How much metal to get?

[Kevin Sevcik]

All square aluminum tube is extruded. Or most all. It's just not fancy extrusion. That said, 1/16" wall 1"x1" square tube isn't my first choice for structural material. For anything seeing over a moderate load, it's probably actually my last choice. Certainly, I don't think you'd need 60' of it unless you're going to prototype your entire robot out of it and then make another one out of 1/8" wall aluminum. It is possible to weld it, but you need to make sure you get an alloy with good weldability. 6061 and 6063 are god choices and you'll likely find square tube in those alloys. However, you might also find it in 2024 or other alloys which are much harder to work with. Also remember that any aluminum welding you do is quite likely to ruin your temper for a fair distance around the weld.

[Cory]

For starters, find out what the standard length of tubing is that your supplier carries. In all likelihood it's 20 feet. Buy as many stock pieces as possible to avoid being charged for cuts, and partial pieces. As your quantity and poundage go up, your price goes significantly down.

I'm sure most people already know this, but don't use McMaster for any type of 6061 Al. I got a quote from a local supplier that's over $1300 cheaper than the same thing would be from McMaster.

If you want to make a frame out of 1x1, use 1/8" wall thickness. I would reccomend 1x2.

It is a good idea to stock up on metal prior to build, but only if you know what you will need.

We're purchasing a lot of metal now, to supply three teams--just so we don't have to wait for it. We're getting 100 feet each of 1x1x0.125 1x1x0.0625 1x2x0.0625 1x2x0.125, plus a bunch of solid bar/round stock, and a couple 4x8 sheets of thin Al plate.

Purchasing a ton of metal will work for us because we know our frame will be made out of 1x2 with some 1x1, and that any subframe/manipulator is also likely to use 1x1 and 1x2. We run through 1x1 and 1x2 tubing so fast that 100 feet of each might barely get us through the end of the year.

Originally Posted by Hachiban VIII

Expect to spend $200. But it really depends on where your getting it from and of course how much .

I would say that the tubing should be significantly less than this--somewhere in the area of $70-100. The plate will be what gets expensive real quick. Unless he's ordering a full sheet he's going to get charged a whole lot to have a smaller piece cut out of a full sheet.

[AdamHeard]

Originally Posted by Cory

We're purchasing a lot of metal now, to supply three teams--just so we don't have to wait for it. We're getting 100 feet each of 1x1x0.125 1x1x0.625 1x2x0.0625 1x2x0.125, plus a bunch of solid bar/round stock, and a couple 4x8 sheets of thin Al plate.

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

[artdutra04]

If you having milling machine/CNC facilities, then using 0.250" aluminum can have its uses in drivetrain/gearbox applications, if you like to mill pockets into it to save weight.

But if you really want to build a lot of stuff out of plates/sheets, I'd look into getting lots of Lexan (polycarbonate). 4'x4' sheets with thickness of 0.0625", 0.125", 0.250", and 0.375" are all great to have in stock.

Originally Posted by Cory

We're purchasing a lot of metal now, to supply three teams--just so we don't have to wait for it. We're getting 100 feet each of 1x1x0.125 1x1x0.625 1x2x0.0625 1x2x0.125, plus a bunch of solid bar/round stock, and a couple 4x8 sheets of thin Al plate.

I'd suggest that you stock up on some of the parts that Cory has described (although I'd add 0.125" and 0.0625" wall aluminum angle to that list), but in general just go to a local metal supply and buy out all their aluminum scrap. Sometimes it's just amazingly useful to have pieces of aluminum in all shapes and sizes.

[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