[FRC Blog] Our Mistake and Q612

[headlight]

I feel like I'm probably missing something huge here, but isn't 4.5x4.5 steel square tube a standard steel tube size? I've used it all the time for machine frame weldments, the corners are rounded too.

4.5 x 4.5 x 3/16 wall: http://www.metalsdepot.com/products/...ml?page=sqtube

4.5x4.5x.12 wall: http://www.tottentubes.com/square-steel-tubing

I kinda assumed it was a solid steel tube, didn't expect them to make it bent sheet metal. I guess maybe the weight savings from not having the bottom wall?

[ratdude747]

Originally Posted by headlight

I feel like I'm probably missing something huge here, but isn't 4.5x4.5 steel square tube a standard steel tube size? I've used it all the time for machine frame weldments, the corners are rounded too.

4.5 x 4.5 x 3/16 wall: http://www.metalsdepot.com/products/...ml?page=sqtube

4.5x4.5x.12 wall: http://www.tottentubes.com/square-steel-tubing

I kinda assumed it was a solid steel tube, didn't expect them to make it bent sheet metal. I guess maybe the weight savings from not having the bottom wall?

It's probably made out of bent sheet for mounting purposes as well. Otherwise they'd have to weld the square to a plate, which would be heavy and possibly significantly more expensive. Two plates on the edges would probably have distortion issues with the welds. Bent sheet is (relativlely) cheaper and/or looks better (cheap means stick/MIG welds which have splatter and/or slag issues, TIG is pretty but relatively expensive).

[headlight]

Originally Posted by ratdude747

It's probably made out of bent sheet for mounting purposes as well. Otherwise they'd have to weld the square to a plate, which would be heavy and possibly significantly more expensive. Two plates on the edges would probably have distortion issues with the welds. Bent sheet is (relativlely) cheaper and/or looks better (cheap means stick/MIG welds which have splatter and/or slag issues, TIG is pretty but relatively expensive).

How are they planning to mount this? The prints don't show any bolt holes, so it seems like they're going to have weld this thing regardless (they are already welding the moat and the rough terrain).

The bent part is already made out of sheet steel. I guess you could TIG weld it if you want, but most welders I've met can do pretty clean welds with a MIG and steel is generally easier to weld than aluminum. The distortion issues are valid, but I think they could be avoided by a competent welder.

[Nathan Streeter]

Glad to hear they're willing to re-make the Rock Walls to avoid giving teams a rock wall that's "too tall" out of spec! That could make a big difference!

As for the widening... if anything it should just make it easier to avoid high-centering.

4.625" tall x 5.25" wide.

[Mike Schreiber]

Props to FIRST for their handling of this. This sort of thing happens all too often in engineering - it's a good experience for students to see. People make mistakes and hard decisions that impact customers need to be made.