pic: New Chassis Concept
 

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This is still being worked on but if you have comments, questions or suggestions feel free to post them.

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Looks good!

With all that pocketing on the front and back rails, I would consider adding a crossbeam in the middle.

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its best to build the chasis heavy and make lighter by cutting holes out as you need that way you dont sacrafice too much strenght. Basic tankdrive?

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what is the wall thickness on the extrusion?

if it is 1/8" and pocketed, I would recommend switching to 1/16" and don't pocket it. Similar weight, less work, and depending on the pocket pattern, stronger.

Re: pic: New Chassis Concept
 

I was waiting to see how the electronics will drop inside and chain paths before adding crossbeams of any sort into the chassis.

The walls are .15 aluminum.

Current holes are just to get an idea of how much weight can be removed while keeping structural integrity.

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.15 is not a common commercially available thickness for extrusion, are these made from sheet metal?

Either way, that's some thick stuff, for that tall of a frame member, I'd recommend thinner material with less pocketing.

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Great job on this and it looks nice. The thing I like about FIRST is that there are so many different designs and they each have pro's and con's to them. This design is a great design and probably a pretty light chassis. Just include someway of tensioning the chain (Andymark's New Chain Tensioner is coming out!). BTW great CAD JOB, more views would be nice.

Re: pic: New Chassis Concept
 

Yeah. I have a few ideas starting to be drawn. Just nothing is final in CAD yet.

Its McMaster 1630T14. So you recommending something thinner with less pocketing. Thats doable. Im still playing around with best ideas for removing weight and keeping strength.

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Oh wow, that's THICK stuff. The base is .15 thick, but the legs are .26. HEAVY stuff, 2.2 lbs a foot or so.

If you do use it, find another supplier; $66 for 5' of that is ridiculous.

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I was hoping to mill down the length of the legs of the U channel. Do you have a reccomentation on a better replacement for this U channel that would work better. Thanks.

EDIT: Not at my computer but I think it was like 1.2 a foot with pocketing and reducing leg length.

Re: pic: New Chassis Concept
 

You could try dropping the middle pairs of wheels just like a half an inch, to make it easier to turn...

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1/8 inch or 3/16 inch drop is usually sufficient.

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Ok. I'm still reading up on differnt distances to drop the middle wheel.

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1/2" is too much. Your robot will be a seesaw. I would recommend 0.125-0.1875.

I would also reccomend against using C-channel. It is a major pain to machine. I think you'd be a lot happier with your results if you made this out of 1x2 extrusion.