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

[Pavan Dave]

I would recommend the kit bot frame. It isn't as adjustable as 80/20 or ITEM or anything like that but it is adjustable enough and you can modify it pretty easily too. No welding required, just some bolts and some bolts and Loctite.

[Branden Ghena]

Our team used to use 80-20 but switched off of it for weight issues. We now use one-inch extruded aluminum (I don't know a specific maker) for most of our robot. Several high strength needs still use 80-20, but extruded forms almost all exterior parts of our robot. It has been very strong despite being hollow on the inside (we don't fill it).

Edit: We do use kitbot frame for the core of our robot. It has been proven strong, and allows us to have a working frame first week.

[Herodotus]

We've had a lot of success the past two years using standard 3/4 in wide, 1/16th in wall aluminum tubing. It's certainly not adjustable without making your own holes, but it is very light, very strong, and very easy to work with. You can use hacksaws and hand drills to build the robot if you want to.

In 2007 Mark Johnson, one of our mentors, did the welding, while in this past year we used screws for initial construction, and then replaced as much of the screws as possible with glue and rivets. (though much of the robot is still held together by screws, for lack of time).

We've used 80/20 in the past, and the problems we had with it were weight and at least I personally never felt like the bolts and sliders held together quite as well as a good bolt and locknut or even screws. However this is just based on feeling, we didn't really have an issue with that. It's very nice for areas that need a lot of adjustment, so don't rule it out altogether.

The kitbot frame is also pretty decent for the most part. You can easily make a very successful robot out of it.

[Richard McClellan]

Originally Posted by Herodotus

In 2007 Mark Johnson, one of our mentors, did the welding, while in this past year we used screws for initial construction, and then replaced as much of the screws as possible with glue and rivets. (though much of the robot is still held together by screws, for lack of time).

What kind of glue and on what parts/materials were you using it?

[MrForbes]

80/20's main advantage is that it requires little effort to make many different designs with it. It is not a very efficient shape as far as it's strength/weight ratio.

If you want to spend more time designing, you should look into using many other sections of aluminum, as well as other metals and non-metals. Steel can be very effective (look at 1501's 2007 robot), sheet aluminum is also used by them to make strong, light structures. We've used fiberglass pultrusions for our frame, and 842 uses it for their entire robot! Some teams use plywood, you could use spruce, or other woods, which take some effort to design but are relatively easy to work with and can be very strong and light (think of the early airplanes, which were made almost entirely of spruce). For aluminum, look into tubing, both round and square, and angle and sheets. Our robot used sheet and angle aluminum this year.

Also look at the various ways you can connect the parts. Rivets are great, they are light, strong, and quick to replace if needed. Bolts and nuts are a bit heavy and cumbersome, but can be removed and replaced many times. Glues are a bit tricky to apply and hard to repair joints made with them, but for some joints they are the best way to go. Welding is great for thicker alumimum parts, and for thinwall steel tubing (such as 1501 has used).

[Herodotus]

What kind of glue and on what parts/materials were you using it?

It was a polyurethane based glue I'm pretty sure, but I don't know exactly what kind or brand of glue. I'll be in the shop Wednesday and if we still have the container of it I'll post back with more detail. We used it on 3/4 inch extruded aluminum tubing held together by flat plates. Before we did any gluing we roughed the surface up with a pneumatic disc grinder to create a surface for the glue to actually stick to.

We never had any of our glued pieces fail, and when we just glued two test pieces together and tried to break the joint we bent the metal before we did anything to the glue itself. We could easily have gotten away with not using the rivets, but we just used them to hold the pieces together till the glue could set.

Of course, don't get it on your hands... or clothes. The other problem I could see is if it is in a high stress location and the part it's holding on is damaged it would be a real pain to fix.

[Richard McClellan]

Cool, I'd definitely be interested to know the details on that. Our team has never tried glue for joining metal to metal before.

[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".