22-02-2010 19:18

hipsterjr

Re: pic: Team 293's Robot

We have a long history of using 80-20 and man that stuff is heavy!

22-02-2010 23:04

O'Sancheski

Re: pic: Team 293's Robot

i know... we use it for prototyping because it is easy to adjust the length of things... i was wondering how much that whole chassis weighs

23-02-2010 11:28

Cyclotron

Re: pic: Team 293's Robot

We're puzzled when people say that 8020 is "heavy". Heavy compared to what?

The most common profile, 1010, weighs exactly as much per foot as 1 x 1 x 1/8 wall aluminum square tube or 1 x 1 x 1/4 angle. 8020 outperforms these materials in every way. The key to using 8020 is knowing how to join it without using joining plates, brackets or excess fasteners. This robot has only two joining plates, selected for convenience in servicing the drive train.

The chassis pictured weighs in at 29 pounds; the entire robot, fully loaded, is 113. Weight was never a problem this season.

23-02-2010 11:31

Collin Fultz

Re: pic: Team 293's Robot

It looks like you're running a bolt through the outside plates and they are tapped into the piece they are connected to? Is this how you're eliminating the need for angle attachments?

How does this method hold up at competition? Do you put locktite or anything on the bolts? Do you have a problem with them staying tight?

Looks great. Good work.

23-02-2010 11:36

nnfuller

Re: pic: Team 293's Robot

Compared to .075 wall 1 inch tube it's rather heavy. But for me it has more to do with the aesthetic look of an 80-20 robot and the fact that doing things like non-45 degree miters seems to always need mending plates. Just my two cents. How do you join it without plates? Do you use those pieces that 80-20 makes that you counter sink into the ends? Or something else?

23-02-2010 15:21

Cyclotron

Re: pic: Team 293's Robot

We counterbore clearance holes for 1/4-20 socket head cap screws (17/64 body, 25/64 head) and screw them into the tapped ends of the extrusion. McMaster sells a step drill bit to do this in one operation (drill press only!) Where 2 or 3 bolts would conflict at a corner, we use 8020 "end fasteners' which require only a #7 clearance hole for the hex key to tighten. Occasionally we use 8020 "anchor fasteners" which require a 9/16 counterbore in one extrusion.

We have done 45 degree and other angled connections. These require a careful drilling setup because of the profile shape.

These connections remain tight without locktite, but we always check everything just in case.

All of the fabrication steps for an 8020 frame can be learned by new team members very quickly, and the results are precise and as strong as they need to be. An 8020 frame is easier to put together than the Kitbot, and it is stronger, stiffer, and straighter.

23-02-2010 15:30

Chris is me

Re: pic: Team 293's Robot

While given the choice between the two I'd probably rather use 80/20 for prototyping, the Kit frame, unmodified, is stronger and stiffer than an 80/20 equivalent part. I've seen 80/20 frames bend and warp (and even more pictures of said destruction), but never a kit frame.

80/20 weight stacks up fast, mostly because of all the fasteners you need, and generally people use more of it to accomplish the same things. I'm looking at how adding a few more feet of it added 25 pounds to the robot the other night :/

23-02-2010 15:37

Dancin103

Re: pic: Team 293's Robot

Looks good. I can't wait to see it in action.
(My 272nd post, Go CyberCrusaders. )

Cass

23-02-2010 15:41

Chris Fultz

Re: pic: Team 293's Robot

There are benefits to square tube and to 8020.
Weight wise, 8020 and 1/8" al are about the same.
8020 is about 2x 1/16" wall, which can be used in many places.

I really like your attachment approach, which provides a big weight savings and space improvement without the corners and extra bolts and t-nuts commonly used.

Very nice, and way to take advantage of capabilities you have and materials you have and come up with a great finished product.