We used a fair amount of the 2x1, and haven’t seen anything like that. Do you have a picture that shows how it was used on the robot?
One thing we noticed was that it was very easy to over tighten bolts on the rev 2x1. When we would crank down on a bolt, the tube would deform slightly and we’d have to back it out. It’s possible that tightening it too much decreases the structural integrity enough to cause a failure.
Do you know what caused the splitting?
We had a small split on the 0.04” side of our front and back drive rail but it was in a worst case loading scenario and it happened when we crashed into the barrier at 18 fps.
None of that was due to overtightening. The grid pattern had all rivnuts in it and the metal cracked which allowed the rivnuts to pull out. The blue you can see it wasn’t overtightened either
Do you know if that hole in the first 2 images elongated from splitting, or was that there from manufacturing?
What size hole is needed for the rivnuts? And where the rivnuts on the 2in or 1in side?
We probably should have used the thick wall grid but it wasn’t instock when we built that part of the robot
The rivnuts were on the 2" side and we use a dill bit gauge and slide the rivnut into the tightest fitting size. We’ve found not all rivnuts are the same diameter so we test fit for the tightest hole possible before installing them.
It was opened up for a 1/4" bolt.
Edit. 1/4" bolts were not used there because we were able to source the rev 2x1 inserts from a local team
We’re not really upset but we replaced all that rev 2x1 with vex 2x1 (it was on hand) so it has a thicker 1" wall and further spacing between the holes. We were worried about weight when first building the robot but after all was said and done we had the lightest robot we’ve ever had. 94lbs
Yeah and come to think about it we didn’t use 1/4" bolts because we were able to get the rev tube inserts from another team and used them there. The upright 2x1 was trimmed to clear our swerve module covers
We experienced some issues with the 2x1 thin wall grid pattern extrusion in our 2 stage arm. Both failures were in the lower arm. We believe that this is primarily due to the use of thin wall in an application that really needed to be thick wall. I do not believe this is a problem with the REV extrusion itself.
- The lower arm consisted of 2 parallel beams. The elbow joint of the arm is a 1/2" hex shaft dead axle supported by a 1/2" hex x 1.125" bearing at the inner wall of the lower arm and then drilled and tapped with a bolt through the outer wall. The wall material around the hole that the bolt passed through broke around the bolt to the point where the hole was enlarged to a size larger than the bolt head leaving the shaft unsupported.
We eventually fixed this with a plate spanning the joint tied in to adjacent, undamaged holes.
- At the shoulder joint at the base of the arm where the sprockets are bolted to the extrusion, we had a large chunk of the material fail when our arm got tangled with the scoring grid.
We are currently re-building the arm using thick wall extrusion. We also are going to be installing standoffs between the two faces of the extrusion and running the bolts for the sprockets through both walls and being able to clamp down on the standoffs in between so that the loads are better carried into the extrusion and not carried by a single wall.
Again, I believe this was an engineering error on our part using the thin wall extrusion in a high load application and not distributing the loads correctly. I do not believe this is a problem with the REV extrusion.
We have seen similar cracking on the 1in face. That metal is .04in thick so if a hole is drilled on the 2in side, the tube suddenly becomes very week.
Is there any other support for the black uprights? If that is the only attachment to the blue tubing you have a very long lever arm twisting your two mounting bolts very close together.
I’d suggest that REV revise the extrusion die to take out the face grooves; those add a lot of stress concentration and take about half of the wall thickness on the thin wall. The drilling guide aspect seems cool, but the wall loss seems troublesome.
I had a kid drag a 10-32 lock nut right through the side of a 2x1 light… Sawing the extrusion the hard way its easy to smoosh it.
Other than those grooves I LOVE this stuff! The corner reinforcement is super sweet!
Oh, i zoomed in a bunch on the pic but there is carbon fiber tube cross bracing on those uprights
You should be able to see the bracing in that pic
Edit: edited pic to remove people in background
I think it’s a flaw to have that groove too. What i question is why continue with the super thin wall on the heavier tubing. I could understand .063 or larger but they used the .040 on the thick wall too. They were trying to save weight but if you need the thick wall for structural reasons then it’s compromised by the thin wall 1" side. Maybe next year they can come out with a full thickness version for the higher stress applications
Any guess on neo 550 ultraplanetary pinions coming back in stock?
@Greg_Needel are there any plans to come out with a max tube with a thicker 1" side? Or a revised heavy wall version?