Construction materials

[mechanicalbrain]

I think my personal favorite is a carbon/Kevlar composite plain weave with a heavy duty epoxy. Yes you do have to form it yourself but its actually pretty easy and not horribly expensive. The shaping is actually good because you can customize the shape of the frame without having to lose strength. Also It has a good strength to weight ratio (the exact ratio escapes me).

Also one critical thing Ive failed to see mentioned are the types of strength materials have . A materials type of strength defines its function. The Kevlar gives a great tensile strength and torsional strength. Yet the carbon gives the weave good transverse strength and amazing impact resistance. However I recommend practicing the process and familiarizing yourself with the materials. If you don't form it evenly or use the right types of epoxy and weave you will create weak points.

[sanddrag]

696 has used welded 6063 1/8" wall aluminum box tubing frames for the past two years. 6061 was not available. Anyway, we have had virtually no problems with the 6063 and have only cracked (very minorly, no repair needed) a weld once ever. The 6063 polishes very nicely too. As with any welding, be prepared for warpage and have a plan to correct it (or prevent it)

[Cory]

Originally Posted by mechanicalbrain

I think my personal favorite is a carbon/Kevlar composite plain weave with a heavy duty epoxy. Yes you do have to form it yourself but its actually pretty easy and not horribly expensive. The shaping is actually good because you can customize the shape of the frame without having to lose strength. Also It has a good strength to weight ratio (the exact ratio escapes me).

I wouldn't use carbon fibre as the sole material in a frame.

There was a thread about using it in different robot applications, about a year ago. I noted then that if you scratch something made of carbon, even cosmetically, you can cause it to catastrophically fail, with no warning like with metals that will bend.

Seeing as a frame is probably going to get the hell scratched out of it, that doesn't sound too appealing to me.

It's not an easy material to work with either. It can be very hazardous to your health if you don't have a good understanding of what you're doing and take safety precautions.

[mechanicalbrain]

Originally Posted by Cory

I wouldn't use carbon fibre as the sole material in a frame.

There was a thread about using it in different robot applications, about a year ago. I noted then that if you scratch something made of carbon, even cosmetically, you can cause it to catastrophically fail, with no warning like with metals that will bend.

Seeing as a frame is probably going to get the hell scratched out of it, that doesn't sound too appealing to me.

It's not an easy material to work with either. It can be very hazardous to your health if you don't have a good understanding of what you're doing and take safety precautions.

Ive worked with carbon fiber on a multitude of modeling projects and Ive never had the problem you've described. Actually if you use the correct epoxy it will be hard enough to scratch it. Actually the structural characteristics of carbon fiber are completely altered by the weave, material, and epoxy. As to being hazardous. Epoxy is essentially a glue. Use a respirator and work in a ventilated area and you'll be fine. It really isn't dangerous as long as your not directly breathing in fumes (I think thats the case with almost all chemicals). Oh and make sure to use gloves and long sleeve shirts.

[Andrew Blair]

Yes, Ti is about the perfect medium between aluminum and steel, but as for frame building, not so much. The more I think about it, it would be useful for small parts though.

[Cory]

Originally Posted by Andrew Blair

Yes, Ti is about the perfect medium between aluminum and steel, but as for frame building, not so much. The more I think about it, it would be useful for small parts though.

http://en.wikipedia.org/wiki/Scandium

[mechanicalbrain]

Originally Posted by Cory

http://en.wikipedia.org/wiki/Scandium

I know they use that in bicycles but i don't know anywhere where you can buy it. I tried to google it but nothing promising showed up. Any good links?

[Cory]

Originally Posted by mechanicalbrain

I know they use that in bicycles but i don't know anywhere where you can buy it. I tried to google it but nothing promising showed up. Any good links?

It's way too cost prohibitive for FIRST use. I don't know where you can buy it in it's raw form.

it's original use was on USSR ICBM's on submarines under the polar ice caps. The missiles would have their fins ripped off, so they started making them out of an alloy of scandium and aluminum, giving them the strength to punch through the ice.

[Andrew Blair]

"Scandium metal powder is combustible and presents a fire hazard."-wikipedia

haha, great, electrical fires and chemical fires!

[Cory]

Originally Posted by Andrew Blair

"Scandium metal powder is combustible and presents a fire hazard."-wikipedia

haha, great, electrical fires and chemical fires!

That's why you wouldn't use it in it's powder form

It's no different than magnesium--it's highly flammable when in strips/powder, but it's used for various other things in a more solid state.

[mechanicalbrain]

http://en.wikipedia.org/wiki/Magnesium cool stuff really. What would FIRST say if we told them our robot was made of magnesium (I know, I know, Its near impossible to burn the bulk stuff) Much lighter than aluminum.

[RogerR]

Originally Posted by mechanicalbrain

I know they use that in bicycles but i don't know anywhere where you can buy it. I tried to google it but nothing promising showed up. Any good links?

whilst looking for an aero seat tube for the composite TT bike i'm (hopefully) going to build, i noticed that easton sells scandium alloy tubes used in high-end mountain and road bikes.the selection is very limited, but if you absolutely have to scratch that scandium itch, here's a trustworthy* place. they also manufacture components made from carbon nano-tubes, but i don't see any tubing made of CNTs...yet.


*i assume since a large number of distributors and manufacturers trust them, we can too.

[Cory]

Originally Posted by RogerR

whilst looking for an aero seat tube for the composite TT bike i'm (hopefully) going to build, i noticed that easton sells scandium alloy tubes used in high-end mountain and road bikes.the selection is very limited, but if you absolutely have to scratch that scandium itch, here's a trustworthy* place. they also manufacture components made from carbon nano-tubes, but i don't see any tubing made of CNTs...yet.


*i assume since a large number of distributors and manufacturers trust them, we can too.

I don't think Easton sells these directly to the consumer. As far as I know, they sell them only to the manufacturer of the bikes (of which, only one or two companies use it).

Easton is most certainly a trustworthy company as far as quality of product goes. I don't know much about their baseball bats/hockey sticks, but their bicycling products routinely exceed their strength parameters by 3-4x.

[RogerR]

Originally Posted by Cory

I don't think Easton sells these directly to the consumer. As far as I know, they sell them only to the manufacturer of the bikes (of which, only one or two companies use it)...

i assume that you'd be able to get materials and components from one of their international distributors. in the US, it appears to be a company called Veltec Sports Inc. I plan to contact them in the future to see about buying some materials, and if it's still relevant, i'll post what kinda response i get.

[Cory]

Originally Posted by RogerR

i assume that you'd be able to get materials and components from one of their international distributors. in the US, it appears to be a company called Veltec Sports Inc. I plan to contact them in the future to see about buying some materials, and if it's still relevant, i'll post what kinda response i get.

When they say "distributor", I think they're referring to finished parts, not semi-raw materials.

At any rate, bicycle tubing is probably fairly hard to work with. I know Scandium isn't easy at all to weld. It's also extremely cost prohibitive. A plain bicycle frame made of the stuff is around $2000+. After all is said and done, for FIRST exotic metals probably wouldn't offer much of a tangible advantage over plain aluminum when used properly.