27-01-2008 22:08

s_forbes

Re: pic: What is that black goo ?

Cool! That's one thing that our team hasn't played with yet, let us know how it holds up.

27-01-2008 22:09

Éowyn

Re: pic: What is that black goo ?

Um . . . hate to sound ignorant, but what is that black goo?

27-01-2008 23:40

Chuck Glick

Re: pic: What is that black goo ?

Quote:

Originally Posted by Éowyn Um . . . hate to sound ignorant, but what is that black goo?

28-01-2008 08:26

Gdeaver

Re: pic: What is that black goo ?

That black goo is System 3 epoxy and 1/2" chopped carbon fiber. I posted this to give an example of how to join the fiberglass pultrusions. I've seen allot of that green and Gray stuff on robots this year. The problem is most teams are using real thick heavy pultrusions. They use fastening techniques that are common for metal. The item in the picture Is our ball lift fork. Both pieces are 1/8" wall 2 and 1 ". 2 holes were cut in the 2 " piece and the 1"" piece slide through extending 1/4" on the back side. A 1/4" piece of wood was inserted in the 2" to form a cavity to epoxy. Believe me that joint is very strong. Other parts of the pultrusion would fail before the joint. Hope fully this will inspire other teams to think of other uses for pultrustion. Our entire arm will be made of them. All made with common hand tools. No fancy CNC.

28-01-2008 09:31

Elgin Clock

Re: pic: What is that black goo ?

Awww... it's not laffy taffy?
I thought maybe Willy Wonka was one of your sponsors.

28-01-2008 10:13

tseres

Re: pic: What is that black goo ?

epoxy=miracle substance, IMO

28-01-2008 11:20

JesseK

Re: pic: What is that black goo ?

Would you epoxy instead of welding? Given the choice, would you epoxy the metal of your drive train frame? I'm of the opinion to weld metal together, but perhaps this is just as well; I've never experimented with it before.

We are trying to think of how to attach fiberglass to metal in ways that don't use heavy mounts: would this really work and stay durable for ~48 (most-case scenario) matches? If the mount broke, it'd be pretty devastating since the epoxy takes at least a day to completely harden.

28-01-2008 11:27

MrForbes

Re: pic: What is that black goo ?

The type of attachment method you use should depend on a lot of variables. For our robot frame we are using fiberglass channel, but needed a plate to cover the bottom for mounting stuff, and to make it more rigid, along with corner braces. We decided that using 1/16" aluminum sheet and 3/16" rivets would be the best way to do this.

The curing time of epoxy makes it pretty much out of the question for quick fixes at competitions, but in the assembly Gdeaver shows above, it is indeed very unlikely that the epoxied joint will fail. You have to use your judgement about how likely it is that a glued joint will fail in a way that you can't repair it quickly if needed, and think about other ways to set up the joint so that it will be more reliable.