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Unread 31-01-2013, 16:08
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JoesephWhite JoesephWhite is offline
Alumni, Mentor for 2341 & 4612
FRC #4612 (RoboRockets)
Team Role: Alumni
 
Join Date: Feb 2010
Rookie Year: 2010
Location: Shawnee, Oklahoma
Posts: 23
JoesephWhite is an unknown quantity at this point
Re: pic: 3247 Robopack Frame Design

Quote:
Originally Posted by Madison View Post
What you've shown doesn't help you avoid parallelograming, to borrow Chris' word, in the least. The plate isn't very resistant to bending along its thickness, so it's as likely to bend in the middle irrespective of how it's attached to the side rails. The giant pockets you've put into it closest to where it meets the side rails exacerbate the problem.

It may be that the additional structure you plan to add is enough to keep everything square and that end plates serve a light-duty or decorative function, but I can't make that call without seeing the rest of the robot -- and I'd be happy to take a look at it in confidence if you wanted to PM me a picture. As things are, though, I'd strongly suggest you do something to those flat plates to increase their resistance to bending. At this stage, riveting or bolting some angle along the top and bottom edges would be the simplest solution. You might also be able to get away with very securely attaching your bumpers several places along the length of those plates. Thick, high-quality plywood will provide a lot of stiffness.

If this happened on my team, I'd insist on a change. A bent frame can cause all kinds of other problems with the machine and can be nearly impossible to correct while at an event. At best, it'll make driving behavior less predictable; at worst, you'll no longer meet frame perimeter or bumper requirements and be unable to compete.

There are other components not shown that will beef it up more then enough. For example where our shooter is mounting, is 2 of the 1.5"x3"x1/8wall tubing laying on the side going across and firmly fastened to the frame, and then there is also pieces of the AndyMark hex shaft connecting the gearboxes. We have already addressed the stability of the frame flexing and have incorporated it into the rest of our design.

I nor my mentors are worried in the slightest of the frame doing as you described. Thank you for the concern though.
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