Proposed New Rule M11

Competition Rules/Strategy
1

FIRST’s answer to a request for relief from rule M11’s limit on energy stored in a spring at the beginning of a match is to ask for a proposed new rule for them to consider.

I propose the following replacement for the second bullet of M11:

Storage achieved by deformation of springs or latex tubing;

However, safety is a very serious concern when using springs as an energy source. Teams should be especially careful because large amount of energy can be stored in springs. More importantly, this potentical energy can be very rapidly converted to kinetic energy possibly endangering workers, drivers, and spectators.

Therefore, if a spring or series of springs in combination are used to power a mechanism of the robot and the energy stored in the spring or springs is stored in the springs prior to the start of the macth, then one of the following two conditions must be met:

  1. the energy stored in the spring or springs must be relatively small (less than 20 ft-lbs = 28 Joules = 28 N-m).

  2. the energy stored in the spring or springs must be released at a controlled rate (under 1000 N-m / second = 1000 Watts).

For example, if the spring has stored 2000 Joules of energy it must take at least 2 second to release all its energy. Similarly, a spring with 500 Joules stored in it can release its energy in .5 seconds.

Safety is the overall concern of this rule. Even if the energy of the spring is stored after the match begins, please be careful to store and release that energy in a safe.

Comments?

Joe J.

2

There should be an absolute cap on the energy storage in springs. Otherwise, a team good gain a real advantage by, say, making a spring powered flywheel.

I would suggest, in addition to your statements:
Total energy stored in all springs cannot exceed ___ Nm.

I don’t have a good number for the blank.

Also, how would you determine the rate of energy release from the spring? Even if FIRST relied on gracious professionalism for teams to honor the energy release restriction, teams would need to have a procedure for determining this themselves. Otherwise, you would need a safety inspection at competition.

FIRST could verify the energy storage restriction by asking for the spring constant and the amount of deformation, both easily obtainable/verifiable.

Andrew, Team 356

3

I like the part reminding teams about Safety. I believe FIRST will gladly add that part to the rules, If nothing else.

A side thing I got to ask: What’s the best way to convince FIRST to change rules into something we think is better? I know petitions are never really effective… Same with sending FIRST massive e-mails. So… How are you going to convince FIRST to change rules?

I am really interested in finding out if FIRST have a process for teams to submit official modification to rules, aside from doing the team forum.

4

I really don’t think that an absolute cap on energy stored in spring is required because it is quite difficult to actually store a HUGE amount of energy in a spring given the other rules of FIRST (weight, safety, cost and size).

The energy in the Battery is very very large in comparison to anything you could pull out a spring with a 1000 Watt removal limit.

The battery can quite easily provide an average of 100 Amp at 10 volts for the entire 2 minutes – that amounts to 1000 Watts for 120 seconds or 12,000 Joules.

It would be difficult to store anything like that about of energy (legally) in anything other than latex tubing. I have not done a sharp pencil analysis but from what I can do in my head, I think it would take over 500 feet of tubing. Not impossible but not exactly easy either.

If we have to put in an absolute limit, I would make it pretty high, perhaps something like 3000 Joules (taking Mike Betts’ number of 2 orders of magnitude higher than the limit FIRST set of 30 Joules). The exact wording would perhaps go like this:

No more than 3000 Joules of the energy stored in springs at the beginning of the match can be used to power your robot.

Comments?

Joe J.

5

As to how will FIRST verify that we are meeting this rule, I agree that gracious professionalism is going to have to rule the day.

But… …even so, it is not rocket science to estimate the amount of energy that your robot uses from springs:

(Force Initial - Force Final) * (Length Initial - Length Final) / 2

It is equally easy to estimate the time it takes to release this energy given a stopwatch or a few lines of PBASIC programming.

Power is a simple matter of division.

I think that this is no more burdensome than the accounting calculations teams are having to go through to keep track of the $3500 limit. In fact, I suppose it is several orders of magnitude easier, given reuse of some raw materials, new labor rules, fair market value of donated goods, etc.

Comments?

Joe J.

P.S. Picky folks may point out that Compression springs will require an abs() in the energy calculation. JJ

6

This is the text I submitted for FIRST for consideration:

I propose the following replacement for the second bullet of M11:

Storage achieved by deformation of springs or latex tubing;

However, safety is a very serious concern when using springs as an energy source. Teams should be especially careful because large amount of energy can be stored in springs. More importantly, this potential energy can be very rapidly converted to kinetic energy possibly endangering workers, drivers, and spectators.

Therefore, if a spring or series of springs in combination are used to power a mechanism of the robot and the energy stored in the spring or springs is stored in the springs prior to the start of the match, then one of the following two conditions must be met:

  1. The energy stored in the spring or springs must be relatively small (less than 20 ft-lbs = 28 Joules = 28 N-m).

  2. The spring energy used to power the mechanism must not be excessive and must be released at a controlled rate. Specifically both of the following two sub-conditions must be met:
    a) No more than 3000 Joules of the energy stored in the spring or springs at the beginning of the match can be used to power the mechanism.
    b) The spring energy must be released no faster than 1000 Joules / second (1000 Watts).

For example, if the spring has 2000 Joules of energy available to power a mechanism of the robot, it must take at least 2 second to release that energy. Similarly, a spring can provide 500 Joules to the mechanism, the robot can access it in .5 seconds.

Safety is the overall concern of this rule. Even if the energy of the spring is stored after the match begins, please be careful to store and release that energy safely.

7

I think Joe’s proposal for revising M11 is quite reasonable. I ran a couple of numbers in coming to this conclusion.

The power or rate of release criterion is no problem for applications of counterbalancing the weight of a mechanism, since the mechanism’s motor does a reasonable job of defining and limiting the speed of motion. I was curious though about applications with less controlled rates of release - like flinging a container - so I looked at that.

Launching a container from the edge of one ramp at an angle of about 54 degrees above the horizontal at a velocity of about 26 ft/sec will allow the container to just clear a 5’ tall 'bot on top of the platform and hit the field just at the end of the opposite ramp. The flight time is about 1.3 seconds. These numbers ignore aerodynamic effects and are idealized and approximate (but close).

I assumed the robot exerted a constant force (a la gas spring) on the container to accelerate it up to 26 ft/sec from rest along a 3’ long path. The force required in this scenario is about 14 lbf, and the energy input (work done) is 42 ft-lbf. The time required to accelerate a 4 lbm container to 26 ft/sec with a 14 lbf net force is about 0.23 sec, so the rate of energy transfer to the container by the mechanism is 42 / 0.23 = 183 ft-lbf/sec ~ 250 w. I didn’t check these numbers very well, but I think they are reasonable.

The point of all this is, I don’t think that Joe’s proposed numbers are restrictive of some crowd-pleasing robot design possibilities, while the original M11 numbers are onerously restrictive. BTW, I realize that M11 deals with energy stored at the beginning of the match, whereas any spring-powered multi-shot container launcher would have to recock itself by motor or pneumatic means during the match. I also realize that the rules restrict launcher powering to the use of elastic tubing, whereas I assumed constant force gas springs in my example for calculation ease. This was just to make sure that clever sheep on 47 wasn’t slipping anything past all the rest of us.

Dodd

8

After an initial promising response from FIRST (a request for a proposal for a new M11 concerning springs), updates 7, 8 and 9 have had no mention of relief from the 30 Joule limit.

I suppose that it is not going to happen.

I think this is a silly rule, but if FIRST has the rule it is a rule.

I recommend that you design your robot without counter balance or figure out a way to do it within the rules as currently written.

Remember that compressing the smallest gas spring from Small Parts Inc. before the match would violate this rule.

FIRST has called for Gracious Professionalism with regard to this rule, but I don’t know exactly where gracious professionalism leads me in this case. Is it gracious professionalism for me to look the other way when I see a robot with an illegal amount of spring energy? Is that fair to the teams that tried to live with the rules FIRST sets, no matter how unreasonable?

I don’t like this rule, but at this point, it is getting a little late in the game to change things now…

…I still think FIRST should change the rule but I am torn again about teams that have tried to live with the rule as it is.

Time will tell…

Joe J.

9

Below is quoted a question and answer from the FIRST BB:

M11 Use of Purchased Gas Springs
Home » Forums » Robot Rules Q/A
posted by: estokely (Jan 15, 2003 4:44 PM)
From: Tacoma Washington
Registered: Jan, 2003

M11 Use of Purchased Gas Springs Posted: Jan 15, 2003 4:44 PM

In the past we have been able to use Small Parts Gas Springs as an aid to arms etc.

If they are not compressed beyond 20 ft lbs at the start will they still be legal?

[Edited by: first on Jan 16, 2003 4:06 PM]

first

Posts: 961
Registered: Dec, 2002

Re: M11 Use of Purchased Gas Springs Posted: Jan 20, 2003 2:13 PM

Yes, gas springs are allowed.

OG1 ____________________________________________________

FIRST’s answer, in their typical terse fashion, fails to clarify whether the relaxed initial condition of the gas spring, as asked in the question, is implicit in their answer. M11 still stands as originally released, as you point out, and it would seem to clearly say that any gas springs on the robot must contain no more than 30 Joules of stored energy (per mechanism) at the beginning of the match. So I assume that FIRST means gas springs may be used if they are (mostly) relaxed at the beginning of the match.

My continuing problem with this rule is that I don’t understand how it improves safety, its presumed intent. Yes, it limits the “spring” energy stored in each mechanism before the match, when people may be in close proximity to the machines. That’s fine.

FIRST seems to be saying however, that cranking unlimited amounts of spring energy into a mechanism during the match, using motors or pneumatics, is allowed. OK, no people are near the machines at this time, so no problem.

Now, match over. Everybody come out onto the field and disentangle your bots’ mechanisms, fold them back up, release those latches, relax those springs. And be quick about it! No rules speak to the hazards involved in this part of the match, and I believe that M11 is in fact counter-productive. It will cause less safe conditions in terms of potential rapid energy release than previous years’ rules, in my opinion.

I’m sorry to just vent unconstructively, but I am confused by FIRST’s inaction. They invited a concrete suggestion, Joe provided a reasonable one, and now they have let too much time go by for teams to incorporate any relief in their designs. Too bad.

Dodd

10

I think that Joe and Dodd are right on the money on this one. The so called spring energy rule is so typical of FIRST, in that it is so ambiguous and difficult to understand that I believe many teams will simply ignore it, hoping that FIRST inspectors won’t have the know how or capability of calling them on it.
It’s just ridiculous to talk about stored energy in springs without including gas struts, and even pnuematic cylinders also.
If this is suppose to be about safety - it doesn’t address the occurrences after the match starts including the time needed to move the robots off the field. If its suppose to be a safety net for the audience it missed the mark even worse, as many machines will potentially have alot more energy in other devices after the match starts.
Unfortunately, the watermark or requirement is set so low that many, many, many team s will violate the rule without even knowing that they did. Teams that do think of creative ways to comply, will not be rewarded if the inspectors simply ignore the rule - FIRST should explain exactly HOW this rule will be validated during inspection, so every team is aware and cannot claim they didn’t know.
It’s hard enough for many teams just to make the weight and size limitations, while still trying to get the darn robot to work, let alone deal with one more nightmare engineering problem in the pits when they find out they are illegal, due to having to much counterbalance holding certain parts in the required starting position.
I recognize that it’s far to late to totally change the rule, but can’t they at least provide something that would help unsuspecting teams, or teams that simply choose to ignore the rule - some kind of guideline to help them do a sense check of if they are legal.

11

I have spoken with anyone who would listen at FIRST, trying to convince them of the case for changing the M11 rule concerning spring energy.

After a lot of soul searching, FIRST has decided to keep the rule as is.

At this point, I cannot disagree with them. They have been clear on what the rule is from the beginning. We may not like it, but it has been a clear answer. To change things now would put teams that tried to follow the rule at a disadvantage.

So… …put your spring winding plans in action or live without effective counter balance.

As to where gracious professionalism leads, I think that teams that do not meet the rule should be forced to remove their counter balance – it is no different than not making weight or not fitting in the box. The rule is clear: If it powers a mechanism of your robot, you can store no more than 20 ft-lbs of energy in it at the beginning of the match, PERIOD.

It is not fair to the teams that expended weight and time and energy complying with the rules to have to compete with folks that are in violation (through ignorance or through deception).

It it not gracious professionalism to look the other way. I don’t think folks should get rude or ugly about it, but I think that FIRST officials should be notified and that FIRST should review the case and enforce the rule if needed.

Calling 'em as I see 'em.

Joe J.

12

Joe,

I agree with your statement, but I believe this is true of all the rules.

13

The reason I am calling for folks to help FIRST realize what teams are in violation on this rule and I have not called for citizen police on other rules is threefold:

  1. FIRST has as much admitted (on the jive.ilearning site and in updates) that they are not going to be able to police this.

  2. FIRST has called on gracious professionalism with respect to this rule. What I don’t want is for teams to feel that a rule that is more or less governed by gracious professionalism does not mean that we cannot help them realize when a team may have crossed the GP line

  3. Finally, I really wanted to start a discussion around the idea that enforcement by GP puts the burden on TEAMS TO COMPLY not on COMPETITORS TO TURN A BLIND EYE TO CLEAR VIOLATIONS. In fact, GP enforcement puts a stronger burden than ever on teams to help FIRST confront clear voilations.

As FIRST grows, I believe peer pressure will become more and more important to make sure that GP is the rule and not the exception.

Sorry for the soapbox, but I feel the point is worth making.

Joe J.

14

I agree with Joe’s points, especially #3, which is essentially a scaling issue with FIRST’s growth model. But I think that FIRST needs to help teams comply professionally with the rules by avoiding the making of rules which contradict standard good engineering practise.

I can understand and sympathize with the engineer who reads the rules and then dives into the design of some of the robot systems as his or her training and experience guide, simply zoning out that some absurd rule forbids good practise.

What do you mean, I can’t null out the gravitational load before applying the system drive motor and its precision control system? You want me to add that load to the system drive train, which may increase the drive train load by an order of magnitude? There can’t possibly be a rule that means that - this is supposed to be about showing kids how to be smart and clever and safe and thorough and to design things that want to work.

If FIRST makes rules that are contrary to good practise, that are inscrutable in their intent, that do not clearly improve safety - and M11 really misses the mark here - then some well intentioned and thoroughly gracious professional engineers are going to run afoul of the rule. Remember, not everybody in this exponentially expanding community reads the Delphi Forums - splendid as they are - and many may be oblivious to the interpretive scrutiny M11 has received here.

So, I’m afraid that it may be ugly. Some teams will show up at Competitions clueless that their robots are crosswise to M11. Other teams must not turn a blind eye. The offending counter balancers/etc are removed. The mechanism drives cannot be re-engineered in the pits, and the teams drive around with a dysfunctional robot. Worse, mechanisms break and fall, fingers smash, motors smoke, fires happen.

What really distresses me, and then I’ll shut up, is that FIRST lost sight of the fact that good practise IS safe. That’s part of why it is good practise. FIRST has a good history of progress in relaxing arbitrary and onerous rules and restrictions on robot construction over the years. I’m hopeful that they will keep their eye on the fact that gracious professionalism and good practise are strongly linked.

Dodd

15

I really think this is just one that got past FIRST.

While we here on the Chief Delphi Forums were worrying our hearts out about the M11 rule, FIRST folks had many other fires they deemed more urgent.

By the time it got through to the right people, FIRST felt too much time had passed to make a such a significant change.

All I can say is it was not for lack of effort on the part of the folks on the Chief Delphi Forums that this one fell through the cracks.

We did our best, it will just have to wait for next year for relief.

I really think this issue makes a strong case for FIRST to publish a “beta” set of (game independent) rules prior to the competition kickoff. This would allow for a comment period which would give FIRST time to make clarifications and changes before any official rules were out there causing confusion and heartburn.

Perhaps in the future…

Joe J.