where can i get strong light materials????

[Tristan Lall]

Originally Posted by Tom Bottiglieri

Carbon Fiber?
Titanium?

Both are hellish to machine. (Titanium eats tools, carbon fibre emits very nasty splinters--and if you're making your own, keep the resin out of your lungs.)

Edit: Heck; Tyler beat me to it. And the welding thing is a good point--in addition to argon, you need very special welding rod; it makes you wonder how the Russians ever managed to put together the Sierra class of titanium-hulled submarines (useless fact...).

[westfalia]

Let's not forget about wood, either. My team has never used it, but take Rage Team 173 for example, they had their little red box (with an awesome ball manipulator) go all the way to the Championship finals (or maybe they won it). All I can say is that you shouldn't necessarily weigh that option out either. We all know it's easy to machine, and it can be pretty light, compared to steel. Aluminum is probably lighter, but I am pretty sure Wood is cheap. I just think carbon fiber and titanium are out of alot of team's budgets... It was on my team.

[greencactus3]

lets not forget Lexan too. im sure most teams have used or uses plenty.

[Peter Matteson]

Originally Posted by greencactus3

lets not forget Lexan too. im sure most teams have used or uses plenty.

Which weighs the same as aluminum.

Also Ti is half the strength of steel at half the weight. As for the welding comment yes you have to properly back gas it but you should be with all you welding already. Granted a Ti fire is is one of the scariest things that can happen in a machine shop.

To use carbon fiber and cure it properly you need to either autoclave or vaccum bag a prepreg, facilities most people don't have access to. And it is important to understand the influence of directional orientation of fibers. For instance in carbon fiber bicycle design you trade off which directions you want to flex in for compliance to road but also where you need rigidity to minimize drivetrain losses due to flex. The advantage to CF is deciding where you want the strength.

Some light strong polymers include Polyetheretherketone, or PEEK. Which is a plastic with a low creep value. Cost is on the order of $30 a lb last I checked. PEI, polyetherimide(?), which has the trade name Ultem is another strong plastic.

The real questions you should ask are:
What property is most important to me?
Tensile strenght, compressive strength, flexural strenght, impact strenght?
Are thermal effects on properties important?
Is corrosion an issue?
There are many more but the material choice is application dependent.

Sorry for the rambling

Pete

[Jon K.]

Originally Posted by westfalia

Let's not forget about wood, either. My team has never used it, but take Rage Team 173 for example, they had their little red box (with an awesome ball manipulator) go all the way to the Championship finals (or maybe they won it). All I can say is that you shouldn't necessarily weigh that option out either. We all know it's easy to machine, and it can be pretty light, compared to steel. Aluminum is probably lighter, but I am pretty sure Wood is cheap. I just think carbon fiber and titanium are out of alot of team's budgets... It was on my team.

Yes we love our wooden robots, they are awesome, and the year was 02' and yes with the help of 71 Beatty, and 66 The Flyers, we won that year. It was my freshman year, and the last year at Disney, it was awesome, but plywood isnt always a good choice, we use a cabinetry grade plywood(I forget what kind wood it is though.), that is meant to deal with a lot of abuse, but it can get heavy depending on how much is used. The best part is, that if it breaks you can just wood glue it back together, there is a picture her on CD in the 2003 gallery from UTC New England of that little incident. But again extremely easy to machine. It all depends on what you are looking for.