Chassis Materials

[neoshaakti]

hey I was curious about what materials teams use to construct their chassis

and what material is the chassis provided in the KOP made of?

thanks

[Billfred]

From IFI's Kitbot page, the kit frame is made of 5052-H34 Aluminum.

To answer your other question, we use kit frame and a dash of plywood.

[DonRotolo]

We use the kitbot frame, along with aluminum for things that need to be strong, and Lexan (Not plexiglass!) for things that just need to hold things. We're experimenting with aviation plywood and composites for non-structural items to save weight. We'll sometimes use whatever seems to fit the bill.

Mostly aluminuum by weight.

Don

[vivek16]

aluminum and plywood.
aluminum frame and plywood for a covering of sorts was our last years design. we will probably use mostly aluminum this year.

-vivek

[MrForbes]

a couple of Arizona teams use fiberglass, you can get it as "pultruded" structural shapes such as I beams, channel, angle, etc. The 1/4" thick version is about as heavy as 1/8" aluminum of the same size, it's very tough (bounces back instead of bending), can be worked with hand tools, can be bolted together, painted, etc. The I beam works great for mounting wheels and protecting them well, and the channel works great for crossmembers such as across the end. Cost is a bit high because you have to buy long lengths and get it shipped by truck freight, but you can use the leftovers for next year's robot.

Surprisingly not many teams have tried it....

Aluminum works well too, it's strong, light, not too difficult to work by hand, and available in many many shapes. Except a 4" x 4" x 1/8" I beam

[lukevanoort]

For the last three years, we've primarily used aluminium for structural parts; in 2005 we used a slab of plywood to reinforce the kit frame and for mounting electronics, in 2006 electronics were on acrylic (never again...) with aluminum chassis reinforcements. Last year we kinda hybridized the two methods, some of the electronics were on polycarbonate and some were on a small piece of plywood; again, the plywood serve a structural stiffening purpose in addition to its mounting job, but this time we also had (smaller) aluminum reinforcements. In '03 and '04 the chassis were entirely plywood, and in 2002 and 2001 they were 80/20 aluminum extrusion. The all out plywood method works, but it can be a bit heavy, the same goes for the 80/20 frame.

[JesseK]

What's the most common grade of aluminum among FIRST teams -- 6063?

[MrForbes]

Which alloy you use depends on what you're doing with it. 5052 is good for making sheet parts that require some forming (such as bending), while 6061 is commonly used for extrusions and parts that will be machined, not formed.

[EricH]

Aluminum tube with a plywood base in between (for electronics and motors). We've never had a problem in my memory.

[AndyB]

269 has used 4130 Chromoly Steel now for the past 4 years and hasn't looked back.

It has three times the strength with about the same weight as aluminum.

We have primarily used 1/2" for areas with little side load or where weight is a concern. 3/4" is used on our chassis although I think we've used 1" as well in the past.

http://aircraftspruce.com/catalog/me...4130square.php

We are surprised that we are still the only team, to our knowledge, to be using this stuff.

The only downside to this stuff is it goes through drill bits and drill batteries like crazy. I think we replaced our bansaw blade this year 1 or 2 times this year as well. We just bought a corded dewault so drilling should be much easier. We always use .035" thickness. We have never had a break.

If you buy this stuff, they give you welding rod as well. Although I don't know if we've ever used it.

[AdamHeard]

Originally Posted by AndyB

It has three times the strength with about the same weight as aluminum.

It's about 3 times heavier.... but, it is offered in thinner wall thickness than aluminum usually. But still, it's a good deal heavier.

294 used the kit frame in 05, a welded 2x1 extrusion frame similar to 4/22/60/254/968 in '06 and a plate sandwich concept (similar to 233 in 2006) for '07 and our current prototype.

[lukevanoort]

Originally Posted by JesseK

What's the most common grade of aluminum among FIRST teams -- 6063?

I'd wager that 5052-H34, 6061-T6, 6063-T52, and 6105-T5 are the most common alloys: 5052-H34 because it's in the kit; 6061-T6 because it's an excellent balance of price, availability, and strength; 6063-T52 because it's cheap and available (not too strong though...); and 6105-T5 because that is what 80/20 makes their extrusions out of. Personally, I like 6061-T6 for the reasons I've listed, but I wouldn't say no to some nice 7068 or 7075!

Originally Posted by AdamHeard

It's about 3 times heavier.... but, it is offered in thinner wall thickness than aluminum usually. But still, it's a good deal heavier.

I dunno, I think it depends heavily on your heat treatment. From some numbers I'm looking at on MatWeb, it seems that some (hardened) 4130 steels are about 2.9 times the weight of 6061-T6 aluminium, while being 3.5 times stronger. So, its strength to weight ratio seems a bit better. However, annealed 4130 and 4130 that hasn't been hardened that much are a different story; the less hardened versions are only about twice the strength.

[MrForbes]

Steel is 2.8 times as dense as aluminum, it doesn't matter what alloy. But strength DOES depend on alloy and treating, and you can find steels that are several times stronger than some types of aluminum...and you can also find aluminum alloys that are several time stronger than mild steel! so you have to be pretty careful in you comparisons, to make sure you are comparing apples to apples, and oranges to oranges.

1501 has used chrome-moly steel tubing.

If you are interested in keeping your robot from falling over, go heavy on the chassis, and save the exotic materials and super lightweight design for all the "up top stuff", such as arms, etc.

[cooker52]

But don't go to heavy, otherwise you will come up at the last minute drilling holes in everything.

As for us, we did use some chromoly this year. For the most part, we use 6061 aluminum. We use the sheets of aluminum and bend and curve it into our robot's form. This technique of making a uniform body is called monocoque and it is very light weight and durable.

Here's a picture of last years (2006) robot.

[AdamHeard]

Originally Posted by squirrel

If you are interested in keeping your robot from falling over, go heavy on the chassis, and save the exotic materials and super lightweight design for all the "up top stuff", such as arms, etc.

Good advice for rookies, but I still cringe every time I hear you say that.

I prefer to lighten everything as much as possible AND keep the weight low. That way your not wasting any weight just to get a low CG. Some teams are amazing at that (469 and 1114 come to mind this year)...

If you lighten your frame by 5 lbs, and that frames CG is 3 inches above the floor, and you then mount 5 lbs of something anywhere below that 3 inches, your CG is lower.

But in the end, there's nothing wrong with your idea.