80/20 Inc.

[Jared Russell]

We actually use Bosch-Rexroth 20mm extrusion for structure on our robot (this year we used both 20x20mm and 20x60mm). The 20x20 is .269 lbs/ft and the 20x60 is .605.

The strength/weight ratio for T-slot extrusion is similar but slightly inferior (within 15% IIRC) to square tubing, but what you get in return is an easy way to tap the ends of the profile (we generally use a 1/4-20) and the ability to bolt crosswise through it without having to worry about "caving in" the sides of the tube. If you have limited machining resources, it's a good way to rapidly build structure. It is also a great way to let the students get their "hands dirty". But, as noted, expect to pay a slight penalty in both weight and materials cost. If you are using 1" or 30mm profiles, the weight adds up REALLY quickly. Our use of the 20mm profile helps to alleviate this, but even then there are times where we opt for other materials/profiles to get better stiffness or strength for the weight (our 2011 arm comes to mind).

We generally do not use T-nuts or specialized connecting hardware (the exception is for mounting things like optical sensors that will bear no load) because they drive up weight/cost and slide all over the place. Instead we drill through-holes and/or tap the ends of the profile to build solid connections.

In an ideal world, we would rapidly prototype using extrusion and then go for more streamlined square/rectangular tube + gusset plate or even sheet metal for final mechanisms. In the past (including 2012) we often run out of time before we get to this level of optimization (and have also had widely varying levels of machine shop access from season to season).

[philso]

At one of the tournaments we attended this past year, we saw a team using Micro Rax (www.microrax.com) for parts that did not need the full strenght of the 80/20 extrusions.

[IndySam]

I don't think we have ever built a robot without at least a little 80/20 in it.

This year it was a couple cross braces and we also used it in an extended pickup we added after our first regional. The slots and their adjustability are great for adding devices post-build.

It is great for prototyping and we use it every year for that purpose. We have been using some of the same sticks and hardware for over 10 years. It's re-usability is one of it's big benefits.

[Nemo]

967 uses 20x20mm and 20x40mm Bosch extrusion, and like 341 we often tap the ends for 1/4-20 for making corner connections. We like the 5 mm block nuts and small corner gussets. We sometimes use 10-32 screws in the M5 block nuts, because they fit nicely, and we have lots of 10-32 hardware. For the last three years, we've used a kit frame for the drive with Bosch structure coming up from there. In 2009 we also made the drive base out of Bosch, but that consumes a decent amount of precious time compared to tossing a kit frame together.

The sliding block nuts are pretty nice sometimes. For example, last year our shooter used a pair of 20x20 extrusion rails as fixed ball guides. Before we built it and played around with it, we didn't know the exact angle or distance from the wheel that we'd want, so it was nice to work with an easily adjustable mechanism.
http://www.flickr.com/photos/lmrobot...in/photostream

T slots and block nuts can only handle so much force, and if you exceed that the T slot edges bend outward, allowing the nut to come free. So when something is going to get loaded up, you have to drill it out and bolt it through the extrusion.

We used to build frames out of 30x30mm and 30x60mm extrusion, but we switched away from that because it's heavy. 20x20 mm is a nice FRC size.

It would be cool to prototype with Bosch and then transfer the dimensions we come up with to a lighter, tighter sheet aluminum design, our team has a ways to go before we'll be able to manage that sort of design cycle within a 6 week build season.

[ToddF]

2363 has a presentation we give on how we use 8020 in our frames in a weight efficient manner. I've tried to upload it as a white paper, but this doesn't seem to work. The file may be too large. You can see the presentation here.

Our 2011 robot:


Our 2012 robot:

[cgmv123]

We love it.

It's easy to work with, easy to change around, doesn't bend or deform (that I know of) and we seem to have a lot of it lying around.



We even used it for our pit:


It's kind of on the heavy side, but we feel it's worth the extra pounds.

[ToddF]

Originally Posted by cgmv123

We love it.
We even used it for our pit:

Hey, us too!

[Trish Fisher]

Thank you everyone for your comments, suggestions and ideas!!!! I will get some 80/20 and look at some of the other materials you all have suggested.

This will hopefully get us through the first year. Right now we have 18 interested students and only 5 have done FIRST before for which 2 are programmers, and in the "building team" 2 have 1 year experience and 1 has 3 yrs exp. I hope to have everyone prototyping immediately and try to get some depth with knowledge and fabrication experience as soon as possible. I'm hoping for "Fail sooner to succeed sooner"... a slogan used by IDEO

If anyone else has ideas on how you used it that would benefit this young team, please let me know.

Thanks again for your help, the FIRST Community is the best ever!

[Trish Fisher]

Thank you everyone for your replies!!!

The FIRST Community is the best!

Trish
Parent Volunteer and FRC2240 Team Mgr.