How Loud is Too Loud? (Cal Games)
 

Team 100 has been spending an enormous amount of time preparing our robot for the California Robot Games.

We have rebuilt our ball-lifter, completely redesigned our 3-pt shooter, tuned up the drive train, and rebuilt our hopper.

But we have a problem. Due to a lack of sophisticated tools we were never able to balance our shooter. When spun at top speed it releases the most deafening racket I have ever heard on a FIRST robot. It quite literally sounds like a jackhammer or possibly even a machine gun. :eek: .

We don't know what causes this problem. The best hypothesis seems to be that at a certain speed the shooter's chain begins to vibrate making noise.

In fact, if it weren’t for the noise it wouldn't seem that anything was wrong. It seems to run fine, nothing breaks. We have also encased the entire shooter mechanism in fine-mesh chicken wire so that if anything did go wrong it probably wouldn't go flying.

My question: is our robot safe enough to compete? It sounds dangerous but it really isn't.

Re: How Loud is Too Loud? (Cal Games)
 

Well, it is good in one way I guess. It gives more for the announcers ;) to comment on. :)

Re: How Loud is Too Loud? (Cal Games)
 

From your description, it seems that a mechanical reasonance is being excited in your chain at a specific speed. In general, chains are meant for slow speed operation, where such reasonances do not occur. If you have any flexibility in the mounting, shorten the chain as much as you can.

Safety will be the most important concern of the technical inspectors for the Cal Games, as it always is at a FIRST competition. If you are concerned about whether a mechanism on your robot is safe (making sounds like a jackhammer or machine gun are not great indicators) you can be sure that technical inspectors will be concerned as well. It can't be judged, however, until it is seen (and heard) at the Cal Games.

See you there...
Eugene Brooks

Re: How Loud is Too Loud? (Cal Games)
 

our team had a problem like this at last years Davis Regional except along with making noise we kept throwing our chain off too. We fixed the problem by going to a belt drive and never had a problem after. Chains are just to troublesome when the are long. If you need to connect something long use a belt!!!!! hope this helps

Re: How Loud is Too Loud? (Cal Games)
 

I'm sorry,
but I believe our robot was the loudest... Even at 20% of the max speed the refs constatly said it was too loud and annoying.


Too bad I won't be at the cal games to truly see which team has the loudest robot ever.

I really wish I could check yours out because I can't even imagine a robot being more obnoxious...

Re: How Loud is Too Loud? (Cal Games)
 

heh heh - I smell a new award in the making: "Most Obnoxious Robot"!!!

I think that Team 116 would certainly have been a contender with their robot from 2003. That year we used treads, with large tread "bumps" that interacted with the sprockets on the interior of the treads. A series of 3-inch long 1/4-20 spacer bolts held the side plates of our drive modules in place. The spacer bolts just happened to be positioned so they just barely cleared the bumps on the treads as the treads were running. So we took a set of 2-1/2 inch lengths of copper plumbing pipe, and put one loosely over each spacer bolt. The pieces of pipe were thus positioned so that every time one of the tread bumps hit it, the pipe was slammed into the spacer bolt with a nice loud metal-on-metal "clang!" With two treads running at about 9 feet per second over 12 of these pipe-covered bolts, we were pounding out about 2600 very loud impacts per second. We never actually stuck a decibel meter up against the thing to know exactly how loud it was. But it was loud enough that when it was running in the pits at the Richmond Regional, you could hear it out on the playing field over the sound of the amplified music from the DJ!

-dave

Re: How Loud is Too Loud? (Cal Games)
 

Everyone knows that electronics are pumped full of smoke. When the smoke leaks out electronics stop working.

Most people dont realize that mechanical parts are pumped full of noise. This is why they are made on very noisy machines.

Ideally the noise will be let out of the parts a little bit at a time. The reason is, once all the noise has leaked out, the parts will stop working. Sometimes the noise leaks out all at once: BANG! and then its all over.

Sometimes you can put a little bit of noise back into a mechanical part, either by screaming at it, or wacking it with your fist or a hammer. But usually it has to go back to the machine shop to be pumped full of noise again to work properly.

Having said all this, I dont think your robot is long for this world, if you have a serious noise leak! Something is scraping, ginding, or banging against something else, or your unbalanced shooter is vibrating itself to death. I would be concerned about metal fatigue, and something breaking.

Re: How Loud is Too Loud? (Cal Games)
 

Note to self, another item for the safety checklist. Robot not
to exceed the threshold of pain, nominally 130 db, at a distance
of 5 feet. We'll keep the music down so we can hear ya. :ahh:

Re: How Loud is Too Loud? (Cal Games)
 

By this logic, electronics should be made in smokehouses, like bacon or country hams. ;)

Re: How Loud is Too Loud? (Cal Games)
 

The smoke gets into the electronics with you solder the connections. :rolleyes:

Eugene

Re: How Loud is Too Loud? (Cal Games)
 

So lead-free electronics should contain more smoke, since they are soldered at higher temperatures, right? :confused:

Re: How Loud is Too Loud? (Cal Games)
 

Is it also safe to assume that batteris only have a certain amount of sparks, and after that they don't work anymore?

Re: How Loud is Too Loud? (Cal Games)
 

To get back to the original question of "How Loud is Too Loud?".

This loud:
|----------------------|*


Just use common sense. If it sounds like something is going to break, try to find where the problem is and correct it before it is an issue.

*(not to scale)

Re: How Loud is Too Loud? (Cal Games)
 

I would definitely throw our robot the MegaMaid into this category. When we fired up our intake rollers you could hear it from across the arena.Here is her picture.

Re: How Loud is Too Loud? (Cal Games)
 

To use some Jeff Foxworthy logic...

When the police show up for night-time noise violation laws even though it's the middle of the day,
you might have a shooter that's too loud.

When the sound waves from your robot can register on the Richter scale,
you might have a shooter that's too loud.

When your drive team has bleeding ears after a match,
you might have a shooter that's too loud.

When the CIA shows up to confiscate your robot to use in Iraq to "smoke" terrorists out of buildings,
you might have a shooter that's too loud.

When a deaf spectator shows up and tells you to keep the noise down,
you might have a shooter that's too loud.


For your actual robot, use your best judgement. Try to see if anything can be fixed, tightened, etc. You also might want to try lubing the moving joints, and then run it for several minutes to break it in.

Re: How Loud is Too Loud? (Cal Games)
 

What did you say?

(j/k)

EDIT: Our ball lift made a significant amount of noise this past year and I was impressed. And, my fingers were comfortable in my ears at times.

Re: How Loud is Too Loud? (Cal Games)
 

WHAT?


If you are really concerned about the noise level itself borrow a dB meter from someone and measure the levels.

There are safety standards for noise levels and hearing damage. If your robot is loud enough to cause hearing damage then people standing nearby would need earplugs, and you should not run the shooter in the pit area.

Re: How Loud is Too Loud? (Cal Games)
 

See, this is why I bring earplugs to FIRST events. (And you thought it was because I usually wind up near SPAM.)

I might suggest a rule that MIT's 2.007 course uses in their competition, known as the Naked Phone Booth Rule. Basically, if you wouldn't want to be in a phone booth with your device while naked (for two minutes, for our purposes), it's probably not a good idea to use it.

Re: How Loud is Too Loud? (Cal Games)
 

I have always been of the opinion that if the mechanicals are making noise they are trying to talk to you. I would listen and try to determine the problem. It might just be that at speed a part of the mechanism is hitting another part as in something is just slightly out of alignment. Look for wear spots on your rotating parts. Could be that the sprockets are not parallel and in the same plane. The chain would make a distinctive knock each time a sprocket tooth attempts to engage a chain link. The faster the speed the more (and louder) the knocks.

Re: How Loud is Too Loud? (Cal Games)
 

On a serious note, refer to the table linked to below.
http://www.occupationalhearingloss.c...aring_loss.htm

Under OSHA rules, no exposure above 115 dBA is allowed, however short.

So, this answers the question: How Loud is Too Loud?
If you have concerns, borrow or buy a sound level meter.

Yes, there will be a sound meter available at the Cal Games...

Eugene
(President of the WRRF)

Re: How Loud is Too Loud? (Cal Games)
 

Thanks that's really helpful. I would say our robot measures somewhere around the 90 level :o

Although we haven't found a solution to the problem (a five day solution that is :o ) we have managed to adjust our shooter so that we only have to reach "jackhammer speed" for a very short time.

As for metal fatigue it has surprisingly held together quite nicely and there are no visible signs of damage.

Re: How Loud is Too Loud? (Cal Games)
 

Only 90 dbA?, you can run that all day and we will call it entertainment!


Eugene

Re: How Loud is Too Loud? (Cal Games)
 

If you think the problem is your shooter is out of balance it should be relatively easy to eyeball the system and see where it is not symetrical about the center of rotation

and to guesstimate the amount of weight you would have to add to the other side to balance it - like they do with the lead weights on car tires.

regarding metal fatigue, I dont think you will see any visable signs until something breaks. After a part has failed an experienced M.E. can look at the break and tell why it failed (crystalized, sheared, cut...)

Re: How Loud is Too Loud? (Cal Games)
 

This is a good explanation but adding to this, the "A" scale is a frequency dependent curve that tries to approximate the inverse of human hearing sensitivity. As such it is less sensitive to areas where the human hearing is less sensitive. However, the offending noise is still there.
Many venues and outdoor arenas are now instituting noise level ceilings on performances. 110 dBA seems to be the defacto standard but the measurement is still an issue. Sounds decrease by the inverse square law with distance. So the issue is where do you measure the sound level. In arenas, it is acceptable to take an average of the seating area but any seat that exceeds the standard should be corrected by some means to come into compliance. Outdoor venues have to comply with neighborhood standards such that sound levels at the closest house must stay within local ordinance for the time of day. (local sound level ordinances vary between daytime and nighttime.) With a standard FRC playing field the drivers have less exposure than the judges and field people.

Re: How Loud is Too Loud? (Cal Games)
 

:D QFT! Not like this is a football game where you've got to yell across a field.