring, (and everything the electronics mount to) are all very steadfast items. Even a drive frame, in whatever form, is something that every machine must have. I think that I could conservatively say that 40 lbs of a robot is absolutely non negotiable.

With that said, adding another 10 lbs would really be like adding another 11% to your robots' weight.

And when you really think about it, there aren't a lot of teams that are at 160 lbs (after their rookie year) who are trying to cut down to 130.. they're at 136 or so trying to make it.

I think another 10 lbs would make the game a lot easier for rookie teams. I also think that the powerhouse teams would dominate that 10lbs much more than any rookie team ever could.

And hence I don't like the idea.

Matt

Bcahn836 22-08-2004 11:46

Re: Weight
 
You must also consider the shipping cost. The heavier the robot is the heavier the crate is the heavier the shipping bill is.

Billfred 22-08-2004 12:03

Re: Weight
 
I'm down with the above arguements, but I see two problems.

1) I do recall reading (although I can't say this officially) that FIRST robots as we know and love today are sized so that two average people can lift it and carry them through a normal doorway. Adding another ten pounds would start to make it harder to carry.

2) Adding weight starts us down a slippery slope. If in 2005 we get more weight, everyone'll jump for joy. Then we'll max out that extra ten pounds or so. Then we'll start complaining for more weight, since we got it last year. This, in turn, contributes to problem number one.

Just my thought process.

JAH 22-08-2004 12:38

Re: Weight
 
Quote:

Originally Posted by Cory
If the weight limit is raised 5 pounds, people will find 10 pounds more crap to put on their robot.

No matter what the weight limit is, a large number of teams will *ALWAYS* have trouble making it

Cory is exactly right. If teams got 5 more pounds, then they'd just make things more robust and add more to it and in turn be 5 pounds over that limit. I'm sure there would be some teams who would act blind to the new limit and be over a bit and be ok, but there are many who would not and would want to use every single pound available. The weight problems would stay about the same, in my opinion. I believe it should stay at 130.

Mike Martus 22-08-2004 17:29

Re: Weight
 
There are several important concerns that have been brought up here.

1. The 130 weight is a design constraint, part of the challenge.
2. Safety - 130 divided by two persons 65 each that is still a lot of weight if you fall or have a distance to go. A Major safety concern.
3. Next year I believe that the battery will not be included in the weight and there may be a gain if say FIRST decides that 120 lbs is the weight without the battery. A net gain of about 4 pounds or more.

No matter what the limit is set at, I believe that there will always be the "pushing of the limit" to build the best durable machine.

Teams that are consistently designing and end up with weight problems need to look at their design process and make corrections in "Weight Management".

Swampdude 22-08-2004 18:54

Re: Weight
 
For some strange reason we've never built a robot more than 135 pounds (prior to seriously considering weight reduction). Usually the kit material puts you in a standard range for extra robot material to wind up around 130-135 pounds, it's some kind of natural law. Anyhow, I have faithfully thrown my back out every year carrying these things on and off playing fields. But I still would like to see it go to 135. It has been our magic number.
This year we were really on the ball with weight reduction in the design (120 lbs) but, at the comps we had to beef her up to take the punishment everyone was dishing out, and wound up 131 minus shavings to 129.999.
The thing is, years past without trying too hard we got around 135, then this year we went overboard and got 120. It's not a big difference. Experience has taught me how to do a lot with 5 lbs - true. But inexperience and 5 extra pounds would make making robots (which is extremely stressful) much easier.
It would be good to see a weight study showing what the kit material puts you at for a typical bot configuration. Then see what kind of weight/mass ratio is left over. I bet it's not much.

ChrisH 23-08-2004 00:41

Re: Weight
 
Quote:

Originally Posted by Mike Martus
There are several important concerns that have been brought up here.

1. The 130 weight is a design constraint, part of the challenge.
2. Safety - 130 divided by two persons 65 each that is still a lot of weight if you fall or have a distance to go. A Major safety concern.
3. Next year I believe that the battery will not be included in the weight and there may be a gain if say FIRST decides that 120 lbs is the weight without the battery. A net gain of about 4 pounds or more.

No matter what the limit is set at, I believe that there will always be the "pushing of the limit" to build the best durable machine.

Teams that are consistently designing and end up with weight problems need to look at their design process and make corrections in "Weight Management".

Some tips for Weight Management

1) "budget" no more than 90% of the weight limit. ie if the limit is 130 lbs then the total estimated weight of all systems should be no more than 117 lbs.

2) Identify and quantify non-negotiable weight first. So know how much your controller, breakers, lights etc. weigh. Subtract this weight from the budget.

3) what is left is available for adding non-essential systems. Note: depending on the game, a drive system may be negotiable.

4) Assign budgets for all subsystems based on criticality. A really critical system should have a bigger budget than a nice-to have.

5) Do a weight estimate for any proposed subsystem BEFORE you build it. Hint we've found that Inventor is pretty good at weight estimates if you put in the correct material data.

6) Use your estimates to trade off between systems.

7) Resist the temptation to say "I think I can get a couple of pounds out" and then use the lower number. Every item in your estimate should have documentation to back it up. If you think you can take weight out, fine. Prove it first, then change the number.

8) Track the weight of each subsystem continually. If possible weigh each part before it goes onto the robot.

9) Use a spreadsheet for your weight tracking. Constantly compare actual vs estimated weight. Beat on the designers of subsystems that are over weight to get the weight out. The spreadsheet can also be used to identify "heavy hitters". Items that are extraordinarily heavy (and thus prime targets for speed holes) or items that use a lot of weight for minimal functionality.

10) Assign a single person whose whole job is to make sure you meet weight. We call ours the "weight czar" a term that comes straight out of the aircraft biz. In fact, at the "bird factory" I work in, every program has a whole department dedicated to tracking the current estimated and actual weight of the aircraft. We wouldn't do that if we didn't think it was important, there too many other things we need to throw bodies at to waste them on something unimportant.

11) Remember that nothing ever gets done within the budget. That's why you only allowed 90% at the beginning, to account for unknowns and overruns. If that doesn't work this year, then next year cut the budget to 85%

Stu Bloom 23-08-2004 09:24

Re: Weight
 
Quote:

Originally Posted by ChrisH
Some tips for Weight Management

...at the "bird factory" I work in, every program has a whole department dedicated to tracking the current estimated and actual weight of the aircraft. We wouldn't do that if we didn't think it was important, there too many other things we need to throw bodies at to waste them on something unimportant ...

Chris is ABSOLUTELY correct. Regardless of what the numerical limit is, it would benefit us all to use these weight management ideas.

Here at Rolls Royce we also have several people dedicated to tracking the weight of our engines. Any change that is proposed for any flight engine is heavily scrutinized for weight impact. We pay a hefty financial penalty if our engines exceed contractual weight limits.

dlavery 23-08-2004 10:16

Re: Weight
 
Quote:

Originally Posted by punkrawker303
Who want[s] a little more weight for there[sic] robot instead of 130lbs? I mean at the last couple days you [could] have more weight then you need or should have. I think they should add 5 more pound[s] to the weight limit. [W]ith this 5 pounds you could open the possibles [possibilities] with 5 more pounds. What could you add to your robot that is 5 pounds that could really help you? [S]o who likes the idea[?]

Have we considered the possibility that the teams that run up against weight problems each year just aren't taking 130 as a serious limitation until much too late in the process. They tend to do this because they are unconsciously thinking "130 pounds - that's a lot. We don't have anything to worry about - if we run into problems, then we will just cut a bunch of holes at the end." As a result, they don't plan their robot weight budget properly, and have to resort to hacking off entire subsystems or drilling 1482 lightening holes at the last minute.

I think we need to be going the other way. Rather than promote the belief that 130 pounds is a rather generous number, why not reduce the weight restriction to 120 pounds (or less)? I theorize that at 120 pounds, including the battery, nearly all teams will recognize that the weight restriction is a hard problem right up front and will begin to plan accordingly. As a result of the earlier (and arguably better) planning, I would predict that teams will have more weight-conscious designs and the number of last minute "slash-and-hack" weight reduction efforts will be reduced.

So, rather than increasing the weight restriction, we need to decrease it by 10 pounds or so (or just increase the mass of the battery or other non-negotiable parts by 10 pounds while keeping the restriction where it is, which would have the same effect). And then have FIRST throw a copy of the Atkins diet book in with each kit...

-dave

Greg Needel 23-08-2004 11:31

Re: Weight
 
i think i am going to take this discussion in another direction for a second. in this past year it seemed like it was a huge scandal about adding stuff to the robot during the competition and not getting re-weighted. while part of me would love to see the weight increased (make my hair stay in) part of me would like more of a challenge of decreasing the weight limit to 12o (giving a new challenge for the upcoming year) i think that as long as people still tend to bend the rules at the competition adding up to 5 lbs over weight and still competing i think that the weight limit should remain the same as it is still a great ch allege to some teams.

i personally think we should go back to alot of old rules like only using whats in the kit + 200 from small parts. that would be a challenge!

Peter Matteson 23-08-2004 12:00

Re: Weight
 
Two points:

1.) We used every motor except for a seat motor at the UTC Regional and still made weight with a 59 inch tall robot. This said the weight goal is not out reach. With a tighter electronics package to reduce wire we could have been under weight, but then we would have added more functions because we could. Most teams seem to feel if the goal is 130 you want to be no less that 129.

2.) I feel the weight is already too high to be safely handled by two people. I belive the OSHA policy is a 35 lb max without lift assist devices. As a guideline the company I work for likes to keep lifts even lower. I would actually like to see a weight reduction to challenge the veteran/powerhouse teams. Having to trade off weight durabillity and functionallity more in a game like last years would make an even better contest.

My $0.02

Gary Dillard 23-08-2004 12:29

Re: Weight
 
Our weight budgeting always seems to start something like this:

battery: 12 lbs
electronics / wiring: 10 lbs
chassis: 10 lbs
gearboxes/drivetrain: 100 lbs

remaining functionality: -2 lbs

I probably see it that way because I'm always in charge of remaining functionality, and it never seems like enough. I think 130 pounds is a good, aggressive weight limit, but truthfully we'll work to whatever the requirement is (higher or lower) and budget according to what's most important. We feel our drive train is the most important so we make it robust, but we have to make choices - is having two speeds worth not picking up a widget in this game?

Weights and cost work this way: start with a top down budget to all the components from the requirement (with margin) to see where you need to be, then do a bottoms up detail roll-up early on to make sure you can get there. We use goals and requirements - requirements add up to 130 and goals usually about 110. Update it frequently to make sure you're on track.

Bharat Nain 23-08-2004 12:43

Re: Weight
 
Quote:

Originally Posted by Dzdconfusd

2.) I feel the weight is already too high to be safely handled by two people. I belive the OSHA policy is a 35 lb max without lift assist devices. As a guideline the company I work for likes to keep lifts even lower. I would actually like to see a weight reduction to challenge the veteran/powerhouse teams. Having to trade off weight durabillity and functionallity more in a game like last years would make an even better contest.

My $0.02


I totally agree with you about the weight being a little too much for 2 people to handle. It's good we have carts and don't actually carry the robot everywhere.

I also think that 130 is just about right to include max.functionallity and still let two people carry it with moderate difficulty. I like the weight limit as of now because it is just enough to let us build what our wild imaginations tell us, yet safe. Reducing might limit us to a lot things, and increasing is a safety hazard.

Stu Bloom 23-08-2004 12:51

Re: Weight
 
Quote:

Originally Posted by dlavery
... And then have FIRST throw a copy of the Atkins diet book in with each kit...

How many carbs in aluminum?? :eek: :D :yikes:

miketwalker 23-08-2004 16:02

Re: Weight
 
I agree with Lavery, I think that 130 is pretty generous (even though I've seen us go over it, but usually by just a little). I think 120 would be a better idea then 135 or 140. In real life you can't just hope they'll bump up the weight limit. For example, shooting a payload into orbit (and especially if going out of orbit) you have to be very cautious with how you use your resources, because it costs much much more to launch something that weighs more.

One thing I would like to throw into the mix though as a thought, over the past 3 years I have noticed every year that the scales vary so much from competition to competition. In 2002, for example... at the local regional we weighed 129 pounds, yet when we got to Epcot for nationals... we were weighing in at 134. I think many others have run into this issue as well, and I personally wish that the scales were all calibrated equally... but at the same time... it makes you want to try to keep as far under the 130 pounds as possible, in case you happen to run into a scale that overweighs you by 5 pounds. The teams who don't look into that possibility could run into this problem, even if you design right around 130... so I'd suggest working around 125 because of this issue. Trust me, it'll save you tons of frustration.

Cory 23-08-2004 18:36

Re: Weight
 
Quote:

Originally Posted by miketwalker
One thing I would like to throw into the mix though as a thought, over the past 3 years I have noticed every year that the scales vary so much from competition to competition. In 2002, for example... at the local regional we weighed 129 pounds, yet when we got to Epcot for nationals... we were weighing in at 134. I think many others have run into this issue as well, and I personally wish that the scales were all calibrated equally... but at the same time... it makes you want to try to keep as far under the 130 pounds as possible, in case you happen to run into a scale that overweighs you by 5 pounds. The teams who don't look into that possibility could run into this problem, even if you design right around 130... so I'd suggest working around 125 because of this issue. Trust me, it'll save you tons of frustration.

At nationals in 2002 I remember that there were two scales that varied almost four pounds I think, so this is a very good point.

Mike Ciance 23-08-2004 20:27

Re: Weight
 
i remember a speech by Dave Lavery talking about the mars mission, and how he thought it was incredible how so many of the same aspects that go into FIRST also went into the building of the mars robots. size, weight, and material limits, objective tasks, required functions, etc. he said that the game really helps you with possibe real-life objectives. did he call up the people building the rocket and say "Hey guys, it's Dave. Uh, listen, could you maybe improve the rocket a little bit so I can make my bot 5 pounds heavier?" No, he accomplished the mission as it was, and did better than anybody ever imagined. doing the game every year within the 130lb weight limit is all part of the challenge, and i think it should stay the same.

Katie Reynolds 23-08-2004 21:56

Re: Weight
 
Quote:

Originally Posted by miketwalker
One thing I would like to throw into the mix though as a thought, over the past 3 years I have noticed every year that the scales vary so much from competition to competition.

I've noticed that too - it's frustrating but, unfortunately, it's another real-world thing we've got to deal with.

I agree with keeping the weight limit as it is. Having a weight limit of 130 lbs is something teams have been able to count on year after year for a long time. While it would add to the challenge of next year's game, I think lowering the weight limit would cause a lot of frustration among teams especially if it's lowered by as much as 10 lbs.

Upping the weight limit wouldn't help at all. Like Cory said earlier, if you upped it 5 lbs, people would find 10 lbs of stuff to put on their robot. If you upped it 15 lbs, they'd find 20 more lbs to add on. If you want to play that game, why have a weight limit at all? Oh yeah, because it's part of the challenge. It's a constraint teams have to deal with. If you don't want to worry about weight restrictions, go join Battlebots.

Sean Schuff 23-08-2004 22:58

Re: Weight
 
Quote:

Originally Posted by dlavery
Have we considered the possibility that the teams that run up against weight problems each year just aren't taking 130 as a serious limitation until much too late in the process.
-dave

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

dlavery 23-08-2004 23:46

Re: Weight
 
Quote:

Originally Posted by Katie Reynolds
Having a weight limit of 130 lbs is something teams have been able to count on year after year for a long time. While it would add to the challenge of next year's game, I think lowering the weight limit would cause a lot of frustration among teams especially if it's lowered by as much as 10 lbs.

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

Sean Schuff 23-08-2004 23:55

Re: Weight
 
Quote:

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

-dave

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

Stu Bloom 24-08-2004 00:17

Re: Weight
 
Quote:

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

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.

ChrisH 24-08-2004 10:35

Re: Weight
 
Quote:

Originally Posted by Stu Bloom
II 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.

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.

dachickindapit 24-08-2004 11:57

Re: Weight
 
Quote:

Originally Posted by ChrisH
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 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.


Quote:

Originally Posted by miketwalker
One thing I would like to throw into the mix though as a thought, over the past 3 years I have noticed every year that the scales vary so much from competition to competition. In 2002, for example... at the local regional we weighed 129 pounds, yet when we got to Epcot for nationals... we were weighing in at 134.

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.

Mike Betts 25-08-2004 17:09

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!

Andrew 26-08-2004 09:45

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?

phrontist 26-08-2004 15:24

Re: Weight
 
I think we're heading towards less weight actually...

Mike Ciance 27-08-2004 22:26

Re: Weight
 
Quote:

Originally Posted by dlavery
It would do more to "level the playing field" between veteran and rookie teams than almost anything else FIRST could do.

"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.

Chris Fultz 28-08-2004 00:39

Re: Weight
 
Quote:

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

-dave

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.....

Steve W 28-08-2004 00:53

Re: Weight
 
Quote:

Originally Posted by Chris Fultz
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.....


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

Biff 30-08-2004 22:53

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.

Matt Adams 16-01-2005 10:09

Re: Weight
 
Quote:

Originally Posted by Mike Martus
3. Next year I believe that the battery will not be included in the weight and there may be a gain if say FIRST decides that 120 lbs is the weight without the battery. A net gain of about 4 pounds or more.

Congrats on an accurate FIRST prediction!

Matt


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