Durability of tetras
 

Seeing all the pictures of the robots come together, I have noticed that those tetras really will be extended pretty high into the air. It is also a good chance that many will fall from great heights also. It seems that they may break easily after being dropped from 10'+ a few times. Has anyone dropped a tetra from a height as such and noticed any damage? Or has anyone noticed any damage at all to tetras that you have built and tested with?

Re: Durability of tetras
 

Umm, we scratched them up really good. Not structural damage, but they're not pretty to look at anymore.

And due to some mishaps with testing, our vision tetra has some scratches in its vision panels. I'm afraid the vision tetras are going to get beat up on the most...

Re: Durability of tetras
 

ours have been breaking like crazy. Our Advisor goes to pick them up and they just fall apart... although maybe that is just due to his super strength ;)

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Our tetras have been falling apart too. Last night, we were engaged in a tetra, it was lifted above the larger tetra and it simply fell apart. I think that several tetras will be replaced this season, but hey, it's part of the game. :cool:

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ours are fine we broke one but thats cuz we made our won corner peices to attach the 3 side and it broke.

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I think it depends on the properties of the clovers used to assemble the tetras. The real field tetras at the kickoff seemed pretty sturdy, and didn't look like they would come apart too easily. See here.

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Our tetras have been holding up.... eh, decently. We haven't really put them through their paces completely (the robot's in pieces at the moment, so it can't do anything... :p) but none of the tetras we were using have shattered beyond repair.

Also... here's a question: are the tetras y'all are using PVC? 'Cause the USF specs on the tetras say they're to be made of aluminum and I'd figure they would hold up better than the PVC has been...

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Lol, same here :p

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All I can say is I hope they stock a lot of extras at the competitions. Our cap system is tearing them up. It's not as much the bot's fault as it is the fact that these things are heavy with a rather weak joint. I don't think they were designed with rapid play in mind. Then to compound that with a couple bots fighting over one, there's going to be a big pile of dead tets after each competition. Or at least those clover things. They need to make metal ones.

Re: Durability of tetras
 

Those of you that are saying that your tetras are falling apart like crazy...have you glued the end caps on to the PVC pipe like the competition tetras will be? And how have the tetras been breaking? Like have the clovers been breaking or falling off or are the end caps falling off?

The scoring tetras will be made of PVC. The tetra goals will be made of aluminum.

Re: Durability of tetras
 

Also, keep in mind that the ends are going to be injection molded, as opposed to a thin piece of lexan (or something similar) that most teams are using. I think they'll hold up.

Re: Durability of tetras
 

The plastic clovers started shearing very early on in our testing. So we quit on those early. The glued end caps entombed the hardware inside the PVC once the clover tore the pipe was no good. So the whole thing quickly became trash. The ones we practice with are duct-taped end caps, then used the conduit strapping in a triangle pattern like someone suggested on here (I'll look for that picture and link it here). That holds up for a while, but the strapping isn't thick enough gage. Maybe if we doubled them up it would stay. But like you said, just dropping them busts em open. The plastic clovers were the easiest to break. That metal flange they made to hold the magnet would work good.
The stress concentration in the folded corners of that plastic will never hold up. But the bolted points tore out also. It's just not a capable material. I originally was worried we would get penalized for breaking these things, but I later convinced myself they were going to be breaking all over the place by design issues within.
http://www.chiefdelphi.com/forums/at...achmentid=2807

Re: Durability of tetras
 

Our tetras have steel clovers and the end caps are not glued. They come apart all the time, but it's not a big deal to stick it back together.
Our tetras do not like to be thrown. They don't even like to be slid along the ground. I have broken too many just tossing them while resetting our field.

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One of our tetras broke yesterday, it was accidentally dropped from way up in the air. It just snapped...but it could be fixed! :o

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yeah, I remember that.

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Someone correct me if I am wrong, but I also believe that the ones FIRST will be using are of a different material then the PVC ones we are all building ours out of. From what I heard, they are using a plastic that lawn furniture is made out of, and therefore there are probably some different characteristics.

Re: Durability of tetras
 

Perhaps you need to rethink your robot design. You have a system that you like, but is "tearing them up." Because your design was breaking the official tetras, you made stronger ones to practice with. However, the tetras are as they are. With the Sterlite bins in Stack Attack, FIRST intentionally chose a weaker container as part of the challenge. Having custom injection molded parts, and lots of them, made it is unlikely for FIRST to spend a lot of money to redesign the major game piece now.

You don't get to engineer how strong a human chest is, you need to engineer your car to not exceed the loads a chest can take in a car accident. A foot can only take so much energy, you need to design the boot to keep the energy below that threshold.

In FIRST as in life, there are design criteria that can not be changed.

Wetzel

Re: Durability of tetras
 

i beat the snot out of our stock. A little pvc clue and they will not fall apart for me. I constantly take out some anger on them if there is nothing to beat with the BFH. Other than scratches, i have noticed no real damage. I guess that if one drops it from 10-15' up, the pvc might shatter, but since i sell the stuff at work, ive noticed it isnt easy to break.

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we havent broken ours yet but thats probubly because we havent practiced yet

Re: Durability of tetras
 

Today at our practice competition, a bunch of the tetras broke. None of ours broke because i believe we were the only team that clued the PVC, used IFI clovers, and used T-Nuts. With a bunch of them, the caps just shattered. If you are running a practice competition, make sure to HAVE EXTRA CAPS! There were extra caps where we were, so our team fixed all of the ones that broke.

Re: Durability of tetras
 

i cant even tell you how many tetras we've broken in practice. while switching out different drivers, i think i might have racked up the most tetra casualties ^^; we've made clovers out of lexan and aluminum, and they still come apart at the bolts or rip in the center section of the clover. its has nothing to do with how we perform, its just the wear and tear of constant handling. we had a PVC goal just collapse on us just because of the wind.

-shrugs- i guess thats life... and the drivers will just have to be a little careful, because i dont think that they'll start a match over just because the tetra you are handling decided to collapse right as you were about to cap. sure that can directly affect the outcome of the game... but if it happens often, there may not be anything anyone can do about it and you'll just have to deal with it.

best of luck everyone... i'm praying competition tetras hold up well.

Re: Durability of tetras
 

I'd say if we drop them from our full height, or swing them from any height, they have a 5% chance of breaking. We've broken and had to fix about 3 so far. The vision tetras especially, since our zip ties break pretty easily

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I, myself, broke about 2 or 3...I can't imagine the total we have broke. But then again, our end caps were made of Lexan...what could I expect.(BTW..the one metal capped one we have hasn't broke yet...so I think the FIRST ones will be unbreakable)

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After the stuggle to find end caps that actually fit and enough of them to make like 12 tetras, we have only broke one or two at practice, and we too are using the pvc glue, but those clovers snap easily, our mentor broke one in his hand, and we broke several of them dropping a single tetra. We machined our own and those didn't work either, so when we saw the plumbers tape idea we used it and combined with the glue they were among the only tetras at the Corvallis Scrimmage to not take a large beating.

We however did take some of the weaker tetras and break them apart accidently many times. But in the last 5 or 6 matches we competed in we learned how not to break the tetras, slow non sudden movements and not dropping them leads to a good scrimmage.

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Yeah, expecially when your throwing them across the field... :ahh:

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At the UTC invitational yesterday, there was a dedicated "tetra-fixer" I will call him. He has a ryobi drill with a socket driver on it and he was fixing all or any of the broken tetras. If tetras break, it isnt a big deal to replace it as there were no more than about 15 or so on a field at once, the most that I saw.

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They also only broke a couple of them from what I saw, altho the green part of the vision tetras had to be replaced a few times, as they were using some sort of green sticky paper or something which would just peel off.

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our practice tet end-pieces were just lexan, so not the sturdiest stuff, but we murdered those things, of the five built, none survived. Honestly, just a little toss (across the room) or drop (from the ten foot ceiling) and the things just came apart like the pipe cleaner tetras we made for grabber brainstorming.

Re: Durability of tetras
 

So to revive this old thread, how do you feel the tetras held up? I know that while our team was at FLR we only broke 2 tetras, at GLR we broke 3 (taking into account that we were stacking a lot more) and at Nat's we only broke 1. I noticed that FIRST wasn't using the same color clovers as the white ones that they supplied us with. I cant help but wonder if the color that they used to dye the clovers affected how they handled stress... possibly FIRST was on to this because many of the clovers at Nat's were either white or made from a different material as the original ones, they seemed to stretch more rather than brake

Also, at GLR the tetras that broke when we stacked them were not counted toward the score for our match, shouldn't this fall under field malfunction and thus we be awarded our points? it never really mattered much with the outcome of matches, either we were ahead by enough to not have to worry about it or behind so far that it wouldn't have helped anyway.. :rolleyes:

Re: Durability of tetras
 

I think the tetra held up OK, it seemed like they only broke at the worst possible time like when they are placed on our bot or when they are being stacked. I helped repair the tetras at the Philly regional and most held up pretty good for the most part. The only problem was those clovers, they would break or the screws would strip inside the pole and the tetra would become loose and unplayable.

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I think that on the grand scale of FIRST gamepieces I've seen, they held up well.

Well, so long as you didn't do anything extreme, like drop them from player-station height or higher.

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From what I saw the Tetras held up very well. Even when they did break they were at least fixable, unlike the balls last year or the bins back in 03. I hope that next years game pieces will be as durable as the Tetras.

In regards to practice tetras we tried several different cheap clover materials sheet metal was too flexible, Lexan held up but not for long, we finally ended up using some 1/8" Delrin sheet and that seems to be working well.

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Having worked closely with the tetras (too close) during the Florida Regional, I have to say that the tetras held up pretty well. The clovers could have been designed differently to reduce the stress on them. But, as it was pointed out to me, wouldn't you want the weakest link to be something easy to replace? It would have been much worse if the endcaps or the PVC pipes were the things that broke rather than the clovers.

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During the build season, I was given the task of fixing tetras that were broken. I would fix one, put it on the station and be given another broken one.

The ones at VCU were somewhat stronger.
However, i saw very few broken tetras on Newton field. One brok cause of a tipped bot crushing it.

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I served as a volunteer at the SoCal Regional this year performing tetra repair on both days of competition and was dubbed "Dr. Tetra". Woodie autographed my FIRST crew t-shirt right under the Dr. Tetra "insignia" :cool:.

FIRST had just acquired new clovers that were punched from colored poly-propylene to replace the thicker low density polyethylene clovers. On Friday, broken tetras came off of the field frequently - sometimes 2 or 3 in a single match. On Saturday, I was joined field-side by my son, Clayton - he had a blast assisting "Dr. Tetra". By time we reached the elimination round, most of the tetras had the newer clovers, which seemed much more durable. In the semifinals and finals, I think there was only one broken tetra is spite of the much more intense play.

I was surprised to see many tetras in Atlanta with the thicker polyethylene clovers, probably something only a tetra repair specialist would notice...

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I held the same job as you, at UTC. We had two different clover styles, the original, soft ones, and then the much harder ones. We replaced all the originals with the new ones, which worked out much better.

At SVR, I noticed that a good number of the clovers were very thin compared to the others. They also seemed to be breaking a whole lot more. There was one point where there were around 6+ tetras out of play all being repaired. I imagine the SVR field went to SoCal the next week and you got these tetras.