Chief Delphi - sneak peak

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Robot Showcase (http://www.chiefdelphi.com/forums/forumdisplay.php?f=58)

- - sneak peak (http://www.chiefdelphi.com/forums/showthread.php?t=68701)

Quote:

Originally Posted by c9ollie (Post 760238)

i can assure you that 1/10 is as thick as it needs to be anymore more is just a waste of time and pocketing 1/4 plate is just waste of aluminum. we ran this exact setup last year with zero issues. the frame of our robot bent before these "PODs" did. also since this is a super rough draft and i havnt really got to making the spacers for it. there is more support in these PODs but im more concerned about the geartrain layout.

As you said earlier you used 1/10, was it for this type of swerve/crab setup or for a 6-wheel? As a mechanical engineer I would take the advice of fellow mech-heads and increase the width of your side plates, 1/8th is the smallest I would go with major cross bracing. Looking at your setup your main drive shaft is about 6" away from your main mounting point for those side plates, and that type of torque on 1/10" sheet won't last long. Take a look at some of the more successful crab drives of the last couple years (i.e. 71, 111, 1625), and make your modules beffey to start and slowly cut away the fat as you improve the design.

Quote:

Originally Posted by Al Skierkiewicz (Post 760242)

Ollie,
Don't forget that a 140lb robot running at 12 ft./sec imparts a pretty big side load to your module and all the force will be transmitted to the frame through the ring and a small amount to the top bearing. You can't keep your friction numbers unless all the tread is on the floor.

i understand that. we ran this same setup last year with zero issues. we even ran it without the lower support bearing for our 2 regionals. we did break 2 of the top posts but that was because of faulty welds. we redid them in billet and they held more than ok. the lower bearing is there for secondary lateral support and is not our main means of lateral stabilization. yes the forces are so great but they are so instantaneous that even if it does make something bind it will do it for such a short period of time it would be insignificant. the module is designed to be 100% support by the top post. the lower bearing is there for redundancy. i just put it where it was because i was just to lazy to redo the side panels, but it will probably be located closer to or below the axle of the wheel

Lol crab drive is really awe some

Quote:

Originally Posted by c9ollie (Post 760238)

i can assure you that 1/10 is as thick as it needs to be anymore more is just a waste of time and pocketing 1/4 plate is just waste of aluminum.

I'm asking for a stress analysis. You probably won't convince 99% of us without one. Just run it in the worst-case scenario that you can think of and post the results picture, or something like that. If you can show us that it won't fail, more teams might wind up using .1" metal on their robots next year. We all win. If you don't show one, there's a good chance that the first time it breaks, someone will say, "I told you so" or "Why didn't you use..." or "What were you thinking?". We all lose. You've got the CAD files, so it should be pretty simple to run the analysis, and if you don't know how, it's a pretty good way to learn.