which is better aluminum or steel????

[sanddrag]

Originally Posted by Andrew

How come no one talks about riveting? Yet another alternative to welding (permanent) and bolting (removable but heavy).

We used tons of rivets on the arm. It was all made from flat .040 sheet metal (aluminum) that was lasercut then bent picture In some (higher stress) areas the rivets worked a little loose over time. While it did come out very nice, I still think extruded aluminum box tubing is the way to go for any frames or arms or anything. With the sheet metal we were able to make a very thin wall box for light weight but with extruded box tubing you could just surface (machine) down the sides to make it thin too and it would be stronger because it is one piece.

As for the issue of cracking welds, if you have a good welds then you will not have a problem. If the welds are not coming out nice, then of course they are likely to crack.

You can see a picture of our frame and the nice welds (lower structure, upper structure was a rush job) here picture For the frame itself, it is only 11 lbs. It is all 1/8" wall tubing. Thinking back, we probably could have gotten it down to about another 1/2 lb by going a little narrower on the tubing on the side rails.

The only steel in our robot besides gears, sprockets, and chain is in shafts. All the shafts are steel but some of the larger ones are bored out through the center for weight savings.