Types of Metal
 

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.

Re: Types of Metal
 

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

Re: Types of Metal
 

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

Re: Types of Metal
 

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.

Re: Types of Metal
 

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.

Re: Types of Metal
 

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.

Re: Types of Metal
 

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

Re: Types of Metal
 

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).

Re: Types of Metal
 

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.

Re: Types of Metal
 

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

Re: Types of Metal
 

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

Re: Types of Metal
 

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.

Re: Types of Metal
 

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...)

Re: Types of Metal
 

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.

Re: Types of Metal
 

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".

Re: Types of Metal
 

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.

Re: Types of Metal
 

I was mistaking 80/20 for starbar.

Re: Types of Metal
 

ttldomination,

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

Re: Types of Metal
 

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.

Re: Types of Metal
 

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.

Re: Types of Metal
 

we use the same stuff as 842 (that and PVC was almost our entire robot this year). We even buy it from the same place and we love it. I really hope more teams use it its great.

Re: Types of Metal
 

What place do you buy from, and how much does it typically cost?

Re: Types of Metal
 

Amen. I would love to see more teams use chromoly.

Re: Types of Metal
 

I'm not sure that you aren't using the best method already. Most of the best bicycles in the world before the advent of aluminum in the late 1980's were made out of brazed chromoly. Gas welded or brazed joints in 4130 chromoly should be at least as strong as the tubes themselves. It would be interesting to build a competition robot frame using full racing bike chromoly techniques, with butted tubing and even lugs in the joints. I understand that metallurgical advantages mean that welded joints work just as well as lugged and brazed joints, but it would certainly look old-school cool... :]

Re: Types of Metal
 

I'm pretty sure that 1501 welds their tubing, instead of brazing it.

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What, exactly, is "ITEM?" I can't just google it cuz I get a million results about video games.

Our team has been extremely reliant on 80/20, with 1'' tube stock where we need to decrease weight. We're building a new robot cart this summer, and I was wondering what you guys would suggest to carry a much heavier load than a FRC robot would be expected to stand up to. Most of the guys are leaning towards 80/20, but I'd rather avoid it because of cost, durability, and weight.

Also, where do you get chromoly?

Re: Types of Metal
 

It's very similar to 80/20, with a few minor differences in features, but overall, it's going to have the same durability/weight. The cost may be a little cheaper, but I'm not certain about that.

http://www.item.info/en

Re: Types of Metal
 

Its also metric... Which would make it annoying to use.

Re: Types of Metal
 

Don't tell the Canadians that...

-Vivek

Re: Types of Metal
 

here's one way to find this type of stuff...

http://www.google.com/search?hl=en&q...=Google+Search

Re: Types of Metal
 

its not my job to buy it so i dont know just ask someone on 842 (im sorry) but i do know its worth its mass in gold

Re: Types of Metal
 

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

Re: Types of Metal
 

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

http://www.creativepultrusions.com/

Re: Types of Metal
 

Starbar may be a local nickname, It is a t-slot style aluminum extrusion bar that has special slot nuts and brackets. It is very versatile and many team use it for their frames because it is strong and easy to fabricate with. IMO it is crazy heavy though. Weight/ft is significantly higher than most other materials, but it is strong and if it saves you 1 week in the build season the weight penalty can be worth it.

Here is a link showing the cross section
http://www.aline1.com/products/?categoryID=16
When you see the cross section you get the nickname.

I know 494 used this through 2006. When I asked them why they sighted 2 weeks of practice with the robot. Hard to argue with that. We will likely stick to a sheet metal chassis, or a welded stickframe.

Re: Types of Metal
 

Our team used "Alumicore" for the plate where out arm was held. Alumicore is usually used to make outdoor signs. Its plastic sandwiched in between two 1/32 aluminum. Its REALLY light! the frame of our bot is made out of aluminum sheet and 80/20.

Re: Types of Metal
 

A couple materials from this post are interesting to me and I would like to know where our team could buy them.
The 1X1X1/6" square tubing with the hole pattern as used by 1216 appears to be very useful and easy to work with. Does anyone have a source for this?
How about the Alumicore? When I google it, I find many sign companies. Does anyone have a source for this where we can get it before the sign companies mark it up?

For panels on our robot, we have been using 8mm Twin-Wall Polycarbonate Sheet material from Farmtek.com. It weighs 1.5 KG/m2 or about about 0.3 lb/sq ft.

Re: Types of Metal
 

Yep, using acetylene and oxygen. A nice warm job in the middle of winter. Took a while to get used to doing it, the thin walls made it hard not to make holes in the tubes. All part of the learning experience.

Re: Types of Metal
 

Team 104 used 8020 quick frame material this year. We used the EZ tube connectors. The quick frame tube is a good alloy and the anodizing gives a nice appearance. Cuts nice with a miter saw. It allows a frame to be made very quickly. No bolting or drilling for pop rivets. We bought the material from the 8020 ebay store and saved allot. We had no problems with the plastic fiber reinforced connectors. It's a viable option for low budget low skill teams.
This is a link for the connectors.
http://www.eztube.com/connectors/connectors.html

Re: Types of Metal
 

Gas welding thinwall steel tubing is challenging...fortunately once you learn how, you never forget (just like falling off a unicycle!)

I took a couple welding classes at the local community college back when, and patiently learned the techniques to weld thin steel with a torch. Then I got a MIG welder and never did it again...until last week when I had to fix the steer tube (top of the fork) on an old bike, and I decided to gas weld it, and it worked just fine.

Re: Types of Metal
 

After several class sessions welding thin little plates with oxy-acetylene it was a revelation the day we tried the MIG welder for the first time. I remember thinking two things: 1. This is all? That's it? All you have to do is keep the wire moving?, and 2. Who wants to go back to gas welding?

Re: Types of Metal
 

[quote=Bruce Newendorp;751402]A couple materials from this post are interesting to me and I would like to know where our team could buy them.
The 1X1X1/6" square tubing with the hole pattern as used by 1216 appears to be very useful and easy to work with. Does anyone have a source for this?
QUOTE]

When I talked to 1216 they bought 1x1x1/16 wall and then drilled it to a usefule size on a cnc mill. (you can email them to get more details). I know most of us don't have cnc mills so in the off season we will be making a drill guide out of 1/4 steel or aluminum. We made a couple of them for sheet metal stuff and it worked really well. If you use 1/4 architectural angle, you can make a nice drill guide by taking your time or on a conventional mill. do 1/8" holes and then clamp it to your box tube and any newbie can make a nice piece. Unclamp, slide, pin repeat. For some unkown reason this seems to go under the lightening hole mystery where kids love to drill lots of holes. File an edge, never! Drill lots of holes, yeah. A bit of caution: only drill through 1 side at a time otherwise you will get bit-walk with a thin drill. If you do this when the stock come in you will have a nice straight starting edge to work with.

Re: Types of Metal
 

Using hole patterns is what 1501 does best. We have found that the best way to make a hole pattern that lasts for half the build season is to have a nice piece of steel laser cut to make the hole patterns. The laser cutting hardens the metal around the hole, making it harder for the drill to distort (which leads to a lot of awkward holes).

They lasted us a while, and we drill thousands of holes a build season.

Re: Types of Metal
 

[quote=IKE;751674]Another solution would be to press a drill bushing into each hole.

Re: Types of Metal
 

drill guides work great, but can get a bit expensive ($10/guide). Aluminum patterns can wear out quickly. A cheap way to fix them is as they start to wear out drill them out and press in small piece of steel tubing. Significantly cheaper but not as nice as drill guides.

Re: Types of Metal
 

team 270 uses the kitbot frame and secures another frame about 5 inches up from the main one out of 1x2 hollow box aluminum
its very strong
for most of our bot, we use box aluminum and plate aluminum and the occasional piece of plexi-glass or plastic lexan.