Springs?? (10 lbs. at 22 ft/s)
 

Does anybody know if there is a kind of spring with enough force to fire 10 lbs. at 22 feet per second? If so, where is the website? Thank You.

Re: Springs?? (10 lbs. at 22 ft/s)
 

http://coilspring.com/

- Renton Coil Spring (where I work)

They specialize in high performance materials and applications, titanium and steel for aerospace, nascar, nhra etc. I doubt you would be able to get anything sub 500$ though as it is a job/specialty shop :/

Seems like a garage door spring or something similar could get you in the right ballpark but for that much force and acceleration the systems would be come quite scary and heavy!

Find one of those playground toy springs :) You could look into gas springs, but I think generally they will be slower than you are looking for. Maybe with a lever or other way of adjusting speed/force.

Re: Springs?? (10 lbs. at 22 ft/s)
 

I'll do the calculations for you, but you should be VERY careful about launching a 10lb ball at such a speed. FIRST may deem it a safety hazard.

You want to accelerate 10lbs to 22 ft/s. The potential energy stored in a spring is .5*k*x^2, where k is the spring constant (basically, the stiffness of the spring) and x is the deformation or extension of the spring.

10lbs traveling at 22 ft/s means a kinetic energy of .5*m*v^2, or 102 Joules (after conversion to SI units). Thus, you need at least 102 Joules of potential energy from the spring.

There are two ways to do this - either get a higher spring constant, or compress the spring more. So for a given spring constant or compression, you can alter the other factor to yield the potential energy you need.

Now let's look at McMaster's website.
http://www.mcmaster.com/param/dsc/dsc.aspx?dsc=Springs

All you have to do is find a combination of spring constant (also called rate on some pages) and compression distance that work for you. There are plenty of options there.

Re: Springs?? (10 lbs. at 22 ft/s)
 

I did the math assuming that you wanted to launch the ball at a 45-degree angle in order to maximize the 'sweet spot' for shooting, and found that the spring requirements are unreasonable. (From the floor to over the overpass was 221 J not including losses due to the game happening in real-life as opposed to a physics classroom -- the spring constants needed were **huge**.)

The other problem is that you cannot transfer the energy fast enough to launch the ball without running awry of the safety requirements.

Patrick

Re: Springs?? (10 lbs. at 22 ft/s)
 

emphasis added ...I am curious where you located any specific "safety requirements", and what the defined limits are?

Re: Springs?? (10 lbs. at 22 ft/s)
 

I wouldn't advise using a 45 - the force required is nuts and if that device fails it could potentially hurt someone. We thought about a garage door spring as well but those are dangerous - people have gotten cut badly by them.
60 is a little steep but you don't need to spend so much energy in the horizontal if you fire your device while moving forward. You only need to get the ball up 6.5 + a little, you don't have to clear the entire overpass.
Someone on here in another thread calculated an estimated 44.7% energy recovery on impact for a trackball. That's just in estimate - but the ball should in theory bounce off the overpass rails if you get it up there.

Don't take my words as your 100% valid source - the majority of the time I'm wrong. But in seeing my wrongs I learn.

Re: Springs?? (10 lbs. at 22 ft/s)
 

I honestly think that 22 ft/s is way too fast. They limited AIM high balls to 10m/s which is 32 ft/s. That is for 6 inch poof ball of 3 ounces or so and the game was designed to shoot the ball. We are hurdling the ball. 2/3 of the speed for a ball that is 40 times the mass and about 7x the size. In addition, you cannot even begin to pull that back. The springs that could do that are car springs which are compressed by 500 pounds of force for a light car. The 2 inch cylinders can provide at absolute maximum 189 pounds ( and that's not for compression!). You'd need 3 2 inch bore cylinders to do so. Even if you pull it back like this... they your not going to have enough air to do so. 189 pounds is at 60 PSI and your psi would significantly drop because the amount of air you would need.

Re: Springs?? (10 lbs. at 22 ft/s)
 

I think we calculated it would take about 80 J to launch the ball over the overpass.

But we also assumed this would be an acceptable means of hurdling--could someone please explain their safety concerns, as specific rules apply?

We are NOT planning on using a metal spring, in case you're concerned about that....

Re: Springs?? (10 lbs. at 22 ft/s)
 

I think the concept of launching has many people in first worried. The calculations we did about launching a ball came out to be
65-75 degrees is the ideal angle, but you need something about 7.8m/s just to get the ball over the rack when ur 3 meters away from it. Something that fast in Very dangerous in the wrong hands :P

Re: Springs?? (10 lbs. at 22 ft/s)
 

There are no rules expressly mentioned that limit the amount of throwing force or the velocity of a launched ball.

If FIRST plans to add some they better do it quick...cause we're launching and we've already started. :eek:

IMHO part of the intent this year is to have teams design all sorts of mechanisms that do their job safely.

If you want to launch you better have your ducks in a row when an inspector asks you to demonstrate its safety features.

Re: Springs?? (10 lbs. at 22 ft/s)
 

If your mechanism is designed properly, then all of the stored energy will go into the ball. Hopefully the teams trying this will use a smaller force over a longer distance to accelerate the ball, which would mean that there really wouldn't be any super fast moving parts if it fired while a ball was loaded. The real danger is if it fires without a ball to put all of it's energy into, but hopefully teams will design safety features that will (mostly) eliminate this problem.

I really don't see where the danger is if it's working properly. A ball that was thrown over will hit the ground with about the same speed as a ball that was dropped over. Unless we should all be required to set the ball down on the ground for ultimate safety? :)

Re: Springs?? (10 lbs. at 22 ft/s)
 

I don't believe the inherent danger is from the ball.
It is from the "cocked" mechanism.

If this mechanism is ready to shoot the ball...the mechanism, if tripped accidently, will impart the same force to whatever object or human body part is in it's way.

Stored energy of any form can be quite a pain to deal with... no pun intended.

Here is the rule that I think is relevant to this discussion:

(R01) ….. Teams must very careful when incorporating springs or other items to store energy on their ROBOT by means of part or material deformation. A ROBOT may be rejected at inspection, if, in the judgement of the inspector, such items are unsafe.

This gives the inspector considerable latitude in deciding the safety of the ROBOT.

Good luck to eveyone...

Hi Stu!!!

When you control the ball...you control the game.... PELE

Re: Springs?? (10 lbs. at 22 ft/s)
 

Exactly. The rules regarding safety are vague enough to give the judges/refs sufficiently leeway to keep us all safe -- and that means you need to be really careful about putting that kind of load on springs.

Patrick

Re: Springs?? (10 lbs. at 22 ft/s)
 

I think that Most judges will allow robots to have "Springs" or other devices ont heir robot no matter what it is they do as long as it is confined and not able to dismantle another robot. Like if a robot had some device that shot 1+ feet in any direction thats outside of their starting box, they would probably deem it unsafe, especially if you need 7+m/s force to get a ball up.

Re: Springs?? (10 lbs. at 22 ft/s)
 

These numbers are similar to what we've come up with. I'm not sure where 22m/s came from...

From the rules:
Inherently, to hurdle one must also have a vertical projection on the ball. They have left the door open for teams to shoot the ball over the overpass. I think <R01> is there to ensure a compressed spring isn't being held back by shoestrings or other objects that could easily release energy outside of the arena and really hurt someone. I do not believe it's there to inhibit how you get the ball over the overpass.

You can't be afraid to fail if you want to launch the ball. It's a gambit, and the rules have technically left the option open for you. However, if you keep shooting balls out of the arena at refs, then perhaps they will deem your bot unsafe, but that's your driver's fault ;)

Re: Springs?? (10 lbs. at 22 ft/s)
 

22 ft/s is about 6 or 7 m/s

(English units vs. metric units)

Re: Springs?? (10 lbs. at 22 ft/s)
 

Whoops :o

Re: Springs?? (10 lbs. at 22 ft/s)
 

Well I guess it's safe to say that the majority of us agree that any type of spring would be dangerous to use for this. The massive amount of force required requires a LARGE spring which are dangerous.

What I find interesting though is that so many people are getting different energy requirements for launching it though. I've seen numbers ranging from 5 J to 80 J. I know it depends on the angle but my teams estimated 7.5 J at 65 (I think degrees) is vastly different then then post above that gives that 80 J estimate.

Re: Springs?? (10 lbs. at 22 ft/s)
 

If you figure that the mass of the ball is ~3.5 kg and you want to shoot it to a height of 2.5 meters (a little over 8 feet) then:

(3.5 kg)*(9.8 m/s^2)*(2.5 M) ~ 86 Joules

This is assuming that the horizontal componant of the balls velocity comes from your moving robot.

(posted by s_forbes on dad's computer)

Re: Springs?? (10 lbs. at 22 ft/s)
 

I believe you've misread the definition of CROSSING. For "it", read "line". The definition refers to projecting the line to indicate a theoretical flat surface through which a ball or 'bot will move. Imagine light shining straight upwards from the line. It's not talking about throwing the ball.

Re: Springs?? (10 lbs. at 22 ft/s)
 

squirrel I am with you 100% on this one. I do not see this being a safety hazard if design correctly.

And as for some of you people who are thinking of a large spring being pulled back to hit the ball with brute force, i think you should try thinking outside the box for a few ;).

Re: Springs?? (10 lbs. at 22 ft/s)
 

What if you were the inspector, what would you be looking for?

How secure is the spring attached to the robot?
How secure is the launching pad between the trackball and spring?
What has been done to protect against pinch points between the launcher and robot?

These are just a few of the questions I would have (not and inspector). What other ones could you ask.

Aside: Putting your robot on display (grade schools, sponsors etc) will be a riot if you can hurdle the trackball 7-8 feet in the air! The only problem will be getting that blasted 41" trackball through a standard door.

Re: Springs?? (10 lbs. at 22 ft/s)
 

If you're imparting 100-200 joules into the ball, be sure that the centerline extends back inside the wheelbase, or do the math carefully so your bot doesn't do a back flip.:yikes:

If I were an inspector, I would also try to be sure that nobody's head is likely to be launched instead of the ball.

Re: Springs?? (10 lbs. at 22 ft/s)
 

How would we go about testing the amount of force needed to propel the ball 8 feet in the air and once we go about testing that, and based on that calculation how would we quantify that in order to find how much energy would have to go into the ball? For example, we did a lever arm experiment where a mentor jumped on a lever and the ball was on the other side. We have the numbers and have calculated the energy lost from the jumping onto the lever to the ball leaving the lever. But we don't understand where to go from that point and I also don't believe that we calculated correctly. Any help would be greatly appreciated. Also based on that number, how do we determine what strength of spring we need.

Re: Springs?? (10 lbs. at 22 ft/s)
 

As an inspector, in addition to the intended function of the launcher, I would look for possible unintentional means of sudden release of this stored energy. Having a strong spring release accidentally while the robot is being carried on the field or in the pits can have very dire consequences. FIRST inspectors must decide whether your launcher is safe and that is a subjective judgment call. Expect to show the inspector how the spring can be inhibited from releasing accidentally (including failure of the firing restraint), how you can slowly/gradually release the energy in case you don't want it to fire and how the launcher responds when it fires without a ball.

You're probably not going to find a written, official checklist from FIRST, so you have to keep asking yourself what can go wrong and how can I avoid accidents as you design your launcher.

Re: Springs?? (10 lbs. at 22 ft/s)
 

This is my point. I'm not trying to rain on anyone's parade, but better to hear it now than to get to competition and be disqualified for safety reasons (so that you have to dismantle your launcher and just be a race-bot for the rest of the tournament).

I did the math at 45 degrees and 2.5 meters and found the initial kinetic energy requirement to be 221 Joules (accounting for reasonable assumptions on energy loss, etc.).

I think that teams who try this method will (a) be disappointed in just how -hard- it is to throw that ball with a robot and (b) will be disqualified from play until they disengage their springs.

That said -- more power to you if you want to try.

Patrick

Re: Springs?? (10 lbs. at 22 ft/s)
 

I think that you'll be amazed at the designs the different teams come up with to solve this challenge....putting twenty or thirty thousand creative minds to work to solve a problem can result in wonderful things.

Re: Springs?? (10 lbs. at 22 ft/s)
 

Patrick,
I think you need to sit back and think long and hard about what you just said, especially to other young minds around this forum.

"That said -- more power to you if you want to try"

Do you know how many great inventions probably started with the exact same sentence?? I would bet almost all of the great ones.

Teams WILL throw this ball, and teams WILL do it safely, and teams WILL do it effectively.

The bigger the risk, the bigger the reward...

For the teams jumping "into the deep end", we're with you, and we're proud..


Brando

Re: Springs?? (10 lbs. at 22 ft/s)
 

I'd love to see it, and I hope it works out well -- nowhere in my remarks was I being in any way sarcastic. I wasn't even being _pessimistic_.

It is not unreasonable to point out that certain approaches are harder than others, and also that the act of physically launching the ball carries a great deal more safety issues tied up in it than lifting the ball in some manner.

I certainly _do_ hope to see safely-launched balls. I certainly _do_ hope that all teams rise to the challenge of this game in the best way that they know how. I certainly _do not_ want to see teams that cannot hurdle at all because they haven't fully considered all of the ramifications of their approach, and now have a robot that will not be allowed to play based on safety concerns.

How awful would it be to show up with a fully-functional, killer-app bot and then not be allowed to use it? The fact that the judging of the safety is both discretionary and subjective just means that even more caution needs to be taken.

It _is_ quite amazing what thirty-thousand minds bent to a single task can accomplish. I'm sure some teams will pull off safely-launched balls, and be both effective and amazing. I'm *not* so sure that they'll do it with a spring capable of throwing 10 lbs at 22 ft/sec, which is the topic of this thread.

Patrick

Re: Springs?? (10 lbs. at 22 ft/s)
 

I think you're probably right about it being quite difficult to do this safely with a spring.

Which is why I suggested considering using something else (perhaps compressed air?) instead....here where those folks thinking about using a spring might be likely to see it.

Anyways, if you are a team that is thinking of shooting the ball using a spring type mechanism, it might be wise to post your ideas here so others might be able to point out safety issues, or suggest other ways to do it better. My opinion is that you have little to lose by posting your designs, and a lot to gain if it helps you improve it in ways you didn't realize it could use improvement.

Re: Springs?? (10 lbs. at 22 ft/s)
 

The energy to launch a ball is lot. I'm concerned with having that much energy stored in a mechanism on a robot. If the release mechanism fails and the energy can not be released by remote means how is a team going to defuse the bomb. What happens if the device is cocked with out a ball and it is accidentally released. What if a small object like a bolt was on it when it was accidentally released or a hand was in the way. This seams like a risky path for teams to take. Think long and hard before going down it. Because something can be done does not mean it should be done.

Re: Springs?? (10 lbs. at 22 ft/s)
 

The energy to launch a ball is similar to the energy the ball has when it's sitting on the overpass. Hmmmm.....

A nice thing about air, is that it can be released with a valve that is accessible away from the launch mechanism.

Re: Springs?? (10 lbs. at 22 ft/s)
 

An idea from team 885

What about using an "air spring?" (See McMaster Carr catalog.) I'm not talking about those gas springs that hold up the trunk of your car, but an industrial air spring.
The spring could be charged up for every shot by the compressor, and then left discharged (relaxed) to reset the device. You would need a sturdy release mechanism acting upon some kind of sturdy boinker.

jim wick
mentor for team 885

Re: Springs?? (10 lbs. at 22 ft/s)
 

You can use the Bimba cylinders that are listed in the pneumatics manual, but you cannot use other pneumatic devices, so it would probably be illegal to use what you suggest.

But the Bimba cylinders can be used the same way, if you think about it....start out with the cylinder partly extended, fill it up with compresssed air, release a catch, and the ball goes flying.

Re: Springs?? (10 lbs. at 22 ft/s)
 

Patrick,
I apologize if you think I was be condescending earlier. And you are correct that it is not an easy task to launch a ball safely.

However, I am 100% certain it is going to happen, as I'm sure you are. I just feel you may want to be more careful in what you say (as what you said sounded pretty pessimistic, even if you said it in an optimistic way).

Brando

Re: Springs?? (10 lbs. at 22 ft/s)
 

Im not saying this will be safe but. use a Constant force spring, they dont even look like springs haha, they use them in car seatbelts. Our sponsor Vulcan spring corp. Is the sole manufacturer.