Team 104's succcessful use of composites

This year, team 104 built a 30" ball grabber arm out of fiberglass pultrusions
and other composites. The arm was tested in battle this weekend at
the Drexel regional. It preformed extremely well, taking severe impacts
and stress with no damage. We saved about 40% in weight over our
calculated weight in aluminum. I did not see any other robot structure
at Drexel that used composites other than plywood. Love that carbon
fiber weave look. Any other team use composites for a major structure
this year? We used 1/8" wall 2" and 1" square box tube fiberglass pulltrustions
5.7 oz plain weave dry carbon, 1/4" chopped cabon fiber, laminating
epoxy and 2lb 2 part expanding foam. After all the posts about team
trying to loose weight and all the bent aluminium I saw this weekend
many teams could benefit from some use of composite materials. Get
your robot off a diet of all metal and give it some fiber. Any coments?

I cant remember which team number, but i was snooping around NYC FIRST and there was a team with an all fiberglass chassis. It was mainly 2"x2"x1/8" with 1/4" L brackets at the corners. The L brackets were just normal bicomponent epoxied on. It looked pretty sturdy, but the weight a team member quoted was pretty high for the chassis. Something like 30 or 40 lbs. Maybe he was including other structures too, because a steel chasis shouldnt even weigh that much. Exactly how light is your chasis? I

Im pretty confident that i can build a pretty sturdy 7lb chassis out of aluminum tube and our chasis this year, which seems to have held up pretty well, is probably under 10 lb (20mm item extrusion).

A few questions:

How does the density of fiberglass compare with aluminum? I’ve tried looking this up but I don’t exactly know what type of fiberglass I’m looking for anyways :p. I mean, .80lb/ft^3 probably means I’m looking at an insulator, not a structural material :-P.
Also, how much does fiberglass cost usually? I would check McMaster, but I’m not exactly sure what I’m looking for.

How good is the 20mmX20mm that Item sells? Are the fasteners better or worse, in your opinion, than Bosch, in terms of durability and utility?

Thanks,
Shrenik

Team 668- The Apes of Wrath of San Jose built their entire robot out of carbon fiber this year, and constructed it to look like a hummer. definitely one of the cutest little robots I’ve seen so far.
I can’t give you details, but just thought I’d mention another carbon fiber team.
Their 'bot (PH4) performed exceptionally well (compared with their last three years), and took some heavy hits. Very nicely done.

Team 842 has used the fiberglass from creative protursions for several years. It’s the material of choice for us. Several reasons:
5 times stronger than steel for its weight.
it will float. (less dense than alumnimum)
It can be worked with hand tools - drill, hacksaw, screwdriver.
If anything breaks, we can fix it in the pit wihout welding, machine shop, etc.

Its fantastic stuff.
We’ll be at nationals. Stop by and talk.
And … no they don’t sponsor us – we tried, though.

last year we (293) had kevlar bin herding arms. They were very very strong and weighed next to nothing. 2 years ago we had a spinning drum on our bot that would shoot the balls up into the air and into the goals which was made of fiberglass. I’ve have always used http://www.cstsales.com/ for composites and they have good prices. If you only need a little bit than car body repair kits are great. They come with epoxy, hardener, and cloth and their great to learn with. They’re about 20 dollars and you can find them at most auto parts stores.

Ben Van Selous

Where can you get carbon fiber for winding your own tubes,
or buy pre-wound tubes in standard sizes?

use a search engine before posting…

google’s #1 result

well team 842 we have built our whole frame from fiberglass its pretty sweet. our arm is made of combinationhttp://imc_1080 of fiberglass and aluminum. ill post a pic of the arm when i find one

95 used a fiberglass backed cardboard honeycomb composite board this year, in places we would have otherwise used plywood. The main use was as the electronics board, which ended up becoming another structural member, helping to tie the frame together.

We mainly used it because we found an appropriate sized piece that a sponser had left over. It was attractive not only because the price was right, but because it is extremely stiff in most planes and weighs a fraction of the equivalent piece of plywood. It is the perfect material for mounting internal components or as a structure that needs to be rigid in the appropriate dimension. It is also non conductive, easy to work with and for all purposes transparent to radio waves.

It also lends a certian ‘high tech’ look to the 'bot. I like that. Carbon fiber is cool, but I would fear my robot would end up looking like a K&M cold air intake ;).

There are lots of ways to use non metal/wood/PVC materials. Composites are great. But I still like a good aluminum or bracketed plywood frame any day. It’s tried and true technology, and it can be cheaper in a lot of cases.