pic: New Chassis Concept

The start of a chassis I am working on. There is a lot of stuff that needs to be tweaked and changed but I figured I would upload a render of what I have so far.

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

Looks good!

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

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?

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.

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.

.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.

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.

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.

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.

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.

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

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

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

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.

Chris I like your stuff and if you need any help with CAD, please email me. Try using 1x2 aluminum. We have using a 1/16 wall and it is fairly light. You can even pocket some out on the sides but none on the top. We created a frame that had a ton of cnc work and played battle bots with it to see if it would crumble. Plus stress testing told us it would be fine. Make sure you have a safety factor of 10 ((Just to be extremely Safe)) :wink:

Just the 6 pieces of C channel totally 14.13 pounds whereas the same length of 1x2 with 1/6in walls is about 7.7 so I see what you are saying about weight.

Cory, whats so hard about machining C channel? Im not a machinist but the machinist didnt say anything when I drew a quick concept for him.

Both the cutter and the vice exert lots of force on the part. Square/rectangular tubing has walls that resist forces rather well in all directions square to a face. C channell is “missing” a side which often can make it hard to clamp in certain orientations (for example, vertically you’d only be holding the ends of the bottom leg), and hard to actually cut in certain orientations (the legs will deflect from the cutter probably, leaving poor finishes). There are ways to get around that of course, but ideally you’d make machining as easy as possible.

The 2x1 will also result in a much more rigid frame, it doesn’t twist along it’s own long axis as easily as the C channel will.

Our team’s robot for the last few years has had the motors directly drive the middle wheel. This could make turning easier if you drove those wheels instead

not to be negative but,

could just save yourself the trouble and use the kitbot chasssis…

would loose the cool factor though…