Carbon Fiber

[Jeff K.]

Ooh wow thanks for all the replies.
Yeah, we are aware that it is hazardous to deal with, so most of the machining, such as cutting and drilling will be done by a sponsor machining company. We may build it with the composite sponsor, working along side them with all the proper safety precautions in the right work environment. For safety also, whenever we work with it, we may wear resperators to not inhale the dust and will also wipe it with a wet cloth every now and then, and definitely whenever it comes back from being machined.

For connections and interfaces, there won't be any since it will all just be one single molded chassis. For upper structures, if we choose to go with a modular design, it'll probably just have an aluminum bracket or angle aluminum with nuts and bolts to attach.

Tytus, thanks for the support of just giving it a shot and trying it out. No team, that has publicly announced it, has yet to make their whole bottom chassis out of molded composites, all one piece with no connections or interfaces. 842 has made much of their chassis using composites, but with interfaces and components to connect them.
If we do plan to try it out, we will definitely experiment on it in the offseason before we ever use it during the actual season to see if it can really take a beating or if it is just impractical.

[KenWittlief]

Originally Posted by Stonefan5271138

...
Yeah, we are aware that it is hazardous to deal with, so most of the machining, such as cutting and drilling will be done by a sponsor machining company. We may build it with the composite sponsor, working along side them with all the proper safety precautions in the right work environment. For safety also, whenever we work with it, we may wear resperators to not inhale the dust and will also wipe it with a wet cloth every now and then, and definitely whenever it comes back from being machined.
....

exactly! But how would you do that in the pit area of an event? I dont remember the exact rules from last year, but I dont think you are allowed to take the robot anywhere you want during an event, only to the designated offsite machine shop

and they may not allow CF to be fabricated or machined in their shop.

[Andy A.]

Start small. Before investing a season and a good deal of money (potentially), work with the sponsor to develop smaller, key parts that can best take advantage of the carbon fibers properties. It will also give you a season or two to devolp your relationship with the sponser- I've had plenty of sponsers change thier mind after a season, deciding that it wasn't at all what they had imgained it.

In the future, when you're team has built up some experience with the material, you will better be able to answer your own questions. Successful teams in FIRST usually evolve the basic designs and technologies behind their robots over the course of many seasons, rather then trying to make tectonic changes in techniques and materials. But the progress has been steady- teams today regurally feild robots today that wouldn't have seemed remotely feasible when I first joined (multi gear transmissions are so 2 seasons ago- It's all about going sideways these days).

A great deal of attention is paid to composite materials great strength and low weight, but I've always been more interested in it's incredible stiffness. Aluminum has always struck me as being a fine material where strength (most measures of strength anyways) and low weight is a concern, but it's softness can worry me. If the bicycle and R/C car industry are any indicators, Carbon Fiber's stiffness sure is winning people over.

I suggest that you consider the composite for any part that you feel requires the extreme stiffness and strength, or perhaps an odd shape. Keep them small to start with, and keep a backup plan for producing the same part in aluminum or some such. Producing a whole frame with an untested, in FIRST, material with a brand new sponser sounds risky to me.

-Local

[Andrew Blair]

First of all, if I knew there was a one piece composite frame at a competition, CF or not, I'd go check it out, and probably ogle it.

That said, I just have one thing to add to what everyone else has said- think damage control. If you can use all clamps on tube, and set up a way to quick change a broken frame, then by all means, if you have the resources, go for it. But, remember, if your frame breaks (And it likely will at some point unless overdesigned - just the way Murphy and robot prototypes tangle), that particular one is pretty mush toast. You'll have either a crack with layers and a few fibers sticking out all over the place that will propagate, or a massive composite explosion, but either way, a replacement will be in order. So just design with an option out, and bring some gloves.

The best of luck- I think this could turn out to look really good!

[Jeff K.]

Thanks for all the help.
I'm not sure if I mentioned this or not, but our main reason for going CF is for weight, in hopes of saving weight. We had a problem this past year with weight. We're already using different design tools such as Inventor to help and CF would be able to help out in some places to also save weight. Another reason is how it is stiff, unlike aluminum which will bend. Also unlike aluminum, it just shatters, which is a definite minus. Another reason though that we are considering it is because it is sort of an unchartered territory for design and would just be interesting.

I think we can all agree for now, that a CF does seem kind of on the impractical side.

From all the concerns of it shattering from a FIRST competition, I think modularity is the way to go with this. Having different tubes to swap out, and some aluminum connectors and adapters so we can do a quick fix if it were to shatter sounds pretty good. We're not exactly sure about weight though, but 0.25" thick CF should be pretty strong, and somewhat lighter than .25" thick 6061 tubing.

Also, we would go CF ONLY if we could use bumpers. This past season, most of our main chassis lasted. The only part that got tweaked was where the bumper wasn't, in the front for our collector. I'm already scared thinking of what bare unprotected CF would be like after a single regional.

But yeah, going CF is def an idea, but we're going to experiment with it first. We're not planning on building a beautiful CF chassis, bringing it to competition, and finding out that it can't get rammed by another 130+lb robot without totally failing.

[Jon Jack]

Originally Posted by Stonefan5271138

I'm already scared thinking of what bare unprotected CF would be like after a single regional.

My team may have picture some where of what unprotected carbon fiber looks like after a COUPLE MATCHES!. This was our first year using carbon fiber, even though it was just tubing. Luckily we brought plenty of spare rods with us to every competition. I'd say that we were breaking or shattering some rods after 2 or 3 matches.

While carbon fiber is light and can save a ton of weight, I wouldn't recommend using it for a chassis or some other component that is exposed to frequent impacts from other robots.

[Matt H.]

Team 1726 also used fiberglass to build and prepare the chassis of our robot last year. This helped us to win a regional and we never had a fiberglass piece break. We decided not to use the provided bumpers and the fiberglass was taking numerous direct hits at full speed. The bot is still fully functional today. I would also note that some of the impacts we suffered bent aluminum crash bars at 45 degree angles while similar hits on the fiberglass had no effect at all. While fiberglass is not exactly the same as carbon fiber I can vouch for the use of composites. I'd urge your team to experiment with these building methods. I hope this has helped.

[Qbranch]

we used fiberglass for our ball transport parts (conveyors, ball tubes) and for protecting sensitive components (camera helmet) and found it very durable, easy to cut with a rotozip, easy to put together, and relatively cheap.

I realize it isnt as durable/strong as carbon fiber but overall it seems to me a better material due to its ease of use and application.

-Q

[Peter Matteson]

Originally Posted by Andy A.

A great deal of attention is paid to composite materials great strength and low weight, but I've always been more interested in it's incredible stiffness. Aluminum has always struck me as being a fine material where strength (most measures of strength anyways) and low weight is a concern, but it's softness can worry me. If the bicycle and R/C car industry are any indicators, Carbon Fiber's stiffness sure is winning people over.

Not entirely true I can get a sub kilo Titanium bike frame (litespeed) as well as a CF one (Look, Giant, Trek, etc.). The true advantage with carbon fiber, in that specific application, is the ability to tune the frame through the layup. By putting the material where it is needed for stiffness and making structural shapes not necessarilly possible in metal a frame builder can make a lateraly stiff structure that is vertically compliant to dampen road shock (vibrations transmitted from uneven pavement) and minimize rider fatigue. Anyone with a CF bike who's had an AL one will tell you this.

This is harder to do with aluminum because the tubes need to be stiff to minimize deflection in order to have a reasonable fatigue life. They do this by using large OD Al tubing. The result is a frame that transmits a lot of bumps.

CF alone isn't stiff, think of a CF fishing pole. Uni-directional fibers laid cured together in a matrix to have flexibility. It is the structural shapes and fiber orientations that you can use with it that allows is to be stiff.

Once again it all comes down to knowing the material you are working with and how to optimize it. Don't just use something because you can. Learn the whys and hows so you can use it correctly.

[sporno]

i would love to see some CF on a robot .. like on a part that dosent take any damage at all... like a shooter on one fo this years bots

[Jon Jack]

Originally Posted by sporno

i would love to see some CF on a robot .. like on a part that dosent take any damage at all... like a shooter on one fo this years bots

We almost used CF for out shooter, but we realized we wouldn't have enough time to properly make our shooter out of CF. We did use it for the shaft on our feeding mechanism among other places.

Perhaps we'll use it for our fuselage in this years air game

[Tristan Lall]

Originally Posted by jjack

We almost used CF for out shooter, but we realized we wouldn't have enough time to properly make our shooter out of CF. We did use it for the shaft on our feeding mechanism among other places.

If you had used carbon fibre for the shooter wheel itself, I hope that you would also have had the presence of mind to do some serious investigation into the effects of that thing shattering when struck or jammed suddenly. As an inspector, I would have been very concerned about the potential for carbon fibre shards to be expelled from such a device as it failed.

[Jon Jack]

Originally Posted by Tristan Lall

If you had used carbon fibre for the shooter wheel itself, I hope that you would also have had the presence of mind to do some serious investigation into the effects of that thing shattering when struck or jammed suddenly. As an inspector, I would have been very concerned about the potential for carbon fibre shards to be expelled from such a device as it failed.

We weren't going to use it for the wheel, just the shell around the wheel. We decided to stick with aluminum as you can see in This Picture

[Karthik]

I've split this thread, placing the posts mainly discussing the legality of Carbon Fiber, and the associated cost determination discussions here:

http://www.chiefdelphi.com/forums/sh...threadid=49552

[falconmaster]

Originally Posted by Ben Piecuch

Team 842 has used fiberglass for their robot chassis for several years now. It's thick and beefy fiberglass, but it seems to hold up very well. I would assume that Carbon Fiber frame rails would be quite similar in robustness.

From my experiences in designing around Carbon Fiber, the connections and interfaces with other components are always the toughest challenges. CF is so strong and can handle so much load, that the connections tend to be bigger and heavier than the metal component the CF replaced.

I love CF, as two of my road bicycles can prove. But I'm not quite sure the advantages it provides in the FIRST world outweigh its difficultly in use, and the obvious time constraint to design around it. YMMV, best of luck.

BEN

Yes its true, we have been using it very great success for years.

http://www.phxhs.k12.az.us/education...88&pagecat=136

Team 842 , the material is from www.creativepultrusions.com

We have never broken our fiberglass frame.