Types of Metal

[ttldomination]

Hello All,

My team uses 80-20 and like 99% of our robot is 80-20. Now, in the past years we've been heavy and it seems like our metal is heavy 80-20 is strong but we are looking into other options.

I would like to know what kind of metal do you guys use? Besides 80-20.

[tseres]

this year since we couldnt afford enough 80/20, we used 3/4 inch square box aluminum and filled it with plastic. worked perfect

[ComradeNikolai]

ttldomination,
Generally, you can't beat the strength to weight ratio of Mithral. That stuff is tough! Your robot will be able to withstand just about anything you can throw at it (or stab it with).

-ComradeNikolai

[vivek16]

Originally Posted by ComradeNikolai

ttldomination,
Generally, you can't beat the strength to weight ratio of Mithral. That stuff is tough! Your robot will be able to withstand just about anything you can throw at it (or stab it with).

-ComradeNikolai

Yeh, too bad the balrog destroyed the mine

We used 1/8" 1x1 and 1x3 this year (ack, heavy!).

We will most likely switch partially to 1/16".

Kitbot chassis with modifications of course.

-Vivek

[Aren_Hill]

1x1x1/16th box tubing for the entire frame and lots above that. aside from that we use alot of 1x1x1/16th angle, all aluminum of course.

[EricH]

Originally Posted by vivek16

Yeh, too bad the balrog destroyed the mine

Nah, just the access is blocked. Without the Balrog, it's wide open.

Mithril may, however, fall under the metal type Unobtanium.

Kit frame, or if you like custom, 1" by 1"-2" by 1/8" wall tubing is pretty good for a drive frame. Higher up, 1/16" wall works well. Thing about the drive base is, it takes a beating even with the bumpers, so 1/16" wall might not be the best option. (Then again, properly braced and with a decent material on top, 1/16" can support a robot climbing on top of it, so...)

[Herodotus]

Originally Posted by EricH

Nah, just the access is blocked. Without the Balrog, it's wide open.

Mithril may, however, fall under the metal type Unobtanium.

Kit frame, or if you like custom, 1" by 1"-2" by 1/8" wall tubing is pretty good for a drive frame. Higher up, 1/16" wall works well. Thing about the drive base is, it takes a beating even with the bumpers, so 1/16" wall might not be the best option. (Then again, properly braced and with a decent material on top, 1/16" can support a robot climbing on top of it, so...)

I believe we only used 1/8th wall thickness in four pieces of the base frame, those being the four blocks that the axle( a dead axle) for the wheels go through. We did have one incident at Western where we hit the wall and bent our entire frame, but we fixed it, and then glued a solid piece of diamond plate at the weak point to give it a little more structure, without too much weight increase. If we had just incorporated a few triangles into the base in the first place it probably wouldn't have been an issue at all.

[AndyB]

3/4"x3/4"x.035" Chromoly Steel (Available at Aircraft Spruce) is wonderful if you can weld (not as tricky as aluminum i don't think).

You can use 1/2"x1/2"x.035" as well for areas under less stress. The stuff is super light, (about the same as aluminum), more compact than 1"x1"x1/8" box aluminum, and three times as strong. Cost is the only downfall but it isn't anything too unrealistic. Teams 269 and 1501 tend to work with this stuff and both come out with VERY solid frames.

ITEM is a similar solution to 80-20. Don't have a source but I've heard it is stronger than 80-20 as well.

Other than that, on 171, we use Kit of Parts frame and 1"x1"x1/8" or 1"x2"x1/8".

[IKE]

We on 33 have been doing a folded sheet metal chassis for the last few years. Once you learn how to work with sheet, it is pretty easy, very light and very effective. You do need to learn rivet techniques and how to bend metal accurately an effectivele. We use heat treated 6061 T6. Before everyone tells me you can't bend it, that is not true. Heat treated (T6) means you need to be very careful bending it and use an ample radius.

For the big structures we have generally been going with space frame welded aluminum tubing both square and round. I have a lot of race car chassis construction experience so it helps. One of our students did most of the welding this year. While she is not a pro, she gets the job done.

What material you decide to use depends on budget, equipment, and skill sets. 80/20 or Star bar is very easy to use but extremely heavy (from a KB33 perspective). 1/16" is the beefy stuff on our machine and we often go down to 0.035" wall round tube.

If you do not have a skilled welder, I would recommend visiting the Team 1216's website and check out their chassis. The pre-drill 1x1x1/16 box with a very specific hole pattern. This technique gives 90% of the strength of 1x1 box with the flexibility of Star-bar or the kit rails with a TON less weight. These guy are pretty modest and only went to 1 regional so you won't see a lot of buzz about them. As a structures guy, I have a lot of repect for this technique as it has the 4-way threat of strong, lightweight, flexible design, and easy to use/manufacture.

Another good source are the 2 "Behind the Design" books. You can almost tell what line of work the sponsors are in by the construction of the robot. With aircraft companies you will see a lot of sheet metal. Nasa and Robotics related sponsor teams seem to have a lot of CNC. Big 3 teams seem to have a lot of welding.

As far as material sponsors to order from Aircraft Spruce has an awesome selection but can be a bit slow to certain areas. They have some truly amazing materials line a strut material that is 11oz. for 8 feet. Online metals is a good plae to order small quantities, but were extremely slow on their delivery for us (I did find a way to expedite future orders). Mcmaster Carr is fast but expensive.

[IKE]

I was mistaking 80/20 for starbar.

[sdcantrell56]

ttldomination,

I sent you a pm. Just get in touch with me and we'll discuss some things.

[JesseK]

Bleh, the less 80/20 that's used on a bot the lower my blood pressure is. It leaves too much room for last-second decisions that haven't been thought through.

We've used 1/16 wall 1x1" 6061 Aluminum tubing for our frame for 3 years now. It's always been welded. We have students that practice welding on our prototype frames, then they assist the pros who do the welding of the actual frame during build season. From there the frame goes straight to powder-coating at the same sponsor, which also adds strength and rigidity to the frame.

Our drive base frame this year came out to 6.1lbs after powder coating, and had zero CNC work or cheese-holes added to it. In future years we will probably experiment with 1"x1/2" tubing that has a 1/16" wall and sturdy injection foam in order to produce a more compact frame.

[cooker52]

1501 has used Chromolly tubing on our past two robots. It's light and strong. We gas weld it, but I believe you can use better methods of welding.

[Billfred]

Originally Posted by IKE

I was mistaking 80/20 for starbar.

I did some googling to no avail, since I haven't heard of it before: What is starbar?

[MrForbes]

We've bought fiberglass pultrusion from Creative Pultrusions. shipping is a bit expensive....

http://www.creativepultrusions.com/