How much metal to get?

[Cory]

Originally Posted by AdamHeard

Ooooh.... Care to let us know who is joining you and RAWC?

Haha. I was wondering how long it would take for someone to notice that.

No third team. Just the other team (1868) that's sponsored by Ames and works in our lab with us.

[EricH]

I wouldn't make a drive frame out of 1"x1"x1/16". Period. Superstructure, you bet, if it won't see a lot of hits or needs to be light. See 330's 2006 shooter frame or 2007 ramp frames for an example.

Typical drive for the BeachBots is 1"x1.5"(or 2")x1/8" aluminum. Superstructure may be the same and/or (the last two years) 1"x1"x1/16".

Why you don't use thinwall is simple: It doesn't like holes. You can only put functional holes in if you want it to last. No speed holes here.

[Aren_Hill]

I'd like to defend 1x1x.0625" tubing a bit.
What material you use for your base totally depends on what type of base it is.
Such as us (1625) wildstang (111), and the BEAST (71) who had swerve drives this past year. Our robot used 1x1x.0625" for the frame and i believe 111 and 71 did also, just because of what had to fit and how many supporting members are needed.

If we use a different drivetrain i'm pretty confident we'll use other materials.

[Dick Linn]

Our supplier has a pile of "shorts and dings", sometimes known as "drops". You can sometimes get short pieces of odds and ends at reduced price, or at least not have to buy a 20 foot stick of everything. This is very useful if you need a couple of inches of thick stuff for a bracket of something.

Overall, we've found 1 x 1 x 1/8" square tube very useful, with occasional uses for 3/4 x 3/4 x 1/8". We usually have a collection of 1/8" thick angle - 1/2", 3/4", 1" and maybe 1 1/4" or 1 1/2". We generally don't buy more than one 20 ft. piece of anything until we know our design. We don't stock much plate due to the cost.

[EricH]

Originally Posted by Aren_Hill

I'd like to defend 1x1x.0625" tubing a bit.
What material you use for your base totally depends on what type of base it is.
Such as us (1625) wildstang (111), and the BEAST (71) who had swerve drives this past year. Our robot used 1x1x.0625" for the frame and i believe 111 and 71 did also, just because of what had to fit and how many supporting members are needed.

If we use a different drivetrain i'm pretty confident we'll use other materials.

The folks who don't like the 1/16" thickness don't like it in a particular application. Namely, the drivetrain. For a swerve, a different frame is needed from a 6-wheel. If you need extra strength at a light wait, 1/16" is great.

My team has only used it for superstructure, primarily because we don't like the loads it'll see down low.

[Andy A.]

My experience has been with inch square aluminum tubing with a 1/8th wall thickness. 6061 is the default alloy of choice for the majority of FIRST applications, tube or plate. It offers good strength characteristics while being weldable. It's also very common which increases your options for quantity and shape and decreases lead time. There are probably some places where other alloys would be better suited, but few where 6061 is a bad choice.

Welding will toast the heat treatment. I've seen very few clear cut cases of the joint failing because of this, but it's worth considering.

Polycarbonate can often be substituted in place of aluminum plate where stiffness is not critical. Both materials weigh about the same but the plastic is easy to worth with, non conductive, transparent to light and radio and a whole litany of other pros.

Plywood is another good substitute for aluminum in some cases. It is again easier to work with, non conductive and with quality wood very tough. It is cheaper and can be easily found. I've often used it to 'prototype' aluminum parts, only to find that the wood works perfectly well. It can quickly be replaced modified or glued back together if need be.

Just don't invest your team to heavily before the season starts. For all we know aluminum may be banned this coming season.

-Local