The Chassis Project.

[sanddrag]

Adam Y,

Nothing got "pushed back." We used custom 1/4" T6 plates that joined the extrusion by the top of the frame members, not the insides and we put massive torque (and lock-tite) on all fasteners. All of the corners on the machine got smashed in where the extruxion became about half it's normal width and there was no longer an channel there.

Additionally, what I was really talking about. Was the front and rear frame rails on our robot of 30x30 extrusion. If you took it off and set it on a level plane, the center of the piece would be about an inch above that plane. It got bent. Not to mention the severely warped channel.

Cory,

The Skyway 9x2 Bead-Lok wheels really do suck UNTIL you turn them down on a lathe to have a flat profile. This gives really good traction (even though they are smooth) on carpet while still allowing enough sliding for 4wd tank style turning.

Oh, and the T-nut can be rotated in from anywhere in the channel, it does not have to be slid in from the end.

M,

As for limitations to extrusion, I haven't found anything you can't do with it that you can do with square tube of the same size. But there are many things you can do with extrusion that you can't do with equivalent square tube.

The T-nuts are fairly expensive at about $0.50 apiece. The fastening gussets and the such are absurd at over $8 apiece for some.

I am totally for extrusion (30x30) but fastener pieces need to be custom made for cheaper.



Now, another interesting concept I saw at the SCRRF scrimmage was a team that used the FIRST provided chassis, but added two more helical gearboxes at the other end of the robot and had a shaft running down each side of the chassis linking the two for 4 wheel tank drive. That was really cool.

A couple pictures of the beginnings of a basic 4wd universal tank setup chassis made of 30x30 extrusion. Is uses 1/4" plate "triangles" to keep together all the joints. The upper deck is for arms. Gearbox and electronics mounting plates are not shown. Chains drive the rear wheels and chains link the front and rear wheels. There are four chains total after the output of the gearboxes. It weighs 18-19 lbs in the first picture.

BTW, that top plate was made with a drill and circular saw with a wood blade and a file.